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Evexta Bio Advancing Rupitasertib, Orserdu Combo to Phase II ESR1-Mutant Breast Cancer Trial

NEW YORK – Evexta Bio expects to begin a Phase II trial of its lead therapeutic candidate rupitasertib plus Menarini Group's selective estrogen receptor degrader Orserdu (elacestrant) in patients with estrogen receptor (ER)-positive, HER2-negative advanced breast cancer harboring an ESR1 mutation.

The firm on Monday said it met with the US Food and Drug Administration last month to get input on the development plan for rupitasertib, an S6K and AKT1/AKT3 inhibitor designed to block the PI3K/AKT/mTOR pathway and control the AKT feedback loop. In the Phase II trial slated to begin in Q4 2024, Evexta will enroll breast cancer patients who have progressed on or after a CDK4/6 inhibitor.

This is a group that typically has few treatment options due to acquired resistance mutations, Evexta CSO Dominique Bridon said in a statement. "In addition, S6K has been shown to be closely associated with the emergence of cancer resistance, particularly in breast cancer, through ER modulation," Bridon continued. "Rupitasertib, which inhibits S6K while controlling the AKT compensatory feedback loop, could be a major advance to better treat these patients who are in need of alternative therapies."

In a Phase I trial of rupitasertib, which reported out last year, the firm explored the drug as a monotherapy on both ESR1-mutant and wild-type patients. Researchers found the ESR1-mutant group had longer median progression-free survival on rupitasertib, 5.6 months versus the 2.6 months median progression-free survival seen in the wild-type group.

Evexta, based in Paris, is conducting preclinical research on rupitasertib in combination with other agents, including with a CDK4/6 inhibitor in ER-positive, HER2-negative breast cancer and with Genentech's Herceptin (trastuzumab) in HER2-positive breast cancer. The firm is also testing the drug's activity in glioblastoma and gastric cancer in preclinical studies.