Day One Raises $150 Million on Heels of Positive Initial Data from Rare Pediatric Cancer Study

Day One Biopharmaceuticals raised $150 million to advance its pipeline targeting pediatric cancers, as it capitalized on a doubling of its share price on positive initial data from its pivotal mid-stage trial of lead candidate tovorafenib in relapsed pediatric low-grade glioma.

Photo: Samuel Blackman, co-founder and chief medical officer of Day One

The company priced an upsized underwritten public offering of 10 million shares of its common stock at $15.00 per share. The gross proceeds to Day One from the offering, before deducting underwriting discounts and commissions and other offering expenses, are expected to be $150.0 million. In addition, Day One has granted the underwriters a 30-day option to purchase up to an additional 1.5 million shares at the public offering price, less underwriting discounts and commissions.

Day One shares skyrocketed 109 percent to $13.82 after the company announced initial data in the ongoing showing an overall response rate (ORR) of 64 percent and clinical benefit rate (CBR) of 91 percent in the first 22 evaluable patients enrolled in the ongoing, open-label, single-arm, pivotal phase 2 FIREFLY-1 clinical trial. FIREFLY-1 is evaluating tovorafenib (DAY101) as once-weekly monotherapy in patients aged 6 months to 25 years with relapsed or progressive pediatric low-grade glioma (pLGG), which is the most common brain tumor diagnosed in children.

Pediatric low-grade glioma can impact a child’s health in many ways depending on tumor size and location, including vision loss and motor dysfunction. There are no approved therapies for pLGG, and current treatment approaches are associated with significant acute and life-long adverse effects. While most children with pLGG survive their cancer, children who do not achieve remission following surgery may face years of increasingly aggressive therapies that can have lasting effects on learning, cognition, and quality of life. Due to the indolent nature of pLGG, patients receive multiple years of systemic therapy.

Tovorafenib is an investigational, oral, brain-penetrant, highly-selective type II pan-RAF kinase inhibitor designed to target a key enzyme in the MAPK signaling pathway. Initial results from the FIREFLY-1 study in the heavily-pretreated population showed 14 partial responses (13 confirmed responses and 1 unconfirmed response), 6 patients with stable disease all of whom had tumor shrinkage ranging between 19 percent and 43 percent. The median-time-to-response was 2.8 months. Responses were observed in patients with both BRAF fusions and BRAF V600E mutations who received prior MAPK-targeted therapy. All patients who responded remain on therapy 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. Most adverse events (AEs) were grade 1 or 2 in nature; the most common (≥25 percent 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.

“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, 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.”

The company expects to initiate a pivotal phase 3 clinical trial of tovorafenib in front-line pediatric low-grade glioma (pLGG), with first patient dosed expected in the third quarter of 2022.

Day One plans to present additional interim trial results from FIREFLY-1 at an upcoming medical conference in the second half of 2022 and 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 in the first half of 2023.

Author: Rare Daily Staff