Austin, Texas-based Faeth Therapeutics (Nasdaq: FTH) announced receipt of US FDA Fast Track Designation for sapanisertib and serabelisib (PIKTOR) in combination with paclitaxel for patients with advanced or recurrent endometrial cancer whose tumors harbor a PI3K/AKT/mTOR pathway alteration and who have previously received platinum-based chemotherapy and an immune checkpoint inhibitor (ICI). PIKTOR is an all-oral combination of serabelisib, a selective PI3K-alpha inhibitor, and sapanisertib, a dual mTORC1/mTORC2 inhibitor, designed to block multiple nodes of the PI3K/AKT/mTOR pathway simultaneously.
The designation applies to a population with limited post-ICI options and is supported by Phase 1b data from NCT03154294, in which PIKTOR plus paclitaxel produced an 80% overall response rate (ORR) in patients with advanced endometrioid endometrial cancer — comprising three complete responses and one partial response in five evaluable patients — and a median progression-free survival of 11 months against a historical chemotherapy benchmark of three to four months. No p-value was reported given the small sample size. Across the broader Phase 1b cohort of 15 response-evaluable patients with mixed solid tumors, the ORR was 47%, rising to 71% in patients with confirmed PI3K pathway mutations.
These data directly underpin the ongoing Phase II trial FTH-PIK-201 (GOG-3111), a multicenter, open-label, single-arm study of approximately 40 patients with second-line advanced endometrial cancer, which enrolled its first patient in March 2025. Fast Track status enables more frequent FDA interactions and rolling review, and Faeth has said it expects topline data from FTH-PIK-201 by year-end 2026.