Dose-finding Study of GSK2636771 When Administered in Combination With Enzalutamide in Male Subjects With Metastatic Castration-Resistant Prostate Cancer

Study Summary

This Phase I, open-label, dose-finding, multicenter study is designed to determine the recommended Phase II dose (RP2D) for the combination of an orally administered Phosphatidylinositol-4,5-bisphosphate 3-kinase beta (PI3K-beta) inhibitor (GSK2636771) with enzalutamide. Subjects with phosphatase and tensin homolog (PTEN)-deficient metastatic castration-resistant prostate cancer (mCRPC) who are receiving a stable dose of enzalutamide with a recently demonstrated progression (either by RECIST \[Response Evaluation Criteria In Solid Tumors\] version 1.1, prostate-specific antigen \[PSA\] progression, and/or progression in bone) per the Prostate Cancer Working Group 2 (PCWG2) criteria will be enrolled. Eligible subjects will be enrolled in the Dose-Escalation Phase to determine the maximum tolerated dose (MTD) of the combination therapy using a modified 3+3 dose escalation procedure. The safety, pharmacokinetics (PK) and clinical efficacy will also be assessed to guide the selection of the RP2D. The starting dose will be GSK2636771 300 mg once daily in combination with the recommended dose (160 milligram \[mg\] once daily) of oral enzalutamide. Once the RP2D has been established, additional subjects will be enrolled in the Dose Expansion Phase to further evaluate the safety, PK and preliminary clinical activity. Safety assessments will be performed throughout the study including physical examinations, vital signs, clinical laboratory tests, 12 lead electrocardiograms and monitoring of adverse events. Blood samples will be collected for pharmacokinetic analysis. Subjects will continue treatment until an unacceptable toxicity, disease progression, withdrawal of consent or death occurs. A post-treatment follow-up visit will be performed within 30 days of the last dose of study treatment. Xtandi is a registered trademark of Astellas Pharma Inc

Primary Outcome

An adverse event (AE) is any untoward medical occurrence in a participant or clinical investigation participants, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An SAE is any untoward medical occurrence that, at any dose: results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, is a congenital anomaly/birth defect, protocol-specific SAEs: A

Interventions

• DRUG Enzalutamide
• DRUG GSK2636771