Relay Therapeutics (RLAY) Status update summary

Clinical Efficacy and Patient Outcomes

• Zovegalisib achieved a 60–65% volumetric response rate across all doses in vascular anomalies, with 100% at 300 mg BID and 29–43% at 100 mg BID, outperforming standard of care.

• 95% of patients experienced lesion reduction, with responses seen in both PROS and LM subtypes and across a spectrum of PIK3CA mutations.

• Symptomatic improvement was observed in 89% of patients at week 12, with 79% reporting benefit and deepening responses over time.

• Four patients with 24-week scans showed sustained and deepening lesion reduction.

• Efficacy and safety were consistent across mutation types, prior treatments, and lesion sizes.

Safety and Tolerability Profile

• No patients discontinued due to adverse events; dose reductions occurred in 23% at 100 mg and 300 mg BID.

• Only 9–15% experienced Grade 3+ treatment-related adverse events, with low rates of hyperglycemia, diarrhea, rash, or stomatitis.

• Most adverse events were mild to moderate, reversible, and did not require prophylactic treatment.

• No Grade 3 hyperglycemia, diarrhea, rash, or stomatitis observed; all patients remain on therapy.

• 400 mg BID dose was deprioritized due to less optimal safety; 300 mg BID chosen for expansion.

Market Opportunity and Strategic Positioning

• Zovegalisib targets three major indications: 2L breast cancer ($2–3B TAM), 1L breast cancer ($7–8B TAM), and vascular anomalies ($6–8B TAM), representing significant commercial potential.

• The U.S. addressable market for vascular anomalies is estimated at 25,000 patients.

• The mutant-selective approach is positioned to unlock greater market penetration and chronic use.

• Early commercial focus will be on underdiagnosed adults and pediatric populations, aiming for chronic, lifelong therapy.

• $642 million in cash provides runway into 2029, supporting multiple data catalysts and potential commercial launches.