Coadministration of Apalutamide and Relugolix in Patients with Localized Prostate Cancer at High Risk for Metastases.

The Apa-RP study evaluates the combination of apalutamide with drugs that lower male sex hormones for reducing the risk of prostate cancer recurrence. Patients in this study had their prostate gland surgically removed and were at high risk for disease recurrence. Relugolix, a newly approved oral drug for advanced prostate cancer, lowers blood testosterone (the primary male sex hormone) and, in combination with apalutamide, may reduce the risk of prostate cancer recurrence. The Apa-RP substudy goal was to test whether relugolix lowers blood testosterone and maintains these low levels when administered with apalutamide. Researchers looked at the testosterone levels of 12 patients with early prostate cancer who received standard doses of relugolix alone for 2 weeks followed by apalutamide and relugolix for an additional 28 days. Testosterone was measured before and after 2 weeks of relugolix treatment, and then again 28 days after apalutamide was added. All 12 substudy patients achieved low testosterone levels (< 50 ng/dL) after 2 weeks of relugolix treatment. Testosterone was measured at Day 28 of relugolix + apalutamide treatment in 11 patients, all of whom maintained low testosterone without adjustment of their relugolix dose. Adverse effects were consistent with those previously reported for each drug when administered alone. All 12 patients completed the substudy and moved onto the main study, the longer-term results of which will be reported in the future. In summary, relugolix administered at the same time as apalutamide was effective in maintaining low testosterone levels in patients with prostate cancer, without any new safety concerns.