06:47 AM EDT, 04/27/2026 (MT Newswires) -- Relay Therapeutics (RLAY) said Monday that it plans to advance its drug candidate zovegalisib in combination with Pfizer's (PFE) investigational CDK4 inhibitor atirmociclib into a Phase 3 trial for frontline treatment of HR+/HER2- metastatic breast cancer with PI3Ka mutations.

The move follows early-stage data showing a 44% objective response rate in heavily pre-treated patients, with most participants experiencing tumor reduction, Relay said. The combination, administered alongside endocrine therapy, also showed manageable safety, with limited discontinuations and no reported febrile neutropenia, it added.

The company said that the planned randomized Phase 3 study will compare the triplet regimen against standard CDK4/6 inhibitor-based therapy, with progression-free survival as the primary endpoint.

Pfizer will supply atirmociclib and palbociclib for the trial, while Relay will sponsor and fund the study, targeting a potential start in early 2027, it added.