A phase 1/2, open-label, randomized, dose-finding and dose expansion study of gedatolisib in combination with darolutamide in metastatic castration-resistant prostate cancer (mCRPC).

TPS5109 Background: Progression to metastatic castration-resistant prostate cancer (mCRPC) occurs in most patients treated with androgen receptor signaling inhibitors (ARSi) for advanced disease. Preclinical studies demonstrate that AR and PI3K - AKT - mTOR (PAM) pathways interact through reciprocal negative feedback, whereby inhibition of one pathway activates the other. Thus, combining a PAM inhibitor with an ARSi may deliver improved anti-cancer activity in patients with mCRPC. A Phase 2 trial in 129 patients with mCRPC who progressed on abiraterone demonstrated improved median radiographic progression-free survival (rPFS) when samotolisib, a dual PI3K-mTOR inhibitor, was added to enzalutamide. These results form the basis for this clinical trial of gedatolisib, a potent PAM inhibitor, in combination with darolutamide in men with mCRPC who have previously progressed on ARSi. Methods: This open-label, multicenter, Phase 1/2 study will evaluate the safety and efficacy of gedatolisib in combination with darolutamide in men with mCRPC who have progressed on ARSi. In Phase 1, 36 patients will be randomized to one of two dose arms to evaluate dose limiting toxicities (DLTs) and determine the recommended Phase 2 dose (RP2D). Gedatolisib will be administered once weekly for 3-weeks-on/1-week-off: Arm 1 – 120 mg and Arm 2 – 180 mg, with darolutamide 600 mg orally administered twice daily. Arm 2 may be dose de-escalated depending on the number of DLTs observed. In Phase 2, 12 additional patients will be enrolled at the RP2D (n= 30). Key inclusion criteria include adult males (≥ 18 years) with mCRPC who have progressed on or after treatment with one next-generation ARSi. Key exclusion criteria include males with adenocarcinoma with a small cell component and with ≥10% neuroendocrine type cells; prior treatment with PI3K, AKT, or mTOR inhibitor; prior chemotherapy or radiopharmaceutical therapy for mCRPC; uncontrolled type 1/2 diabetes; or active brain or leptomeningeal metastases. Primary endpoints for Phase 1 are safety and tolerability (incidence of DLTs, adverse events, and determination of maximum tolerated dose) determination of the recommended Phase 2 dose (RP2D), PK, and Bayesian Optimal Interval utility score. Primary endpoints for Phase 2 are rPFS rate at 6 months based on Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 with modifications as specified in Prostate Cancer Working Group 3 criteria. Secondary endpoints include rPFS rates at 9 and 12 months, overall rPFS, prostate-specific antigen response of ≥50% decrease from baseline at 4, 8, 12, and 16 weeks, overall response rate, duration of response, clinical benefit rate, overall survival rate at 18 and 24 months, and safety. The trial is currently open for enrollment (NCT06190899). Clinical trial information: NCT06190899 .