Our Science

RLY-2608 is designed to be the first allosteric, pan-mutant (including Kinase mutations like H1047X and non-Kinase mutations like E542X and E545X) and isoform-selective PI3Kα inhibitor.

PI3Kα is the central regulator of a signaling pathway that has been linked to a diverse group of cellular functions related to cancer including cell growth, proliferation and survival. Data collected as a part of large sequencing efforts identifies PI3Kα as the most frequently mutated kinase in cancer.

Traditionally, the development of PI3Kα inhibitors has focused on the active, or orthosteric, site. The therapeutic index of orthosteric inhibitors is limited by the lack of clinically meaningful selectivity for mutant versus WT PI3Kα and off-isoform activity. Toxicity related to inhibition of WT PI3Kα and other PI3K isoforms results in sub-optimal inhibition of mutant PI3Kα with reductions in dose intensity and frequent discontinuation. RLY-2608 is designed to overcome these limitations.

We solved the full-length cryo-EM structure of PI3Kα, performed computational long time-scale molecular dynamic simulations to elucidate conformational differences between WT and mutant PI3Kα, and leveraged these insights to support the design of RLY-2608.

The first-in-human ReDiscover trial for RLY-2608 evaluates the safety and efficacy of RLY-2608 in combination with fulvestrant and a CDK inhibitor in patients with HR+, HER2-, PI3Kα-mutated advanced breast cancer.

In mid-2025, we initiated the Phase 3 ReDiscover-2 trial, which evaluates the safety and efficacy of RLY-2608 plus fulvestrant in PI3Kα-mutated, HR+/HER2- advanced breast cancer patients previously treated with a CDK4/6 inhibitor in either the adjuvant or metastatic setting.