Celcuity Inc. announced that it plans to initiate a Phase 3 clinical trial to evaluate gedatolisib plus a CDK4/6 inhibitor and fulvestrant as first-line treatment for patients with HR+/HER2- advanced breast cancer who are endocrine therapy resistant. In conjunction with its plan to conduct this study, Celcuity entered into an amendment to an existing debt facility agreement and received an additional term loan of approximately $62 million. The Phase 3 VIKTORIA-2 clinical trial will be an open-label, randomized study to evaluate the efficacy and safety of gedatolisib combined with fulvestrant plus a CDK4/6 inhibitor in comparison to fulvestrant plus a CDK4/6 inhibitor as first-line treatment for patients with HR+/HER2- ABC who are endocrine therapy resistant.

For the CDK4/6 inhibitor, investigators may choose either ribociclib or palbociclib. The safety profile of gedatolisib combined with fulvestrant and palbociclib is well described, but the investigational combination of gedatolisib with ribociclib has not yet been clinically tested. Therefore, a safety run-in of approximately 12-36 subjects will evaluate the safety profile of gedatolisib combined with ribociclib and fulvestrant.

The safety run-in will be completed, and gedatolisib?s Phase 3 dose confirmed, before enrolling patients in the Phase 3 portion of the study. For the Phase 3 study, approximately 638 subjects who meet the eligibility criteria will be assigned to a cohort based on their PIK3CA mutation status. After the investigator selects the CDK4/6 inhibitor for a subject, the subject will then be randomly assigned on a 1:1 basis to either Arm A (gedatolisib, fulvestrant, and Investigator?s choice of ribociclib or palbociclib) or Arm B (fulvestrant and Investigator?s choice of ribociclib or palbociclib).

The clinical trial primary endpoints are progression free survival, per RECIST 1.1 criteria, as assessed by blinded independent central review. The primary PFS endpoints will be evaluated separately in subjects who are PI3KCA wild type and PI3KCA mutant. The study?s design was reviewed and discussed with the U.S. Food and Drug Administration during a Type C meeting.

This global trial is expected to enroll subjects at up to 200 clinical sites across North America, Europe, Latin America, and Asia. Celcuity expects to enroll the first patient in the second quarter of 2025.