FIREFLY-1: A phase 2 study of the pan-RAF inhibitor DAY101 in pediatric patients with low-grade glioma.

Abstract

TPS10056 Background: The mitogen-activated protein kinase (MAPK) signaling pathway is an essential pathway that regulates key cell functions such as growth, survival, and differentiation. Genomic alterations and dysregulation of the MAPK pathway including BRAF fusions, point mutations (e.g. BRAF V600) and in-frame deletions have been described in many different types of malignancies, including pediatric low-grade glioma (pLGG) and other pediatric cancers. The identification of the KIAA1549:BRAF fusion in 2008 led to deeper understanding of the genomic events driving growth of pLGG (Jones, Cancer Res 2008). Despite the low-grade histology and excellent long-term survival, pLGGs are often associated with tumor- and treatment-associated morbidity and significant late-effects that persist throughout the lifespan of the patient. DAY101 is an oral, highly selective, CNS-penetrant small-molecule, Type II pan-RAF kinase inhibitor that is being developed for patients with pLGG harboring an activating BRAF-alteration. DAY101 has demonstrated tumor inhibition in preclinical models and has achieved clinically meaningful and durable responses in 7/8 patients with RAF-altered LGG in a pediatric phase 1 trial, including 2 complete responses, 3 partial responses, 2 stable disease and 1 progressive disease with a median time to response of 10.5 weeks. Patients have been treated for up to two years with no discontinuations due to toxicity or disease progression (Wright, SNO 2020). Methods: FIREFLY-1 is an open-label, multi-center, international Phase 2 study with DAY101 in pediatric and young adult patients between the ages of 6 months and 25 years with LGG harboring a documented BRAF-alteration as determined by local laboratory testing. DAY101 is administered orally once a week on a continuous 28-day schedule. Patients who respond will be treated for a minimum of two years after which they may at any point, opt to enter a “drug holiday” discontinuation period. Dosing is based on body surface area. DAY101 is available in a pediatric-friendly oral liquid formulation and tablets. The primary endpoint is objective response rate based on Response Assessment for Neuro-Oncology (RANO) as determined by an independent review committee. Secondary endpoints include objective response rate based on Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group criteria, duration of response and safety. Exploratory endpoints include quality-of-life measurements as well as functional outcomes. Molecular abnormalities will be characterized through the analysis of archival tissue. Enrollment began in February 2021 and is ongoing. Clinical trial information: NCT03429804.