Exhibit 99.1

Allakos Reports First Quarter 2020 Financial Results

REDWOOD CITY, Calif., May 11, 2020 – Allakos Inc. (the “Company”) (Nasdaq: ALLK), a biotechnology company developing antolimab (AK002) for the treatment of eosinophil and mast cell-related diseases, today reported financial results for the first quarter ended March 31, 2020.

First Quarter 2020 Financial Results

Research and development expenses were $18.3 million in the first quarter of 2020 as compared to $15.1 million in the same period in 2019, an increase of $3.2 million.

General and administrative expenses were $11.6 million in the first quarter of 2020 as compared to $5.8 million in the same period in 2019, an increase of $5.8 million.

Allakos reported a net loss of $27.8 million in the first quarter of 2020 as compared to $20.0 million in the same period in 2019, an increase of $7.8 million. Net loss per basic and diluted share was $0.57 for the first quarter of 2020 compared to $0.47 in the same period in 2019.

Allakos ended the first quarter of 2020 with $479.8 million in cash, cash equivalents and marketable securities.

About Allakos

Allakos is a late-stage biotechnology company developing antibodies that target immunomodulatory receptors present on immune effector cells involved in allergic, inflammatory, and proliferative diseases. The Company’s lead antibody, antolimab (AK002), is being evaluated in a Phase 3 study in eosinophilic gastritis (EG) and/or eosinophilic duodenitis (EoD) and a Phase 2/3 study in eosinophilic esophagitis (EoE). Antolimab targets Siglec-8, an inhibitory receptor selectively expressed on human mast cells and eosinophils. Inappropriately activated eosinophils and mast cells have been identified as key drivers in a number of severe diseases affecting the gastrointestinal tract, eyes, skin, lungs and other organs. Antolimab has been tested in multiple clinical studies, in which antolimab eliminated blood and tissue eosinophils, inhibited mast cells and improved disease symptoms in patients with eosinophilic gastritis and/or eosinophilic duodenitis, eosinophilic esophagitis, mast cell gastrointestinal disease, severe allergic conjunctivitis, chronic urticaria and indolent systemic mastocytosis. For more information, please visit the Company's website at www.allakos.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995 as contained in Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Such forward-looking statements include, but are not limited to, Allakos’ progress and business plans. Such statements are subject to numerous important factors, risks and uncertainties that may cause actual events or results to differ materially from current expectations and beliefs, including but not limited to: Allakos’ early stages of clinical drug development; Allakos’ ability to timely complete clinical trials for, and if approved, commercialize antolimab (AK002), its lead compound; Allakos’ ability to obtain required regulatory approvals for its product candidates; uncertainties related to the enrollment of patients in its clinical trials; Allakos’ ability to demonstrate sufficient safety and efficacy of its product candidates in its clinical trials; uncertainties related

to the success of later-stage clinical trials, regardless of the outcomes of preclinical testing and early-stage trials; market acceptance of Allakos’ product candidates; uncertainties related to the projections of the size of patient populations suffering from the diseases Allakos is targeting; Allakos’ ability to advance additional product candidates beyond antolimab (AK002); Allakos’ ability to obtain additional capital to finance its operations; and other important risk factors set forth in Allakos’ most recent Annual Report on Form 10-K filed with the SEC on February 25, 2020, Quarterly Report on Form 10-Q filed with the SEC on May 11, 2020 and future reports to be filed with the SEC. These documents contain and identify important factors that could cause the actual results for Allakos to differ materially from those contained in Allakos’ forward-looking statements. Any forward-looking statements contained in this press release speak only as of the date hereof, and Allakos specifically disclaims any obligation to update any forward-looking statement, except as required by law. These forward-looking statements should not be relied upon as representing Allakos’ views as of any date subsequent to the date of this press release.

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Source: Allakos Inc.

Allakos Inc.

Statements of Operations and Comprehensive Loss

(in thousands, except per share data)

(unaudited)

allakos inc.

CONDENSED balance sheets

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