Relay Therapeutics reported Phase 2 efficacy for zovegalisib (RLY-2608) in patients with PIK3CA-driven vascular anomalies, posting a 60% volumetric response. The signal exceeded expectations and extends the drug’s development beyond breast cancer into a second indication group. The PI3Kα inhibitor is described as isoform-selective, and the readout comes alongside Relay’s broader clinical strategy exploring combinations in PI3K-mutated, HR+/HER2- advanced breast cancer. Analysts had pointed to vascular anomalies as a meaningful commercial opportunity. For Relay and the class, the updated Phase 2 data provide a practical evidence point that PI3Kα inhibition can translate into measurable lesion shrinkage in a genetically defined rare disease setting.