Relugolix (OrgovyxTM, Myovant Sciences) has been FDA approved for the treatment of patients with advanced prostate cancer. A gonadotropin-releasing hormone (GnRH) receptor antagonist, relugolix is the first oral hormone therapy to be approved for this disease.
The approval was based on the phase 3 HERO trial (NCT03085095). "Relugolix was developed as an oral, highly selective, GnRH antagonist that is given once daily with an effective half-life of 25 hours," write the investigators in their June 2020 publication in The New England Journal of Medicine, led by Neal Shore, MD, FACS, Medical Director of the Carolina Urologic Research Center in South Carolina. "Relugolix rapidly inhibits pituitary release of luteinizing hormone and follicle stimulating hormone (FSH) and has been shown to lower testosterone levels in multiple phase 1 and 2 studies."
HERO enrolled 930 patients with advanced prostate cancer who had evidence of biochemical or clinical relapse after local primary treatment, newly diagnosed hormone-sensitive disease, or advanced localized disease unlikely to be cured by local primary treatment. Patients were randomized in a 2:1 ratio to receive 120 mg relugolix orally once daily or leuprolide once every three months for 48 weeks. The primary end point was sustained testosterone suppression to castrate levels, with secondary end points of noninferiority with respect to the primary end point, castrate levels of testosterone on Day 4, and profound castrate levels (under 20 ng/dL) on Day 15.
After 48 weeks of treatment, a higher proportion of patients receiving relugolix maintained castration compared with those receiving leuprolide (96.7% vs 88.8%), a difference which reached statistical noninferiority and superiority. At Day 4, 56.0% of patients receiving relugolix had castrate levels of testosterone, compared with 0% of the patients treated with leuprolide. In a subgroup of patients who were evaluated for testosterone recovery, relugolix produced a mean testosterone level of 288.4 ng/dL at 90 days following the end of treatment, compared with 58.6 ng/dL for leuprolide.
The most common adverse events associated with relugolix were hot flush, increased glucose, increased triglycerides, musculoskeletal pain, decreased hemoglobin, fatigue, constipation, diarrhea, and increased liver enzyme levels. Major adverse cardiovascular events were experienced by fewer patients receiving relugolix compared with leuprolide (2.9% vs 6.2%), a 54% lower risk.
The prescribing information for relugolix contains a warning that this agent may cause embryo-fetal toxicity and QT interval prolongation. Relugolix is contraindicated for patients taking drugs that inhibit P-glycoprotein. Because relugolix may affect the heart's electrical properties or cause electrolyte abnormalities, periodic electrocardiograms and monitoring of electrolytes should be performed.
"In this trial involving men with advanced prostate cancer, relugolix achieved rapid, sustained suppression of testosterone levels that was superior to that with leuprolide," concluded Dr. Shore and colleagues in their publication.
The recommended dosage of relugolix is a 360 mg loading dose on the first day, followed by 120 mg administered orally once daily, with or without food, at approximately the same time each day.
For More Information
Clinicaltrials.gov (2020). A study to evaluate the safety and efficacy of relugolix in men with advanced prostate cancer (HER0). NLM identifier: NCT03085095.
US Food & Drug Administration (2020). FDA approves first oral hormone therapy for treating advanced prostate cancer. Available at: https://www.fda.gov/news-events/press-announcements/fda-approves-first-oral-hormone-therapy-treating-advanced-prostate-cancer
Image credit: Nephron. Licensed under CC BY-SA 3.0