Relay Therapeutics’ combination for breast cancer shows efficacy and safetyPfizer

Relay Therapeutics (RLAY) announced plans to move zovegalisib + atirmociclib, Pfizer’s (PFE) investigational, potential first-in-class CDK4 inhibitor, into Phase 3 development for frontline patients with PI3Kalpha-mutated, HR+/HER2- metastatic breast cancer. Zovegalisib is currently being evaluated in ReDiscover, an ongoing first-in-human study designed to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics and preliminary antitumor activity of zovegalisib in combination with fulvestrant and CDK inhibitors in patients with PI3Kalpha-mutated, HR+/HER2- metastatic breast cancer. These data are from the zovegalisib + atirmociclib + fulvestrant dose finding portion of the study. Only 2 of 62 patients discontinued zovegalisib and 6 patients dose reduced zovegalisib due to treatment-related adverse events. Adverse events were consistent with those previously reported by each molecule. Grade 3 hyperglycemia was 0% despite 47% of patients being pre-diabetic. Overall grade 3+ TRAE rate in these median third-line patients is 40%. 34 patients had measurable disease to be evaluated for response: objective response rate was 44% and was also 44% in both kinase and non-kinase patients; 85% of patients experienced tumor reduction, 48 of 62 patients remain on study as of the data cut-off date. Data not yet mature enough to estimate median progression-free survival. Pfizer has agreed to supply atirmociclib for the experimental arm in combination with zovegalisib and the palbociclib portion of the control arm for use in the planned study. Relay Tx will sponsor, fully operationalize and fund the planned Phase 3 trial. Relay Tx retains full global rights for zovegalisib. Next steps include conducting regulatory interactions to finalize Phase 3 design and dose with the goal of initiating the study in early 2027 and continued execution of Phase 1/2 dose finding and expansion as part of the ReDiscover study.