Day One was founded to address a critical unmet need: children with cancer are being left behind in a cancer drug development revolution. Our name was inspired by the “The Day One Talk” that physicians have with patients and their families about an initial cancer diagnosis and treatment plan. We aim to re-envision cancer drug development and redefine what’s possible for all people living with cancer—regardless of age—starting from Day One.

We are a clinical-stage biopharmaceutical company dedicated to developing and commercializing targeted therapies for patients of all ages with genetically defined cancers. Initially, we focus our clinical development efforts on pediatric patients living with cancer, a vulnerable population that has been underserved in the recent revolution in targeted therapeutics and immuno-oncology. Our lead product candidate, DAY101, is an oral, brain-penetrant, highly-selective type II pan-rapidly accelerated fibrosarcoma, or pan-RAF, kinase inhibitor. DAY101 has been studied in over 250 patients and has been shown to be well-tolerated as a monotherapy. DAY101 has demonstrated encouraging anti-tumor activity in pediatric and adult populations with specific genetic alterations that result in the over-activation of the RAS/mitogen-activated protein kinase, or MAPK, pathway leading to uncontrolled cell growth. We have initiated a pivotal Phase 2 (FIREFLY-1) trial of DAY101 for pediatric patients with relapsed or progressive low-grade glioma, or pLGG, the most common brain tumor diagnosed in children, for which there are no approved therapies and no standard of care. We dosed the first patient in this trial in the second quarter of 2021 and we expect to report initial data from this trial in the first half of 2022. DAY101 has been granted Breakthrough Therapy designation by the U.S. Food and Drug Administration, or FDA, for the treatment of pLGG, based on initial results from a Phase 1 trial which showed evidence of rapid anti-tumor activity, a greater than 50% monotherapy response rate and durable responses in pLGG patients. We also plan to study DAY101 alone or in combination with additional agents that target other key signaling nodes in the MAPK pathway in patient populations where various genetic alterations are believed to play an important role in driving disease.

(Note: Day One Biopharmaceuticals, Inc., priced its IPO on May 26, 2021, in sync with its recently upsized terms – 10 million shares at $16, the top of its $14-to-$16 range – to raise $160 million. Early on the morning of May 26th, Day One Biopharmaceuticals increased the size of its IPO to 10 million shares, up from 8.4 million initially, and kept the price range the same at $14 to $16 each – according to an S-1/A filing.)