Relugolix (brand name Orgovyx) is an oral gonadotropin-releasing hormone (GnRH) antagonist, also referred to as an LHRH antagonist, used for the treatment of advanced prostate cancer. It works by competitively binding to pituitary GnRH receptors, which leads to a decrease in the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), subsequently lowering testosterone levels.
Dosing and Administration
- Loading Dose: The treatment begins with a single 360mg oral loading dose (three 120mg tablets) on the first day.
- Maintenance Dose: Following the loading dose, patients take 120mg (one tablet) orally once daily.
- Interruption: If the medication is interrupted for seven days or more, a new loading dose is required.
Clinical Efficacy (The HERO Trial)
The efficacy of relugolix was established in the HERO Phase III trial, which compared it to leuprolide injections. Key findings included:
- Testosterone Suppression: Relugolix demonstrated a higher rate of sustained testosterone suppression through 48 weeks compared to leuprolide (96.7% vs. 88.8%).
- Speed of Action: It offers a fast onset and offset of action for testosterone suppression. Unlike LHRH agonists, it does not cause an initial testosterone surge (flare), eliminating the need for co-administration with antiandrogens at the start of therapy.
Cardiovascular Benefits
Relugolix is specifically noted for its lower risk of major cardiovascular adverse events (MACE) compared to LHRH agonists.
- In the HERO trial, the incidence of MACE was 2.9% for relugolix versus 6.2% for leuprolide.
- For patients with a pre-existing history of MACE, the benefit was even more pronounced, with an event rate of 3.6% for relugolix compared to 17.8% for leuprolide.
Side Effects and Limitations
- Common Adverse Events: Side effects are generally similar to other forms of androgen deprivation therapy (ADT), but diarrhea was reported more frequently with relugolix (12.2% vs. 6.8% for leuprolide). It can also cause QTc prolongation.
- Survival Data: Currently, most published outcomes for relugolix relate to the speed and maintenance of testosterone suppression; data regarding overall survival or progression-free survival are not yet available.
- Combination Therapy: It has not been extensively studied in combination with other prostate cancer therapies and is generally recommended for patients requiring ADT alone. It is also considered an ideal option for intermittent androgen deprivation (IAD) due to its oral administration and fast recovery of testosterone levels.