Day One Biopharmaceuticals, Inc.

Day One Biopharmaceuticals, Inc. is a commercial-stage biopharmaceutical company that identifies, develops, and commercializes medicines for childhood and adult diseases in the United States. The company's primary product candidate is tovorafenib, an oral and brain-penetrant type II rapidly accelerated fibrosarcoma kinase inhibitor. Tovorafenib is currently in a Phase II clinical trial for pediatric patients with relapsed or refractory low-grade glioma, and in a Phase III clinical trial for Ipsen, a frontline raf-altered pLGG. Day One Biopharmaceuticals is also developing DAY301, a PTK7 targeted antibody-drug conjugate (ADC). DAY301 consists of a novel humanized anti-PTK7 immunoglobulin G1 monoclonal antibody conjugated with a topoisomerase I inhibitor via a modified valine-alanine (VA) cleavable linker, and is being developed for the treatment of patients with advanced solid tumors. Additionally, the company is developing Emi-Le, an antibody-drug conjugate that targets B7-H4, conjugated to an auristatin anti-tubulin payload. Emi-Le is part of a proprietary linker-payload platform developed by Mersana Therapeutics and is in a Phase 1 clinical trial for the treatment of breast cancer, ovarian cancer, endometrial cancer, and adenoid cystic carcinoma (ACC). Day One Biopharmaceuticals, Inc. was incorporated in 2018 and is headquartered in Brisbane, California. As of April 22, 2026, Day One Biopharmaceuticals, Inc. operates as a subsidiary of Servier Pharmaceuticals LLC.