Real-world experience with relugolix.

Abstract

57 Background: Gonadotropin-releasing hormone (GnRH) antagonists were developed in part to avoid testosterone flare to achieve faster and more consistent testosterone suppression. Relugolix (Rel) was given FDA approval for use in prostate cancer (PCa) based on the phase 3 HERO trial but some real-world concerns include compliance, affordability, and performance in patients transitioning from another GnRH agent or in combination with other therapeutic agents. The aim of our study was to evaluate the real-world implications of prescribing and/or switching to Rel. Methods: A single institution retrospective study was conducted on patients prescribed Rel. Treatment data including concomitant therapeutic agents were collected. Compliance data was measured via chart review and pharmacy dispensary records. Patients were classified as either newly castrated or transitioning from another agent. PSA and testosterone levels were tabulated. Reported adverse effects (AE), and reasons for discontinuation if applicable including financial toxicity were noted. Results: 50 patients were reviewed; 15 (30%) treated for adjuvant, 18 (36%) for biochemical recurrence, and 17 (34%) for metastatic PCa. 12% were on concomitant therapy with abiraterone, 4% with enzalutamide, and 2% with apalutamide. 80% reported compliance to Rel. 5 (10%) never filled the prescription. 30 (60%) were newly castrated (castration restart or naïve) while 16 (36%) were transitioned from another GnRH. No changes in PSA or testosterone were noted in patients switched form injected GnRH to Rel. The most common documented AE effects included hot flashes 24%, fatigue, 29%, and weight gain 9%. No unexpected toxicity was reported in combination with abiraterone. Of 11 patients who discontinued therapy, 45% did so due to cost, 36% due to AE, and 27% due to therapy completion. 4 of 16 (25%) of those who transitioned from injection GnRH felt symptoms were worse on Rel. Conclusions: In our early experience with Rel, patients did comply to therapy based on self-reporting, pharmacy fill dates, and laboratory evidence of castration. However, financial toxicity was and remains a significant barrier both accessing Rel and remaining on Rel therapy. While a differential toxicity was reported by those who switched from injection GnRH, sometimes leading to discontinuation, there were no new safety signals reported, especially in combination with abiraterone.