Oral gonadotrophin antagonist shows promise

A novel oral gonadotropin-releasing hormone (GnRH) antagonist has shown superior testosterone suppression compared to a standard injectable luteinizing hormone–releasing hormone (LHRH).

In the phase 3 trial 622 patients with advanced prostate cancer received the new agent relugolix (120 mg orally once daily) and 308 received leuprolide (injections every three months) for 48 weeks.

In the trial, 97% (95% confidence interval [CI], 94.9–97.9) of men given relugolix maintained castration levels of testosterone throughout 48 weeks, compared with 89% (95% CI, 84.6–91.8) of men receiving leuprolide. The difference of 8% (95% CI, 4.1–11.8) was significantly superior in favour of relugolix (p<0.001). The percentage of patients with castrate levels of testosterone on day 4 was 56% with relugolix and zero with leuprolide. In the subgroup of 184 patients followed for testosterone recovery, the mean testosterone levels 90 days after treatment discontinuation were 288ng per decilitre in the relugolix group and 58ng per decilitre in the leuprolide group.

The incidence of major adverse cardiovascular events was 2.9% in the relugolix group and 6.2% in the leuprolide group (hazard ratio, 0.46; 95% CI, 0.24–0.88).

Injectable LHRH agonists are the standard drugs for achieving androgen deprivation in prostate cancer despite the downside of causing an initial testosterone surge and a delayed therapeutic effect. Dagarelix is the only currently available GnRH antagonist and it to is injectable. Relugolix would be the first oral GnRH antagonist.

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