Pharmacokinetic study of capivasertib and the CYP3A4 substrate midazolam in patients with advanced solid tumors.

ABSTRACT

PURPOSE: Capivasertib, a potent, selective inhibitor of all three AKT serine/threonine kinase (AKT) isoforms, is being evaluated in phase 3 trials in advanced breast and prostate cancer. This study evaluated the drug-drug interaction risk of capivasertib with the cytochrome P450 3A substrate midazolam in previously treated adults with advanced solid tumors. METHODS: Patients received oral capivasertib 400 mg twice daily (BID) on an intermittent schedule (4 days on/3 days off) starting on day 2 of cycle 1 (29 days) and on day 1 of each 28-day cycle thereafter. In cycle 1 only, patients received oral midazolam (1 mg) on day 1 (alone), and days 8 and 12 (3rd day off and 4th day on capivasertib, respectively). Midazolam pharmacokinetics on days 8 and 12 were analyzed versus day 1. Capivasertib, with or without standard-of-care treatment, was continued in patients deemed likely to benefit. Safety and exploratory efficacy analyses were conducted. RESULTS: Capivasertib-midazolam coadministration increased midazolam exposure (n = 21) geometric mean ratio (90% confidence interval) AUCinf and Cmax was 1.13 (0.97-1.32) and 1.15 (0.99-1.33) for day 8 versus day 1, and 1.75 (1.50-2.05) and 1.25 (1.08-1.46) for day 12 versus day 1. The capivasertib safety profile was manageable when administered with or without midazolam. Two patients had partial responses to treatment. CONCLUSION: The up to 1.75-fold increase in midazolam exposure indicates capivasertib is a weak CYP3A inhibitor at 400 mg BID on an intermittent schedule. Capivasertib was well tolerated; exploratory efficacy analysis demonstrated evidence of clinical activity in this heavily pre-treated population. CLINICALTRIALS gov NCT04958226.