A Phase 1b/2 Study of the Oral CDK4/6 Inhibitor LEE011 in Combination with Docetaxel plus Prednisone in Metastatic Castration Resistant Prostate Cancer

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Investigator: Rahul R. Aggarwal, MD

Location(s): United States

Description

This is a Phase Ib/II open label clinical trial in patients with metastatic castration resistant prostate cancer. The objective of the phase Ib portion of the study is to establish the maximum tolerated dose (MTD) and dose limiting toxicities (DLT) of docetaxel (75 mg/m2 IV q21 days) and prednisone (5mg orally BID) in combination with ribociclib in escalating oral daily doses in patients with metastatic CRPC with prior resistance to abiraterone and/or enzalutamide who have not undergone prior chemotherapy for metastatic disease. Up to three cohorts will be enrolled to determine the MTD and DLT profile of this combination during Phase 1b. Dose escalation will follow the standard 3+3 design. The dosing schedule is being chosen to allow patients to be exposed to the most efficacious dosing schedule of docetaxel (75 mg/m2 every 3 weeks). If there is excess toxicity observed with the treatment combination at the first dose level (dose level I), an alternative dosing schema may be pursued with weekly docetaxel treatment (35 mg/m2 weekly), which has demonstrated activity in mCRPC and decreased risk of cytopenias compared with every 3 week dosing schedule.

The Phase II portion (N = 29) of the study is a single arm, two stage, open-label study of ribociclib (dosed at the RP2D) in combination with docetaxel and prednisone to determine the efficacy and further define the safety of the treatment combination. Patients will be treated with the combination of ribociclib plus docetaxel + prednisone for up to 9 cycles. If there is no evidence of radiographic or clinical disease progression after 9 cycles of protocol therapy, patients may continue on single agent maintenance ribociclib until the time of disease progression. Patients will have the option of starting maintenance ribociclib after 6 cycles of docetaxel if stable disease or better on re-staging scans. The dose of ribociclib used during maintenance will be the same dose as that immediately preceding cessation of docetaxel treatment.