Relay Therapeutics jumps 7% on FDA Breakthrough Therapy designation for breast cancer drug
Zovegalisib targets 40% of HR+/HER2- patients with PIK3CA mutations in underserved post-CDK4/6 market
Relay Therapeutics shares surged 7% on Tuesday after the U.S. Food and Drug Administration granted Breakthrough Therapy designation to its experimental breast cancer treatment, marking a significant milestone for the Cambridge-based biotechnology company.
The stock rose to $8.72, giving Relay Therapeutics a market capitalization of $1.33 billion, as investors responded to the regulatory endorsement for zovegalisib in combination with fulvestrant. The therapy targets approximately 40% of patients with HR+/HER2- advanced breast cancer who harbor PIK3CA mutations, a population that has experienced disease recurrence or progression after treatment with CDK4/6 inhibitors.
The Breakthrough Therapy designation, which accelerates development and regulatory review for serious conditions, was based on clinical data from the Phase 1/2 ReDiscover trial. The application included data across all PIK3CA mutations for two doses with comparable exposures: 600mg twice daily fasted and 400mg twice daily fed—the latter being the dose currently used in the ongoing Phase 3 ReDiscover-2 trial.
Relay Therapeutics estimates that zovegalisib, if approved, could address approximately 140,000 patients with HR+, HER2- breast cancer with a PI3Kα mutation per year in the United States. This represents a substantial commercial opportunity in a market where the global PI3K/AKT/mTOR pathway inhibitor segment for breast cancer is projected to grow from $2.5 billion in 2025 to $8 billion by 2033.
"This Breakthrough Therapy designation underscores the FDA's recognition of the potential of zovegalisib in combination with fulvestrant to meaningfully improve outcomes for these patients," said Don Bergstrom, M.D., Ph.D., President of Research and Development at Relay Therapeutics, in the company announcement. "Reinforcing the impact of the encouraging clinical evidence we have demonstrated to date."
The stock's advance extends Relay Therapeutics' strong performance, with shares now trading well above their 50-day moving average of $7.85 and 200-day moving average of $5.09. The stock has gained substantially from its 52-week low of $1.78, though it remains below its recent peak of $9.04.
Analysts remain broadly optimistic about the company's prospects. The consensus analyst target price stands at $14.55, representing approximately 67% upside potential from current levels, according to market data. Of 12 analysts covering the stock, 11 rate it as a buy or strong buy, with only one holding a neutral recommendation.
Relay Therapeutics faces competition in the PI3K inhibitor space from established and emerging players. Novartis's alpelisib, marketed as Piqray, was approved in May 2019 for HR+/HER2- PIK3CA-mutated advanced breast cancer and currently leads the market. More recently, Roche's inavolisib, branded as Itovebi, received FDA approval in November 2024 for advanced breast cancer, with Roche projecting peak sales potential of $2.3 billion.
Celcuity's gedatolisib, a pan-PI3K/mTOR inhibitor, is also advancing through the regulatory process, with its New Drug Application accepted for priority review by the FDA in January 2026 and a target action date of July 17, 2026. The company expects to release Phase 3 data for PIK3CA-mutant cancer in the first half of 2026.
Relay Therapeutics is pursuing a differentiated approach with zovegalisib as a mutant-selective PI3Kα inhibitor, which the company believes may offer a superior safety and efficacy profile compared to broader PI3K inhibitors. The company's platform leverages an advanced protein motion technology to target allosteric sites, aiming to develop innovative therapeutics for patients with specific genetic mutations.
Investors will be watching for several upcoming catalysts. Initial Phase 1/2 data of zovegalisib plus fulvestrant at the 400mg BID fed dose in CDK4/6-experienced patients are scheduled to be presented at the ESMO Targeted Anticancer Therapies Congress on March 16, 2026. Topline Phase 3 ReDiscover-2 data are expected in mid-2026, which could serve as a pivotal driver for the stock if positive.
The broader breast cancer therapeutics market is estimated at $35.23 billion in 2026, growing from $32.90 billion in 2025, according to market research. The overall breast cancer drugs market size is expected to reach $45.35 billion in 2026, with a compound annual growth rate of 6.8%.
Relay Therapeutics, which went public in July 2020, focuses on precision medicine in oncology and other areas with significant unmet medical needs. The company reported revenue of $8.4 million over the trailing twelve months, with an operating margin of negative 38.9%. Despite the lack of profitability, investors have been willing to support the company given its promising pipeline and the large commercial opportunity represented by its lead program.