Relay Therapeutics Shares Plunge After Initial Data From Potential Breast Cancer Treatment - Relay Therapeutics (NASDAQ:RLAY)

Relay Therapeutics Inc RLAY announced initial clinical data for RLY-2608, an investigational allosteric, pan-mutant, and isoform-selective inhibitor of PI3Kα.
RLY-2608 is currently being evaluated in an ongoing dose-escalation portion of ReDiscover Phase 1 trial across two arms.
The first-in-human trial evaluates the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity.
The monotherapy arm started in December 2021 and enrolled 19 patients with unresectable or metastatic solid tumors with a PI3Kα mutation.
Also Read: Relay Therapeutics' Stock Price Premium Vs. Peers Is Justified By Its Platform Technology, Analyst Says.
The RLY-2608 + fulvestrant combination arm started in April 2022 and enrolled 23 patients with PI3Kα-mutant, HR+, and HER2– locally advanced or metastatic breast cancer.
Multiple doses achieved sustained target exposure of ~80%+ mutant PI3Kα inhibition.
A patient with metastatic HR+/HER2- breast cancer, with two PI3Kα mutations, who progressed following 12 lines of prior therapy, received RLY-2608 400mg BID monotherapy.
An unconfirmed partial response was recorded at eight weeks. After the data cut-off, the partial response was confirmed, and the patient remains on treatment with no AEs reported as of April 4, 2023.
Early anti-tumor activity was seen across various doses and helical, kinase, and other mutations, demonstrating selective target engagement of mutant PI3Kα.
Nine of the 16 breast cancer patients with measurable disease experienced radiographic tumor reductions. Twelve exhibited a best overall response of stable disease and one partial response.
Relay Therapeutics anticipates initiating dose expansion cohorts (part 2) in 1H of 2023.
Price Action: RLAY shares are down 34.10% at $12 on the last check Tuesday.

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Why Relay Therapeutics Stock Is Plunging Today