Magenta Therapeutics Appoints Steve Mahoney as Chief Financial and Operating Officer

Magenta Therapeutics Appoints Steve Mahoney as Chief Financial and Operating Officer

CAMBRIDGE, Mass. November 9, 2020 Magenta Therapeutics (NASDAQ: MGTA), a clinical-stage biotechnology company developing

novel medicines to bring the curative power of immune reset to more patients, today announced the appointment of Steve Mahoney as Chief Financial and Operating Officer.

We welcome Steve to Magenta as a seasoned biotech executive with a strong leadership background, said Jason Gardner, D.Phil., Chief Executive

Officer and President, Magenta Therapeutics. I look forward to partnering with Steve as we continue to grow Magenta and further establish our long-term clinical and commercial operations.

As Chief Financial and Operating Officer, Mr. Mahoney will serve as a member of the Company s Executive Team and will oversee all aspects of

financial planning and analysis, as well as investor community engagement, including investor relations and other external stakeholder communications, in addition to R&D capital allocation strategy and operations and facilities management.

Mr. Mahoney comes to Magenta with more than 20 years of global biotechnology sector industry experience. Most recently, Mr. Mahoney served as

President and Chief Operating Officer of Kiniksa Pharmaceuticals, Ltd., where the company raised capital in three private financing rounds, an initial public offering and a follow-on financing. Prior to his

time at Kiniksa, Mr. Mahoney served as Chief Commercial Officer, among other executive titles of increasing responsibilities, at Synageva Biopharma. Previous to that, he was Regional Director, Legal Asia Pacific Region for Genzyme

Corporation, following other roles for the organization.

Mr. Mahoney holds a JD/MBA from Boston College and a BA from Colorado College.

About Magenta Therapeutics

Magenta Therapeutics is a clinical-stage biotechnology company developing medicines to bring the curative power of immune system reset through stem cell

transplant to more patients with autoimmune diseases, genetic diseases and blood cancers. Magenta is combining leadership in stem cell biology and biotherapeutics development with clinical and regulatory expertise, a unique business model and broad

networks in the stem cell transplant world to revolutionize immune reset for more patients.

Magenta is based in Cambridge, Mass. For more information,

please visit www.magentatx.com.

Follow Magenta on Twitter: @magentatx.

Forward-Looking Statement

This press release may contain

forward-looking statements and information within the meaning of The Private Securities Litigation Reform Act of 1995 and other federal securities laws. The use of words such as may, will, could ,

should, expects, intends, plans, anticipates, believes, estimates, predicts, projects, seeks, endeavor,

potential, continue or the negative of such words or other similar expressions can be used to identify forward-looking statements. The express or implied forward-looking statements included in this press release are only

predictions and are subject to a number of risks, uncertainties and assumptions, including, without limitation risks set forth under the caption Risk Factors in Magenta s Annual Report on Form

10-K filed on March 3, 2020, as updated by Magenta s most recent Quarterly Report on Form 10-Q and its other filings with the Securities and Exchange

Commission. In light of these risks, uncertainties and assumptions, the forward-looking events and circumstances discussed in this press release may not occur and actual results could differ materially and adversely from those anticipated or implied

in the forward-looking statements. You should not rely upon forward-looking statements as predictions of future events. Although Magenta believes that the expectations reflected in the forward-looking statements are reasonable, it cannot guarantee

that the future results, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur. Moreover, except as required by law, neither Magenta nor any other person assumes

responsibility for the accuracy and completeness of the forward-looking statements included in this press release. Any forward-looking statement included in this press release speaks only as of the date on which it was made. We undertake no

obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law.

Magenta Therapeutics:

Lyndsey Scull, Director, Corporate

Communications, Magenta Therapeutics

Jill Bertotti, W2O Group