Mutant - Selective PI3Kα Inhibitor

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Relay Therapeutics Announces Updated Data for RLY-2608 + Fulvestrant Further Demonstrating Clinically Meaningful Progression Free Survival at ASCO 2025
Globenewswire· 2025-06-02 11:00
Core Insights - Relay Therapeutics announced updated interim clinical data for RLY-2608, showing a median progression-free survival (PFS) of 11.0 months in second-line patients with PI3Kα-mutated, HR+/HER2- metastatic breast cancer [1][2] - The company plans to initiate a pivotal Phase 3 trial, ReDiscover-2, in mid-2025 [2][16] - RLY-2608 is the first known allosteric, pan-mutant, and isoform-selective inhibitor of PI3Kα, designed to improve tolerability and efficacy compared to standard treatments [11][12] Clinical Data Summary - The updated data indicate a median PFS of 10.3 months overall and 11.0 months for second-line patients, with a clinical benefit rate of 67% [7][8] - Among 64 patients receiving the recommended Phase 3 dose (RP3D) of 600mg BID, 44% had received two or more prior lines of therapy [5][8] - The study enrolled 118 patients with PI3Kα-mutated, HR+, HER2- locally advanced or metastatic breast cancer [4][8] Safety and Tolerability - RLY-2608 + fulvestrant was generally well tolerated, with low-grade treatment-related adverse events (TRAEs) being manageable and reversible [8][15] - Only 36% of patients experienced a Grade 3 TRAE, with no Grade 4-5 TRAEs reported [15] Future Directions - The company is progressing two front-line triplet regimens, one with atirmociclib and another with ribociclib, both currently in dose escalation [9][16] - Continued enrollment in the Phase 1/2 ReInspire study for vascular malformations is also planned [16]