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Relay Therapeutics Advances Trials of PI3Kα, FGFR2 Inhibitors

NEW YORK – Relay Therapeutics on Tuesday said it began the first-in-human trial of its PI3Kα inhibitor, RLY-2608, and initiated the dose expansion cohorts in the Phase I trial of its FGFR2 inhibitor RLY-4008.

RLY-2608 is being studied in patients with advanced solid tumors that harbor a PIK3CA/PI3Kα mutation. The trial will have two arms: One will evaluate RLY-2608 as a single agent for patients with unresectable or metastatic solid tumors with PI3Kα mutations; and the second arm will explore RLY-2608 in combination with fulvestrant for patients with PI3Kα-mutant, hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer. The study will assess safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity.

The trial will have a dose escalation and dose expansion phase. In the single-agent dose expansion phase, researchers will evaluate RLY-2608 in certain biomarker-defined populations, including PI3Kα-mutated cell ovarian, head and neck, and cervical cancer, along with unresectable or metastatic solid tumors with PIK3CA double mutations defined as major.

The RLY-2608-fulvestrant arm expansion phase will include patients with PI3Kα-mutant, HR-positive, HER2-negative advanced or metastatic breast cancer who have not received prior PI3Kα inhibitor treatment and patients who are intolerant to PI3Kα inhibitors.

The Phase I expansion phase of RLY-4008 will also evaluate the drug in genetically defined patients with FGFR2-altered intrahepatic cholangiocarcinoma and solid tumors. The trial will enroll patients with intrahepatic cholangiocarcinoma with an FGFR2 fusion previously treated with a pan-FGFR inhibitor; intrahepatic cholangiocarcinoma with an FGFR2 fusion not previously treated with a pan-FGFR inhibitor; solid tumors with an FGFR2 fusion; unresectable solid tumors with focal FGFR2 amplification; and advanced, unresectable solid tumors with an oncogenic FGFR2 mutation.

In October, Relay raised $350 million in a public offering of common stock to help advance clinical development of its pipeline. Along with RLY-2806 and RLY-4008, the company is also developing a SHP2 inhibitor.