Relay Therapeutics disclosed that its lead PI3Kα inhibitor, zovegalisib (RLY‑2608), achieved a median progression‑free survival of 11.1 months in heavily pre‑treated, PI3Kα‑mutated, HR+/HER2‑ metastatic breast cancer patients. The data were presented at the European Society for Medical Oncology Targeted Anticancer Therapies Congress in Paris and represent the first published efficacy signal for the drug’s Phase 3‑ready 400 mg twice‑daily dose taken with food.
The median PFS was consistent across mutation subgroups, with 11.2 months for kinase‑domain mutations and 11.0 months for non‑kinase mutations. Safety mirrored the 600 mg fasted‑dose profile, with only low‑grade, reversible treatment‑related adverse events reported in the 60 patients treated to date. The results reinforce Relay’s strategy of advancing a single, allosteric, pan‑mutant PI3Kα inhibitor that may offer a differentiated safety and efficacy profile compared to existing PI3Kα inhibitors.
Relay’s Q4 2025 financial results, released on February 26 2026, showed revenue of $7.0 million and a net loss of $54.9 million, while cash and investments stood at $554.5 million as of December 31 2025. The liquidity is projected to support operations through 2029, providing a solid financial foundation for the ongoing Phase 3 ReDiscover‑2 trial.
Dr. Don Bergstrom, President of R&D, said, "As supported by the data presented, the 400mg BID fed regimen maintains robust efficacy with a safety profile consistent with mutant‑selective PI3Kα inhibition." He added, "These results further support our decision to advance this regimen into the ongoing Phase 3 ReDiscover‑2 trial and reinforce our confidence in selectively targeting PI3Kα mutations as a potentially differentiated approach for CDK4/6‑experienced patients."
Analysts have responded positively to the data, noting the breakthrough therapy designation and the promising median PFS. While some analysts remain cautious about valuation multiples, the consensus view highlights the potential for a differentiated product in a sizable unmet‑needs market of approximately 140,000 U.S. patients with HR+/HER2‑ metastatic breast cancer and a PI3Kα mutation.
The data position zovegalisib as a strong contender in the PI3K inhibitor space, competing directly with alpelisib and capivasertib. The Phase 3 ReDiscover‑2 trial, which compares zovegalisib plus fulvestrant to capivasertib plus fulvestrant, will be critical in determining whether the drug can achieve regulatory approval and commercial launch in the near future.
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