Relugolix update shared as FDA weighs approval in prostate cancer

September 29, 2020

Under the Prescription Drug User Fee Act, the FDA is scheduled to make its decision on relugolix by December 20, 2020.

Relugolix did not improve castration resistance–free survival through 48 weeks versus leuprolide acetate in patients with metastatic prostate cancer, according to updated data from the phase 3 HERO study shared by Myovant Sciences, the manufacturer of the oral GnRH receptor antagonist.1

In this population of men, 74% of men who received relugolix were castration-resistance free through 48 weeks versus 75% of patients who received leuprolide acetate injection (HR, 1.03; P = .84)

The FDA previously granted a priority review designation to a new drug application (NDA) for relugolix in this setting based on previously reported data from the HERO study. Those findings showed that in patients randomized to relugolix, 96.7% maintained castration through 48 weeks, compared with 88.8% of patients in the leuprolide cohort. The benefit was statistically significant (P <.001).2

Beyond meeting this primary study end point, the benefit with relugolix was sustained across all major secondary end points (P <.001). Relugolix was also associated with a 54% lower risk of major adverse cardiovascular events compared with leuprolide (HR, 0.46). Under the Prescription Drug User Fee Act, the FDA is scheduled to decide on the NDA on or before December 20, 2020.

“These new data from the phase 3 HERO study show that 3 out of 4 men with metastatic prostate cancer remained castration resistance-free through 48 weeks while on oral relugolix, in-line with leuprolide acetate injections, the current standard of care,” Dan George, MD, a professor of medicine and surgery at the Duke University School of Medicine and HERO program steering committee member, stated in a press release. “I continue to be excited by relugolix as a potential new and differentiated treatment option for men with prostate cancer given its robust clinical and safety data, including the lower risk of major adverse cardiovascular events compared to leuprolide acetate.”

The open-label international phase 3 HERO trial included 930 patients treated at 155 clinical sites. The median patient age was 71 years (range, 47-97), with 28.6% of patients being aged ≥75 years. Overall, 31.7% of patients had metastatic disease, 15.5% of patients had a Gleason score of 5-6, 38.6% of patients had a Gleason score of 7, and 43.1% of patients had a Gleason score of 8-10. Half (50.2%) of patients had evidence of biochemical or clinical relapse after local primary intervention with curative intent.

The median PSA level at baseline was 10.8 ng/ml and the average testosterone level at baseline was 427.5 ± 156.2 ng/ml. The ECOG performance status was 0 in 88.1% of patients, 11.9% of patients, had prior androgen-deprivation therapy, and 30.3% had prior radiotherapy.

Patients were randomized in a 2:1 ratio to relugolix at 120 mg orally once daily or leuprolide injections every 3 months. Treatment was administered for 48 weeks, with a primary end point of sustained testosterone suppression to castrate levels (<50 ng/dL) through 48 weeks.

On day 4 of treatment, 56% of the relugolix cohort had castrate levels of testosterone versus 0% of the leuprolide group. On day 15, the rates were 98.7% versus 12%, respectively. Also on day 15, 79.4% of the relugolix arm had a confirmed PSA response, compared with 19.8% of patients on the leuprolide arm (P <.001).

Among a subgroup of men followed for testosterone recovery (n = 184), the mean testosterone levels 90 days following discontinuation of treatment were288.4 ng/dL versus 58.6 ng/dL, respectively.

The incidence of adverse events (AEs) was similar across the study arms. In the relugolix group, all-grade AEs occurred in 92.9% of patients compared with 93.5% in the leuprolide arm. Grade 3/4 AEs occurred in 18% versus 20.5% of the 2 arms, respectively. There were 7 AE-related deaths in the relugolix cohort compared with 9 in the leuprolide arm.

The most common AE across all grades in both arms was hot flash, occurring in 54.3% and 51.6% of the relugolix and leuprolide cohorts, respectively. There was a higher incidence of all-grade diarrhea with relugolix at 12.2% versus 6.8% with leuprolide. All diarrhea cases were grade 1/2 and did not lead to any patient discontinuations.

Major adverse cardiovascular events occurred in 2.9% of the relugolix arm compared with 6.2% of the leuprolide cohort. The study defined major adverse cardiovascular events as nonfatal stroke or myocardial infarction, or death due to any cause.

“We believe the totality of data—Including previously reported data from the Phase 3 HERO program, published in the New England Journal of Medicine—presents compelling evidence for the potential use of relugolix in men with advanced prostate cancer,” Lynn Seely, MD, chief executive officer of Myovant Sciences, stated in the press release. “With our new drug application under priority review by the FDA, we look forward to our target action date in December 2020 and hope to advance our commitment to redefining care by bringing once-daily, oral relugolix to men with prostate cancer.”

References

1. Myovant Sciences Announces Results of Additional Secondary Endpoint of Castration Resistance-Free Survival from Phase 3 HERO Study of Relugolix in Advanced Prostate Cancer. Myovant. Published online September 29, 2020. Accessed September 29, 2020. https://bit.ly/3iiHtLs.

2. Shore ND, Saad F, Cookson MS, et al. Oral relugolix for androgen-deprivation therapy in advanced prostate cancer. N Engl J Med. 2020;382(23):2187-2196. doi: 10.1056/NEJMoa2004325.