Testosterone suppression, safety, and adherence with relugolix in patients with metastatic prostate cancer: 6-month subgroup analysis of the OPTYX study.

Abstract

e17057 Background: Relugolix is an oral androgen deprivation therapy used for the treatment of advanced prostate cancer (PC). OPTYX (NCT05467176) is an ongoing multicenter, prospective, observational study of relugolix treatment in the United States. There is limited published literature regarding patients with metastatic PC (mPC) initiating relugolix monotherapy or combination systemic therapy. We report testosterone suppression, serious adverse events (SAEs), and adherence data from baseline through 6 months in a subgroup of patients with mPC initiating relugolix monotherapy or relugolix in combination with other systemic prostate therapies. Methods: Patients with PC were enrolled in OPTYX if they initiated relugolix ≤1 month prior to study enrollment and intended to remain on relugolix for ≥4 months. Six-month testosterone suppression, SAEs, and adherence were assessed in patients with mPC. Monotherapy or combination therapy categorization was based on baseline use. Adherence is assessed by the Simplified Medication Adherence Questionnaire. All patients have ≥6 months of data after enrollment. The study is ongoing and data will be collected for a minimum of 2 years with no mandatory study visits required. Results: A total of 255/999 patients enrolled in OPTYX had mPC. Median age at baseline was 71 years; 14.5% were Black and 0.4% were Asian. At relugolix initiation, 64.7% received monotherapy and 35.3% received combination therapy. Of patients with available testosterone data at 1 month (earliest timepoint assessed), 95% (n = 38/40) and 81% (n = 17/21) of patients who initiated monotherapy and combination therapy, respectively, achieved castrate levels ( < 50 ng/dL). All patients assessed at 3 months (monotherapy, n = 47/47; combination therapy, n = 28/28) and 92% (n = 55/60) and 97% (n = 33/34) of patients (monotherapy and combination therapy, respectively) assessed at 6 months achieved castrate testosterone levels. Overall, 7.8% (20/255) of patients (monotherapy, 9.1%; combination therapy, 5.6%) initiating relugolix experienced ≥1 SAE; most common SAEs were anemia (n = 2) and atrial fibrillation (n = 2). One patient in each group (monotherapy, 0.6%; combination therapy, 1.1%) experienced cardiovascular (CV)-related SAEs. Patient adherence was high at 6 months, with 96% of patients (monotherapy, 96%; combination, 95%) reporting taking relugolix at the appropriate time each day and 81% (monotherapy, 80%; combination, 83%) reporting never forgetting to take relugolix even once. Conclusions: Using clinical practice data, relugolix treatment led to successful testosterone suppression, low rates of documented SAEs and CV-related SAEs, and high adherence at 6 months in patients with mPC. These results were similar in patients initiating monotherapy and combination therapy. Clinical trial information: NCT05467176 .