(NASDAQ: DAWN) shares soared this morning in premarket trading up more than 91% on positive FDA phase results.

Initial data from the first 25 patients enrolled in the trial demonstrate:

• 64% ORR and 91% CBR (partial response/unconfirmed partial response + stable disease) in the 22 RANO-evaluable patients:
  • 14 partial responses (13 confirmed responses and 1 unconfirmed response)
  • 6 patients with stable disease
• All patients with stable disease (n=6) were noted to have tumor shrinkage, ranging between 19% and 43%
• Responses were observed in patients with both BRAF fusions and BRAF V600E mutations who received prior MAPK-targeted therapy
• The median-time-to-response was 2.8 months
• A heavily-pretreated population, with a median of 3 prior lines of therapy (range: 1-9)
• All patients who responded remain on therapy (n=14) and no patients have discontinued treatment due to treatment-related adverse events.

Initial safety data, based on the first 25 patients, indicated monotherapy tovorafenib to be generally well-tolerated. The majority of adverse events (AEs) were grade 1 or 2 in nature; the most common (≥25% any grade) treatment related AEs were increase in blood creatine phosphokinase, rash, and hair color changes. Treatment-related AEs of grade 3 or greater occurred in nine patients (36%).

“These initial findings underscore the potential of tovorafenib monotherapy to become a significant and transformative new option for relapsed/progressive pLGG, a pediatric brain tumor with no approved treatments today,” said Samuel Blackman, M.D., Ph.D., co-founder and chief medical officer of Day One. “With the registrational cohort fully enrolled, patient follow-up is ongoing, and we look forward to the topline data from the complete study population in the first quarter of 2023. Based on these positive initial data, we plan to begin the pivotal Phase 3 FIREFLY-2 clinical trial evaluating tovorafenib as a front-line therapy in pLGG to evaluate whether tovorafenib can provide benefit early in the disease development.”

“These initial data demonstrate significant anti-tumor activity in children with relapsed/progressive pLGG, including children who are refractory to available therapies. Pediatric low-grade glioma is a truly challenging disease in which children face years of aggressive regimens that can carry a long-term impact on learning, cognition, and quality of life,” said Roger Packer, M.D., senior vice president, Center for Neuroscience and Behavioral Medicine, and director, Brain Tumor Institute, Children’s National Hospital.

Day One plans to present additional interim trial results from FIREFLY-1 at an upcoming medical conference in the second half of 2022. Day One anticipates releasing topline results for the full FIREFLY-1 pivotal study population in the first quarter of 2023. If the data are supportive, Day One expects to submit a new drug application (NDA) to the United States Food and Drug Administration (FDA) in the first half of 2023.