The most frequent adverse event seen in both groups was hot flashes (54.3% in the relugolix group and 51.6% in the leuprolide group). The second most common adverse event report was fatigue, which occurred in 21.5% of patients in the relugolix arm and 18.5% in the leuprolide arm. Diarrhea was reported more frequently with relugolix than with leuprolide (12.2% vs 6.8%); however, diarrhea did not lead to discontinuation of therapy in any patient. Fatal events were reported more frequently in the leuprolide group (2.9%) compared with the relugolix group (1.1%). MACE were defined as nonfatal myocardial infarction, stroke, and death from any cause. After completing the intervention period of 48 weeks, the relugolix group had a 2.9% incidence of major cardiovascular events, compared with 6.2% in the leuprolide group. In patients having a medical history of cardiovascular events, the adverse event rate during the trial period was 3.6% in the relugolix group and 17.8% in leuprolide group. This translated into a 54% lower risk of MACE in the relugolix arm compared with the leuprolide arm.
Conclusion. The use of relugolix in advanced prostate cancer led to rapid, sustained suppression and faster recovery of testosterone level compared with leuprolide. Relugolix appeared safer to use for men with a medical history of cardiovascular events and showed a 54% lower risk of MACE than leuprolide.
Commentary
Relugolix is a highly selective oral GnRH antagonist that rapidly inhibits pituitary release of luteinizing hormone and FSH. The current phase 3 HERO trial highlights the efficacy of relugolix in regard to testosterone suppression, adding to potential therapeutic options for these men. Relugolix yielded superior sustained testosterone suppression to less than 50 ng/dL throughout the 48-week study period, meeting its primary endpoint. Additionally, relugolix showed superiority in all secondary endpoints across all subgroups of patients. To date, the only GnRH antagonist on the market is degarelix, which is given as a monthly subcutaneous injection.1 Injection-site reactions remain an issue with this formulation.
Cardiovascular disease is the leading cause of death in the United States, and it is known that men with prostate cancer have a higher incidence of cardiovascular disease.2 While data regarding adverse cardiac outcomes with androgen deprivation therapy have been mixed, it is thought that this therapy increases the risk for MACE. There is mounting evidence that GnRH antagonists may have a less detrimental effect on cardiovascular outcomes compared with GnRH agonists. For example, a pooled analysis of 6 phase 3 trials showed a lower incidence of cardiovascular events in men with preexisting cardiovascular disease using the GnRH antagonist degarelix compared with GnRH agonists after 12 months of treatment.3 Furthermore, a more recent phase 2 randomized trial showed that 20% of patients treated with a GnRH agonist developed cardiovascular events, compared to 3% in the GnRH antagonist group. The absolute risk reduction of cardiovascular events at 12 months was 18%.4 The results of the current trial support such findings, showing a 54% reduction in MACE after 48 weeks of therapy when compared with leuprolide (2.9% in relugolix arm vs 6.2% in leuprolide arm). More importantly perhaps, in the subgroup of men with preexisting cardiovascular disease, the benefit was even greater, with a MACE incidence of 3.6% with relugolix compared with 17.8% with leuprolide.
Studies have also shown that second-generation antiandrogens such as enzalutamide are associated with an increased risk of death from cardiovascular causes. For example, data from the recently updated PROSPER trial, which evaluated the use of enzalutamide in men with nonmetastatic, castration-resistant prostate cancer, showed an increased risk of adverse events, including falls, fatigue, hypertension, and death from cardiovascular events.5 Furthermore, adding second-generation antiandrogens to GnRH-agonist therapy is associated with a high risk of cardiovascular events in men with preexisting cardiovascular disease.3 These results were noted in all of the trials of second-generation antiandrogens, including enzalutamide, apalutamide, and darolutamide, in combination with GnRH agonists.6-8 Taken together, one might consider whether the use of a GnRH antagonist would result in improved cardiovascular outcomes in high-risk patients.