Successful Phase I trial of BLU 285 for gastrointestinal stromal tumors is basis for initiating Phase III trial in 2018.- BluePrint Medicines

Blueprint Medicines Corporation announced new Phase 1 clinical data and outlined registration plans for BLU 285, a potent and highly selective PDGFR alpha and KIT inhibitor in development as a potential treatment for patients with advanced gastrointestinal stromal tumors (GIST). In patients with PDGFR alpha-driven GIST harboring a D842 mutation, the data showed an objective response rate (ORR) of 60 percent and an estimated 9-month progression free survival (PFS) of 87 percent. Among patients with treatment-resistant KIT-driven GIST, tumor reduction was observed in eight of 14 evaluable patients treated at dose levels of at least 300 mg once daily (QD). BLU-285 was well tolerated, and most adverse events (AEs) reported by investigators were Grade 1 or 2.

Based on feedback from the FDA at a recent End-of-Phase 1 meeting, additional data from the expansion portion of the ongoing Phase 1 clinical trial of BLU 285 may be sufficient to support a New Drug Application (NDA) for the treatment of patients with PDGFR alpha D842V-driven GIST. Blueprint Medicines currently estimates it will complete enrollment of the PDGFR alpha D842V expansion cohort, which is expected to include approximately 50 patients, by the middle of 2018. The Company also plans to initiate a global, pivotal Phase III clinical trial of BLU 285 in the first half of 2018, with the goal of supporting the registration of BLU 285 in a broader GIST patient population.

Comment: The FDA indicated that approval of BLU 285 for the treatment of what is a small group of patients with PDGFR alpha D842V mutation � about 500 people in the US, Japan and top 5 EU markets � is possible without initiating an additional trial. Blueprint is also considering a larger market and has near-term plans for a Phase III study in KIT-driven GIST.