Day One Announces Updated FIREFLY-1 Data for Tovorafenib and Completion of Rolling NDA Submission to FDA for Relapsed or Progressive Pediatric Low-Grade Glioma (pLGG)

Overall response rate (ORR) greater than 50% across three assessment criteria

Median duration of tovorafenib treatment of 15.8 months as of June 5, 2023, with 66% of patients remaining on treatment

FDA filing decision expected by mid-November

BRISBANE, Calif., Sept. 11, 2023 (GLOBE NEWSWIRE) -- Day One Biopharmaceuticals (Nasdaq: DAWN) (“Day One” or the “Company”), a clinical-stage biopharmaceutical company dedicated to developing and commercializing targeted therapies for people of all ages with life-threatening diseases, today announced the recently completed submission of the rolling New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for tovorafenib as a monotherapy in relapsed or progressive pediatric low-grade glioma (pLGG). The Company anticipates the FDA will file the rolling NDA by mid-November 2023.

pLGG is the most common brain tumor diagnosed in children, with patients suffering profound tumor and treatment-associated morbidities that can impact their life trajectory over the long term. For the majority of patients in the relapsed setting, there is no standard of care and no approved therapies.

“We believe that tovorafenib, if approved, could change the treatment landscape for children living with this chronic and relentless disease,” said Jeremy Bender, Ph.D., chief executive officer of Day One. “The NDA submission of tovorafenib is a significant milestone for Day One and an important step towards bringing a potential new targeted therapy to children with brain cancer.”

The Company initiated the rolling submission of the NDA in May 2023 based on data from the FIREFLY-1 trial with a data cutoff as of December 22, 2022. An updated Clinical Study Report (CSR) was submitted to the FDA with an additional six months of safety and efficacy data through June 5, 2023.

FIREFLY-1 is an open-label, pivotal Phase 2 trial, which treated a total of 137 patients across two study arms. Arm 1 evaluated tovorafenib in 77 patients as a once-weekly monotherapy in patients aged 6 months to 25 years with relapsed or progressive pLGG. The primary endpoint of the trial is ORR by Response Assessment for Neuro-Oncology High-Grade Glioma (RANO-HGG) criteria. Secondary endpoints include ORR by Response Assessment in Pediatric Neuro-Oncology Low-Grade Glioma (RAPNO-LGG), progression-free survival (PFS), duration of response (DOR), time to response, clinical benefit rate and safety. The NDA submission also includes an exploratory analysis of ORR by Response Assessment for Neuro-Oncology Low-Grade Glioma (RANO-LGG). All data have been assessed by a blinded Independent Review Committee (IRC).