BOSTON — Sensei Biotherapeutics said it has dosed the first patient in a Phase 1b/2 clinical trial evaluating PIKTOR in patients with HR-positive, HER2-negative advanced breast cancer.
PIKTOR is an investigational all-oral combination of serabelisib and sapanisertib. The treatment is designed to inhibit multiple points in the PI3K/AKT/mTOR pathway, a signaling network involved in cancer growth and survival that is altered in about half of HR-positive, HER2-negative breast cancer cases.
Sensei said PIKTOR became its lead program after the company acquired Faeth Therapeutics in February 2026. The company described PIKTOR as a multi-node inhibitor intended to target escape routes in the pathway that may remain active when single-node inhibitors are used.
The trial, known as Study FTH-PIK-101, is a multicenter, dose-escalation Phase 1b/2 study evaluating sapanisertib and serabelisib in combination with fulvestrant and other anticancer therapies. The study is enrolling patients with HR-positive, HER2-negative advanced or metastatic breast cancer, regardless of mutational status.
Sensei said patients with this form of breast cancer have limited options after tumors stop responding to current therapies, especially when the cancer is driven by the PI3K/AKT/mTOR pathway. Existing drugs that target the pathway typically block one component, while PIKTOR is designed to block multiple nodes through PI3K-alpha and dual mTORC1/2 targeting.
The company said PIKTOR has previously been tested in cancer patients. In a completed investigator-initiated Phase 1b study, patients with advanced breast, endometrial and ovarian tumors who had failed an average of four prior treatments received PIKTOR plus paclitaxel. Sensei said the study showed a 47% overall response rate among 15 patients, with a 71% response rate among patients whose tumors carried PI3K pathway mutations. Three complete responses were reported, all in patients with endometrial cancer.
Sapanisertib in combination with fulvestrant has also shown activity in HR-positive, HER2-negative advanced breast cancer in an earlier Phase 2 study, according to the company.
“In our earlier trial, patients who had exhausted multiple lines of therapy, including chemotherapy, responded to the PIKTOR plus paclitaxel combination, and several had complete responses,” said Anand Parikh, Chief Operating Officer of Sensei Biotherapeutics. “PIK-101 now takes that same oral combination into breast cancer, where a large share of tumors carry the pathway alterations that PIKTOR is designed to target.”
Sensei is also conducting Study FTH-PIK-201, a multicenter, open-label, single-arm Phase 2 study of PIKTOR in patients with advanced endometrial cancer.
