SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13D

(Rule 13d-101)

Under the Securities Exchange Act of 1934

(Amendment No. 11)*

Mirati Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.001 par value

(Title of Class of Securities)

60468T105

(CUSIP Number)

David A. Brown

Alston & Bird LLP

950 F Street, N.W.

Washington, DC 20004-1404

202-239-3463

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

June 22, 2017

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box  ☐.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

This Amendment No. 11 (“Amendment No. 11”) amends and supplements the statement on Schedule 13D filed on November 4, 2013 (the “Original Filing”) by Boxer Capital, LLC (“Boxer Capital”), Boxer Asset Management Inc. (“Boxer Management”), MVA Investors, LLC (“MVA Investors”) and Joe Lewis, as amended by Amendment No. 1 filed on February 2, 2015, Amendment No. 2 filed on September 18, 2015, Amendment No. 3 filed on January 6, 2016 (“Amendment No. 3”), Amendment No. 4 filed on January 15, 2016 (“Amendment No. 4”), Amendment No. 5 filed on March 17, 2016, Amendment No. 6 filed on June 8, 2016, Amendment No. 7 filed on June 24, 2016, Amendment No. 8 filed on September 28, 2016, Amendment No. 9 filed on January 10, 2017 and Amendment No. 10 filed on January 30, 2017. Amendment No. 3 was an original filing for Braslyn Ltd. (“Braslyn”). Amendment No. 4 was an original filing for Aaron I. Davis, Shehan B. Dissanayake, Christopher Fuglesang, Rodney W. Lappe, Ivan M. Lieberburg and Neil Reisman. Boxer Capital, Boxer Management, MVA Investors, Braslyn, Joe Lewis, Aaron I. Davis, Shehan B. Dissanayake, Christopher Fuglesang, Rodney W. Lappe. Ivan M. Lieberburg and Neil Reisman are collectively referred to herein as the “Reporting Persons.” The Original Filing, as amended, remains in effect except to the extent that it is amended, restated or superseded by information contained in this Amendment No. 11. Capitalized terms used and not defined in this Amendment No. 11 have the meanings set forth in the Original Filing, as amended.

Item 4. Purpose of Transaction.

Item 4 is hereby amended as follows:

On June 27, 2017, the Issuer announced that Neil Reisman was appointed to its board of directors effective as of June 22, 2017. Pursuant to the Securities Purchase Agreement (as defined in the Original Filing), Mr. Reisman was nominated by Tavistock Life Sciences, an affiliate of Boxer Capital, to serve on the Issuer’s board of directors. Rodney W. Lappe was re-elected to the Issuer’s board at the Issuer’s 2017 Annual Meeting of Stockholders held on May 17, 2017. Mr. Reisman is employed by Tavistock Group, Inc. and Mr. Lappe is employed by Tavistock Life Sciences, both affiliates of Boxer Capital. Additionally, pursuant to the Securities Purchase Agreement, Tavistock Life Sciences continues to have the right to designate a representative as a board observer to the board of the Issuer.

Item 5. Interest in Securities of the Issuer.

Item 5 is hereby amended and restated in its entirety as follows:

All percentages are based on 25,406,841 shares of Common Stock outstanding which is the sum of (i) 24,939,797 shares of Common Stock reported to be outstanding as of May 1, 2017 according to the Issuer’s Form 10-Q filed with the SEC on May 4, 2017, (ii) 189,780 shares of Common Stock, which Boxer Capital currently has the right to acquire pursuant to the Boxer 2012 Warrant, (iii) 78,186 shares of Common Stock, which MVA Investors currently has the right to acquire pursuant to the MVA 2012 Warrant, (iv) 112,763 shares of Common Stock, which Boxer Capital currently has the right to acquire pursuant to the Boxer 2017 Warrant, and (v) 86,315 shares of Common Stock subject to options exercisable within the next 60 days.

(a) The Reporting Persons may be deemed to beneficially own, in the aggregate, 5,078,827 shares of Common Stock, representing 19.99% of the Issuer’s outstanding Common Stock.

Boxer Capital and Boxer Management beneficially own 1,340,537 shares of Common Stock which represents 5.3% of the Issuer’s outstanding Common Stock. Braslyn beneficially owns 2,880,702 shares of Common Stock which represents 11.3% of the Issuer’s outstanding Common Stock. Joe Lewis beneficially owns 4,221,239 shares of Common Stock which represents 16.6% of the Issuer’s outstanding Common Stock. MVA Investors beneficially owns 513,630 shares of Common Stock which represents 2.0% of the Issuer’s outstanding Common Stock. Aaron I. Davis beneficially owns 87,052 shares of Common Stock which represents 0.3% of the Issuer’s outstanding Common Stock. Shehan B. Dissanayake beneficially owns 77,038 shares of Common Stock which represents 0.3% of the Issuer’s outstanding Common Stock. Christopher Fuglesang beneficially owns 30,518 shares of Common Stock which represents 0.1% of the Issuer’s outstanding Common Stock. Ivan M. Lieberburg beneficially owns 37,241 shares of Common Stock which represents 0.2% of the Issuer’s outstanding Common Stock.

Neil Reisman beneficially owns 14,520 shares of Common Stock, which includes 1,389 shares of Common Stock subject to options exercisable within the next 60 days, and represents 0.1% of the Issuer’s Common Stock. Rodney W. Lappe beneficially owns 97,589 shares of Common Stock, which includes 84,926 shares of Common Stock subject to options exercisable within the next 60 days, and represents 0.4% of the Issuer’s outstanding Common Stock.

The table below reflects options to purchase shares of Common Stock of the Issuer owned by Rodney W. Lappe and Neil Reisman that are not currently exercisable within the next 60 days:

The 2012 Warrants represent a right for Boxer Capital and MVA Investors to purchase 189,780 and 78,186 shares of Common Stock, respectively, at an exercise price of $7.86 (subject to adjustment). The 2012 Warrants are only exercisable to the extent that the holders thereof and their affiliates and joint actors would beneficially own no more than 19.99% of the outstanding Common Stock after exercise.

The 2017 Warrants represent a right for Boxer Capital, MVA Investors and Braslyn to purchase 2,341,786, 51,047 and 4,865,430 shares of Common Stock, respectively. The 2017 Warrants have been pre-paid at a price of $5.599 per share with exercise price of $0.001 per share. The 2017 Warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 19.99% of the outstanding Common Stock after exercise.

(b) With respect to any rights or powers to vote, or to direct the vote of, or to dispose of, or direct the disposition of, the Common Stock owned by the Reporting Persons:

(i) Sole power to vote or direct the vote:

MVA Investors has the sole power to vote the 513,630 shares of Common Stock it beneficially owns. Aaron I. Davis has the sole power to vote the 87,052 shares of Common Stock he beneficially owns. Shehan B. Dissanayake has the sole power to vote the 77,038 shares of Common Stock he beneficially owns. Christopher Fuglesang has the sole power to vote the 30,518 shares of Common Stock he beneficially owns. Rodney W. Lappe has the sole power to vote the 97,589 shares of Common Stock he beneficially owns. Ivan M. Lieberburg has the sole power to vote the 37,241 shares of Common Stock he beneficially owns. Neil Reisman has the sole power to vote the 14,520 shares of Common Stock he beneficially owns.

(ii) Shared power to vote or to direct the vote:

Boxer Capital and Boxer Management have shared voting power with respect to the 1,340,537 shares of Common Stock they beneficially own. Braslyn has shared voting power with respect to the 2,880,702 shares of Common Stock it beneficially owns. Joe Lewis has shared voting power with respect to the 4,221,239 shares of Common Stock he beneficially owns.

(iii) Sole power to dispose or direct the disposition of:

MVA Investors has the sole power to dispose of the 513,630 shares of Common Stock it beneficially owns. Aaron I. Davis has the sole power to vote the 87,052 shares of Common Stock he beneficially owns. Shehan B. Dissanayake has the sole power to vote the 77,038 shares of Common Stock he beneficially owns. Christopher Fuglesang has the sole power to vote the 30,518 shares of Common Stock he beneficially owns. Rodney W. Lappe has the sole power to vote the 97,589 shares of Common Stock he beneficially owns. Ivan M. Lieberburg has the sole power to vote the 37,241 shares of Common Stock he beneficially owns. Neil Reisman has the sole power to vote the 14,520 shares of Common Stock he beneficially owns.

(iv) Shared power to dispose or to direct the disposition of:

Boxer Capital and Boxer Management have shared dispositive power with respect to the 1,340,537 shares of Common Stock they beneficially own. Braslyn has shared dispositive power with respect to the 2,880,702 shares of Common Stock it beneficially owns. Joe Lewis has shared voting power with respect to the 4,221,239 shares of Common Stock he beneficially owns.

(c) The Reporting Persons have not engaged in any transactions in the Common Stock in the past 60 days.    

(d) No other person has the right to receive or the power to direct the receipt of dividends, or proceeds of sale of such securities outlined in this report.

(e) Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer.

Except as otherwise described in the Original Filing, as amended, there are no contracts, arrangements, understandings or relationships (legal or otherwise) among the persons named in Item 2 and between such persons and any person with respect to any securities of the Issuer, including, but not limited to, transfer or voting of any of the securities, finder’s fees, joint ventures, loan or option arrangements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies

Item 7. Material to Be Filed as Exhibits.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: June 27, 2017

EXHIBIT INDEX