Relay Therapeutics (RLAY) TD Cowen's 6th Annual Oncology Innovation Summit summary

Clinical data and trial updates

• RLY-2608, a selective PI3Kα inhibitor, demonstrated median PFS of 9.2 months overall and 11.4 months in second-line patients, with ORR of 39% and 67% in kinase-mutant subgroups, outperforming historical controls.

• Upcoming ASCO update will provide over 12 months of follow-up, focusing on durability and consistency of efficacy data in hormone-receptor positive, HER2-negative, PI3Kα-mutated breast cancer.

• Phase III ReDiscover II trial will enroll 540 patients, randomizing RLY-2608 vs. Capivasertib, targeting CDK4/6-experienced patients, including those progressing within 12 months of adjuvant CDK4/6 therapy.

• Hierarchical primary analysis will first assess kinase-domain mutations, then all PI3Kα mutations, aiming for broad label approval.

• Exclusion criteria include prior PI3K pathway inhibitor use; PTEN and AKT mutations are largely mutually exclusive with PI3Kα mutations.

Dosing strategy and combination studies

• Phase III will use a 400 mg BID fed dose of RLY-2608, shown to be equivalent to 600 mg fasted, simplifying dosing across indications.

• Triplet studies with ribociclib and abemaciclib are ongoing, with dose exploration addressing drug-drug interactions and combinability.

• Data from triplet combinations will be disclosed once robust packages are available; timelines are not yet specified.

• Additional dose-finding studies with next-generation endocrine therapies or aromatase inhibitors are under consideration.

Vascular malformations and market opportunity

• RLY-2608 is being studied in vascular malformations, primarily PROS and lymphatic malformations, with a US patient population of 170,000 for PIK3CA-driven disease and 5,000–15,000 in PROS.

• Vijoice (Alpelisib) holds accelerated approval for PROS but failed its confirmatory trial, leaving no agent with full approval in this setting.

• Initial RLY-2608 studies in PROS are open-label, with a potential for a future placebo-controlled arm if needed for full approval.