Day One announces top line data from pivotal Phase 2 FIREFLY-1 trial

Day One Biopharmaceuticals announced positive top line results from the ongoing, open-label, pivotal Phase 2 FIREFLY-1 trial evaluating the investigational agent, tovorafenib, as a monotherapy in recurrent or progressive pediatric low-grade glioma. Pediatric low-grade glioma is the most common brain tumor diagnosed in children and for which there is no standard of care, and for which there are no approved therapies for the majority of patients. Additional data will be submitted for presentation at an upcoming medical meeting in the second quarter of 2023. The primary endpoint of the FIREFLY-1 trial is overall response rate by Response Assessment for Neuro-Oncology criteria as assessed by blinded independent central review. Top line results as of September 28, 2022 include: among 69 RANO-evaluable patients — 64% ORR and 91% clinical benefit rate; 4% confirmed complete responses; 59% partial responses; 28% patients with stable disease; 86% of patients had a BRAF fusion alteration, for which there are no approved systemic therapies, while the remaining 14% had a BRAF mutation. Safety data, based on 77 treated patients, indicated monotherapy tovorafenib to be generally well-tolerated. Among a total of 77 treated patients: Participants were heavily pretreated, with a median of three prior lines of systemic therapy; The median duration of tovorafenib treatment was 8.4 months, with 77% of patients on treatment at the time of the data cutoff; Nearly 60% of patients had already received at least one prior MAPK inhibitor prior to study participation. In addition to FIREFLY-1, Day One is expanding the development of tovorafenib as a front-line therapy for patients newly diagnosed with pLGG. The global, Phase 3, registrational FIREFLY-2/LOGGIC clinical trial is evaluating once-weekly monotherapy tovorafenib in newly-diagnosed patients with pLGG harboring a known activating RAF alteration.