Relay Therapeutics has received Breakthrough Therapy designation from the U.S. Food and Drug Administration for its investigational drug zovegalisib in combination with fulvestrant for certain patients with advanced breast cancer, a move intended to accelerate development of the targeted treatment.
The designation applies to adults with PIK3CA-mutant, hormone receptor–positive, HER2-negative locally advanced or metastatic breast cancer whose disease has recurred or progressed following treatment with CDK4/6 inhibitors. This group represents a significant portion of patients with advanced breast cancer and currently faces limited treatment options after standard therapies stop working.
According to Relay Therapeutics, roughly 40% of patients with this form of breast cancer carry PIK3CA mutations, a genetic alteration associated with tumor growth and resistance to therapy. The company said most of these patients eventually experience disease progression after receiving CDK4/6 inhibitor therapy, highlighting the need for new targeted approaches.
The FDA’s Breakthrough Therapy designation is reserved for treatments addressing serious or life-threatening conditions where early clinical evidence suggests substantial improvement over existing therapies. The status provides more frequent interactions with regulators, senior FDA guidance, and eligibility for features of the Fast Track program, potentially shortening development and review timelines.
The decision was supported by early clinical findings from the Phase 1/2 ReDiscover trial evaluating zovegalisib combined with fulvestrant, with or without CDK inhibitors. The study assessed safety, tolerability, pharmacokinetics and preliminary antitumor activity across multiple PIK3CA mutation types.
Data presented in 2025 showed encouraging activity in patients treated with a 600 mg twice-daily fasted dose. Additional subgroup analyses were later shared at the San Antonio Breast Cancer Symposium the same year. A second dosing regimen — 400 mg twice daily with food — is currently being used in the ongoing Phase 3 ReDiscover-2 trial, and results from that cohort are expected to be presented at the ESMO Targeted Anticancer Congress in March 2026.
Relay Therapeutics said the designation validates the potential of zovegalisib to improve outcomes in a population with few effective post-progression therapies. The company plans to continue working closely with the FDA to advance late-stage development.
The announcement underscores continued industry investment in precision oncology, where therapies are designed to target specific genetic mutations driving cancer growth rather than treating tumors broadly.