Sermonix announces initiation of Phase 3 ELAINE-3 study of lasofoxifene

Sermonix Pharmaceuticals and Guardant Health (GH) announced the initiation of a registrational Phase 3 clinical study comparing targeted lasofoxifene, which Sermonix licensed globally from Ligan (LGND) in combination with the CDK 4/6 inhibitor abemaciclib versus fulvestrant plus abemaciclib in pre- and post-menopausal subjects with locally advanced or metastatic ER+/HER2- breast cancer with an ESR1 mutation. This global randomized study will enroll 400 subjects with locally advanced or metastatic ER+/HER2- breast cancer with an ESR1 mutation, who have progressed on palbociclib or ribociclib plus an aromatase inhibitor and up to one line of chemotherapy. Subjects will be randomized 1:1 to receive either lasofoxifene or fulvestrant, and both groups will also receive 150 mg of abemaciclib twice daily. Study subjects will be prospectively screened for an ESR1 mutation using the Guardant360 CDx liquid biopsy, a next generation sequencing-based test that detects genomic alterations using circulating tumor DNA from blood. Eli Lilly and Company – which provided abemaciclib for the ELAINE-2 study – has entered into a new clinical trial collaboration and drug supply agreement with Sermonix and will provide abemaciclib for the ELAINE-3 study. The primary efficacy endpoint is progression-free survival. Key secondary endpoints include overall response rate and overall survival. Additional secondary endpoints to be assessed include clinical benefit rate, duration of response, time to disease recurrence, time to chemotherapy, quality of life, patient reported outcomes on vaginal and sexual health, and safety. Sermonix anticipates dosing the first subject in the first half of 2023.