GlobeNewswire Inc | Jun 1, 2021 04:01PM EDT

June 01, 2021

SOUTH SAN FRANCISCO, Calif., June 01, 2021 (GLOBE NEWSWIRE) -- Day One Biopharmaceuticals, Inc. (Nasdaq: DAWN), a clinical-stage biopharmaceutical company dedicated to developing and commercializing targeted therapies for patients of all ages with genetically defined cancers, today announced the closing of its initial public offering of 11,500,000 shares of its common stock, including the full exercise of the underwriters option to purchase up to 1,500,000 additional shares of common stock, at a public offering price of $16.00per share. All of the shares were offered by Day One. The gross proceeds from the offering, before deducting underwriting discounts and commissions and other offering expenses payable by Day One, were $184.0 million. The shares began trading on the Nasdaq Global Select Market on May 27, 2021 under the ticker symbol DAWN.

J.P. Morgan, Cowen and Piper Sandler acted as joint bookrunning managers for the offering. Wedbush PacGrow acted as lead manager for the offering.

A registration statement relating to these securities has been filed with theSecurities and Exchange Commissionand was declared effective onMay 26, 2021. The offering was made only by means of a prospectus. A copy of the final prospectus, when available, may be obtained from J.P. Morgan Securities LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, by telephone at (866) 803-9204, or by email at prospectus-eq_fi@jpmchase.com; Cowen and Company, LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, Attention: Prospectus Department, by telephone at (833) 297-2926 or by email at PostSaleManualRequests@broadridge.com; or Piper Sandler & Co., 800 Nicollet Mall, J12S03, Minneapolis, MN 55402, Attention: Prospectus Department, by telephone at (800) 747-3924, or by email at prospectus@psc.com.

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 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 jurisdiction.

About Day One Biopharmaceuticals, Inc.

Day One is a clinical-stage biopharmaceutical company dedicated to developing and commercializing targeted therapies for patients of all ages with genetically defined cancers. Day One was founded to address a critical unmet need: children with cancer are being left behind in a cancer drug development revolution. Day Ones name was inspired by the The Day One Talk1 that physicians have with patients and their families about an initial cancer diagnosis and treatment plan. Day One aims to re-envision cancer drug development and redefine whats possible for all people living with cancerregardless of agestarting from Day One.

Day One partners with leading clinical oncologists, families, and scientists to identify, acquire, and develop important emerging cancer treatments. The Companys lead product candidate, DAY101, is an oral, brain-penetrant, highly-selective type II pan-RAF kinase inhibitor, and is being evaluated in a pivotal Phase 2 clinical trial (FIREFLY-1) in pediatric, adolescent and young adult patients with relapsed or progressive low-grade glioma (pLGG). The Companys pipeline also includes the investigational agent pimasertib, a clinical-stage, oral, highly-selective small molecule inhibitor of mitogen-activated protein kinase kinases 1 and 2 (MEK). Day One is based in South San Francisco.

1Jennifer W. MackandHolcombe E. Grier; Journal of Clinical Oncology200422:3,563-566

Contacts:

Media: 1ABDan Budwickdan@1abmedia.com

Investors: LifeSci AdvisorsHans Vitzthumhans@lifesciadvisors.com