Repare Therapeutics Announces Proposed Public Offering of Common Shares Cambridge, Mass & Montreal, Quebec

Repare Therapeutics Announces Proposed Public Offering of Common Shares

Cambridge, Mass & Montreal, Quebec, October 27, 2021 Repare Therapeutics Inc. (Nasdaq: RPTX), a

leading precision oncology company enabled by its proprietary synthetic lethality approach to the discovery and development of novel therapeutics, today announced the commencement of a proposed underwritten public offering of $75.0 million of

its common shares. All common shares to be sold in the proposed offering will be sold by Repare. Repare also intends to grant the underwriters a 30-day option to purchase up to an additional

$11.25 million of its common shares at the public offering price, less underwriting commissions. The offering is subject to market conditions, and there can be no assurance as to whether or when the offering may be completed or the actual size

or terms of the offering.

Morgan Stanley, Goldman Sachs & Co. LLC, Cowen and Piper Sandler are acting as joint book-running managers for the

The securities described above are being offered pursuant to an automatically effective shelf registration statement that was previously filed

with the U.S. Securities and Exchange Commission (SEC) on July 2, 2021. This offering will be made only by means of a prospectus supplement and the accompanying prospectus which forms a part of the effective shelf registration statement. A

preliminary prospectus supplement related to the offering (including the accompanying prospectus) will be filed with the SEC and will be available on the SEC s website located at www.sec.gov.

When available, copies of the preliminary prospectus supplement and the accompanying prospectus relating to these securities may be obtained for free by

contacting: Morgan Stanley & Co. LLC, Attention: Prospectus Department, 180 Varick Street, 2nd Floor, New York, New York 10014; Goldman Sachs & Co. LLC, Attention: Prospectus Department, 200 West Street, New York, NY 10282, by

telephone: 1-866-471-2526 or by emailing prospectus-ny@ny.email.gs.com; Cowen and

Company, LLC c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY, 11717, Attn: Prospectus Department, by email at PostSaleManualRequests@broadridge.com or by telephone at (833) 297-2926;

or Piper Sandler & Co., Attn: Prospectus Department, 800 Nicollet Mall, J12S03, Minneapolis, Minnesota 55402, by telephone at 800-747-3924 or by email at

prospectus@psc.com. The final terms of the offering will be disclosed in a final prospectus supplement to be filed with the SEC.

This press release shall

not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of, these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification

under the securities laws of any such state or jurisdiction.

About Repare Therapeutics, Inc.

Repare Therapeutics is a leading clinical-stage precision oncology company enabled by its proprietary synthetic lethality approach to the discovery and

development of novel therapeutics. The Company utilizes its genome-wide, CRISPR-enabled SNIPRx platform to systematically discover and develop highly targeted cancer therapies focused on

genomic instability, including DNA damage repair. The Company s pipeline includes its lead product candidate, RP-3500, a potential leading ATR inhibitor currently in Phase 1/2 clinical development, its

second clinical candidate, RP-6306, a PKMYT1 inhibitor currently in Phase 1 clinical development, a Pol inhibitor program, as well as eight other early-stage,

pre-clinical programs.

SNIPRx is a registered trademark of Repare

Forward-Looking Statements

press release contains certain forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including statements with regard to Repare s expectations regarding

the anticipated final terms, timing and completion of the proposed securities offering. Words such as anticipates, believes, expects, intends, projects, and future or similar

expressions are intended to identify forward-looking statements. These forward-looking statements are subject to the inherent uncertainties in predicting future results and conditions and no assurance can be given that the proposed securities

offering discussed above will be consummated on the terms described or at all. Completion of the proposed offering and the terms thereof are subject to numerous factors, many of which are beyond the control of Repare, including, without limitation,

market conditions, failure of customary closing conditions and the risk factors and other matters set forth in Repare s Quarterly Report on Form 10-Q for the quarter ended June 30, 2021 and other

filings Repare makes with the SEC from time to time. Repare undertakes no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required by law.

Chief Financial Officer

Repare Therapeutics Inc.