Magenta Therapeutics Launches Proposed Public Offering

Magenta Therapeutics, Inc. (Nasdaq: MGTA), a clinical-stage biotechnology company developing novel medicines to bring the curative power of stem cell transplant to more patients, announced that it has commenced an underwritten public offering of $60 million of its common stock. Magenta also intends to grant the underwriters a 30-day option to purchase up to an additional fifteen percent (15%) of the shares of common stock offered in the public offering. All of the shares in the proposed offering are to be sold by Magenta.

Goldman Sachs & Co. LLC and Cowen are acting as joint bookrunning managers for the offering. The proposed offering is subject to market and other conditions, and there can be no assurance as to whether or when the proposed offering may be completed, or as to the actual size or terms of the proposed offering.

Magenta intends to use the net proceeds of the offering to advance its clinical and earlier stage programs and for research and development, working capital and general corporate purposes.

The securities described may be offered pursuant to a shelf registration statement on Form S-3 (File No. 333-233127), including a base prospectus. The proposed offering will be made only by means of a prospectus. A preliminary prospectus supplement and a final prospectus supplement relating to, and describing the terms of, this offering will be filed with the U.S. Securities and Exchange Commission (the “SEC”) and will be available on the SEC’s website at www.sec.gov. When available, copies of the preliminary prospectus may also be obtained from: Goldman Sachs & Co. LLC, Attn: Prospectus Department, 200 West Street, New York, NY 10282, telephone: [phone], facsimile: 212-902-9316, e-mail: [e-mail]; or Cowen and Company, LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, New York 11717, Attn: Prospectus Department, by telephone at [phone], or by email at [e-mail].

Important Information

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be any offer or sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or other jurisdiction.