Relay Therapeutics (NASDAQ:RLAY) announced clinical data from its Phase 1/2 ReDiscover trial on Monday, providing a significant update on the efficacy and safety of zovegalisib (formerly RLY-2608).
The study focused on patients with PI3Kα-mutated, HR+/HER2- metastatic breast cancer (mBC), a population where existing treatments are often limited by significant toxicities.
The data, with a cut-off of January 13, 2026, evaluated 57 efficacy-evaluable patients receiving a 400mg twice-daily (BID) dose of zovegalisib administered with food, in combination with fulvestrant.
The results demonstrated a median progression-free survival (mPFS) of 11.1 months (95% CI: 7.3–13.0).
Among the 35 patients with measurable disease at baseline, the objective response rate (ORR) was 43%.
A critical component of this update involved the optimization of dosing.
Pharmacokinetic (PK) analysis confirmed that the 400mg fed dose achieved drug exposures comparable to the 600mg fasted dose used in earlier cohorts.
This transition to a "fed" dosing regimen is expected to improve patient compliance and convenience.
On the safety front, the combination was characterized primarily by low-grade treatment-related adverse events (TRAEs).
Notably, only four patients discontinued treatment due to adverse events, suggesting a superior tolerability profile compared to first-generation PI3K inhibitors, which are often hindered by high rates of hyperglycemia and rash.
Zovegalisib currently holds FDA Breakthrough Therapy designation, a status that accelerates the development and review of drugs intended to treat serious conditions.
Relay Therapeutics is already building on this momentum with the ongoing Phase 3 ReDiscover-2 trial, which aims to confirm these findings in a larger, randomized setting.
The company's Dynamo™ platform, which integrates experimental and computational approaches to understand protein motion, was instrumental in designing zovegalisib to selectively target the mutant form of PI3Kα while sparing the wild-type protein.