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The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and we are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated January 4, 2012

Filed pursuant to Rule 424(b)(5)
Registration No.: 333-178653

Preliminary Prospectus Supplement

(To Prospectus dated December 20, 2011)

$60,000,000

SYNAGEVA BIOPHARMA CORP.

Shares of Common Stock

We are offering up to $60,000,000 of shares of our common stock in this offering.

Our common stock is traded on the NASDAQ Global Market under the symbol “GEVA.” On January 3, 2012, the last reported sale price of our common stock was $25.65 per share.

Entities affiliated with one of our directors, Felix Baker, have indicated an interest in purchasing up to an aggregate of 36.2% of the common stock offered in this offering at the price offered to the public. Because these indications are not binding agreements or commitments to purchase, any or all of these entities may elect not to purchase any shares in this offering, or the underwriters may elect not to sell any shares in this offering to any or all of these entities. In the event that these entities confirm their interest, we will request that the underwriters sell to them such percentage of the common stock offered in this offering.

Investing in our common stock involves risks that are described in the “Risk Factors” section beginning on page S-5 of this prospectus supplement and the risk factors described in the other documents incorporated by reference herein.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

We have granted the underwriters an option for a period of up to 30 days from the date of this prospectus supplement to purchase up to $9,000,000 of additional shares of common stock at the public offering price less the underwriting discounts and commissions to cover over-allotments, if any.

We estimate the expenses of this offering, excluding underwriting discounts and commissions, will be approximately $650,000.

Delivery of the securities is expected to be made on or about January             , 2012, subject to the satisfaction of certain conditions.

The date of this prospectus supplement is January             , 2012.

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is part of the registration statement that we filed with the Securities and Exchange Commission (the “SEC”) using a “shelf” registration process and consists of two parts. The first part is this prospectus supplement, including the documents incorporated by reference, which describes the specific terms of this offering. The second part, the accompanying prospectus, including the documents incorporated by reference, gives more general information, some of which does not apply to this offering. Generally, when we refer only to the “prospectus,” we are referring to both parts combined. This prospectus supplement may add to, update or change information contained in the accompanying prospectus and the documents incorporated by reference into this prospectus supplement or the accompanying prospectus.

If information in this prospectus supplement is inconsistent with the accompanying prospectus or with any document incorporated by reference that was filed with the SEC before the date of this prospectus supplement, you should rely on this prospectus supplement. This prospectus supplement, the accompanying prospectus and the documents incorporated into each by reference include important information about us, the common stock being offered and other information you should know before investing in our common stock. You should also read and consider information in the documents we have referred you to in the section of this prospectus supplement and the accompanying prospectus entitled “Where you can find more information.”

You should rely only on this prospectus supplement, the accompanying prospectus and the information incorporated or deemed to be incorporated by reference in this prospectus supplement, the accompanying prospectus, and any free writing prospectus . We have not authorized anyone to provide you with information that is in addition to or different from that contained or incorporated by reference in this prospectus supplement, the accompanying prospectus, and any free writing prospectus. If anyone provides you with different or inconsistent information, you should not rely on it. We are not offering to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained or incorporated by reference in this prospectus supplement or the accompanying prospectus is accurate as of any date other than as of the date of this prospectus supplement or the accompanying prospectus, as the case may be, or in the case of the documents incorporated by reference, the date of such documents regardless of the time of delivery of this prospectus supplement and the accompanying prospectus or any sale of our common shares. Our business, financial condition, liquidity, results of operations and prospects may have changed.

All references in this prospectus supplement or the accompanying prospectus to “Synageva,” the “Company,” “we,” “us,” or “our” mean Synageva BioPharma Corp., unless we state otherwise or the context otherwise indicates.

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RISK FACTORS

Investing in our securities involves risk. Prior to making a decision about investing in our securities, you should carefully consider the specific risk factors discussed below and all of the other information contained or incorporated by reference in this prospectus supplement or the accompanying prospectus. You should also consider the risks, uncertainties and assumptions discussed under the heading “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2010 filed with the SEC on March 14, 2011, as amended April 28, 2011, as updated by our Quarterly Reports on Form 10-Q and our other filings with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) filed after such Annual Report. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations. If any of these risks were to occur, our business, financial condition or results of operations would likely suffer. In that event, the trading price of our common stock could decline, and you could lose all or part of your investment. This prospectus supplement also contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in these forward-looking statements as a result of certain factors, including the risks faced by us described below and elsewhere in this prospectus supplement and the accompanying prospectus. See “Note Regarding Forward-Looking Statements” for a discussion of certain qualifications regarding such statements.

Risks Related to Our Business

We are largely dependent on the success of our leading product candidate, SBC-102. All of our product candidates, including SBC-102, are still in either preclinical or clinical development. Clinical trials of our product candidates may not be successful. If we are unable to commercialize SBC-102, or experience significant delays in doing so, our business will be materially harmed.

Our business prospects are largely dependent upon the successful development and commercialization of SBC-102. In February 2011, we initiated Phase I/II clinical trials for SBC-102 to evaluate the safety and tolerability of SBC-102 in adult patients with liver dysfunction due to late onset LAL Deficiency. We began enrolling patients in May 2011 and completed enrollment in December 2011. We also initiated a Phase I/II clinical study in children with growth failure due to early onset LAL Deficiency in February 2011. Before we can commercialize product candidates related to SBC-102 we need to:

This process involves a high degree of risk and takes many years. Our product development efforts with respect to a product candidate may fail for many reasons, including:

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Few research and development projects result in commercial products, and success in preclinical studies or early clinical trials often is not replicated in later studies.

We may decide to abandon development of a product candidate or service at any time, or it may be required to expend considerable resources repeating clinical trials or conducting additional trials, either of which would increase costs of development and delay any revenue from those programs.

In addition, a regulatory authority may deny or delay an approval because it is not satisfied with the structure or conduct of clinical trials or due to its assessment of the data we supply. A regulatory authority, for instance, may not believe that we have adequately addressed negative safety signals. Clinical data is subject to varied interpretations, and regulatory authorities may disagree with our assessments of data. In any such case, a regulatory authority could insist that we provide additional data, which could substantially delay or even prevent commercialization efforts, particularly if we are required to conduct additional pre-approval clinical studies.

Initial interim results from a clinical trial do not ensure that the trial will be successful and success in early stage clinical trials does not ensure success in later-stage clinical trials.

We will only obtain regulatory approval to commercialize a product candidate if we can demonstrate to the satisfaction of the FDA or the applicable non-U.S. regulatory authority, in well-designed and conducted clinical trials, that the product candidate is safe and effective and otherwise meets the appropriate standards required for approval for a particular indication. Clinical trials are lengthy, complex and extremely expensive processes with uncertain results. A failure of one or more clinical trials may occur at any stage of testing.

Success in preclinical testing and early clinical trials does not ensure that later clinical trials will be successful, and initial results from a clinical trial do not necessarily predict final results. We cannot be assured that these trials will ultimately be successful. Our leading product candidate, SBC-102, entered clinical trials recently, and the results of these clinical trials may be disappointing.

Even if early stage clinical trials are successful, we may need to conduct additional clinical trials for product candidates with patients receiving the drug for longer periods before we are able to seek approvals to market and sell these product candidates from the FDA and regulatory authorities outside the U.S. If we are not successful in commercializing any of our lead product candidates, or are significantly delayed in doing so, our business will be materially harmed.

We may find it difficult to enroll patients in our clinical trials.

SBC-102 is being developed to treat LAL Deficiency, which is very rare. Many potential patients for our product candidates have not been diagnosed with the diseases being targeted by our product candidates. We may not be able to initiate or continue clinical trials if we are unable to locate a sufficient number of eligible patients to participate in the clinical trials required by the FDA or other non-U.S. regulatory agencies. We have completed enrollment in December 2011 of our first clinical trial with SBC-102. We intend to eventually enroll a total of approximately eight pediatric subjects into the Phase I/II study for early onset LAL deficiency. Our inability to enroll a sufficient number of patients for any of our current or future clinical trials would result in significant delays or may require us to abandon one or more clinical trials altogether.

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If our preclinical studies do not produce positive results, if our clinical trials are delayed or if serious side effects are identified during drug development, we may experience delays, incur additional costs and ultimately be unable to commercialize our product candidates.

Before obtaining regulatory approval for the sale of our product candidates, we must conduct, at our own expense, extensive preclinical tests to demonstrate the safety of our product candidates in animals, and clinical trials to demonstrate the safety and efficacy of our product candidates in humans. Preclinical and clinical testing is expensive, difficult to design and implement, and can take many years to complete. A failure of one or more preclinical studies or clinical trials can occur at any stage of testing. We may experience numerous unforeseen events during, or as a result of, preclinical testing and the clinical trial process that could delay or prevent our receipt of regulatory approval for, or the commercialization of, our product candidates, including:

If we are required to conduct additional clinical trials or other testing of our product candidates beyond those that we currently contemplate or are unable to successfully complete our clinical trials or other testing or if the results of these trials or tests are not positive or are only modestly positive or if there are safety concerns, we may:

The product development costs will also increase if we experience delays in testing or approvals. We do not know whether any preclinical tests or clinical trials will be initiated as planned, will need to be restructured or

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will be completed on schedule, if at all. Significant preclinical or clinical trial delays could also shorten the patent protection period during which we may have the exclusive right to commercialize our product candidates. Such delays could allow our competitors to bring products to market before we do and impair its ability to commercialize our products or product candidates.

We have not obtained marketing approval, including by the FDA, nor commercialized any of our current rare disease product candidates.

We have not obtained marketing approval nor commercialized any of our current rare disease product candidates and do not expect to receive marketing approval or generate revenue from the direct sale of our rare disease products, including SBC-102, for several years, if ever. We have completed a Phase I/II clinical trial for SBC-102 in adults but still have only limited experience in conducting clinical trials for SBC-102. Additionally, we are conducting preclinical studies for various other indications. Our limited experience might prevent us from successfully designing or implementing a clinical trial for any of these diseases. We may not be able to demonstrate that our product candidates meet the appropriate standards for regulatory approval. If we are not successful in conducting and managing our preclinical development activities or clinical trials or obtaining regulatory approvals, we might not be able to commercialize our lead rare disease product candidates, or might be significantly delayed in doing so, which will materially harm our business.

If the market opportunities for our product candidates are smaller than we believe they are, our revenues may be adversely affected and our business may suffer.

We focus our research and product development on treatments for rare diseases. Our projections of both the number of people who have these diseases, as well as the subset of people with these diseases who have the potential to benefit from treatment with our product candidates, are based on estimates.

Currently, most reported estimates of the prevalence of these diseases are based on studies of small subsets of the population of specific geographic areas, which are then extrapolated to estimate the prevalence of the diseases in the broader world population. These estimates may prove to be incorrect and new studies may change the estimated prevalence of these diseases.

The commercial success of any product candidate that we may develop, including SBC-102, will depend upon the degree of market acceptance by physicians, patients, third party payors and others in the medical community.

Any future product that we bring to the market, including SBC-102, may not gain market acceptance by physicians, patients, third party payors and others in the medical community. If these rare disease products do not achieve an adequate level of acceptance, we may not generate significant product revenue and may not become profitable. The degree of market acceptance of these product candidates, if approved for commercial sale, will depend on a number of factors, including:

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Even if a potential product displays a favorable efficacy and safety profile in preclinical and clinical trials, market acceptance of the product will not be known until after it is launched. Our efforts to educate the medical community and third party payors on the benefits of the product candidates may require significant resources and may never be successful. Such efforts to educate the marketplace may require more resources than are required by the conventional technologies marketed by our competitors.

If we are unable to obtain adequate reimbursement from governments or third party payors for any future products that we may develop or if we are unable to obtain acceptable prices for those products, our prospects for achieving profitability will suffer.

Our prospects for achieving profitability will depend heavily upon the availability of adequate reimbursement for the use of our approved rare diseases product candidates from governmental and other third party payors, both in the U.S. and in other markets. Reimbursement by a third party payor may depend upon a number of factors, including the third party payor’s determination that use of a product is:

Obtaining reimbursement approval for a product from each governmental or other third party payor is a time consuming and costly process that could require us to provide supporting scientific, clinical and cost effectiveness data for the use of its products to each payor. We may not be able to provide data sufficient to gain acceptance with respect to reimbursement or might need to conduct post-marketing studies in order to demonstrate the cost-effectiveness of any future products to such payors’ satisfaction. Such studies might require us to commit a significant amount of management time and financial and other resources. Even when a payor determines that a product is eligible for reimbursement, the payor may impose coverage limitations that preclude payment for some uses that are approved by the FDA or non-U.S. regulatory authorities. In addition, there is a risk that full reimbursement may not be available for high priced products. Moreover, eligibility for coverage does not imply that any product will be reimbursed in all cases or at a rate that allows us to make a profit or even cover its costs. Interim payments for new products, if applicable, may also not be sufficient to cover costs and may not be made permanent.

We are exposed to product liability and preclinical and clinical liability risks which could place a substantial financial burden upon us, should we be sued, if we do not have adequate liability insurance or general insurance coverage for such a claim.

Our business exposes us to potential product liability and other liability risks that are inherent in the testing, manufacturing and marketing of pharmaceutical formulations and products. Such claims may be asserted against us. In addition, the use in our clinical trials of pharmaceutical formulations and products that our potential collaborators may develop and the subsequent sale of these formulations or products by us or our potential collaborators may cause us to bear a portion or all of the product liability risks. As is common for companies sponsoring such clinical testing, we carry product liability insurance. The limit of this insurance may in some instances may be insufficient to offset a negative judgment or settlement payment. As a result, a successful liability claim or series of claims brought against us could have a material adverse effect on our business, financial condition and results of operations.

We are subject to regulations regarding manufacturing therapeutic proteins.

We are subject to ongoing periodic unannounced inspections by the FDA and corresponding state agencies to ensure strict compliance with cGMP and other government regulations and corresponding foreign standards.

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The cGMP requirements govern quality control and documentation policies and procedures. Complying with cGMP and non-U.S. regulatory requirements will require that we expend time, money, and effort in production, recordkeeping, and quality control to assure that the product meets applicable specifications and other requirements. We must also pass a pre-approval inspection prior to FDA approval. Failure to pass a pre-approval inspection might significantly delay FDA approval of our products. If we fail to comply with these requirements, we would be subject to possible regulatory action and might be limited in the jurisdictions in which it is permitted to sell our products. As a result, our business, financial condition, and results of operations might be materially harmed.

We currently manufacture the therapeutic protein products used in SBC-102; however, we have limited experience in manufacturing or procuring products in commercial quantities. We may not be able to manufacture enough product to conduct clinical trials or for later commercialization at an acceptable cost or at all.

Even if we receive regulatory approval of our rare disease product candidates, we may have to rely on third parties to manufacture the product and/or complete the manufacturing process, including to purify, finish and fill any product for commercial sale.

We may have to rely on third parties to complete the manufacturing process. Our anticipated future reliance on a limited number of third-party manufacturers exposes us to the following risks:

Each of these risks could delay our clinical trials or the approval, if any, of our product candidates by the FDA or the commercialization of our product candidates and could result in higher costs or deprive us of potential product revenues. As a result, our business, financial condition, and results of operations might be materially harmed.

We face significant competition from other pharmaceutical and biotechnology companies. Our operating results will suffer if we fail to compete effectively.

The pharmaceutical and biotechnology industries are intensely competitive and subject to rapid and significant technological change. Our major competitors include organizations such as major multinational pharmaceutical companies, established biotechnology companies and specialty pharmaceutical and generic drug

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companies. Many competitors have greater financial and other resources than we have, such as larger research and development staff, more extensive marketing, distribution, sales and manufacturing organizations and experience, more extensive clinical trial and regulatory experience, expertise in prosecution of intellectual property rights and access to development resources like personnel generally and technology. As a result, these companies may obtain regulatory approval more rapidly than we are able to and may be more effective in selling and marketing their products.

Our business depends on protecting its intellectual property.

We are aggressively pursuing intellectual property protection for SBC-102 and other product candidates in the form of patent applications that have been and will continue to be filed in the U.S. and in other countries; however, there can be no assurance that patents will issue with the scope for which they are originally filed, if at all.

If we and our licensors do not obtain protection for our respective intellectual property rights and our products are not, or are no longer, protected by regulatory exclusivity protection, such as orphan drug protection, our competitors might be able to take advantage of our research, development, and manufacturing efforts to develop and commercialize competing drugs.

Our success, competitive position, and future revenues, if any, depend in part on our ability and the abilities of our licensors to obtain and maintain patent protection for our products, methods, processes, and other technologies, to preserve our trade secrets, to prevent third parties from infringing on our proprietary rights, and to operate without infringing on the proprietary rights of third parties. To date, we hold various issued patents and exclusive rights to issued patents and own and have licenses to various patent applications, in each case in the U.S. as well as rights under foreign patents and patent applications. We anticipate filing additional patent applications both in the U.S. and in other countries, as appropriate. However, the patent process is subject to numerous risks and uncertainties, and there can be no assurance that we will be successful in protecting our products by obtaining and defending patents. These risks and uncertainties include the following:

In addition, the U.S. Patent and Trademark Office and patent offices in other jurisdictions have often required that patent applications concerning pharmaceutical and/or biotechnology-related inventions be limited or narrowed substantially to cover only the specific innovations exemplified in the patent application, thereby limiting the scope of protection against competitive challenges. Thus, even if we or our licensors are able to obtain patents, the patents might be substantially narrower than anticipated.

Patent and other intellectual property protection is crucial to the success of our business and prospects, and there is a substantial risk that such protections will prove inadequate. Our business and prospects will be harmed if these protections prove insufficient.

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We rely on trade secret protections through confidentiality agreements with our employees and other parties, and the breach of these agreements could adversely affect our business and prospects.

We rely on trade secrets, which we seek to protect, in part, through confidentiality and non-disclosure agreements with our employees, collaborators, suppliers, and other parties. There can be no assurance that these agreements will not be breached, that we would have adequate remedies for any such breach, or that our trade secrets will not otherwise become known to or independently developed by our competitors. We might be involved from time to time in litigation to determine the enforceability, scope, and validity of its proprietary rights. Any such litigation could result in substantial cost and divert management’s attention from operations. If any of these events occurs, or we otherwise lose protection for our trade secrets or proprietary know-how, the value of this information may be greatly reduced.

If we infringe the rights of third parties we might have to forgo selling our future products, pay damages, or defend litigation.

If our product candidates, methods, processes, and other technologies infringe the proprietary rights of other parties, we could incur substantial costs and might have to:

Any of these events could substantially harm our earnings, financial condition, and operations.

Although no infringement, misappropriation, or similar claim or action is pending or threatened, we are aware of a patent issued by the European Patent Office, and subsequently validated in Great Britain, France, Germany, Italy, and Spain, that relates generally to the use of LAL and may therefore be relevant to SBC-102. We believe that such patent does not currently affect our freedom to conduct clinical trials for SBC-102. We also believe that the patent is invalid due to a substantial body of prior art. We have recently taken proactive steps and intends to take further steps to accelerate resolution of this matter, which further steps may include contacting the patentee, bringing additional prior art documents to the attention of the European Patent Office, initiating revocation of the patents in one or more European countries, seeking reassurance of non-infringement or other actions. This patent is currently under opposition at the European Patent Office. If, however, the patent is maintained in unamended form by the European Patent Office, then we may not be able to commercialize SBC-102 in these countries until the patent expires in these countries or sooner if the patent is otherwise invalidated by the relevant national courts before expiration. In addition, the same patentee has been granted a U.S. patent on the use of LAL to treat atherosclerosis, and has two pending patent applications in the U.S., which have currently been rejected by the U.S. patent office, and one each in Canada and Brazil. We believe that we will not be infringing this patent in commercializing SBC-102 for the indications for which we are seeking approval and that the issued U.S. patent is invalid due to the prior art described above. We further believe that the pending applications will not issue due to the substantial body of prior art and, if they were to issue reciting claims that would encompass our contemplated activities, would be invalid due to the prior art. If, however, these patents are granted in a form which covers SBC-102, then our ability to commercialize SBC-102 in these countries before the patent expires in these countries could be adversely affected and/or halted if the patent is not otherwise invalidated by the relevant national courts or otherwise revoked before expiration.

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We are dependent on certain license relationships.

We have licensed technology from the University of Georgia, University of Minnesota and Pangenix that is related to our proprietary expression technology and we might enter into additional licenses in the future. Licenses to which we are a party contain, and we expect that any future licenses will contain, provisions requiring up-front, milestone, and royalty payments to licensors and other conditions to maintaining the license rights. If we fail to comply with our obligations under any such license, the applicable licensor may have the right to terminate the license on relatively short notice and as a result, we would not be able to commercialize drug candidates or technologies that were covered by the applicable license. Also, the milestone and other payments associated with these licenses will make it less profitable for us to develop our drug candidates.

We will be dependent on orphan drug status to commercialize SBC-102, and a competitor may receive orphan drug marketing authorization prior to us for the same indication for which we are seeking approval.

We expect to rely heavily on the orphan drug exclusivity for SBC-102, which grants seven years of marketing exclusivity under the Federal Food, Drug, and Cosmetic Act, and up to 10 years of marketing exclusivity in Europe. While the orphan drug exclusivity for SBC-102 will provide market exclusivity in the U.S., Europe, and other countries, we will not be able to exclude other companies from manufacturing and/or selling drugs using the same active ingredient for the same indication beyond that timeframe. Furthermore, the marketing exclusivity in Europe can be reduced from 10 years to six years if the initial designation criteria have significantly changed since the market authorization of the orphan medicinal product. Even if we have Orphan Drug Designation for a particular drug indication, we cannot guarantee that another company also holding Orphan Drug Designation will not receive marketing authorization for the same indication before we do. If that were to happen, ours applications for that indication may not be approved until the competing company’s period of exclusivity expired. Even if we are the first to obtain marketing authorization for an orphan drug indication, there are circumstances under which a competing product may be approved for the same indication during the seven-year period of marketing exclusivity, such as if the later product is shown to be clinically superior to the orphan product, or if the later product is a different drug than SBC-102. Further, the seven-year marketing exclusivity would not prevent competitors from obtaining approval of the same compound for other indications or the use of other types of drugs for the same use as the orphan drug.

If we are unable to retain and recruit qualified scientists and advisors, or if any of our key executives, key employees or key consultants discontinues his or her employment or consulting relationship with us, it may delay our development efforts or otherwise harm our business.

The loss of any of our key employees or key consultants could impede the achievement of our research and development objectives. Furthermore, recruiting and retaining qualified scientific personnel to perform research and development work in the future is critical to our success. We may be unable to attract and retain personnel on acceptable terms given the competition among biotechnology, biopharmaceutical, and health care companies, universities, and non-profit research institutions for experienced scientists and other disciplines. Although we have not experienced difficulty attracting and retaining qualified employees to date, these circumstances may impact our ability to recruit and retain qualified personnel in the future. Certain of our officers, directors, scientific advisors, and/or consultants or certain of the officers, directors, scientific advisors, and/or consultants hereafter appointed may from time to time serve as officers, directors, scientific advisors, and/or consultants of other biopharmaceutical or biotechnology companies. We may not maintain “key man” insurance policies on any of its officers or employees. We currently have employment contracts with our Chief Executive Officer, Sanj K. Patel, and other executive officers which provide for certain severance benefits. Consistent with our current employment policies, all of our employees are employed “at will” and, therefore, each employee may leave our employment at any time. If we are unable to retain our existing employees, including qualified scientific personnel, and attract additional qualified candidates, our business and results of operations could be adversely affected. We are not aware of any key personnel who intend to retire or otherwise leave us in the near future.

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We derive substantially all of our income from royalties on sales of FUZEON. If FUZEON sales continue to decline, our business will suffer.

Royalties on sales of FUZEON are currently our only significant source of revenue. FUZEON competes with numerous existing therapies for the treatment of HIV. From 2007 through the first quarter of 2011, overall FUZEON sales have declined. We cannot predict if or when sales levels for FUZEON will stabilize.

We are entirely dependent on Roche for the manufacture, sale, marketing, and distribution of FUZEON.

We currently have insufficient internal resources to support and implement the manufacture and worldwide sales, marketing, and distribution of pharmaceuticals. We currently rely solely on Roche for the manufacture, sales, marketing, and distribution of FUZEON pursuant to the Roche License Agreement, and we have no right to control the manufacture, sale, marketing, and distribution of FUZEON pursuant to such agreement. Accordingly, our business and results of operations depend upon Roche continuing to perform its obligations under the Roche License Agreement. Roche may terminate the Roche License Agreement as a whole or with respect to sales in one or more countries at any time with advance notice. If the Roche License Agreement is terminated and we are unable to enter into a new agreement with one or more other marketing partners, we would be required to develop internal manufacturing, sales, marketing, and distribution capabilities in order to continue the business of manufacturing and selling FUZEON. We would likely not be able to establish cost-effective manufacturing, sales, marketing, or distribution capabilities itself and we may not be able to make arrangements with third parties to perform these activities on acceptable terms on a timely basis, if at all. This would have a material adverse effect on our business, financial condition, results of operations, and the market price of our common stock.

The Roche License Agreement gives Roche control over all aspects of the commercialization of FUZEON, including:

If FUZEON does not maintain its market acceptance, our business will be materially harmed.

FUZEON is the only drug candidate for which we have obtained FDA approval. We anticipate that for the foreseeable future, our ability to generate revenues and profits, if any, will depend entirely on the success of FUZEON.

FUZEON is delivered via a twice daily dosing by injection under the skin. All of the other currently approved drug treatments for HIV are delivered orally. Patients and physicians often do not readily accept daily injections of an anti-HIV drug treatment, which limits FUZEON’s acceptance in the market compared to competing drugs. Moreover, because peptides are expensive to manufacture, the price of FUZEON is higher than the prices of other currently approved anti-HIV drug treatments. The wholesale acquisition cost of one year’s supply of FUZEON in the U.S. is approximately $32,200. This price is significantly higher than any of the other approved anti-HIV drugs. Furthermore, the indication approved by the FDA is for the use of FUZEON in combination with other anti-HIV drugs and is more restrictive than the indication for other approved anti-HIV drugs. Physicians may not readily prescribe FUZEON due to cost-benefit considerations when compared with other anti-HIV drug treatments. Higher prices could also limit reimbursement coverage for FUZEON from third-

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party payors, such as private or government insurance programs. If Roche is unable to obtain and maintain reimbursement from a significant number of third-party payors, it would have a material adverse effect on our business, financial condition, and results of operations.

Future events could substantially decrease our royalty payments from Roche for sales of FUZEON.

Pursuant to the Roche License Agreement, if Roche determines in good faith that it must make payments under patent rights or know-how controlled by a third party that are necessary for the sale of FUZEON, it may reduce the royalties paid to us by 50% of the amount paid to such third party.

We cannot prevent the issuance or granting of valid third-party intellectual property rights in any jurisdiction or sales of third-party products that contain T-20. If such intellectual property rights emerge and Roche incurs payment obligations with respect to those rights, or a third party achieves significant market penetration with a product containing T-20, our business will suffer as royalty rates paid by Roche to us for sales of FUZEON could be substantially reduced.

If Roche cannot manufacture sufficient amounts of FUZEON, our financial condition and results of operations will be materially and adversely affected.

Peptide-based therapeutics are made from long chains of molecular building blocks called amino acids. FUZEON is a large peptide composed of a precise 36-amino acid sequence. Large peptides are difficult and expensive to manufacture because the process of creating commercial quantities of a large peptide is lengthy and complicated. The process Roche is currently using to manufacture FUZEON bulk drug substance requires approximately five months to complete and is extremely complicated, requiring over 100 separate, precisely controlled chemical reactions. As a result of this complex manufacturing process, Roche may encounter unexpected difficulties or expense in manufacturing FUZEON in the future.

Roche, or other third-party manufacturers that we may engage in the future, may not perform as agreed or may not remain in the contract manufacturing business for the time required to successfully produce and market FUZEON. The number of third-party manufacturers with the expertise and facilities to manufacture FUZEON bulk drug substance on a commercial scale is extremely limited. In addition, only a limited number of third-party manufacturers have the capability to produce a finished drug product on a commercial scale through a process involving lyophilization.

If Roche, or other third-party manufacturers that we may engage in the future, fails to produce the required commercial quantities of FUZEON bulk drug substance or finished drug product and we fail to promptly find one or more replacement manufacturers or develop its own manufacturing capabilities, our business and results of operations would suffer.

HIV is likely to develop resistance to FUZEON, which could adversely affect demand for FUZEON and harm our competitive position.

HIV is prone to genetic mutations that can produce viral strains resistant to particular drug treatments. HIV has developed resistance, in varying degrees, to each of the currently approved anti-HIV drug treatments, including FUZEON. As a result, combination therapy, or the prescribed use of three or more anti-HIV drugs, has become the preferred method of treatment for HIV-infected patients because in combination these drugs may prove effective against strains of HIV that have become resistant to one or more of the drugs in the combination. HIV has demonstrated the ability to develop resistance to FUZEON, as it has with respect to all other currently marketed anti-HIV drugs. If HIV, in a wide patient population, develops resistance to FUZEON when used in combination therapy, it would adversely affect demand for FUZEON and harm our competitive position.

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If Roche does not maintain good manufacturing practices, it could negatively impact our business.

The FDA and other regulatory authorities require that FUZEON be manufactured according to the FDA’s current good manufacturing practice (“cGMP”) regulations. The failure by Roche or any other third-party manufacturers to maintain compliance with cGMP and/or maintain the manufacturing processes needed to meet the demand for FUZEON could lead the FDA to withdraw approvals previously granted or could lead to other regulatory action that could harm our business.

If the sale of FUZEON infringes the proprietary rights of third parties, we may need to obtain licenses, pay damages or defend litigation.

If the sale of FUZEON infringes the proprietary rights of third parties, we could incur substantial costs and may have to:

Any of these events could substantially harm our earnings, financial condition, and operations.

On November 20, 2007, Novartis Vaccines and Diagnostics, Inc. (“Novartis”) filed a lawsuit against us, Roche and certain of its affiliated entities, alleging infringement of Novartis’ U.S. Patent No. 7,285,271 B1, entitled “Antigenic Composition Comprising an HIV gag or env Polypeptide” (the “‘271 Patent”), related to the manufacture, sale and offer for sale of FUZEON. On September 23, 2010, Trimeris, Inc. (“Trimeris”) and Roche entered into a settlement agreement (the “Settlement Agreement”) with Novartis settling the lawsuit and the lawsuit was dismissed with prejudice from the Eastern District of North Carolina on September 28, 2010. Under the terms of the Settlement Agreement, we, in collaboration with Roche, have the right to continue to sell FUZEON under a license to Novartis’ ‘271 Patent in exchange for the payment of royalties to Novartis on net sales of FUZEON. Roche and we will share responsibility for payment of these royalties equally.

Uncertainties relating to third-party reimbursement and health care reform measures could limit payments or reimbursements for FUZEON and materially adversely affect our results of operations.

In the U.S. and elsewhere, sales of prescription drugs depend in part on the consumer’s ability to obtain reimbursement for the cost of the drugs from third-party payors, such as private and government insurance programs. Third-party payors are increasingly challenging the prices charged for medical products and services in an effort to promote cost containment measures and alternative health care delivery systems. Because of the high cost of the treatment of HIV, many state legislatures are also reassessing reimbursement policies for this therapy. If third-party payor reimbursements for FUZEON are limited or reduced, our results of operations will be materially and adversely affected. In addition, emphasis in the U.S. on the reduction of the overall costs of health care through managed care has increased and will continue to increase the pressure to reduce the prices of pharmaceutical products.

The wholesale acquisition cost of a one-year supply of FUZEON in the U.S. is approximately $32,200. A high drug price could also negatively affect patients’ ability to receive reimbursement coverage for FUZEON from third-party payors, such as private or government insurance programs. If Roche is unable to obtain and maintain reimbursement from a significant number of third-party payors, it would have a material adverse effect on our business, financial condition and results of operations.

Roche has made significant progress in achieving reimbursement from the various payors in the U.S. Currently, FUZEON is covered by Medicaid in all 50 states. In addition, all of the 50 state AIDS Drug

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Assistance Programs and a majority of private insurers provide some amount of access to FUZEON. However, there are reimbursement challenges remaining. Some of the payors require patients to meet minimum medical requirements, such as CD4 cell levels, to receive reimbursement. Other payors limit the number of patients to which they will provide reimbursement for FUZEON, and other payors may require co-payments by the patient in order to receive reimbursement for FUZEON that are significantly higher than those required for other anti-HIV drugs.

Several major pharmaceutical companies have offered to sell their anti-HIV drugs at or below cost to certain countries in Africa and Least Developed Countries (as defined by the United Nations), which could adversely affect the reimbursement climate of, and the prices that may be charged for, HIV medications in the U.S. and the rest of the world. Third-party payors could exert pressure for price reductions in the U.S. and the rest of the world based on these lower costs offered in Africa and Least Developed Countries. This price pressure could limit the price that Roche would be able to charge for FUZEON, thereby adversely affecting our results of operations.

The failure to integrate successfully the businesses of Trimeris and Synageva BioPharma Corp. (“Private Synageva”) could adversely affect our future results.

The success of the merger of Trimeris and Private Synageva (the “Merger”), which was completed on November 2, 2011 pursuant to the Agreement and Plan of Merger and Reorganization, dated June 13, 2011, between Trimeris, Private Synageva and Tesla Merger Sub, Inc., a wholly-owned subsidiary of Trimeris, will depend, in large part, on our ability to realize the anticipated benefits from combining the businesses of Trimeris and Private Synageva.

The failure to integrate successfully and to manage successfully the challenges presented by the integration process may result in our failure to achieve some or all of the anticipated benefits of the Merger.

Potential difficulties that may be encountered in the integration process include the following:

Our success will depend in part on relationships with third parties. Any adverse changes in these relationships could adversely affect our business, financial condition, or results of operations.

Our success will be dependent on our ability to maintain and renew the business relationships of both Trimeris and Private Synageva and to establish new business relationships. There can be no assurance that our management will be able to maintain such business relationships, or enter into or maintain new business contracts and other business relationships, on acceptable terms, if at all. The failure to maintain important business relationships could have a material adverse effect on our business, financial condition, or results of operations.

Our charter documents and indemnification agreements require us to indemnify its directors and officers to the fullest extent permitted by law, which may obligate us to make substantial payments and to incur significant insurance-related expenses.

Our charter documents require that we indemnify our directors and officers to the fullest extent permitted by law. This could require us, with some legally prescribed exceptions, to indemnify its directors and officers

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against any and all expenses, judgments, penalties, fines, and amounts reasonably paid in defense or settlement of an action, suit, or proceeding brought against any of them by reason of the fact that he or she is or was our director or officer. In addition, expenses incurred by a director or officer in defending any such action, suit, or proceeding must be paid by us in advance of the final disposition of that action, suit or proceeding if we receive an undertaking by the director or officer to repay us if it is ultimately determined that he or she is not entitled to be indemnified. We have also entered into indemnification agreements with each of our directors and officers. In furtherance of these indemnification obligations, we maintain directors’ and officers’ insurance in the amount of $25,000,000. For future renewals, if we are able to retain coverage, we may be required to pay a higher premium for its directors’ and officers’ insurance than in the past and/or the amount of its insurance coverage may be decreased.

Risks Relating Our Financial Position and Capital Requirements

We may be unable to raise the substantial additional capital that we will need to further develop and commercialize our products.

As is typical of biotechnology companies at our stage of development, our operations consume substantial amounts of cash and we will need substantial additional funds to further develop and commercialize its products. Based on our current operating plans, our current resources are expected to be sufficient to fund our planned operations into the first half of 2013, at which point we expect to be conducting double-blind, placebo-controlled trials for SBC-102.

While we will need to seek additional funding, we may not be able to obtain financing on acceptable terms, or at all. In addition, the terms of our financings may be dilutive to, or otherwise adversely affect, holders of our common stock. We may also seek additional funds through arrangements with collaborators or other third parties. These arrangements would generally require us to relinquish rights to some of our technologies, product candidates or products, and we may not be able to enter into such agreements, on acceptable terms, if at all. If we are unable to obtain additional funding on a timely basis, we may be required to curtail or terminate some or all of our development programs, including some or all of our product candidates.

We have incurred significant losses since our inception and anticipate that we will continue to incur losses for the foreseeable future. We are a clinical-stage company with limited historical revenues, which makes it difficult to assess our future viability.

We are a clinical-stage biopharmaceutical company with a limited operating history. Biopharmaceutical product development is a highly speculative undertaking and involves a substantial degree of risk. We continue to incur significant research and development and other expenses related to our ongoing operations. If any of our product candidates fail in clinical trials or do not gain regulatory approval, or if any of our product candidates, if approved, fail to achieve market acceptance, we may never become profitable. Even if we achieve profitability in the future, we may not be able to sustain profitability in subsequent periods. Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital.

Our ability to utilize Trimeris’ net operating loss and tax credit carryforwards in the future is subject to substantial limitations and may be further limited as a result of the Merger.

Federal and state income tax laws impose restrictions on the utilization of net operating loss (“NOL”) and tax credit carryforwards in the event that an “ownership change” occurs for tax purposes, as defined by Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”). In general, an ownership change occurs when shareholders owning 5% or more of a “loss corporation” (a corporation entitled to use NOL or other loss carryforwards) have increased their aggregate ownership of stock in such corporation by more than 50 percentage points during any three-year period. If an “ownership change” occurs, Section 382 of the Code imposes an annual limitation on the amount of post-ownership change taxable income that may be offset with

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pre-ownership change NOLs of the loss corporation experiencing the ownership change. The annual limitation is calculated by multiplying the loss corporation’s value immediately before the ownership change by the greater of the long-term tax-exempt rate determined by the IRS in the month of the ownership change or the two preceding months. This annual limitation may be adjusted to reflect any unused annual limitation for prior years and certain recognized built-in gains and losses for the year. Section 383 of the Code also imposes a limitation on the amount of tax liability in any post-ownership change year that can be reduced by the loss corporation’s pre-ownership change tax credit carryforwards.

In 2008, an “ownership change” occurred with respect to Trimeris, and the Merger resulted in another “ownership change” of Trimeris. Accordingly, our ability to utilize Trimeris’ NOL and tax credit carryforwards may be substantially limited. These limitations could, in turn, result in increased future tax payments for us, which could have a material adverse effect on our business, financial condition.

Our management is required to devote substantial time to comply with public company regulations.

As a public company, we will incur significant legal, accounting and other expenses. The Sarbanes-Oxley Act of 2002 (“Sarbanes-Oxley”) as well as rules implemented by the SEC and the NASDAQ Global Market, impose various requirements on public companies, including those related to corporate governance practices. Our management and other personnel will need to devote a substantial amount of time to these requirements. Certain members of our management do not have experience in addressing these requirements.

Sarbanes-Oxley requires, among other things, that we maintain effective internal controls for financial reporting and disclosure controls and procedures. In particular, we must perform system and process evaluation and testing of our internal controls over financial reporting to allow management and our independent registered public accounting firm to report on the effectiveness of our internal controls over financial reporting, as required by Section 404 of Sarbanes-Oxley (“Section 404”). We will incur substantial accounting and related expenses to comply with Section 404. We may need to hire additional accounting and financial staff to satisfy the ongoing requirements of Section 404. Moreover, if we are not able to comply with the requirements of Section 404, or if we or our independent registered public accounting firm identifies deficiencies in our internal controls over financial reporting that are deemed to be material weaknesses, the market price of our stock could decline and we could be subject to sanctions or investigations by the NASDAQ Global Market, the SEC, or other regulatory authorities.

We rely on Roche to timely deliver important financial information relating to sales of FUZEON. In the event that this information is inaccurate, incomplete, or not timely, we will not be able to meet our financial reporting obligations as required by the SEC.

Under the Roche License Agreement, Roche has exclusive control over the flow of information relating to sales of FUZEON that we require to meet our SEC reporting obligations. Roche is required under the Roche License Agreement to provide us with timely and accurate financial data related to sales of FUZEON so that we may meet our reporting requirements under federal securities laws. In the event that Roche fails to provide us with timely and accurate information, we may incur significant liability with respect to the federal securities laws, our disclosure controls and procedures under Sarbanes-Oxley, and possibly be forced to restate our financial statements, any of which could adversely affect the market price of our common stock.

Risks Related to Ownership of Our Common Stock

The market price and trading volume of our common stock may be volatile.

The market price of our common stock could fluctuate significantly for many reasons, including the following factors:

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In addition, factors beyond our control may also have an impact on the price of our stock. For example, to the extent that other large companies within our industry experience declines in their stock price, our stock price may decline as well. In addition, when the market price of a company’s common stock drops significantly, stockholders often institute securities class action lawsuits against the company. A lawsuit against us could cause us to incur substantial costs and could divert the time and attention of our management and other resources.

Future sales of substantial amounts of our common stock, or the perception that such sales could occur, could adversely affect the market price of our common stock.

Future sales of substantial amounts of our common stock, or securities convertible or exchangeable into shares of our common stock, into the public market, including shares of our common stock issued upon exercise of options and warrants, or perceptions that those sales could occur, could adversely affect the market price of our common stock and our ability to raise capital in the future.

Ownership of our common stock is highly concentrated, and it may prevent you and other stockholders from influencing significant corporate decisions and may result in conflicts of interest that could cause our stock price to decline.

Our executive officers and directors, together with their respective affiliates, beneficially own or control approximately 48% of our issued and outstanding common stock. Accordingly, these executive officers, directors and their affiliates, acting individually or as a group, have substantial influence over the outcome of a corporate action requiring stockholder approval, including the election of directors, any merger, consolidation or sale of all or substantially all of our assets or any other significant corporate transaction. These stockholders may also exert influence in delaying or preventing a change in control, even if such change in control would benefit our other stockholders. In addition, the significant concentration of stock ownership may adversely affect the market value of the our common stock due to investors’ perception that conflicts of interest may exist or arise.

Anti-takeover provisions in our charter and bylaws may prevent or frustrate attempts by stockholders to change the board of directors or current management and could make a third-party acquisition of us difficult.

Our certificate of incorporation and bylaws, each as amended, contain provisions that may discourage, delay or prevent a merger, acquisition or other change in control that stockholders may consider favorable, including transactions in which stockholders might otherwise receive a premium for their shares. These provisions could limit the price that investors might be willing to pay in the future for shares of our common stock.

We have never declared or paid dividends on our common stock and do not anticipate paying dividends in the foreseeable future.

Our business requires significant funding, and we do not anticipate paying any cash dividends on our common stock in the foreseeable future.

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We have broad discretion in how we use the net proceeds of this offering, and we may not use these proceeds effectively or in ways with which you agree.

Our management will have broad discretion as to the application of the net proceeds of this offering and could use them for purposes other than those contemplated at the time of this offering. Our stockholders may not agree with the manner in which our management chooses to allocate and spend the net proceeds. Moreover, our management may use the net proceeds for corporate purposes that may not increase the market price of our common stock.

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NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the other documents we have filed with the SEC that are incorporated herein by reference contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21C of the Securities Exchange Act of 1934 as amended, (the “Exchange Act”). Such forward-looking statements involve risks and uncertainties, as well as assumptions that, if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such statements. All statements other than statements of historical fact are statements that could be deemed forward-looking statements, including any projections of financing needs, revenue, expenses, earnings or losses from operations, or other financial items; any statements of the plans, strategies and objectives of management for future operations; any statements concerning product research, development and commercialization plans and timelines; any statements regarding safety and efficacy of product candidates; any statements of expectation or belief; and any statements of assumptions underlying any of the foregoing. In addition, forward-looking statements may contain the words “believe,” “anticipate,” “expect,” “estimate,” “intend,” “plan,” “project,” “will be,” “will continue,” “will result,” “seek,” “could,” “may,” “might,” or any variations of such words or other words with similar meanings.

Given these uncertainties, you should not place undue reliance on these forward-looking statements. You should read this prospectus supplement, the accompanying prospectus and the documents that we reference in this prospectus supplement or the accompanying prospectus with the understanding that our actual future results may be materially different from what we expect. Except as required by law, we do not undertake any obligation to update or revise any forward-looking statements contained in this prospectus supplement or the accompanying prospectus, whether as a result of new information, future events or otherwise.

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USE OF PROCEEDS

We estimate that the net proceeds from the sale of the              shares of common stock in this offering and after deducting underwriting discounts and commissions and estimated offering expenses payable by us, will be approximately $55.7 million, based on an assumed public offering price of $25.65 per share (the last reported sale price of our common stock on the Nasdaq Global Market on January 3, 2012) (or approximately $64.2 million if the underwriters exercise their option to purchase an additional shares from us in full). If we were to price the offering at a price 5% above or below such assumed offering price, expected net proceeds would increase or decrease by approximately $2.8 million (approximately $3.2 million if the underwriters’ option to purchase additional shares of our common stock is exercised in full).

We currently intend to use the net proceeds from the sale of the common stock in this offering for general corporate purposes, which may include working capital, capital expenditures, research and development expenditures, pre-clinical and clinical trial expenditures, commercial expenditures, acquisitions of new technologies or businesses that are complementary to our current technologies or business focus and investments. As of the date of this prospectus supplement, we cannot specify with certainty all of the particular uses of the proceeds from this offering. As a result, our management will retain broad discretion in the allocation and use of the net proceeds from this offering. Pending these uses, we intend to invest the net proceeds from this offering in short-term, interest-bearing investment grade securities, certificates of deposit or direct or guaranteed obligations of the U.S. government.

DILUTION

If you invest in our common stock, you will experience dilution to the extent of the difference between the price per share you pay in this offering and the net tangible book value per share of our common stock immediately after this offering. Net tangible book value per share is equal to our total tangible assets minus total liabilities, divided by the number of shares of common stock outstanding as of September 30, 2011.

On a pro forma basis, after giving effect to the consummation of the Merger with Trimeris, including the 5-for-1 reverse stock split of the common stock of Trimieris immediately prior to the Merger, our net tangible book value as of September 30, 2011 would have been approximately $61.2 million, or $3.42 per share of common stock. After giving effect to the assumed sale of 2,339,181 shares of common stock by us at an assumed public offering price of $25.65 per share (the last reported sale price of our common stock on the Nasdaq Global Market on January 3, 2012), and after deducting our estimated underwriting discounts and commissions and estimated offering expenses payable by us, our pro forma, as adjusted, net tangible book value would have been approximately $117.0 million or approximately $5.77 per share of common stock, as of September 30, 2011. This represents an immediate increase in net tangible book value of approximately $2.35 per share to existing stockholders and an immediate dilution of approximately $19.88 per share to investors participating in this offering. The following table illustrates this calculation on a per share basis:

Each 5% increase (decrease) in the assumed offering price would increase (decrease) our pro forma as adjusted net tangible book value by $2.8 million, the pro forma as adjusted net tangible book value per share after this offering by $0.14 per share and the dilution in pro forma as adjusted net tangible book value to investors in this offering by $0.14 per share, assuming the number of shares offered by us, as set forth on the cover page of this prospectus supplement, remains the same and after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us.

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If the underwriters’ over-allotment option is exercised in full, the pro forma as adjusted net tangible book value per share after giving effect to this offering would be $6.09 per share, which amount represents an immediate increase in pro forma net tangible book value of $2.67 per share of our common stock to existing stockholders and an immediate dilution in net tangible book value of $19.56 per share of our common stock to new investors purchasing shares of common stock in this offering.

The number of shares of common stock shown above to be outstanding after this offering is based on 17,920,000 shares outstanding as of September 30, 2011, on a pro forma basis, and excludes:

The exercise of outstanding options having an exercise price less than the offering price will increase dilution to new investors.

DESCRIPTION OF SECURITIES WE ARE OFFERING

In this offering, we are offering a maximum of $60,000,000 of shares of common stock.

Common Stock

The material terms and provisions of our common stock are described under the caption “Description of Common Stock” starting on page 23 of the accompanying prospectus.

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UNDERWRITING

Under the terms and subject to the conditions in an underwriting agreement dated the date of this prospectus supplement, the underwriters named below, for whom Morgan Stanley & Co. LLC and J.P. Morgan Securities LLC are acting as representatives, have severally agreed to purchase, and we have agreed to sell to them, severally, the number of shares of common stock indicated below:

The underwriters and the representatives are collectively referred to as the “underwriters” and the “representatives,” respectively. The underwriters are offering the shares of common stock subject to their acceptance of the shares from us and subject to prior sale. The underwriting agreement provides that the obligations of the several underwriters to pay for and accept delivery of the shares of common stock offered by this prospectus supplement are subject to the approval of certain legal matters by their counsel and to certain other conditions. The underwriters are obligated to take and pay for all of the shares of common stock offered by this prospectus supplement if any such shares are taken. However, the underwriters are not required to take or pay for the shares covered by the underwriters’ over-allotment option described below.

The underwriters initially propose to offer part of the shares of common stock directly to the public at the offering price listed on the cover page of this prospectus supplement and part to certain dealers. After the initial offering of the shares of common stock, the offering price and other selling terms may from time to time be varied by the representatives.

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase up to              additional shares of common stock at the public offering price listed on the cover page of this prospectus supplement, less underwriting discounts and commissions. The underwriters may exercise this option solely for the purpose of covering over-allotments, if any, made in connection with the offering of the shares of common stock offered by this prospectus supplement. To the extent the option is exercised, each underwriter will become obligated, subject to certain conditions, to purchase about the same percentage of the additional shares of common stock as the number listed next to the underwriter’s name in the preceding table bears to the total number of shares of common stock listed next to the names of all underwriters in the preceding table.

Entities affiliated with one of our directors, Felix Baker, have indicated an interest in purchasing up to an aggregate of 36.2% of the common stock offered in this offering at the price offered to the public. Because these indications are not binding agreements or commitments to purchase, any or all of these entities may elect not to purchase any shares in this offering, or the underwriters may elect not to sell any shares in this offering to any or all of these entities. In the event that these entities confirm their interest, we will request that the underwriters sell to them such percentage of the common stock offered in this offering.

The following table shows the per share and total public offering price, underwriting discounts and commissions, and proceeds before expenses to us. These amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase up to an additional              shares of common stock.

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The estimated offering expenses payable by us, exclusive of the underwriting discounts and commissions, are approximately $650,000. The underwriters have agreed to reimburse us for certain expenses incurred in connection with this offering.

Our common stock has been approved for quotation on the NASDAQ Global Market under the trading symbol “GEVA.” Our registrar and transfer agent for all shares of common stock is Computershare Trust Company, N.A.

We have agreed, for the period ending 90 days after the date of this prospectus supplement (the “restricted period”), not to without the prior written consent of Morgan Stanley & Co. LLC and J.P. Morgan Securities LLC on behalf of the underwriters:

whether any such transaction described above is to be settled by delivery of common stock or such other securities, in cash or otherwise; provided that the foregoing prohibitions shall not apply to:

All of our directors and officers have agreed, subject to certain exceptions, for the restricted period, not to, without the prior written consent of Morgan Stanley & Co. LLC and J.P. Morgan Securities LLC on behalf of the underwriters:

whether any such transaction described above is to be settled by delivery of common stock or such other securities, in cash or otherwise.

The restricted period will be extended if:

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in which case the restrictions on us, our directors and officers and certain holders of our outstanding stock and stock options described in the preceding paragraphs will continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event.

Although funds managed by Baker Bros. Advisors LLC New Leaf Ventures II, L.P. and the Tisch Investors, who collectively beneficially own approximately 59.8% of our common stock (of which approximately 93.2% was issued to them in the merger described below), have not entered into the lock-up described above, they are subject to lock-up arrangements entered into in connection with the Merger. In connection with the Merger, such entities and each other former stockholder of Private Synageva agreed not to sell, transfer, pledge, encumber, or otherwise dispose of such holder’s shares of our common stock received in the Merger for a staggered 180-day period with certain exception, including transfers (i) with respect to individual stockholders, to a member of such individual’s immediate family, trust for the benefit of such holder or such holder’s heirs, (ii) with respect to partnership or limited liability company stockholders, to one or more partners, members or affiliated corporations or business entities under common control, (iii) with respect to trust stockholders, to a beneficiary, and (iv) with respect to all stockholders, to another holder of our capital stock who received shares of our common stock in the Merger. These transfer and sale restrictions will lapse with respect to such shares such that 25% are free from the transfer and sale restrictions on and after each of the 90th, 120th, 150th and 180th day following the completion of the Merger. These transfer and sale restrictions may also be waived by our board of directors (including at least one director who was a director of Trimeris and not Private Synageva prior to the completion of the Merger) if such waiver applies to all holders on a pro rata basis. In connection with this offering, we will agree with the underwriters that we will not waive any such transfer restrictions without the approval of the representatives of the underwriters during the 90-day period following the date of this prospectus supplement, subject to certain extensions that are applicable to the lock-up agreements described above.

In order to facilitate the offering of the common stock, the underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the common stock. Specifically, the underwriters may sell more shares than they are obligated to purchase under the underwriting agreement, creating a short position. A short sale is covered if the short position is no greater than the number of shares available for purchase by the underwriters under the over-allotment option. The underwriters can close out a covered short sale by exercising the over-allotment option or purchasing shares in the open market. In determining the source of shares to close out a covered short sale, the underwriters will consider, among other things, the open market price of shares compared to the price available under the over-allotment option. The underwriters may also sell shares in excess of the over-allotment option, creating a naked short position. The underwriters must close out any naked short position by purchasing shares of common stock in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common stock in the open market after pricing that could adversely affect investors who purchase in this offering. As an additional means of facilitating this offering, the underwriters may bid for, and purchase, shares of common stock in the open market to stabilize the price of the common stock. These activities may raise or maintain the market price of the common stock above independent market levels or prevent or retard a decline in the market price of the common stock. The underwriters are not required to engage in these activities and may end any of these activities at any time.

We and the underwriters have agreed to indemnify each other against certain liabilities, including liabilities under the Securities Act.

A prospectus supplement in electronic format may be made available on websites maintained by one or more underwriters participating in this offering. The representatives may agree to allocate a number of shares of common stock to underwriters for sale to their online brokerage account holders. Internet distributions will be allocated by the representatives to underwriters that may make Internet distributions on the same basis as other allocations.

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Other Relationships

The underwriters and their affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The underwriters and certain of their affiliates have, from time to time, performed, and may in the future perform, various financial advisory and investment banking services for us, for which they received or will receive customary fees and expenses.

In the ordinary course of their various business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments issued by us. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Selling Restrictions

European Economic Area

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a “Relevant Member State”) an offer to the public of any shares of our common stock may not be made in that Relevant Member State, except that an offer to the public in that Relevant Member State of any shares of our common stock may be made at any time under the following exemptions under the Prospectus Directive, if they have been implemented in that Relevant Member State:

For the purposes of this provision, the expression an “offer to the public” in relation to any shares of our common stock in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares of our common stock to be offered so as to enable an investor to decide to purchase any shares of our common stock, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State, the expression “Prospectus Directive” means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member State), and includes any relevant implementing measure in the Relevant Member State, and the expression “2010 PD Amending Directive” means Directive 2010/73/EU.

United Kingdom

Each underwriter has represented and agreed that:

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LEGAL MATTERS

The validity of the issuance of the securities offered hereby will be passed upon for us by Ropes & Gray LLP, Boston, Massachusetts. Willkie Farr & Gallagher LLP, New York, New York, is acting as counsel for the underwriters in connection with certain legal matters related to this offering.

EXPERTS

The financial statements of Trimeris as of December 31, 2010 and 2009, and for each of the two years in the period ended December 31, 2010, incorporated by reference into this prospectus supplement have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon appearing elsewhere herein, and are included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

The financial statements of Trimeris for the year ended December 31, 2008 (which include disclosures relating to Trimeris’ adoption of the provisions of FASB ASC Topic 808, Collaborative Arrangements, as of January 1, 2009, as described in note 1 and in paragraph 8 of note 7 to the December 31, 2010 financial statements) incorporated by reference into this prospectus supplement have been included herein in reliance upon the report of KPMG LLP, independent registered public accounting firm, appearing elsewhere herein, and upon the authority of said firm as experts in accounting and auditing.

The financial statements of Private Synageva as of December 31, 2010 and 2009 and for each of the two years in the period ended December 31, 2010, incorporated by reference into this prospectus supplement have been so included in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

We have filed a registration statement on Form S-3 with the SEC for the securities we are offering by this prospectus supplement and the accompanying prospectus. This prospectus supplement and the accompanying prospectus do not include all of the information contained in the registration statement. You should refer to the registration statement and its exhibits for additional information.

We are required to file annual and quarterly reports, current reports, proxy statements, and other information with the SEC. We make these documents publicly available, free of charge, on our website at www.synageva.com as soon as reasonably practicable after filing such documents with the SEC. You can read our SEC filings, including the registration statement, on the SEC’s website at http://www.sec.gov. You also may read and copy any document we file with the SEC at its public reference facility at:

Public Reference Room

100 F Street N.E.

Washington, DC 20549.

Please call the SEC at 1-800-732-0330 for further information on the operation of the public reference facilities.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” into this prospectus supplement and accompanying prospectus the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus supplement and accompanying prospectus, and information in documents that we file later with the

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SEC will automatically update and supersede information in this prospectus supplement and accompanying prospectus. We incorporate by reference into this prospectus supplement and accompanying prospectus the documents listed below and any future filings made by us with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act until the termination of this offering. We hereby incorporate by reference the following documents:

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address:

Synageva BioPharma Corp.

128 Spring Street, Suite 520

Lexington, Massachusetts 02421

(781) 357-9900

Copies of these filings are also available, without charge, through the “Investor Relations” section of our website (www.synageva.com) as soon as reasonably practicable after they are filed electronically with the SEC. The information contained on our website is not part of this prospectus supplement and accompanying prospectus.

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PROSPECTUS

$100,000,000

SYNAGEVA BIOPHARMA CORP.

Common Stock

Preferred Stock

Warrants

Debt Securities

We may offer and sell from time to time, in one or more series or issuances and on terms that we will determine at the time of the offering, any combination of the securities described in this prospectus, up to an aggregate amount of $100,000,000.

We will provide specific terms of any offering in a supplement to this prospectus. Any prospectus supplement may also add, update, or change information contained in this prospectus. You should carefully read this prospectus and the applicable prospectus supplement as well as the documents incorporated or deemed to be incorporated by reference in this prospectus before you purchase any of the securities offered hereby.

These securities may be offered and sold in the same offering or in separate offerings; to or through underwriters, dealers, and agents; or directly to purchasers. The names of any underwriters, dealers, or agents involved in the sale of our securities and their compensation will be described in the applicable prospectus supplement.

General Information

Our common stock is traded on the Nasdaq Global Market under the symbol “GEVA.” On December 16, 2011, the closing price of our common stock was $22.07.

Investing in our securities involves risks. See “Risk Factors” on page 4.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is December 20, 2011

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You should rely only on the information contained in, or incorporated by reference into, this prospectus. We have not authorized anyone to give you information different from that contained in this prospectus. We are not making an offer to sell these securities in any jurisdiction where the offer is not permitted. The information contained in this prospectus is accurate only as of the date on the front cover of this prospectus, regardless of when this prospectus is delivered or when any sale of our securities occurs. Our business, financial condition, results of operations and prospects may have changed since that date.

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ABOUT THIS PROSPECTUS

This prospectus is a part of a registration statement that we filed with the Securities and Exchange Commission (the “SEC”) using a “shelf” registration process. Under this shelf registration process, we may offer to sell any combination of the securities described in this prospectus in one or more offerings up to a total dollar amount of $100,000,000. Each time we sell securities under this shelf registration, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and the applicable prospectus supplement, including all documents incorporated herein by reference, together with additional information described under “Where You Can Find More Information” below.

This prospectus does not include all of the information that is in the registration statement. We omitted certain parts of the registration statement from this prospectus as permitted by the SEC. We refer you to the registration statement and its exhibits for additional information about us and the securities that may be sold under this prospectus.

We have not authorized any dealer, agent or other person to give any information or to make any representation other than those contained or incorporated by reference in this prospectus and any accompanying prospectus supplement. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus or an accompanying prospectus supplement. This prospectus and the accompanying prospectus supplement, if any, do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the registered securities to which they relate, nor do this prospectus and the accompanying prospectus supplement constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus and the accompanying prospectus supplement, if any, is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus and any accompanying prospectus supplement is delivered or securities are sold on a later date.

Unless the context otherwise requires, “Synageva,” the “Company,” “we,” “us,” “our” and similar names refer to Synageva BioPharma Corp. and its subsidiaries unless we state otherwise or the context otherwise requires.

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OUR COMPANY

We are a clinical stage biopharmaceutical company focused on the discovery, development and commercialization of therapeutic products for patients with life-threatening rare diseases and unmet medical need. We have several protein therapeutics in our pipeline, including two enzyme replacement therapies for lysosomal storage disorders and two additional programs for other life-threatening genetic conditions for which there are currently no approved treatments. We have assembled a team with a proven record of bringing orphan therapies to patients.

Our lead program, SBC-102, is a recombinant human lysosomal acid lipase currently under clinical investigation for the treatment of patients with early onset and late onset Lysosomal Acid Lipase (LAL) Deficiency. We believe that this lead program will offer patients and health care practitioners a unique therapy to treat LAL Deficiency, which is a rare, devastating genetic disease that causes significant morbidity and mortality. There are currently no approved treatments for LAL Deficiency. LAL Deficiency is an autosomal recessive lysosomal storage disorder that is caused by a marked decrease or almost complete absence of the LAL enzyme. Although a single disease, LAL Deficiency presents as a clinical continuum with two major phenotypes, early onset LAL Deficiency, frequently referred to as Wolman Disease, and late onset LAL Deficiency, frequently referred to as CESD. The marked reduction of LAL activity in patients with LAL Deficiency leads to the accumulation of lipids in various tissues and cell types. This leads to a range of abnormalities, including enlargement of the liver and spleen, severe liver dysfunction, liver fibrosis, cirrhosis, and ultimately hepatic failure as well as severe malabsorption. Early onset LAL Deficiency is characterized by malabsorption, significant growth failure, and hepatic failure and is usually fatal within the first year of life. In late onset LAL Deficiency, liver involvement and type II hyperlipidemia (high cholesterol and triglycerides) dominate the clinical picture.

SBC-102 has been granted Orphan Drug Designations by the U.S. Food and Drug Administration (“FDA”) and the European Medicines Agency and a Fast Track Designation by the FDA. We have received regulatory clearance in the U.S. and EU to conduct clinical trials in patients with LAL Deficiency. In February 2011, we initiated Phase I/II clinical trials for SBC-102 and in May 2011 began enrolling patients into our Phase I/II studies to evaluate the safety and tolerability of SBC-102 in adult patients with liver dysfunction due to late onset LAL Deficiency and its Phase I/II study in children with growth failure due to early onset LAL Deficiency. SBC-102 is currently being dosed in humans as part of its global clinical development plan. We also plan to initiate a global trial to evaluate the long-term safety and efficacy of SBC-102 in both adults and children with the late onset form of LAL Deficiency. Additionally, we have initiated natural history studies in approximately 20 countries. These studies will be used to investigate and characterize key aspects of the clinical course of LAL Deficiency to inform the evaluation and care of affected patients and to provide a reference for pivotal studies of SBC-102 by identifying appropriate clinical endpoints.

In addition to SBC-102, we have several other protein therapeutic programs targeting rare diseases in various stages of preclinical development. These include enzyme replacement therapies for other lysosomal storage disorders as well as programs for rare, life-threatening conditions beyond the lysosomal storage disorders. These protein therapeutic programs were selected based on scientific rationale, unmet medical need, potential to impact disease course and strategic alignment with our corporate focus. These pipeline programs (SBC-103, SBC-104, SBC-105, and SBC-106) have the potential to offer patients and health care providers effective therapies to treat the rare and devastating diseases targeted by these programs. As with LAL Deficiency, these diseases are characterized by significant morbidity and mortality, currently have high unmet medical need and are conditions in which protein replacement treatment has the potential to have a meaningful impact on disease progression.

In addition to our development activities for rare diseases, we also pioneered the development of a class of antiviral drug treatments called fusion inhibitors. Fusion inhibitors prevent viral fusion, a complex process by which viruses attach to, penetrate, and infect host cells. If a virus cannot enter a host cell, the virus cannot

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replicate. By inhibiting the fusion process of particular types of viruses, like HIV, our first and, to date, only commercial product, FUZEON (whose generic name is enfuvirtide, originally known as T-20), offers a novel mechanism of action to treat and potentially prevent the transmission of HIV.

FUZEON was developed in collaboration with Roche, and is our only currently marketed product. FUZEON, which is administered by subcutaneous injection, has been shown to inhibit HIV viral fusion with host cells by blocking the conformational rearrangement of an HIV protein called gp41. The FDA approved the use of FUZEON in combination with other anti-HIV drugs for the treatment of HIV-1 infection in treatment-experienced patients with evidence of HIV-1 replication despite ongoing anti-HIV therapy. The standard approach to treating HIV infection has been to lower viral loads by using a combination of drugs. There are approximately 32 FDA-approved drugs for the treatment of HIV. Following the receipt of accelerated approval from the FDA, commercial sales of FUZEON began in March 2003. Full approval of FUZEON was granted by the FDA in October 2004. We currently rely solely on Roche for the manufacturing, sales, marketing, and distribution of FUZEON. Roche also filed an application for European marketing approval of FUZEON in September 2002 and was granted marketing approval under exceptional circumstances by the EMA in May 2003. FUZEON is widely available through retail and specialty pharmacies across the U.S. and Canada and in over 55 other countries around the world, including all of the major countries in Europe.

On May 25, 2011, we entered into a license agreement (the “Roche License Agreement”), effective as of January 1, 2011, pursuant to which Roche has an exclusive license to manufacture and sell FUZEON worldwide and we receive royalty payments equal to 16% of worldwide net sales of FUZEON occurring from and after January 1, 2011. The Roche License Agreement superseded and replaced all prior agreements between us and Roche.

We are headquartered in Lexington, Massachusetts, and our principal offices are located at 128 Spring Street, Suite 520, Lexington, Massachusetts 02421 and our telephone number is (781) 357-9900.

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RISK FACTORS

Investing in our securities involves risk. Prior to making a decision about investing in our securities, you should carefully consider the specific risk factors discussed below, together with those under the heading “Risk Factors” in the applicable prospectus supplement and all of the other information contained or incorporated by reference in this prospectus or such prospectus supplement. You should also consider the risks, uncertainties and assumptions discussed under the heading “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2010 filed with the Securities and Exchange Commission (“SEC”) on March 14, 2011, as amended April 28, 2011, as updated by our Quarterly Reports on Form 10-Q and our other filings with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) filed after such Annual Report. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations. If any of these risks were to occur, our business, financial condition or results of operations would likely suffer. In that event, the trading price of our common stock could decline, and you could lose all or part of your investment.

Risks Related to Our Business

The failure to integrate successfully the businesses of Trimeris, Inc. (“Trimeris”) and Synageva BioPharma Corp. (“Private Synageva”) could adversely affect our future results.

The success of the merger of Trimeris and Private Synageva (the “Merger”), which was completed on November 2, 2011 pursuant to the Agreement and Plan of Merger and Reorganization, dated June 13, 2011, between Trimeris, Private Synageva and Tesla Merger Sub, Inc., a wholly-owned subsidiary of Trimeris, will depend, in large part, on our ability to realize the anticipated benefits from combining the businesses of Trimeris and Private Synageva.

The failure to integrate successfully and to manage successfully the challenges presented by the integration process may result in our failure to achieve some or all of the anticipated benefits of the Merger.

Potential difficulties that may be encountered in the integration process include the following:

Our success will depend in part on relationships with third parties, which relationships may be affected by third-party preferences or public attitudes about the Merger. Any adverse changes in these relationships could adversely affect our business, financial condition, or results of operations.

Our success will be dependent on our ability to maintain and renew the business relationships of both Trimeris and Private Synageva and to establish new business relationships. There can be no assurance that our management will be able to maintain such business relationships, or enter into or maintain new business contracts and other business relationships, on acceptable terms, if at all. The failure to maintain important business relationships could have a material adverse effect on our business, financial condition, or results of operations.

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We are largely dependent on the success of our leading product candidate, SBC-102. All of our product candidates, including SBC-102, are still in either preclinical or clinical development. Clinical trials of our product candidates may not be successful. If we are unable to commercialize SBC-102, or experiences significant delays in doing so, our business will be materially harmed.

Our business prospects are largely dependent upon the successful development and commercialization of SBC-102. In February 2011, we initiated Phase I/II clinical trials for SBC-102 and in May 2011 began enrolling patients into its Phase I/II study to evaluate the safety and tolerability of SBC-102 in adult patients with liver dysfunction due to late onset LAL Deficiency and its Phase I/II study in children with growth failure due to early onset LAL Deficiency. Before we can commercialize product candidates related to SBC-102 we need to:

This process involves a high degree of risk and takes many years. Our product development efforts with respect to a product candidate may fail for many reasons, including:

Few research and development projects result in commercial products, and success in preclinical studies or early clinical trials often is not replicated in later studies.

We may decide to abandon development of a product candidate or service at any time, or it may be required to expend considerable resources repeating clinical trials or conducting additional trials, either of which would increase costs of development and delay any revenue from those programs.

In addition, a regulatory authority may deny or delay an approval because it is not satisfied with the structure or conduct of clinical trials or due to its assessment of the data we supply. A regulatory authority, for instance, may not believe that we have adequately addressed negative safety signals. Clinical data is subject to varied interpretations, and regulatory authorities may disagree with our assessments of data. In any such case, a regulatory authority could insist that we provide additional data, which could substantially delay or even prevent commercialization efforts, particularly if we are required to conduct additional pre-approval clinical studies.

Initial results from a clinical trial do not ensure that the trial will be successful and success in early stage clinical trials does not ensure success in later-stage clinical trials.

We will only obtain regulatory approval to commercialize a product candidate if we can demonstrate to the satisfaction of the FDA or the applicable non-U.S. regulatory authority, in well-designed and conducted clinical

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trials, that the product candidate is safe and effective and otherwise meets the appropriate standards required for approval for a particular indication. Clinical trials are lengthy, complex and extremely expensive processes with uncertain results. A failure of one or more clinical trials may occur at any stage of testing.

Success in preclinical testing and early clinical trials does not ensure that later clinical trials will be successful, and initial results from a clinical trial do not necessarily predict final results. We cannot be assured that these trials will ultimately be successful. Our leading product candidate, SBC-102, entered clinical trials recently, and the results of these clinical trials may be disappointing.

Even if early stage clinical trials are successful, we will need to conduct additional clinical trials for product candidates with patients receiving the drug for longer periods before we are able to seek approvals to market and sell these product candidates from the FDA and regulatory authorities outside the U.S. If we are not successful in commercializing any of its lead product candidates, or is significantly delayed in doing so, its business will be materially harmed.

We may find it difficult to enroll patients in our clinical trials.

SBC-102 is being developed to treat LAL Deficiency, which is very rare. Many potential patients for our product candidates have not been diagnosed with the diseases being targeted by our product candidates. We may not be able to initiate or continue clinical trials if we are unable to locate a sufficient number of eligible patients to participate in the clinical trials required by the FDA or other non-U.S. regulatory agencies. We intend to eventually enroll a total of approximately nine adult subjects and eight pediatric subjects, respectively, in these studies. Our inability to enroll a sufficient number of patients for any of our current or future clinical trials would result in significant delays or may require us to abandon one or more clinical trials altogether.

If our preclinical studies do not produce positive results, if our clinical trials are delayed or if serious side effects are identified during drug development, we may experience delays, incur additional costs and ultimately be unable to commercialize our product candidates.

Before obtaining regulatory approval for the sale of our product candidates, we must conduct, at our own expense, extensive preclinical tests to demonstrate the safety of our product candidates in animals, and clinical trials to demonstrate the safety and efficacy of our product candidates in humans. Preclinical and clinical testing is expensive, difficult to design and implement, and can take many years to complete. A failure of one or more preclinical studies or clinical trials can occur at any stage of testing. We may experience numerous unforeseen events during, or as a result of, preclinical testing and the clinical trial process that could delay or prevent our receipt of regulatory approval for, or the commercialization of, our product candidates, including:

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If we are required to conduct additional clinical trials or other testing of our product candidates beyond those that we currently contemplate or are unable to successfully complete our clinical trials or other testing or if the results of these trials or tests are not positive or are only modestly positive or if there are safety concerns, we may:

The product development costs will also increase if we experience delays in testing or approvals. We do not know whether any preclinical tests or clinical trials will be initiated as planned, will need to be restructured or will be completed on schedule, if at all. Significant preclinical or clinical trial delays could also shorten the patent protection period during which we may have the exclusive right to commercialize our product candidates. Such delays could allow our competitors to bring products to market before we do and impair its ability to commercialize our products or product candidates.

We have not obtained marketing approval, including by the FDA, nor commercialized any of our current rare disease product candidates.

We have not obtained marketing approval nor commercialized any of our current rare disease product candidates and do not expect to receive marketing approval or generate revenue from the direct sale of our rare disease products, including SBC-102, for several years, if ever. We are currently conducting a Phase I/II clinical trial for SBC-102 and have not yet completed a clinical trial for any of our rare disease product candidates. Additionally, we are conducting preclinical studies for various other indications. Our limited experience might prevent us from successfully designing or implementing a clinical trial for any of these diseases. We may not be able to demonstrate that our product candidates meet the appropriate standards for regulatory approval. If we are not successful in conducting and managing our preclinical development activities or clinical trials or obtaining regulatory approvals, we might not be able to commercialize our lead rare disease product candidates, or might be significantly delayed in doing so, which will materially harm our business.

If the market opportunities for our product candidates are smaller than we believe they are, our revenues may be adversely affected and our business may suffer.

We focus our research and product development on treatments for rare diseases. Our projections of both the number of people who have these diseases, as well as the subset of people with these diseases who have the potential to benefit from treatment with our product candidates, are based on estimates.

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Currently, most reported estimates of the prevalence of these diseases are based on studies of small subsets of the population of specific geographic areas, which are then extrapolated to estimate the prevalence of the diseases in the broader world population. These estimates may prove to be incorrect and new studies may change the estimated prevalence of these diseases.

The commercial success of any product candidate that we may develop, including SBC-102, will depend upon the degree of market acceptance by physicians, patients, third party payors and others in the medical community.

Any future product that we bring to the market, including SBC-102, may not gain market acceptance by physicians, patients, third party payors and others in the medical community. If these rare disease products do not achieve an adequate level of acceptance, we may not generate significant product revenue and may not become profitable. The degree of market acceptance of these product candidates, if approved for commercial sale, will depend on a number of factors, including:

Even if a potential product displays a favorable efficacy and safety profile in preclinical and clinical trials, market acceptance of the product will not be known until after it is launched. Our efforts to educate the medical community and third party payors on the benefits of the product candidates may require significant resources and may never be successful. Such efforts to educate the marketplace may require more resources than are required by the conventional technologies marketed by our competitors.

If we are unable to obtain adequate reimbursement from governments or third party payors for any future products that we may develop or if we are unable to obtain acceptable prices for those products, our prospects for achieving profitability will suffer.

Our prospects for achieving profitability will depend heavily upon the availability of adequate reimbursement for the use of our approved rare diseases product candidates from governmental and other third party payors, both in the U.S. and in other markets. Reimbursement by a third party payor may depend upon a number of factors, including the third party payor’s determination that use of a product is:

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Obtaining reimbursement approval for a product from each governmental or other third party payor is a time consuming and costly process that could require us to provide supporting scientific, clinical and cost effectiveness data for the use of its products to each payor. We may not be able to provide data sufficient to gain acceptance with respect to reimbursement or might need to conduct post-marketing studies in order to demonstrate the cost-effectiveness of any future products to such payors’ satisfaction. Such studies might require us to commit a significant amount of management time and financial and other resources. Even when a payor determines that a product is eligible for reimbursement, the payor may impose coverage limitations that preclude payment for some uses that are approved by the FDA or non-U.S. regulatory authorities. In addition, there is a risk that full reimbursement may not be available for high priced products. Moreover, eligibility for coverage does not imply that any product will be reimbursed in all cases or at a rate that allows us to make a profit or even cover its costs. Interim payments for new products, if applicable, may also not be sufficient to cover costs and may not be made permanent.

We are exposed to product liability and preclinical and clinical liability risks which could place a substantial financial burden upon us, should we be sued, if we do not have adequate liability insurance or general insurance coverage for such a claim.

Our business exposes us to potential product liability and other liability risks that are inherent in the testing, manufacturing and marketing of pharmaceutical formulations and products. Such claims may be asserted against us. In addition, the use in our clinical trials of pharmaceutical formulations and products that our potential collaborators may develop and the subsequent sale of these formulations or products by us or our potential collaborators may cause us to bear a portion or all of the product liability risks. As is common for companies sponsoring such clinical testing, we carry product liability insurance. The limit of this insurance may in some instances may be insufficient to offset a negative judgment or settlement payment. As a result, a successful liability claim or series of claims brought against us could have a material adverse effect on our business, financial condition and results of operations.

We are subject to regulations regarding manufacturing therapeutic proteins.

We are subject to ongoing periodic unannounced inspections by the FDA and corresponding state agencies to ensure strict compliance with cGMP and other government regulations and corresponding foreign standards. The cGMP requirements govern quality control and documentation policies and procedures. Complying with cGMP and non-U.S. regulatory requirements will require that we expend time, money, and effort in production, recordkeeping, and quality control to assure that the product meets applicable specifications and other requirements. We must also pass a pre-approval inspection prior to FDA approval. Failure to pass a pre-approval inspection might significantly delay FDA approval of our products. If we fail to comply with these requirements, we would be subject to possible regulatory action and might be limited in the jurisdictions in which it is permitted to sell our products. As a result, our business, financial condition, and results of operations might be materially harmed.

We currently manufacture the therapeutic protein products used in SBC-102; however, we have limited experience in manufacturing or procuring products in commercial quantities. We may not be able to manufacture enough product to conduct clinical trials or for later commercialization at an acceptable cost or at all.

Even if we receive regulatory approval of our rare disease product candidates, we may have to rely on third parties to manufacture the product and/or complete the manufacturing process, including to purify, finish and fill any product for commercial sale.

We may have to rely on third parties to complete the manufacturing process. Our anticipated future reliance on a limited number of third-party manufacturers exposes us to the following risks:

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Each of these risks could delay our clinical trials or the approval, if any, of our product candidates by the FDA or the commercialization of our product candidates and could result in higher costs or deprive us of potential product revenues. As a result, our business, financial condition, and results of operations might be materially harmed.

We face significant competition from other pharmaceutical and biotechnology companies. Our operating results will suffer if we fail to compete effectively.

The pharmaceutical and biotechnology industries are intensely competitive and subject to rapid and significant technological change. Our major competitors include organizations such as major multinational pharmaceutical companies, established biotechnology companies and specialty pharmaceutical and generic drug companies. Many competitors have greater financial and other resources than we have, such as larger research and development staff, more extensive marketing, distribution, sales and manufacturing organizations and experience, more extensive clinical trial and regulatory experience, expertise in prosecution of intellectual property rights and access to development resources like personnel generally and technology. As a result, these companies may obtain regulatory approval more rapidly than we are able to and may be more effective in selling and marketing their products.

Our business depends on protecting its intellectual property.

We are aggressively pursuing intellectual property protection for SBC-102 and other product candidates in the form of patent applications that have been and will continue to be filed in the U.S. and in other countries; however, there can be no assurance that patents will issue with the scope for which they are originally filed, if at all.

If we and our licensors do not obtain protection for our respective intellectual property rights and our products are not, or are no longer, protected by regulatory exclusivity protection, such as orphan drug protection, our competitors might be able to take advantage of our research, development, and manufacturing efforts to develop and commercialize competing drugs.

Our success, competitive position, and future revenues, if any, depend in part on our ability and the abilities of our licensors to obtain and maintain patent protection for our products, methods, processes, and other technologies, to preserve our trade secrets, to prevent third parties from infringing on our proprietary rights, and to operate without infringing on the proprietary rights of third parties. To date, we hold various issued patents and exclusive rights to issued patents and own and have licenses to various patent applications, in each case in

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the U.S. as well as rights under foreign patents and patent applications. We anticipate filing additional patent applications both in the U.S. and in other countries, as appropriate. However, the patent process is subject to numerous risks and uncertainties, and there can be no assurance that we will be successful in protecting our products by obtaining and defending patents. These risks and uncertainties include the following:

In addition, the U.S. Patent and Trademark Office and patent offices in other jurisdictions have often required that patent applications concerning pharmaceutical and/or biotechnology-related inventions be limited or narrowed substantially to cover only the specific innovations exemplified in the patent application, thereby limiting the scope of protection against competitive challenges. Thus, even if we or our licensors are able to obtain patents, the patents might be substantially narrower than anticipated.

Patent and other intellectual property protection is crucial to the success of our business and prospects, and there is a substantial risk that such protections will prove inadequate. Our business and prospects will be harmed if these protections prove insufficient.

We rely on trade secret protections through confidentiality agreements with our employees and other parties, and the breach of these agreements could adversely affect our business and prospects.

We rely on trade secrets, which we seek to protect, in part, through confidentiality and non-disclosure agreements with our employees, collaborators, suppliers, and other parties. There can be no assurance that these agreements will not be breached, that we would have adequate remedies for any such breach, or that our trade secrets will not otherwise become known to or independently developed by our competitors. We might be involved from time to time in litigation to determine the enforceability, scope, and validity of its proprietary rights. Any such litigation could result in substantial cost and divert management’s attention from operations. If any of these events occurs, or we otherwise lose protection for our trade secrets or proprietary know-how, the value of this information may be greatly reduced.

If we infringe the rights of third parties we might have to forgo selling our future products, pay damages, or defend litigation.

If our product candidates, methods, processes, and other technologies infringe the proprietary rights of other parties, we could incur substantial costs and might have to:

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Any of these events could substantially harm our earnings, financial condition, and operations.

Although no infringement, misappropriation, or similar claim or action is pending or threatened, we are aware of a patent issued by the European Patent Office, and subsequently validated in Great Britain, France, Germany, Italy, and Spain, that relates generally to the use of LAL and may therefore be relevant to SBC-102. We believe that such patent does not currently affect our freedom to operate. We also believe that the patent is invalid due to a substantial body of prior art. This patent is currently under opposition at the European Patent Office. If, however, the patent is maintained in unamended form by the European Patent Office, then we may not be able to commercialize SBC-102 in these countries until the patent expires in these countries, or sooner if the patent is otherwise invalidated by the relevant national courts before expiration.

We are dependent on certain license relationships.

We have licensed technology from the University of Georgia, University of Minnesota and Pangenix that is related to our proprietary expression technology and we might enter into additional licenses in the future. Licenses to which we are a party contain, and we expect that any future licenses will contain, provisions requiring up-front, milestone, and royalty payments to licensors and other conditions to maintaining the license rights. If we fail to comply with our obligations under any such license, the applicable licensor may have the right to terminate the license on relatively short notice and as a result, we would not be able to commercialize drug candidates or technologies that were covered by the applicable license. Also, the milestone and other payments associated with these licenses will make it less profitable for us to develop our drug candidates.

We will be dependent on orphan drug status to commercialize SBC-102, and a competitor may receive orphan drug marketing authorization prior to us for the same indication for which we are seeking approval.

We expect to rely heavily on the orphan drug exclusivity for SBC-102, which grants seven years of marketing exclusivity under the Federal Food, Drug, and Cosmetic Act, and up to 10 years of marketing exclusivity in Europe. While the orphan drug exclusivity for SBC-102 will provide market exclusivity in the U.S., Europe, and other countries, we will not be able to exclude other companies from manufacturing and/or selling drugs using the same active ingredient for the same indication beyond that timeframe. Furthermore, the marketing exclusivity in Europe can be reduced from 10 years to six years if the initial designation criteria have significantly changed since the market authorization of the orphan medicinal product. Even if we have Orphan Drug Designation for a particular drug indication, we cannot guarantee that another company also holding Orphan Drug Designation will not receive marketing authorization for the same indication before we do. If that were to happen, ours applications for that indication may not be approved until the competing company’s period of exclusivity expired. Even if we are the first to obtain marketing authorization for an orphan drug indication, there are circumstances under which a competing product may be approved for the same indication during the seven-year period of marketing exclusivity, such as if the later product is shown to be clinically superior to the orphan product, or if the later product is a different drug than SBC-102. Further, the seven-year marketing exclusivity would not prevent competitors from obtaining approval of the same compound for other indications or the use of other types of drugs for the same use as the orphan drug.

If we are unable to retain and recruit qualified scientists and advisors, or if any of our key executives, key employees or key consultants discontinues his or her employment or consulting relationship with us, it may delay our development efforts or otherwise harm our business.

The loss of any of our key employees or key consultants could impede the achievement of our research and development objectives. Furthermore, recruiting and retaining qualified scientific personnel to perform research and development work in the future is critical to our success. We may be unable to attract and retain personnel on

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acceptable terms given the competition among biotechnology, biopharmaceutical, and health care companies, universities, and non-profit research institutions for experienced scientists and other disciplines. Although we have not experienced difficulty attracting and retaining qualified employees to date, these circumstances may impact our ability to recruit and retain qualified personnel in the future. Certain of our officers, directors, scientific advisors, and/or consultants or certain of the officers, directors, scientific advisors, and/or consultants hereafter appointed may from time to time serve as officers, directors, scientific advisors, and/or consultants of other biopharmaceutical or biotechnology companies. We may not maintain “key man” insurance policies on any of its officers or employees. We currently have employment contracts with its Chief Executive Officer, Sanj K. Patel, and other executive officers which provide for certain severance benefits. Consistent with our current employment policies, all of our employees are employed “at will” and, therefore, each employee may leave our employment at any time. If we are unable to retain our existing employees, including qualified scientific personnel, and attract additional qualified candidates, our business and results of operations could be adversely affected. We are not aware of any key personnel who intend to retire or otherwise leave us in the near future.

We derive substantially all of our income from royalties on sales of FUZEON. If FUZEON sales continue to decline, our business will suffer.

Royalties on sales of FUZEON are currently our only significant source of revenue. FUZEON competes with numerous existing therapies for the treatment of HIV. From 2007 through the first quarter of 2011, overall FUZEON sales have declined. We cannot predict if or when sales levels for FUZEON will stabilize.

We are entirely dependent on Roche for the manufacture, sale, marketing, and distribution of FUZEON.

We currently have insufficient internal resources to support and implement the manufacture and worldwide sales, marketing, and distribution of pharmaceuticals. We currently rely solely on Roche for the manufacture, sales, marketing, and distribution of FUZEON pursuant to the Amended and Restated Agreement by and between Trimeris and Roche, effective as of January 1, 2011 (the “Roche License Agreement”), and we have no right to control the manufacture, sale, marketing, and distribution of FUZEON pursuant to such agreement. Accordingly, our business and results of operations depend upon Roche continuing to perform its obligations under the Roche License Agreement. Roche may terminate the Roche License Agreement as a whole or with respect to sales in one or more countries at any time with advance notice. If the Roche License Agreement is terminated and we are unable to enter into a new agreement with one or more other marketing partners, we would be required to develop internal manufacturing, sales, marketing, and distribution capabilities in order to continue the business of manufacturing and selling FUZEON. We would likely not be able to establish cost-effective manufacturing, sales, marketing, or distribution capabilities itself and we may not be able to make arrangements with third parties to perform these activities on acceptable terms on a timely basis, if at all. This would have a material adverse effect on our business, financial condition, results of operations, and the market price of our common stock.

The Roche License Agreement gives Roche control over all aspects of the commercialization of FUZEON, including:

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If FUZEON does not maintain its market acceptance, our business will be materially harmed.

FUZEON is the only drug candidate for which we have obtained FDA approval. We anticipate that for the foreseeable future, our ability to generate revenues and profits, if any, will depend entirely on the success of FUZEON.

FUZEON is delivered via a twice daily dosing by injection under the skin. All of the other currently approved drug treatments for HIV are delivered orally. Patients and physicians often do not readily accept daily injections of an anti-HIV drug treatment, which limits FUZEON’s acceptance in the market compared to competing drugs. Moreover, because peptides are expensive to manufacture, the price of FUZEON is higher than the prices of other currently approved anti-HIV drug treatments. The wholesale acquisition cost of one year’s supply of FUZEON in the U.S. is approximately $32,200. This price is significantly higher than any of the other approved anti-HIV drugs. Furthermore, the indication approved by the FDA is for the use of FUZEON in combination with other anti-HIV drugs and is more restrictive than the indication for other approved anti-HIV drugs. Physicians may not readily prescribe FUZEON due to cost-benefit considerations when compared with other anti-HIV drug treatments. Higher prices could also limit reimbursement coverage for FUZEON from third-party payors, such as private or government insurance programs. If Roche is unable to obtain and maintain reimbursement from a significant number of third-party payors, it would have a material adverse effect on our business, financial condition, and results of operations.

Future events could substantially decrease our royalty payments from Roche for sales of FUZEON.

Pursuant to the Roche License Agreement, if Roche determines in good faith that it must make payments under patent rights or know-how controlled by a third party that are necessary for the sale of FUZEON, it may reduce the royalties paid to us by 50% of the amount paid to such third party.

We cannot prevent the issuance or granting of valid third-party intellectual property rights in any jurisdiction or sales of third-party products that contain T-20. If such intellectual property rights emerge and Roche incurs payment obligations with respect to those rights, or a third party achieves significant market penetration with a product containing T-20, our business will suffer as royalty rates paid by Roche to us for sales of FUZEON could be substantially reduced.

If Roche cannot manufacture sufficient amounts of FUZEON, our financial condition and results of operations will be materially and adversely affected.

Peptide-based therapeutics are made from long chains of molecular building blocks called amino acids. FUZEON is a large peptide composed of a precise 36-amino acid sequence. Large peptides are difficult and expensive to manufacture because the process of creating commercial quantities of a large peptide is lengthy and complicated. The process Roche is currently using to manufacture FUZEON bulk drug substance requires approximately five months to complete and is extremely complicated, requiring over 100 separate, precisely controlled chemical reactions. As a result of this complex manufacturing process, Roche may encounter unexpected difficulties or expense in manufacturing FUZEON in the future.

Roche, or other third-party manufacturers that we may engage in the future, may not perform as agreed or may not remain in the contract manufacturing business for the time required to successfully produce and market FUZEON. The number of third-party manufacturers with the expertise and facilities to manufacture FUZEON bulk drug substance on a commercial scale is extremely limited. In addition, only a limited number of third-party manufacturers have the capability to produce a finished drug product on a commercial scale through a process involving lyophilization.

If Roche, or other third-party manufacturers that we may engage in the future, fails to produce the required commercial quantities of FUZEON bulk drug substance or finished drug product and we fail to promptly find one or more replacement manufacturers or develop its own manufacturing capabilities, our business and results of operations would suffer.

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HIV is likely to develop resistance to FUZEON, which could adversely affect demand for FUZEON and harm our competitive position.

HIV is prone to genetic mutations that can produce viral strains resistant to particular drug treatments. HIV has developed resistance, in varying degrees, to each of the currently approved anti-HIV drug treatments, including FUZEON. As a result, combination therapy, or the prescribed use of three or more anti-HIV drugs, has become the preferred method of treatment for HIV-infected patients because in combination these drugs may prove effective against strains of HIV that have become resistant to one or more of the drugs in the combination. HIV has demonstrated the ability to develop resistance to FUZEON, as it has with respect to all other currently marketed anti-HIV drugs. If HIV, in a wide patient population, develops resistance to FUZEON when used in combination therapy, it would adversely affect demand for FUZEON and harm our competitive position.

If Roche does not maintain good manufacturing practices, it could negatively impact our business.

The FDA and other regulatory authorities require that FUZEON be manufactured according to the FDA’s current good manufacturing practice (“cGMP”) regulations. The failure by Roche or any other third-party manufacturers to maintain compliance with cGMP and/or maintain the manufacturing processes needed to meet the demand for FUZEON could lead the FDA to withdraw approvals previously granted or could lead to other regulatory action that could harm our business.

If the sale of FUZEON infringes the proprietary rights of third parties, we may need to obtain licenses, pay damages or defend litigation.

If the sale of FUZEON infringes the proprietary rights of third parties, we could incur substantial costs and may have to:

Any of these events could substantially harm our earnings, financial condition, and operations.

On November 20, 2007, Novartis Vaccines and Diagnostics, Inc. (“Novartis”) filed a lawsuit against us, Roche and certain of its affiliated entities, alleging infringement of Novartis’ U.S. Patent No. 7,285,271 B1, entitled “Antigenic Composition Comprising an HIV gag or env Polypeptide” (the “‘271 Patent”), related to the manufacture, sale and offer for sale of FUZEON. On September 23, 2010, Trimeris and Roche entered into a settlement agreement (the “Settlement Agreement”) with Novartis settling the lawsuit and the lawsuit was dismissed with prejudice from the Eastern District of North Carolina on September 28, 2010. Under the terms of the Settlement Agreement, we, in collaboration with Roche, have the right to continue to sell FUZEON under a license to Novartis’ ‘271 Patent in exchange for the payment of royalties to Novartis on net sales of FUZEON. Roche and we will share responsibility for payment of these royalties equally.

Uncertainties relating to third-party reimbursement and health care reform measures could limit payments or reimbursements for FUZEON and materially adversely affect our results of operations.

In the U.S. and elsewhere, sales of prescription drugs depend in part on the consumer’s ability to obtain reimbursement for the cost of the drugs from third-party payors, such as private and government insurance programs. Third-party payors are increasingly challenging the prices charged for medical products and services in an effort to promote cost containment measures and alternative health care delivery systems. Because of the high cost of the treatment of HIV, many state legislatures are also reassessing reimbursement policies for this therapy. If third-party payor reimbursements for FUZEON are limited or reduced, our results of operations will

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be materially and adversely affected. In addition, emphasis in the U.S. on the reduction of the overall costs of health care through managed care has increased and will continue to increase the pressure to reduce the prices of pharmaceutical products.

The wholesale acquisition cost of a one-year supply of FUZEON in the U.S. is approximately $32,200. A high drug price could also negatively affect patients’ ability to receive reimbursement coverage for FUZEON from third-party payors, such as private or government insurance programs. If Roche is unable to obtain and maintain reimbursement from a significant number of third-party payors, it would have a material adverse effect on our business, financial condition and results of operations.

Roche has made significant progress in achieving reimbursement from the various payors in the U.S. Currently, FUZEON is covered by Medicaid in all 50 states. In addition, all of the 50 state AIDS Drug Assistance Programs and a majority of private insurers provide some amount of access to FUZEON. However, there are reimbursement challenges remaining. Some of the payors require patients to meet minimum medical requirements, such as CD4 cell levels, to receive reimbursement. Other payors limit the number of patients to which they will provide reimbursement for FUZEON, and other payors may require co-payments by the patient in order to receive reimbursement for FUZEON that are significantly higher than those required for other anti-HIV drugs.

Several major pharmaceutical companies have offered to sell their anti-HIV drugs at or below cost to certain countries in Africa and Least Developed Countries (as defined by the United Nations), which could adversely affect the reimbursement climate of, and the prices that may be charged for, HIV medications in the U.S. and the rest of the world. Third-party payors could exert pressure for price reductions in the U.S. and the rest of the world based on these lower costs offered in Africa and Least Developed Countries. This price pressure could limit the price that Roche would be able to charge for FUZEON, thereby adversely affecting our results of operations.

Our charter documents and indemnification agreements require us to indemnify its directors and officers to the fullest extent permitted by law, which may obligate us to make substantial payments and to incur significant insurance-related expenses.

Our charter documents require that we indemnify our directors and officers to the fullest extent permitted by law. This could require us, with some legally prescribed exceptions, to indemnify its directors and officers against any and all expenses, judgments, penalties, fines, and amounts reasonably paid in defense or settlement of an action, suit, or proceeding brought against any of them by reason of the fact that he or she is or was our director or officer. In addition, expenses incurred by a director or officer in defending any such action, suit, or proceeding must be paid by us in advance of the final disposition of that action, suit or proceeding if we receive an undertaking by the director or officer to repay us if it is ultimately determined that he or she is not entitled to be indemnified. We have also entered into indemnification agreements with each of our directors and officers. In furtherance of these indemnification obligations, we maintain directors’ and officers’ insurance in the amount of $25,000,000. For future renewals, if we are able to retain coverage, we may be required to pay a higher premium for its directors’ and officers’ insurance than in the past and/or the amount of its insurance coverage may be decreased.

Risks Relating Our Financial Position and Capital Requirements

We may be unable to raise the substantial additional capital that we will need to further develop and commercialize our products.

As is typical of biotechnology companies at our stage of development, we will need substantial additional funds to further develop and commercialize its products. Based on our current operating plans, our current resources are expected to be sufficient to fund our planned operations into the first quarter of 2013, at which point we expect to be conducting double-blind, placebo-controlled trials for SBC-102.

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While we will need to seek additional funding, we may not be able to obtain financing on acceptable terms, or at all. In addition, the terms of our financings may be dilutive to, or otherwise adversely affect, holders of our common stock. We may also seek additional funds through arrangements with collaborators or other third parties. These arrangements would generally require us to relinquish rights to some of our technologies, product candidates or products, and we may not be able to enter into such agreements, on acceptable terms, if at all. If we are unable to obtain additional funding on a timely basis, we may be required to curtail or terminate some or all of our development programs, including some or all of our product candidates.

Our ability to utilize Trimeris’ net operating loss and tax credit carryforwards in the future is subject to substantial limitations and may be further limited as a result of the Merger.

Federal and state income tax laws impose restrictions on the utilization of net operating loss (“NOL”) and tax credit carryforwards in the event that an “ownership change” occurs for tax purposes, as defined by Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”). In general, an ownership change occurs when shareholders owning 5% or more of a “loss corporation” (a corporation entitled to use NOL or other loss carryforwards) have increased their aggregate ownership of stock in such corporation by more than 50 percentage points during any three-year period. If an “ownership change” occurs, Section 382 of the Code imposes an annual limitation on the amount of post-ownership change taxable income that may be offset with pre-ownership change NOLs of the loss corporation experiencing the ownership change. The annual limitation is calculated by multiplying the loss corporation’s value immediately before the ownership change by the greater of the long-term tax-exempt rate determined by the IRS in the month of the ownership change or the two preceding months. This annual limitation may be adjusted to reflect any unused annual limitation for prior years and certain recognized built-in gains and losses for the year. Section 383 of the Code also imposes a limitation on the amount of tax liability in any post-ownership change year that can be reduced by the loss corporation’s pre-ownership change tax credit carryforwards.

In 2008, an “ownership change” occurred with respect to Trimeris, and the Merger resulted in another “ownership change” of Trimeris. Accordingly, our ability to utilize Trimeris’ NOL and tax credit carryforwards may be substantially limited. These limitations could, in turn, result in increased future tax payments for us, which could have a material adverse effect on our business, financial condition.

Our management is required to devote substantial time to comply with public company regulations.

As a public company, we will incur significant legal, accounting and other expenses. The Sarbanes-Oxley Act of 2002 (“Sarbanes-Oxley”) as well as rules implemented by the SEC and the NASDAQ Global Market, impose various requirements on public companies, including those related to corporate governance practices. Our management and other personnel will need to devote a substantial amount of time to these requirements. Certain members of our management do not have experience in addressing these requirements.

Sarbanes-Oxley requires, among other things, that we maintain effective internal controls for financial reporting and disclosure controls and procedures. In particular, we must perform system and process evaluation and testing of our internal controls over financial reporting to allow management and our independent registered public accounting firm to report on the effectiveness of our internal controls over financial reporting, as required by Section 404 of Sarbanes-Oxley (“Section 404”). We will incur substantial accounting and related expenses to comply Section 404. We may need to hire additional accounting and financial staff to satisfy the ongoing requirements of Section 404. Moreover, if we are not able to comply with the requirements of Section 404, or if we or our independent registered public accounting firm identifies deficiencies in our internal controls over financial reporting that are deemed to be material weaknesses, the market price of our stock could decline and we could be subject to sanctions or investigations by the NASDAQ Global Market, the SEC, or other regulatory authorities.

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We rely on Roche to timely deliver important financial information relating to sales of FUZEON. In the event that this information is inaccurate, incomplete, or not timely, we will not be able to meet our financial reporting obligations as required by the SEC.

Under the Roche License Agreement, Roche has exclusive control over the flow of information relating to sales of FUZEON that we require to meet our SEC reporting obligations. Roche is required under the Roche License Agreement to provide us with timely and accurate financial data related to sales of FUZEON so that we may meet our reporting requirements under federal securities laws. In the event that Roche fails to provide us with timely and accurate information, we may incur significant liability with respect to the federal securities laws, our disclosure controls and procedures under Sarbanes-Oxley, and possibly be forced to restate our financial statements, any of which could adversely affect the market price of our common stock.

Risks Related to Ownership of Our Common Stock

The market price and trading volume of our common stock may be volatile.

The market price of our common stock could fluctuate significantly for many reasons, including the following factors:

In addition, factors beyond our control may also have an impact on the price of our stock. For example, to the extent that other large companies within our industry experience declines in their stock price, our stock price may decline as well. In addition, when the market price of a company’s common stock drops significantly, stockholders often institute securities class action lawsuits against the company. A lawsuit against us could cause us to incur substantial costs and could divert the time and attention of our management and other resources.

Future sales of substantial amounts of our common stock, or the perception that such sales could occur, could adversely affect the market price of our common stock.

Future sales of substantial amounts of our common stock, or securities convertible or exchangeable into shares of our common stock, into the public market, including shares of our common stock issued upon exercise of options and warrants, or perceptions that those sales could occur, could adversely affect the market price of our common stock and our ability to raise capital in the future.

Ownership of our common stock is highly concentrated, and it may prevent you and other stockholders from influencing significant corporate decisions and may result in conflicts of interest that could cause our stock price to decline.

Our executive officers and directors, together with their respective affiliates, beneficially own or control approximately 48% of our issued and outstanding common stock. Accordingly, these executive officers, directors and their affiliates, acting individually or as a group, have substantial influence over the outcome of a corporate

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action requiring stockholder approval, including the election of directors, any merger, consolidation or sale of all or substantially all of our assets or any other significant corporate transaction. These stockholders may also exert influence in delaying or preventing a change in control, even if such change in control would benefit our other stockholders. In addition, the significant concentration of stock ownership may adversely affect the market value of the our common stock due to investors’ perception that conflicts of interest may exist or arise.

Anti-takeover provisions in our charter and bylaws may prevent or frustrate attempts by stockholders to change the board of directors or current management and could make a third-party acquisition of us difficult.

Our certificate of incorporation and bylaws, each as amended, contain provisions that may discourage, delay or prevent a merger, acquisition or other change in control that stockholders may consider favorable, including transactions in which stockholders might otherwise receive a premium for their shares. These provisions could limit the price that investors might be willing to pay in the future for shares of our common stock.

We have never declared or paid dividends on our common stock and do not anticipate paying dividends in the foreseeable future.

Our business requires significant funding, and we do not anticipate paying any cash dividends on our common stock in the foreseeable future.

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NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, any prospectus supplement and the other documents we have filed with the SEC that are incorporated herein by reference contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties, as well as assumptions that, if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward-looking statements. All statements other than statements of historical fact are statements that could be deemed forward-looking statements, including any projections of financing needs, revenue, expenses, earnings or losses from operations, or other financial items; any statements of the plans, strategies and objectives of management for future operations; any statements concerning product research, development and commercialization plans and timelines; any statements regarding safety and efficacy of product candidates; any statements of expectation or belief; and any statements of assumptions underlying any of the foregoing. In addition, forward-looking statements may contain the words “believe,” “anticipate,” “expect,” “estimate,” “intend,” “plan,” “project,” “will be,” “will continue,” “will result,” “seek,” “could,” “may,” “might,” or any variations of such words or other words with similar meanings.

Given these uncertainties, you should not place undue reliance on these forward-looking statements. You should read this prospectus, any supplements to this prospectus and the documents that we reference in this prospectus with the understanding that our actual future results may be materially different from what we expect. Except as required by law, we do not undertake any obligation to update or revise any forward-looking statements contained in this prospectus and any supplements to this prospectus, whether as a result of new information, future events or otherwise.

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USE OF PROCEEDS

Except as otherwise provided in the applicable prospectus supplement, we intend to use the net proceeds from the sale of the securities covered by this prospectus for general corporate purposes, which may include working capital, capital expenditures, research and development expenditures, clinical trial expenditures, commercial expenditures, acquisitions of new technologies or businesses, and investments. Additional information on the use of net proceeds from the sale of securities covered by this prospectus may be set forth in the prospectus supplement relating to the specific offering.

PLAN OF DISTRIBUTION

We may sell securities in any of the ways described below or in any combination:

The distribution of the securities may be effected from time to time in one or more transactions:

Each prospectus supplement will describe the method of distribution of the securities and any applicable restrictions.

The prospectus supplement with respect to the securities of a particular series will describe the terms of the offering of the securities, including the following:

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Any offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time.

Only the agents or underwriters named in each prospectus supplement are agents or underwriters in connection with the securities being offered thereby.

We may authorize underwriters, dealers or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in each applicable prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in each applicable prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will be subject only to those conditions set forth in each applicable prospectus supplement, and each prospectus supplement will set forth any commissions we pay for solicitation of these contracts.

Agents, underwriters and other third parties described above may be entitled to indemnification by us against certain civil liabilities, including liabilities under the Securities Act of 1933, or to contribution from us with respect to payments which the agents, underwriters or other third parties may be required to make in respect thereof. Agents, underwriters and such other third parties may be customers of, engage in transactions with, or perform services for us in the ordinary course of business.

One or more firms, referred to as “remarketing firms,” may also offer or sell the securities, if a prospectus supplement so indicates, in connection with a remarketing arrangement upon their purchase. Remarketing firms will act as principals for their own accounts or as our agents. These remarketing firms will offer or sell the securities in accordance with the terms of the securities. Each prospectus supplement will identify and describe any remarketing firm and the terms of its agreement, if any, with us and will describe the remarketing firm’s compensation. Remarketing firms may be deemed to be underwriters in connection with the securities they remarket. Remarketing firms may be entitled under agreements that may be entered into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act of 1933, and may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

Certain underwriters may use this prospectus and any accompanying prospectus supplement for offers and sales related to market-making transactions in the securities. These underwriters may act as principal or agent in these transactions, and the sales will be made at prices related to prevailing market prices at the time of sale.

The securities may be new issues of securities and may have no established trading market. The securities may or may not be listed on a securities exchange. Underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We can make no assurance as to the liquidity of, or the existence of trading markets for, any of the securities.

Certain persons participating in an offering may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with rules and regulations under the Securities Exchange Act of 1934. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a short covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

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DESCRIPTION OF COMMON STOCK

The following summary of the terms of our common stock is subject to and qualified in its entirety by reference to our charter and by-laws, copies of which are on file with the SEC as exhibits to previous SEC filings. Please refer to “Where You Can Find More Information” below for directions on obtaining these documents.

We are authorized to issue 60,000,000 shares of common stock. As of December 19, 2011, we had 17,581,447 shares of common stock outstanding.

General

Our stockholders are entitled to one vote for each share of common stock held on all matters submitted to a vote of our stockholders and do not have cumulative voting rights. Unless otherwise required by law, our certificate of incorporation, or our bylaws, the affirmative vote of a majority of all eligible votes present in person or by proxy at a meeting of the stockholders at which a quorum is present (or if there are two or more classes of stock voting as separate classes, the holders of a majority of the class of stock voting on the matter) is required to decide any matter. Our stockholders are entitled to receive ratable dividends, if any, as may be declared from time to time by the board of directors out of legally available funds, subject to any preferential dividend rights applicable to any outstanding shares of our preferred stock that may be issued in the future. We have not declared or paid cash dividends on our capital stock during the past two fiscal years. Any determination to pay dividends to holders of common stock in the future will be at the discretion of the board of directors and will depend on many factors, including our financial condition, results of operations, general business conditions, and any other factors the board of directors deems relevant.

In the event of a liquidation, dissolution, or winding up of the Company, our stockholders are entitled to share ratably in all of our assets remaining after the payment of all debts and other liabilities, subject to the prior distribution rights of any outstanding shares of preferred stock that may be issued in the future. There are no preemptive, subscription, redemption, sinking fund, or conversion rights applicable to the common stock. All shares of common stock have equal rights and preferences. The outstanding shares of common stock are validly issued, fully paid, and nonassessable. The rights, preferences, and privileges of our stockholders are subject to the rights of the holders of shares of any class or series of our preferred stock that we may designate and issue in the future.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

Nasdaq Global Market

Our common stock is listed for quotation on the Nasdaq Global Market under the symbol “GEVA.”

DESCRIPTION OF PREFERRED STOCK

The board of directors has the authority, without action by the our stockholders, to designate and issue up to 10,000,000 shares of preferred stock in one or more series and to designate the rights, preferences, and limitations of all such series, any or all of which may be superior to the rights of common stock. It is not possible to state the actual effect of the issuance of any shares of preferred stock upon the rights of the holders of common stock until the board of directors determines the specific rights of the holders of preferred stock. However, effects of the issuance of preferred stock include restricting dividends on common stock, diluting the voting power of common stock, impairing the liquidation rights of common stock, and making it more difficult for a third party to acquire us, which could have the effect of discouraging a third party from acquiring, or deterring a third party from paying a premium to acquire, a majority of our outstanding voting stock.

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If we offer a specific class or series of preferred stock under this prospectus, we will describe the terms of the preferred stock in the prospectus supplement for such offering and will file a copy of the certificate establishing the terms of the preferred stock with the SEC. To the extent required, this description will include:

The preferred stock offered by this prospectus, when issued, will not have, or be subject to, any preemptive or similar rights.

Transfer Agent and Registrar

The transfer agent and registrar for any series or class of preferred stock will be set forth in each applicable prospectus supplement.

DESCRIPTION OF WARRANTS

As of December 19, 2011, we had zero warrants outstanding to purchase shares of our common stock. We may issue warrants to purchase shares of our common stock, preferred stock and/or debt securities in one or more series together with other securities or separately, as described in each applicable prospectus supplement. Below is a description of certain general terms and provisions of the warrants that we may offer. Particular terms of the warrants will be described in the applicable warrant agreements and the applicable prospectus supplement for the warrants.

The applicable prospectus supplement will contain, where applicable, the following terms of and other information relating to the warrants:

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Transfer Agent and Registrar

The transfer agent and registrar for any warrants will be set forth in the applicable prospectus supplement.

DESCRIPTION OF DEBT SECURITIES

We will issue the debt securities offered by this prospectus and any accompanying prospectus supplement under an indenture to be entered into between us and the trustee identified in the applicable prospectus supplement. The terms of the debt securities will include those stated in the indenture and those made part of the indenture by reference to the Trust Indenture Act of 1939, as in effect on the date of the indenture. We have filed a copy of the form of indenture as an exhibit to the registration statement in which this prospectus is included. The indenture will be subject to and governed by the terms of the Trust Indenture Act of 1939.

We may offer under this prospectus up to an aggregate principal amount of $100,000,000 in debt securities, or if debt securities are issued at a discount, or in a foreign currency, foreign currency units or composite currency, the principal amount as may be sold for an initial public offering price of up to $100,000,000. Unless otherwise specified in the applicable prospectus supplement, the debt securities will represent direct, unsecured obligations of the Company and will rank equally with all of our other unsecured indebtedness.

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The following statements relating to the debt securities and the indenture are summaries, qualified in their entirety by reference to the detailed provisions of the indenture.

General

We may issue the debt securities in one or more series with the same or various maturities, at par, at a premium, or at a discount. We will describe the particular terms of each series of debt securities in a prospectus supplement relating to that series, which we will file with the SEC.

The prospectus supplement will set forth, to the extent required, the following terms of the debt securities in respect of which the prospectus supplement is delivered:

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We may issue discount debt securities that provide for an amount less than the stated principal amount to be due and payable upon acceleration of the maturity of such debt securities in accordance with the terms of the indenture. We may also issue debt securities in bearer form, with or without coupons. If we issue discount debt securities or debt securities in bearer form, we will describe material U.S. federal income tax considerations and other material special considerations which apply to these debt securities in the applicable prospectus supplement.

We may issue debt securities denominated in or payable in a foreign currency or currencies or a foreign currency unit or units. If we do, we will describe the restrictions, elections, and general tax considerations relating to the debt securities and the foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Exchange and/or Conversion Rights

We may issue debt securities which can be exchanged for or converted into shares of our common stock or preferred stock. If we do, we will describe the terms of exchange or conversion in the prospectus supplement relating to these debt securities.

Transfer and Exchange

We may issue debt securities that will be represented by either:

We will specify in the prospectus supplement applicable to a particular offering whether the debt securities offered will be book-entry or certificated securities.

Certificated Debt Securities

If you hold certificated debt securities, you may transfer or exchange such debt securities at the trustee’s office or at the paying agent’s office or agency in accordance with the terms of the indenture. You will not be charged a service charge for any transfer or exchange of certificated debt securities but may be required to pay an amount sufficient to cover any tax or other governmental charge payable in connection with such transfer or exchange.

You may effect the transfer of certificated debt securities and of the right to receive the principal of, premium, and/or interest, if any, on the certificated debt securities only by surrendering the certificate representing the certificated debt securities and having us or the trustee issue a new certificate to the new holder.

Global Securities

If we decide to issue debt securities in the form of one or more global securities, then we will register the global securities in the name of the depositary for the global securities or the nominee of the depositary, and the global securities will be delivered by the trustee to the depositary for credit to the accounts of the holders of beneficial interests in the debt securities.

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The prospectus supplement will describe the specific terms of the depositary arrangement for debt securities of a series that are issued in global form. None of our Company, the trustee, any payment agent or the security registrar will have any responsibility or liability for any aspect of the records relating to or payments made on account of beneficial ownership interests in a global debt security or for maintaining, supervising or reviewing any records relating to these beneficial ownership interests.

No Protection in the Event of Change of Control

The indenture does not have any covenants or other provisions providing for a put or increased interest or otherwise that would afford holders of our debt securities additional protection in the event of a recapitalization transaction, a change of control of the Company, or a highly leveraged transaction. If we offer any covenants or provisions of this type with respect to any debt securities covered by this prospectus, we will describe them in the applicable prospectus supplement.

Covenants

Unless otherwise indicated in this prospectus or the applicable prospectus supplement, our debt securities will not have the benefit of any covenants that limit or restrict our business or operations, the pledging of our assets or the incurrence by us of indebtedness. We will describe in the applicable prospectus supplement any material covenants in respect of a series of debt securities.

Consolidation, Merger and Sale of Assets

We have agreed in the indenture that we will not consolidate with or merge into any other person or convey, transfer, sell or lease our properties and assets substantially as an entirety to any person, unless:

Events of Default

Unless otherwise specified in the applicable prospectus supplement, the following events will be events of default under the indenture with respect to debt securities of any series:

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The trustee may withhold notice to the holders of the debt securities of any series of any default, except in payment of principal of or premium, if any, or interest on the debt securities of a series, if the trustee considers it to be in the best interest of the holders of the debt securities of that series to do so.

If an event of default (other than an event of default resulting from certain events of bankruptcy, insolvency or reorganization) occurs, and is continuing, then the trustee or the holders of not less than 25% in aggregate principal amount of the outstanding debt securities of any series may accelerate the maturity of the debt securities. If this happens, the entire principal amount, plus the premium, if any, of all the outstanding debt securities of the affected series plus accrued interest to the date of acceleration will be immediately due and payable. At any time after the acceleration, but before a judgment or decree based on such acceleration is obtained by the trustee, the holders of a majority in aggregate principal amount of outstanding debt securities of such series may rescind and annul such acceleration if:

In addition, if the acceleration occurs at any time when we have outstanding indebtedness which is senior to the debt securities, the payment of the principal amount of outstanding debt securities may be subordinated in right of payment to the prior payment of any amounts due under the senior indebtedness, in which case the holders of debt securities will be entitled to payment under the terms prescribed in the instruments evidencing the senior indebtedness and the indenture.

If an event of default resulting from certain events of bankruptcy, insolvency or reorganization occurs, the principal, premium and interest amount with respect to all of the debt securities of any series will be due and payable immediately without any declaration or other act on the part of the trustee or the holders of the debt securities of that series.

The holders of a majority in principal amount of the outstanding debt securities of a series will have the right to waive any existing default or compliance with any provision of the indenture or the debt securities of that series and to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, subject to certain limitations specified in the indenture.

No holder of any debt security of a series will have any right to institute any proceeding with respect to the indenture or for any remedy under the indenture, unless:

These limitations do not, however, apply to a suit instituted for payment on debt securities of any series on or after the due dates expressed in the debt securities.

We will periodically deliver certificates to the trustee regarding our compliance with our obligations under the indenture.

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Modification and Waiver

From time to time, we and the trustee may, without the consent of holders of the debt securities of one or more series, amend the indenture or the debt securities of one or more series, or supplement the indenture, for certain specified purposes, including:

From time to time we and the trustee may, with the consent of holders of at least a majority in principal amount of an outstanding series of debt securities, amend or supplement the indenture or the debt securities series, or waive compliance in a particular instance by us with any provision of the indenture or the debt securities. We may not, however, without the consent of each holder affected by such action, modify or supplement the indenture or the debt securities or waive compliance with any provision of the indenture or the debt securities in order to:

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

The indenture permits us, at any time, to elect to discharge our obligations with respect to one or more series of debt securities by following certain procedures described in the indenture. These procedures will allow us either:

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In order to exercise either defeasance option, we must deposit with the trustee or other qualifying trustee, in trust for that purpose:

which in each case specified above, provides a sufficient amount to pay the principal of, premium, if any, and interest, if any, on the debt securities of the series, on the scheduled due dates or on a selected date of redemption in accordance with the terms of the indenture.

In addition, defeasance may be effected only if, among other things:

If we fail to comply with our remaining obligations under the indenture and applicable supplemental indenture after a covenant defeasance of the indenture and applicable supplemental indenture, and the debt securities are declared due and payable because of the occurrence of any undefeased event of default, the amount of money and/or U.S. Government Obligations and/or Foreign Government Obligations on deposit with the trustee could be insufficient to pay amounts due under the debt securities of the affected series at the time of acceleration. We will, however, remain liable in respect of these payments.

The term “U.S. Government Obligations” as used in the above discussion means securities which are direct obligations of or non-callable obligations guaranteed by the United States of America for the payment of which obligation or guarantee the full faith and credit of the United States of America is pledged.

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The term “Foreign Government Obligations” as used in the above discussion means, with respect to debt securities of any series that are denominated in a currency other than U.S. dollars (1) direct obligations of the government that issued or caused to be issued such currency for the payment of which obligations its full faith and credit is pledged or (2) obligations of a person controlled or supervised by or acting as an agent or instrumentality of such government the timely payment of which is unconditionally guaranteed as a full faith and credit obligation by that government, which in either case under clauses (1) or (2), are not callable or redeemable at the option of the issuer.

Regarding the Trustee

We will identify the trustee with respect to any series of debt securities in the prospectus supplement relating to the applicable debt securities. You should note that if the trustee becomes a creditor of Synageva, the indenture and the Trust Indenture Act of 1939 limit the rights of the trustee to obtain payment of claims in certain cases, or to realize on certain property received in respect of any such claim, as security or otherwise. The trustee and its affiliates may engage in, and will be permitted to continue to engage in, other transactions with us and our affiliates. If, however, the trustee acquires any “conflicting interest” within the meaning of the Trust Indenture Act of 1939, it must eliminate such conflict or resign.

The holders of a majority in principal amount of the then outstanding debt securities of any series may direct the time, method and place of conducting any proceeding for exercising any remedy available to the trustee. If an event of default occurs and is continuing, the trustee, in the exercise of its rights and powers, must use the degree of care and skill of a prudent person in the conduct of his or her own affairs. Subject to that provision, the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request of any of the holders of the debt securities, unless they have offered to the trustee reasonable indemnity or security.

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WHERE YOU CAN FIND MORE INFORMATION

We have filed a registration statement on Form S-3 with the SEC for the securities we are offering by this prospectus. This prospectus does not include all of the information contained in the registration statement. You should refer to the registration statement and its exhibits for additional information.

We are required to file annual and quarterly reports, special reports, proxy statements, and other information with the SEC. We make these documents publicly available, free of charge, on our website at www.synageva.com as soon as reasonably practicable after filing such documents with the SEC. You can read our SEC filings, including the registration statement, on the SEC’s website at http://www.sec.gov. You also may read and copy any document we file with the SEC at its public reference facility at:

Public Reference Room

100 F Street N.E.

Washington, DC 20549.

Please call the SEC at 1-800-732-0330 for further information on the operation of the public reference facilities.

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” into this prospectus the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus, and information in documents that we file later with the SEC will automatically update and supersede information in this prospectus. We incorporate by reference into this prospectus the documents listed below and any future filings made by us with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act until we close this offering, including all filings made after the date of the initial registration statement and prior to the effectiveness of the registration statement. We hereby incorporate by reference the following documents:

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address:

Synageva BioPharma Corp.

128 Spring Street, Suite 520

Lexington, Massachusetts 02421

(781) 357-9900

Copies of these filings are also available, without charge, through the “Investor Relations” section of our website (www.synageva.com) as soon as reasonably practicable after they are filed electronically with the SEC. The information contained on our website is not a part of this prospectus.

LEGAL MATTERS

The validity of the issuance of the securities offered hereby will be passed upon for us by Ropes & Gray LLP, Boston, Massachusetts. The validity of any securities will be passed upon for any underwriters or agents by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The financial statements of Trimeris, Inc. as of December 31, 2010 and 2009, and for each of the two years in the period ended December 31, 2010 appearing in Trimeris, Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2010, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein and incorporated herein by reference. Such financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

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The financial statements of Trimeris for the year ended December 31, 2008 (which include disclosures relating to Trimeris’ adoption of the provisions of FASB ASC Topic 808, Collaborative Arrangements, as of January 1, 2009, as described in note 1 and in paragraph 8 of note 7 to the December 31, 2010 financial statements) have been incorporated by reference herein in reliance upon the report of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The financial statements of Private Synageva as of December 31, 2010 and 2009 and for each of the two years in the period ended December 31, 2010, incorporated by reference into this prospectus have been so included in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

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             Shares of Common Stock

PROSPECTUS SUPPLEMENT

MORGAN STANLEY

J.P. MORGAN

COWEN AND COMPANY

LEERINK SWANN

WEDBUSH PACGROW LIFE SCIENCES

January     , 2012