IGM Announces Closing of $230 Million Public Offering and Full Exercise of Underwriters’ Option to Purchase Additional Shares

IGM Biosciences, Inc. (NASDAQ: IGMS) (IGM) today announced the closing of its upsized underwritten public offering of 1,221,224 shares of its common stock, which includes the exercise of the underwriters’ option to purchase additional shares in full, and pre-funded warrants to purchase 1,334,332 shares of its common stock. The public offering price of common stock was $90.00 per share and the public offering price of each pre-funded warrant was $89.99, with each pre-funded warrant having an exercise price of $0.01. The aggregate gross proceeds to IGM from the offering were approximately $230 million, before deducting the underwriting discounts and commissions and other offering expenses payable by IGM.

Jefferies, Stifel, Guggenheim Securities and RBC Capital Markets acted as joint book-running managers for the offering. Baird and Truist Securities acted as the lead managers for the offering.

The securities were offered by IGM pursuant to a Registration Statement on Form S-3 filed with the Securities and Exchange Commission (SEC) on November 5, 2020, which became effective on November 12, 2020. A final prospectus supplement and accompanying prospectus relating to the offering, was filed with the SEC on December 8, 2020, copies of which can be accessed for free through the SEC’s website at www.sec.gov. Additionally, when available, copies of the final prospectus supplement and the accompanying prospectus relating to the offering may also be obtained by request from: Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, 2nd Floor, New York, NY 10022, by telephone at (877) 821-7388 or by email at Prospectus_Department@Jefferies.com; Stifel, Nicolaus & Company, Incorporated, Attention: Syndicate, One Montgomery Street, Suite 3700, San Francisco, CA 94104, by telephone at (415) 364-2720 or by email at syndprospectus@stifel.com; Guggenheim Securities, LLC, Attention: Equity Syndicate Department, 330 Madison, 8th Floor, New York, NY 10017, by telephone at (212) 518-9658 or by email at GSEquityProspectusDelivery@guggenheimpartners.com; or RBC Capital Markets, LLC, 200 Vesey Street, 8th Floor, New York, NY 10281-8098; Attention: Equity Syndicate; by telephone at (877) 822-4089 or by email at equityprospectus@rbccm.com.

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

About IGM Biosciences, Inc.Headquartered in Mountain View, California, IGM Biosciences is a clinical-stage biotechnology company focused on creating and developing engineered IgM antibodies. Since 2010, IGM Biosciences has worked to overcome the manufacturing and protein engineering hurdles that have limited the therapeutic use of IgM antibodies. Through its efforts, IGM Biosciences has created a proprietary IgM technology platform for the development of IgM antibodies for those clinical indications where their inherent properties may provide advantages as compared to IgG antibodies.

IGM Biosciences Contact:

Argot PartnersDavid Pitts212-600-1902igmbio@argotpartners.com