Relay Therapeutics, Inc. (NASDAQ: RLAY) has recently announced the data from the phase 1/2 rediscover trial of zovegalisib (rly-2608) + fulvestrant at the recommended phase 3 dose of 400mg twice daily (bid) taken with food in patients with pi3kα-mutated, HR+/HER2* metastatic breast cancer. The company revealed that as of the January 13, 2026, data cut-off date, 60 patients had received the 400mg bid fed regimen, with the efficacy population consisting of 57 patients who did not have a PTEN or AKT co-mutation, as planned. Among the 57 efficacy-evaluable patients at the 400mg bid fed dose, the median progression-free survival (PFS) was reported to be 11.1 months.
Furthermore, the pharmacokinetic analyses demonstrated that the 400mg bid fed regimen achieved exposures comparable to the previously evaluated 600mg bid fasted dose, with mean concentrations approaching IC90 in the majority of patients and nearly all patients maintaining exposure above the IC80 throughout the dosing interval. The efficacy of the 400mg bid fed dose was consistent with the 600mg bid fasted dose, with a median PFS of 11.1 months. Notably, among the 35 patients with measurable disease, the confirmed objective response rate (ORR) was 43%, and in second-line only patients, the ORR was 52%.
The safety and tolerability profile of zovegalisib + fulvestrant at the 400mg bid fed dose was reported to be generally well-tolerated in the 60 treated patients as of the January 13, 2026, data cut-off. In terms of safety, the majority of hyperglycemia events were grade 1, with no grade 4-5 hyperglycemia observed. Only four patients discontinued due to treatment-related adverse events.
Relay Therapeutics also provided an update on the ongoing phase 3 trial, rediscover-2, which is evaluating zovegalisib 400mg bid administered in combination with fulvestrant versus capivasertib + fulvestrant in patients with pi3kα-mutated, HR+/HER2* advanced breast cancer who have progressed on prior CDK4/6 inhibitor therapy. This trial, which initiated in mid-2025, is enrolling globally and has received FDA breakthrough therapy designation.
Zovegalisib, the lead program in Relay Therapeutics' efforts to discover and develop mutant-selective inhibitors of pi3kα, has the potential to address a significant portion of the patient population with HR+/HER2* breast cancer with a pi3kα mutation and those with vascular anomalies driven by a pi3kα mutation in the United States.
The company's efforts to advance the phase 3 dose of zovegalisib + fulvestrant into the ongoing phase 3 rediscover-2 trial are bolstered by the robust efficacy and safety profile demonstrated in the phase 1/2 rediscover trial, providing confidence in selectively targeting pi3kα mutations as a potentially differentiated approach for CDK4/6-experienced patients. Today the company's shares have moved -3.67% to a price of $7.35. Check out the company's full 8-K submission here.
