Impact of Baseline Testosterone on Relugolix Outcomes

By Patrick Daly - Last Updated: December 2, 2022

Relugolix is an oral gonadotropin-releasing hormone (GnRH) receptor antagonist approved in the US for patients with advanced prostate cancer. In the phase 3 HERO study, relugolix achieved suppression of testosterone (T) to castrate levels in 96.7% of men at week 48, superior to leuprolide (89%).

In a follow-up analysis of HERO, Michael S. Cookson and colleagues examined the impact of baseline T levels on cancer outcomes. Their data, presented by Cookson at the 23rd Annual Meeting of the Society of Urologic Oncology, showed that relugolix was comparably effective and safe regardless of patients’ baseline T levels.

Baseline Testosterone Doesn’t Affect Relugolix Outcomes

The HERO study enrolled 930 men with advanced prostate cancer who received 3-month leuprolide injections or oral relugolix 120 mg once a day after a single loading dose of 360 mg over 48 weeks. Researchers evaluated subgroups with baseline T levels of <280 ng/dL or ≥280 ng/dL. Patients with baseline serum T levels under 150 ng/dL were excluded.

The <280 ng/dL baseline group contained 96 and 51 relugolix and leuprolide patients, while the ≥280 ng/dL baseline group had 516 and 249 relugolix and leuprolide patients, respectively. The primary end point was sustained T suppression to <50 ng/dL from day 29 through 48 weeks, and other end points included early or profound suppression, prostate-specific membrane antigen levels, and safety.

According to the analysts, both relugolix subgroups had higher point estimates for sustained castration rates through week 48 compared with both leuprolide subgroups (<280 ng/dL, 97.3% vs 84.1%; ≥280 ng/dL, 96.5% vs 89.3%). Additionally, the difference in sustained T suppression at week 48 was 13.2% (95% CI, 2.4-24.0) between the <280 ng/dL relugolix and leuprolide subgroups and 7.2% (95% CI, 3.0-11.4) between the ≥280 ng/dL subgroups.

Lastly, the researchers observed no significant differences in rate or severity of adverse events between the groups, though they did add that results for other key secondary end points “consistently favored relugolix” compared with leuprolide.

Cookson and collaborators determined that relugolix was effective for men with advanced prostate cancer regardless of their baseline T levels, which the report noted was consistent with findings from the overall population of the HERO trial.