Relay Therapeutics Announces Positive Interim Data for RLY-2608 Demonstrating Clinically Meaningful Progression Free Survival

9.2-month median PFS in heavily pre-treated patients with PI3Kα-mutated, HR+/HER2- metastatic breast cancer at RP2D

33% ORR across all patients & 53% ORR in patients with kinase mutations at RP2D

Favorable overall tolerability profile; at RP2D, only 2 patients discontinued treatment due to adverse events & only 1 patient experienced Grade 3 hyperglycemia

Data support planned initiation of 2L pivotal study in 2025

Triplet combination with ribociclib expected to move into dose expansion in 1H 2025 & triplet combination with atirmociclib (CDK4) remains on track to start before year-end

Excerpt from the Press Release:

CAMBRIDGE, Mass., Sept. 09, 2024 (GLOBE NEWSWIRE) — Relay Therapeutics, Inc. (Nasdaq: RLAY), a clinical-stage precision medicine company transforming the drug discovery process by combining leading-edge computational and experimental technologies, today announced positive interim data for RLY-2608, the first known investigational allosteric, pan-mutant and isoform-selective inhibitor of PI3Kα. The data showed that despite heavy pre-treatment, patients with PI3Kα-mutated, HR+, HER2- locally advanced or metastatic breast cancer who received RLY-2608 600mg BID + fulvestrant demonstrated clinically meaningful progression free survival (PFS).

“These interim data suggest that by selectively targeting mutant PI3Kα, RLY-2608 has the potential to offer a level of benefit to patients that has not previously been possible with existing non-selective medicines, while also having significantly less toxicity,” said Don Bergstrom, M.D., Ph.D., President of R&D at Relay Therapeutics. “We are very encouraged to see that RLY-2608 + fulvestrant led to clinically meaningful progression free survival in heavily pre-treated patients with PI3Kα-mutated, HR+, HER2- metastatic breast cancer. We will move quickly to share these data with regulators and align on the design of a pivotal study, which we anticipate starting in 2025.”

ReDiscover – RLY-2608 First-in-Human Study

RLY-2608 is currently being evaluated in ReDiscover, an ongoing first-in-human study, which was designed to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics and preliminary antitumor activity of RLY-2608 alone, in combination with fulvestrant, and in combination with fulvestrant and ribociclib or atirmociclib (Pfizer’s selective CDK4 inhibitor). As of the August 12, 2024 interim data cut-off, the RLY-2608 + fulvestrant arm of the study had enrolled 118 patients with PI3Kα-mutated, HR+, HER2- locally advanced or metastatic breast cancer across all doses in both the dose escalation and dose expansion portions of the study, including 64 patients at the company’s recommended Phase 2 dose (RP2D) of 600mg BID (17 in dose escalation and 47 in dose expansion).

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