Relugolix
Hormonal / ClinicalAlso known as: Orgovyx, Relumina
Mechanism
An oral pill that replaces injectable hormone-suppressing treatments for advanced prostate cancer. One tablet daily achieves the same testosterone suppression as monthly/quarterly injections of leuprolide — with faster onset and quicker recovery when stopped. The HERO trial showed it actually works better than leuprolide for maintaining castrate testosterone levels, and testosterone recovers much faster after stopping (important for intermittent therapy).
Technical detail
Non-peptide, orally bioavailable GnRH receptor antagonist. Competitive antagonist at GnRHR — immediate suppression of LH, FSH, and testosterone without flare. Oral bioavailability ~12% (unaffected by moderate renal/hepatic impairment). Half-life ~25 hours (supports once-daily dosing). Dosing: 360mg loading dose on day 1, then 120mg QD. HERO trial (n=934): sustained testosterone ≤50 ng/dL at 48 weeks in 96.7% (relugolix) vs. 88.8% (leuprolide depot) — p<0.001 for non-inferiority and superiority. Testosterone suppression within 4 days (vs. ~28 days for leuprolide). After discontinuation: median testosterone recovery to >280 ng/dL within 90 days (vs. not reached at 90 days for leuprolide). Key safety advantage: 54% lower risk of major adverse cardiovascular events vs. leuprolide (2.9% vs. 6.2%) — critical for prostate cancer patients with cardiovascular comorbidity. Drug interaction: P-gp inhibitors significantly increase exposure (requires dose adjustment). Also approved as Myfembree (relugolix + E2/NETA) for uterine fibroids (2021). Approved in Japan as Relumina for uterine fibroids (2019).
Effects
ENDOCRINE SYSTEM (REPRODUCTIVE AXIS): Relugolix is a non-peptide oral GnRH receptor antagonist — the first orally bioavailable GnRH antagonist approved for prostate cancer [RCT, FDA-approved 2020]. Unlike GnRH agonists (leuprolide, goserelin, histrelin), relugolix directly blocks the GnRH receptor without initial stimulation — NO testosterone flare [RCT — HERO trial]. Achieves castrate testosterone (<50 ng/dL) in 96.7% of patients by day 15 (median time to castration: 4 days) — significantly faster than GnRH agonists which require 3-4 weeks [RCT — HERO trial, Shore et al., 2020]. CARDIOVASCULAR ADVANTAGE: HERO trial demonstrated a 54% reduction in major adverse cardiovascular events (MACE) compared to leuprolide — 2.9% vs. 6.2% at 48 weeks [RCT]. Proposed mechanism: GnRH agonists activate extra-pituitary GnRH receptors on T-lymphocytes, promoting inflammatory atherosclerotic plaque destabilization; GnRH antagonists block these receptors, reducing cardiovascular inflammation [mechanistic studies, observational data]. This is the single most important clinical differentiator for relugolix. TESTOSTERONE RECOVERY: After discontinuation, testosterone recovers to baseline in ~90% of patients within 90 days (median recovery: 8 weeks) — dramatically faster than depot GnRH agonists (months to over a year for leuprolide 6-month depot) [RCT — HERO trial]. This enables intermittent androgen deprivation therapy with oral convenience. METABOLIC: Similar metabolic effects to other forms of androgen deprivation (weight gain, insulin resistance, dyslipidemia, bone loss) — these are consequences of testosterone suppression itself, not specific to relugolix [clinical]. MUSCULOSKELETAL: Bone density loss with chronic use — same as GnRH agonists. However, faster testosterone recovery may mitigate cumulative bone loss in intermittent therapy protocols [theoretical]. FEMALE REPRODUCTIVE: Also approved as part of Myfembree (relugolix + estradiol + norethindrone acetate) for uterine fibroids and endometriosis — provides GnRH suppression with hormonal add-back to prevent bone loss and vasomotor symptoms [RCT].
Practitioner Guide
ADMINISTRATION: Oral tablet, once daily. Loading dose: 360 mg (three 120 mg tablets) on day 1. Maintenance: 120 mg once daily thereafter. Take at approximately the same time each day, with or without food. CRITICAL DRUG INTERACTION — P-GLYCOPROTEIN: Relugolix is a P-gp substrate. Combined P-gp and strong CYP3A inducers (e.g., rifampin, carbamazepine, phenytoin, St. John's Wort) significantly reduce relugolix exposure and should be AVOIDED — can result in loss of castration. If a combined P-gp and strong CYP3A inducer must be used, increase relugolix to 240 mg/day during co-administration and for 2 weeks after stopping the inducer. P-gp inhibitors (e.g., azithromycin, erythromycin, verapamil, cyclosporine) can increase relugolix exposure — monitor but no dose adjustment needed per current labeling. MONITORING: Testosterone level at 4 weeks (confirm castration <50 ng/dL), then every 3-6 months. PSA every 3-6 months. DEXA scan at baseline, then annually. Metabolic panel, fasting glucose, lipids, HbA1c at baseline and every 6 months. ADVANTAGES OVER GnRH AGONISTS: No flare (no need for antiandrogen cover). Faster castration (days vs. weeks). Faster testosterone recovery after stopping. Cardiovascular safety signal (HERO trial). Oral convenience (no injections, no implant procedures). Enables easier intermittent ADT. INTERMITTENT ADT PROTOCOL (EMERGING): Relugolix is well-suited for intermittent androgen deprivation: treat until PSA nadir, continue 6-8 months, then stop and monitor. Resume when PSA rises to a trigger level (varies by protocol, often 10-20 ng/mL for M0 disease). Rapid testosterone recovery makes this more feasible than with depot formulations. MISSED DOSE: If missed by <12 hours, take immediately. If >12 hours, skip and take next day at regular time. Do NOT double up. Multiple consecutive missed doses may result in testosterone escape — recheck testosterone if 3+ days missed. BONE PROTECTION: Same as GnRH agonists — calcium, vitamin D, denosumab or zoledronic acid for long-term use. SWITCHING FROM GnRH AGONIST: Can start relugolix when next injection is due (no washout needed). COST: Approximately $2,200/month. Generally requires prior authorization. Comparable to or slightly less than GnRH agonist depot formulations when procedure costs are included.
Research Summary
TIER 1: HERO trial (Shore et al., 2020 — NEJM): landmark Phase III RCT, 934 patients with advanced prostate cancer. Relugolix achieved sustained castration in 96.7% vs. 88.8% for leuprolide at 48 weeks (met non-inferiority and superiority). MACE: 2.9% vs. 6.2% favoring relugolix. Testosterone recovery to >280 ng/dL within 90 days: 54% relugolix vs. 3% leuprolide. FDA-approved 2020 (Orgovyx). LIBERTY 1 and 2 trials — relugolix combination (Myfembree) for uterine fibroids, demonstrating reduced menstrual blood loss with acceptable safety [RCT]. SPIRIT 1 and 2 — relugolix combination for endometriosis-associated pain [RCT]. TIER 2: Subgroup analyses of HERO trial (cardiovascular outcomes, PSA response kinetics, quality of life). Systematic reviews comparing GnRH agonists vs. antagonists for cardiovascular safety (consistent signal favoring antagonists). Pharmacokinetic studies of relugolix P-gp interactions. Reviews of oral GnRH antagonist development history. Health economic analyses (favorable vs. injectable GnRH agonists when procedure costs included). TIER 3: Early real-world data from urology practices transitioning from leuprolide to relugolix. Case reports of intermittent ADT using relugolix. Expert opinion and guideline updates incorporating HERO trial data (NCCN now lists relugolix as preferred GnRH option for patients with cardiovascular risk factors). KEY FINDINGS: Relugolix represents a genuine paradigm shift in androgen deprivation therapy — the cardiovascular advantage, rapid onset, rapid recovery, and oral convenience collectively make it the preferred agent for many patients, especially those with cardiovascular comorbidities. The HERO trial is well-designed and the data is compelling. GAPS: Long-term cardiovascular outcomes data beyond 48 weeks needed. Prospective intermittent ADT trials with relugolix not yet completed. Comparison with degarelix (injectable GnRH antagonist) lacking. ACTIVE TRIALS: Extended HERO follow-up for survival outcomes. PRONOUNCE trial (degarelix vs. leuprolide for MACE — addresses the class question). Intermittent ADT studies using relugolix. Combination therapy trials.