Relugolix (Orgovyx): Comprehensive Research Overview

Document Version: 1.0 Last Updated: December 2024 Classification: Hormone Replacement Therapy (HRT) - GnRH Receptor Antagonist / Androgen Deprivation Therapy

1. Executive Summary + Regulatory Classification

Overview

Relugolix is a nonpeptide, small-molecule, potent gonadotropin-releasing hormone (GnRH) receptor antagonist approved by the FDA for the treatment of adult patients with advanced prostate cancer. Unlike injectable GnRH agonists (leuprolide, goserelin) or antagonists (degarelix), relugolix is the first and only oral GnRH receptor antagonist, offering daily oral administration as an alternative to depot injections.

Chemical Identity:

• Generic Name: Relugolix
• Trade Name: ORGOVYX (Myovant Sciences)
• Chemical Name: 1-{4-[1-(2,6-Difluorobenzyl)-5-[(dimethylamino)methyl]-3-(6-methoxypyridazin-3-yl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-6-yl]phenyl}-3-methoxyurea
• Code Name: TAK-385 (Takeda Pharmaceutical)
• CAS Number: 737789-87-6
• Molecular Formula: C₂₉H₂₇F₂N₇O₅S
• Molecular Weight: 627.63 g/mol

Primary Classification

Pharmacologic Class: Gonadotropin-Releasing Hormone (GnRH) Receptor Antagonist Therapeutic Category: Androgen deprivation therapy (ADT); antineoplastic agent Mechanism: Competitive GnRH receptor antagonist; suppresses luteinizing hormone (LH) and follicle-stimulating hormone (FSH), leading to testosterone suppression

Key Mechanisms and Clinical Applications

Mechanism of Action:

1. GnRH Receptor Blockade: Competitively binds GnRH receptors in anterior pituitary
2. LH/FSH Suppression: Prevents endogenous GnRH from stimulating gonadotropin release
3. Testosterone Suppression: Reduced LH leads to testicular testosterone production decline to castrate levels (<50 ng/dL)
4. Prostate Cancer Growth Inhibition: Androgen deprivation slows or stops prostate cancer progression

FDA-Approved Indication:

• Advanced Prostate Cancer: Treatment of adult patients with advanced prostate cancer

Advanced Prostate Cancer Defined:

• Biochemically recurrent prostate cancer with rising PSA despite local therapy
• Metastatic hormone-sensitive prostate cancer (mHSPC)
• Locally advanced prostate cancer requiring neoadjuvant/adjuvant ADT with radiation therapy

Regulatory Status Summary

• Approval Date: December 18, 2020
• Approval Pathway: Standard approval based on Phase 3 HERO trial
• Indication: Treatment of adult patients with advanced prostate cancer
• Prescription Status: Rx (prescription only)

DEA Federal Scheduling:

• Status: Not scheduled
• Controlled Substance: No
• Prescription Requirement: Yes (standard prescription)

International Regulatory Status:

• European Union (EMA): Approved June 17, 2021 (trade name: Orgovyx)
• Canada (Health Canada): Approved May 18, 2021
• United Kingdom (MHRA): Approved June 2021
• Australia (TGA): Approved September 2021
• Japan (PMDA): Approved January 2019 (first global approval under trade name Relumina)

Advantages Over Injectable GnRH Therapies

Relugolix offers several clinical advantages over traditional injectable androgen deprivation therapies:

vs. GnRH Agonists (Leuprolide, Goserelin):

• No testosterone flare: GnRH agonists cause initial testosterone surge (may worsen symptoms); relugolix causes immediate suppression
• Rapid castration: 56% achieve castrate levels by day 4 vs. 0% with leuprolide
• Superior cardiovascular safety: 54% lower risk of major adverse cardiovascular events (MACE) vs. leuprolide
• Rapid testosterone recovery: 54% recover testosterone >280 ng/dL at 90 days post-discontinuation vs. 3.2% with leuprolide

vs. GnRH Antagonist (Degarelix):

• Oral administration: Daily oral tablet vs. monthly subcutaneous injections
• No injection-site reactions: Degarelix causes injection-site reactions in ~40% of patients
• Better adherence: 60.8% adherence at 12 months vs. 13.0% with degarelix
• Faster testosterone recovery: Shorter half-life enables more rapid reversibility

Goal Archetype Integration

Primary Goal Alignment

Unique Value Proposition: Oral GnRH Antagonist

Relugolix is the only oral GnRH receptor antagonist approved for prostate cancer, offering distinct advantages:

vs. GnRH Agonists (Leuprolide, Goserelin, Triptorelin):

• No testosterone flare: Immediate suppression without initial surge
• No flare-related complications: Avoids bone pain, spinal cord compression, urinary obstruction
• No antiandrogen cover required: Simpler initiation protocol
• 54% lower MACE risk: Superior cardiovascular safety profile

vs. Injectable GnRH Antagonist (Degarelix):

• Oral administration: Daily tablet vs. monthly subcutaneous injections
• No injection-site reactions: Degarelix causes reactions in ~40% of patients
• Better adherence: 60.8% vs. 13.0% at 12 months
• Faster testosterone recovery: Shorter half-life (25 hours vs. ~40 days)

When Relugolix Makes Sense

• Advanced prostate cancer requiring androgen deprivation therapy (FDA-approved indication)
• Patients with cardiovascular disease who need ADT (54% lower MACE risk vs. leuprolide)
• Patients preferring oral medication over injections
• Intermittent ADT candidates who need rapid testosterone recovery between cycles
• Patients requiring rapid testosterone suppression without antiandrogen cover
• Metastatic hormone-sensitive prostate cancer requiring ADT backbone with combination therapy (ARPIs, docetaxel)

When to Choose Something Else

• Cost-sensitive patients without CV risk: Generic leuprolide significantly cheaper (~$7,200/year vs. ~$33,000/year)
• Patients who prefer infrequent dosing: Leuprolide depot (every 3-6 months) or histrelin implant (annually) require less frequent administration
• Patients with poor adherence to daily medications: Depot formulations ensure compliance through sustained release
• Non-prostate cancer indications: Relugolix not FDA-approved for endometriosis, fibroids, or CPP (though combination product Myfembree exists for uterine fibroids in women)

2. Chemical Structure & Pharmacology

Molecular Structure

Structural Classification:

Relugolix is a non-peptide, small-molecule compound, structurally distinct from GnRH peptide analogues. It is an N-phenyl urea derivative and a thienopyrimidine compound designed and developed by Takeda Pharmaceutical through chemical modifications of sufugolix (TAK-013).

Chemical Structure Features:

• Thienopyrimidine core: Central heterocyclic ring system providing GnRH receptor binding affinity
• Difluorobenzyl group: 2,6-difluorobenzyl substituent enhances receptor selectivity
• Methoxypyridazine moiety: 6-methoxypyridazin-3-yl group contributes to receptor antagonism
• Phenylurea side chain: 3-methoxyurea phenyl group critical for biological activity
• Dimethylamino group: Improves oral bioavailability and pharmacokinetic properties

Molecular Formula: C₂₉H₂₇F₂N₇O₅S Molecular Weight: 627.63 g/mol

Receptor Binding and Selectivity

GnRH Receptor Antagonism:

• IC₅₀ (half-maximal inhibitory concentration) for human GnRH receptor: 0.33 nM
• IC₅₀ for monkey GnRH receptor: 0.32 nM
• High selectivity: >10,000-fold selectivity for GnRH receptor over other GPCRs
• Competitive antagonist: Binds competitively with endogenous GnRH for receptor occupancy

Comparison to Peptide GnRH Antagonists:

• Degarelix (peptide): Larger molecular weight (~1,632 Da), injectable only
• Relugolix (non-peptide): Smaller molecular weight (628 Da), orally bioavailable
• Binding affinity: Relugolix achieves comparable receptor antagonism with smaller, orally-active structure

Physicochemical Properties

Appearance:

• White to off-white crystalline powder
• Odorless

Solubility:

• Water: Practically insoluble (<0.1 mg/mL)
• Organic solvents: Soluble in DMSO, DMF
• pH: Neutral compound (not ionizable under physiologic conditions)

Stability:

• Temperature: Stable at room temperature (20-25°C)
• Light: Photostable under normal pharmaceutical conditions
• Moisture: Store in tight, moisture-resistant containers
• Oxidation: Stable; no significant oxidative degradation

pKa:

• No ionizable groups within physiologic pH range
• Neutral molecule; does not exist as salt form

GnRH Receptor Mechanism (Molecular Level)

Normal GnRH Signaling (Without Relugolix):

1. Hypothalamus releases GnRH in pulsatile fashion
2. GnRH binds to GnRH receptors (GnRHR) on anterior pituitary gonadotroph cells
3. GnRHR is a G protein-coupled receptor (GPCR) linked to Gq/11 signaling
4. Gq activation → phospholipase C (PLC) → IP₃/DAG second messengers
5. IP₃ triggers calcium release → LH and FSH synthesis and secretion
6. LH stimulates testicular Leydig cells to produce testosterone

Relugolix-Induced Blockade:

1. Relugolix competitively binds GnRH receptors in anterior pituitary
2. Prevents endogenous GnRH from activating GnRHR
3. Blocks downstream Gq/PLC/IP₃ signaling cascade
4. LH and FSH synthesis and secretion rapidly decline
5. Testicular testosterone production decreases to castrate levels (<50 ng/dL)
6. Result: Medical castration without surgical orchiectomy

Key Difference from GnRH Agonists:

• GnRH Agonists (Leuprolide): Initially activate GnRH receptors, causing testosterone surge ("flare"), then desensitize receptors over 2-4 weeks
• Relugolix (Antagonist): Immediate receptor blockade; no testosterone flare; rapid suppression

3. Mechanism of Action (Tissue-Specific Effects)

Primary Mechanism: Hypothalamic-Pituitary-Gonadal (HPG) Axis Suppression

Relugolix acts as a competitive GnRH receptor antagonist, binding to GnRH receptors in the anterior pituitary gland and preventing endogenous GnRH from inducing LH and FSH release.

Step-by-Step Mechanism:

1. Competitive GnRH Receptor Antagonism (Pituitary)

• Relugolix binds to GnRH receptors (GnRHR) on gonadotroph cells in anterior pituitary
• Competitive antagonism: Prevents endogenous GnRH from binding and activating GnRHR
• GnRHR is a G protein-coupled receptor (GPCR); relugolix binding prevents G protein activation
• Result: Suppression of GnRH-induced intracellular signaling

2. Gonadotropin Suppression (Pituitary)

• Without GnRH receptor activation, LH and FSH synthesis declines
• Median time to castration in the relugolix arm was 4 days
• 56% of patients achieved castrate testosterone levels by day 4 (vs. 0% with leuprolide)
• LH and FSH remain suppressed with continued daily relugolix administration

3. Testicular Testosterone Suppression

• Reduced LH stimulation of testicular Leydig cells
• Testosterone synthesis declines rapidly
• Castrate testosterone level: <50 ng/dL (FDA definition for castration)
• Profound castration: <20 ng/dL (achieved in 78.4% of relugolix patients by day 15)

4. Prostate Cancer Growth Inhibition

• Prostate cancer cells are androgen-dependent (majority of advanced prostate cancers)
• Testosterone and dihydrotestosterone (DHT) bind androgen receptors (AR) in prostate cancer cells
• AR activation drives cancer cell proliferation, survival, and metastasis
• Androgen deprivation: Removing testosterone "fuel" slows or stops cancer growth

5. PSA Decline (Biomarker of Treatment Response)

• Prostate-specific antigen (PSA) is produced by prostate cells and regulated by androgens
• Testosterone suppression leads to PSA decline
• PSA monitored as biomarker of treatment response (PSA nadir correlates with survival)

Tissue-Specific Effects

Hypothalamus (No Direct Effect):

• Relugolix does not cross blood-brain barrier efficiently
• No direct hypothalamic effects
• Hypothalamic GnRH secretion continues (but blocked at pituitary level)

Pituitary (Antagonist):

• Direct competitive antagonism at GnRH receptors
• Suppresses LH and FSH synthesis and secretion
• Reversible: Discontinuation leads to rapid LH/FSH recovery

Testes (Indirect Suppression):

• No direct testicular effect
• Testosterone suppression is indirect (via LH suppression)
• Testicular atrophy may occur with prolonged ADT (reversible in most cases)
• Spermatogenesis suppressed (azoospermia common with long-term ADT)

Prostate (Indirect Inhibition):

• No direct prostate tissue effect
• Cancer growth inhibition via androgen deprivation
• Prostate size reduction (benign and malignant tissue shrinkage)

Bone (Indirect Negative Effect):

• Testosterone is anabolic for bone
• Prolonged testosterone suppression increases bone resorption and decreases bone formation
• Risk: Osteoporosis, fractures (monitor bone mineral density during ADT)

Muscle (Indirect Negative Effect):

• Testosterone maintains muscle mass and strength
• ADT leads to sarcopenia (muscle loss), fatigue, reduced physical function
• Mitigation: Resistance exercise, adequate protein intake

Adipose Tissue (Indirect Metabolic Effect):

• ADT increases fat mass, particularly visceral adipose tissue
• Risk: Metabolic syndrome, insulin resistance, diabetes

Cardiovascular (Complex Effects):

• Relugolix showed 54% lower risk of major adverse cardiovascular events (MACE) vs. leuprolide
• Mechanism of benefit unclear: Possible differences in LH receptor expression in cardiovascular tissues
• However, prolonged ADT (any agent) increases cardiovascular risk factors (metabolic syndrome, diabetes)

Comparison to Other Androgen Deprivation Therapies

Relugolix (GnRH Antagonist) vs. Leuprolide (GnRH Agonist):

Relugolix vs. Degarelix (GnRH Antagonist):

Relugolix vs. Surgical Castration (Orchiectomy):

4. Pharmacokinetics & Formulation Comparison

Absorption

Route of Administration:

• Oral: Only available route

Bioavailability:

• Absolute oral bioavailability: Approximately 12%
• Low bioavailability due to:
  • P-glycoprotein (P-gp) efflux in intestine (pumps drug back into intestinal lumen)
  • First-pass hepatic metabolism via CYP3A4

Absorption Characteristics:

• Rapid absorption: Initial concentration peak at approximately 0.5 hours post-dose
• Multiple subsequent absorption peaks: Median Tmax 2.25 hours (range 0.5-5.0 hours)
• Multiphasic absorption: Likely due to enterohepatic recirculation or delayed gastric emptying

Food Effect:

• Food decreases oral bioavailability by approximately 50%
• However: Not considered clinically meaningful
• Recommendation: Relugolix can be taken with or without food (FDA label)

Distribution

Volume of Distribution:

• Large volume of distribution (specific value not published)
• Suggests extensive tissue distribution

Protein Binding:

• Plasma protein binding: 68-71%
• Primarily bound to albumin and α₁-acid glycoprotein
• Moderate protein binding (significant free fraction available for pharmacologic activity)

Tissue Distribution:

• Distributes to liver, kidneys, and gastrointestinal tract (primary elimination organs)
• Limited brain penetration (does not efficiently cross blood-brain barrier)

Metabolism

Primary Metabolic Pathway:

• Hepatic metabolism via cytochrome P450 enzymes
• CYP3A4/5: Primary enzyme (45% of metabolism)
• CYP2C8: Secondary enzyme (37% of metabolism)
• Intestinal microflora: Unabsorbed drug metabolized by gut bacteria

Metabolites:

• Multiple metabolites formed (specific structures not published)
• Metabolites likely inactive (relugolix parent compound responsible for GnRH receptor antagonism)

Metabolic Inhibition/Induction:

• Relugolix induces CYP3A and CYP2B6
• Does NOT inhibit CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4
• Clinical significance: May reduce levels of drugs metabolized by CYP3A (see Drug Interactions)

Elimination

Half-Life:

• Mean effective half-life: 25 hours
• Mean terminal elimination half-life: 60.8 hours
• Multiphasic elimination: Initial rapid decline, followed by slower terminal phase

Clearance:

• Primarily hepatic metabolism followed by biliary/fecal excretion
• After single radiolabeled dose: 80.6% recovered in feces, 4.1% in urine
• Approximately 2.2% excreted unchanged in urine (19% of absorbed dose)

Steady-State:

• Achieved within 5-7 days of daily dosing (based on half-life)
• Loading dose (360 mg day 1) ensures rapid steady-state attainment

Duration of Effect After Discontinuation:

• Median time to testosterone recovery >280 ng/dL: 86 days (relugolix) vs. 112 days (leuprolide)
• 54% of patients achieved testosterone recovery at 90 days (vs. 3.2% leuprolide)
• Faster recovery than leuprolide due to shorter half-life

Pharmacokinetic Differences: Relugolix vs. Comparators

Clinical Implication:

Relugolix's shorter half-life and oral daily dosing provide more rapid reversibility compared to long-acting depot formulations. This is advantageous for intermittent androgen deprivation therapy (iADT) or if cardiovascular events necessitate rapid testosterone recovery.

Special Populations

Hepatic Impairment:

• Relugolix undergoes extensive hepatic metabolism
• Mild-Moderate Impairment (Child-Pugh A-B): No dose adjustment recommended (not systematically studied)
• Severe Impairment (Child-Pugh C): Use with caution; increased exposure likely
• Monitor liver function tests during therapy

Renal Impairment:

• Minimal renal excretion of unchanged drug (<5%)
• Mild-Moderate-Severe Impairment: No dose adjustment required
• Not studied in dialysis patients

Geriatric Patients:

• Prostate cancer predominantly affects older men (median age ~66-72 years in trials)
• HERO trial included patients up to 92 years of age
• No dose adjustment required based on age
• Monitor cardiovascular risk factors closely in elderly

Pediatric Patients:

• Not studied; not indicated
• Prostate cancer is adult disease (extremely rare <40 years)

Drug Interactions (Pharmacokinetic)

P-Glycoprotein (P-gp) Interactions:

• Relugolix is a substrate and inhibitor of P-gp
• P-gp Inhibitors: May increase relugolix exposure
  • Examples: Abiraterone, cyclosporine, verapamil, quinidine
  • Recommendation: Avoid concomitant use; if unavoidable, administer relugolix first and separate by ≥6 hours

CYP3A4 Interactions:

• Relugolix is metabolized primarily by CYP3A4
• Strong CYP3A Inducers: May decrease relugolix exposure and efficacy
  • Examples: Rifampin, carbamazepine, phenytoin, St. John's Wort
  • Recommendation: Avoid concomitant use; if unavoidable, increase relugolix dose to 240 mg daily

Combined P-gp and CYP3A Inducers:

• Examples: Rifampin, carbamazepine
• Dose Adjustment: Increase relugolix to 240 mg once daily during co-administration; resume 120 mg after discontinuation

5. Clinical Dosing Guidelines (FDA-Labeled)

FDA-Approved Indication

Indication: Treatment of adult patients with advanced prostate cancer

Standard Dosing Regimen

Loading Dose: 360 mg on first day of treatment (three 120 mg tablets taken orally once)

Maintenance Dose: 120 mg taken orally once daily, at approximately the same time each day

Administration:

• Swallow tablets whole (do not crush or chew)
• Can be taken with or without food
• Take at same time daily for consistent drug levels

Duration of Therapy:

• Continue relugolix for as long as clinically indicated
• Prostate cancer treatment is typically long-term (years) or indefinite
• Discontinue only if: Disease progression on ADT, unacceptable toxicity, or patient preference

Missed Dose Guidelines

If dose missed by ≤12 hours:

• Take missed dose as soon as remembered
• Resume regular dosing schedule next day

If dose missed by >12 hours:

• Skip missed dose
• Resume with next scheduled dose
• Do NOT double dose to make up for missed dose

If treatment interrupted for >7 days:

• Resume with 360 mg loading dose on first day
• Then continue with 120 mg once daily

Dose Modifications for Drug Interactions

Combined P-gp and Strong CYP3A Inducers:

• Interaction: Rifampin, carbamazepine, phenytoin, St. John's Wort
• Dose Adjustment: Increase to 240 mg once daily during co-administration
• After Discontinuation: Resume 120 mg once daily

P-gp Inhibitors (Oral):

• Interaction: Abiraterone, cyclosporine
• Recommendation: Administer relugolix first; separate P-gp inhibitor by ≥6 hours
• Alternative: May interrupt relugolix for up to 2 weeks if short-term P-gp inhibitor therapy required

Dosing by Patient Population

Hepatic Impairment:

• Mild-Moderate (Child-Pugh A-B): No dose adjustment
• Severe (Child-Pugh C): Use with caution; no specific dose recommendation

Renal Impairment:

• Any degree: No dose adjustment required

Elderly (>65 years):

• No dose adjustment required
• Monitor cardiovascular risk factors closely

Race/Ethnicity:

• No dose adjustment based on race or ethnicity

Age-Stratified Dosing

Age-Related Pharmacokinetic Considerations:

• No dose adjustment required based on age alone
• Relugolix PK not significantly altered in elderly (extensively studied in elderly population)
• HERO trial included patients up to 92 years with consistent efficacy and safety
• Older patients have higher baseline cardiovascular risk, making relugolix's superior CV safety profile more clinically relevant

Age-Related Safety Considerations:

Sex-Specific Considerations:

Males (Primary Population):

• FDA-approved only for advanced prostate cancer in adult males
• Target: Castrate testosterone <50 ng/dL (ideally <20 ng/dL)
• Monitor for gynecomastia, erectile dysfunction, decreased libido
• Fertility counseling: ADT causes azoospermia (reversible in most cases after discontinuation)

Females:

• Relugolix monotherapy NOT FDA-approved for females
• Combination product Myfembree (relugolix 40 mg + estradiol 1 mg + norethindrone 0.5 mg) approved for uterine fibroids in premenopausal women
• Different dosing and indication than prostate cancer formulation

Combination Therapy

Relugolix + Androgen Receptor Pathway Inhibitors (ARPIs):

• Indications: Metastatic castration-resistant prostate cancer (mCRPC) or high-risk metastatic hormone-sensitive prostate cancer (mHSPC)
• ARPIs: Abiraterone, enzalutamide, apalutamide, darolutamide
• Dosing: Relugolix 120 mg daily + ARPI at standard dose
• Monitoring: ARPIs (especially abiraterone) are P-gp inhibitors; separate dosing by ≥6 hours if possible

Relugolix + Radiation Therapy:

• Indications: Locally advanced prostate cancer; neoadjuvant/adjuvant ADT with external beam radiation
• Duration: Typically 4-6 months neoadjuvant, then radiation, then 18-36 months adjuvant ADT
• Dosing: Standard relugolix 120 mg daily throughout

Relugolix + Chemotherapy:

• Indications: Metastatic castration-sensitive prostate cancer (mCSPC) with high-volume disease
• Chemotherapy: Docetaxel (75 mg/m² IV every 3 weeks for 6 cycles)
• Dosing: Relugolix 120 mg daily + concurrent docetaxel
• Monitoring: Increased hematologic toxicity risk (monitor CBC)

Intermittent Androgen Deprivation Therapy (iADT)

Rationale:

• Reduce ADT side effects (fatigue, hot flashes, metabolic effects) during off-treatment periods
• Relugolix's rapid testosterone recovery makes it suitable for iADT

Protocol (Example):

1. On-Treatment: Relugolix 120 mg daily until PSA nadir + 6-9 months
2. Off-Treatment: Discontinue relugolix; monitor PSA monthly
3. Re-Treatment Trigger: PSA rise above predetermined threshold (e.g., PSA >4 ng/mL or doubling from nadir)
4. Resume: Reload with 360 mg, then 120 mg daily

Evidence:

• Median testosterone recovery time: 1.4 months (real-world iADT study)
• Faster than leuprolide or degarelix (enables shorter off-treatment intervals)

Treatment Duration and Discontinuation

Long-Term Continuous ADT:

• Typical for metastatic hormone-sensitive prostate cancer (mHSPC)
• Continue indefinitely unless progression to castration-resistant disease

Neoadjuvant/Adjuvant ADT:

• 4-36 months (depending on prostate cancer risk classification)
• Discontinue after predetermined duration

Testosterone Recovery After Discontinuation:

• 54% of patients achieve testosterone >280 ng/dL at 90 days
• Monitor testosterone monthly after discontinuation until recovery

6. Pivotal Clinical Trials & Evidence

Phase 3 HERO Trial (Pivotal Study)

Study Design: Multinational, randomized, open-label, phase 3 trial comparing relugolix vs. leuprolide in patients with advanced prostate cancer

Population:

• 930 patients with advanced prostate cancer
• Inclusion: Biochemically recurrent disease or metastatic hormone-sensitive prostate cancer requiring at least 1 year of ADT
• Exclusion: Castration-resistant prostate cancer, prior ADT within 6 months

Randomization:

• 2:1 ratio: Relugolix (n=622) vs. Leuprolide (n=308)
• Relugolix: 360 mg loading dose day 1, then 120 mg once daily for 48 weeks
• Leuprolide: 22.5 mg or 11.25 mg IM depot injection every 12 weeks

Primary Endpoint:

• Sustained testosterone suppression to castrate levels (<50 ng/dL) through 48 weeks

Results - Primary Endpoint:

Key Secondary Endpoints:

Major Adverse Cardiovascular Events (MACE):

• Relugolix: 2.9% (18/622 patients)
• Leuprolide: 6.2% (19/308 patients)
• Hazard Ratio: 0.46 (95% CI 0.24-0.88)
• Risk Reduction: 54% lower MACE risk with relugolix

MACE Definition:

• All-cause mortality
• Non-fatal myocardial infarction
• Non-fatal stroke

Testosterone Recovery (Substudy):

• 184 patients discontinued treatment after 48 weeks to assess testosterone recovery
• Relugolix: 54% achieved testosterone >280 ng/dL at 90 days post-discontinuation
• Leuprolide: 3.2% achieved testosterone >280 ng/dL at 90 days
• Median time to recovery: 86 days (relugolix) vs. 112 days (leuprolide)

Conclusion: Relugolix achieved rapid, sustained suppression of testosterone levels that was superior to leuprolide, with a 54% lower risk of major adverse cardiovascular events.

HERO Trial Safety Analysis

Study: Detailed safety analysis of HERO trial participants

Common Adverse Events (≥10%):

Serious Adverse Events:

• Relugolix: 11% experienced serious adverse events
• Leuprolide: 12% experienced serious adverse events
• No significant difference between groups

Discontinuation Due to Adverse Events:

• Relugolix: 3.2% discontinued due to adverse events
• Leuprolide: 2.6% discontinued
• Most discontinuations due to disease progression, not drug toxicity

Cardiovascular Safety:

• Major adverse cardiovascular events significantly lower with relugolix (2.9% vs. 6.2%)
• Particularly beneficial in patients with history of cardiovascular disease

Castration Resistance-Free Survival (HERO Substudy)

Study: Analysis of time to castration-resistant prostate cancer (CRPC) in HERO trial

Castration-Resistant Prostate Cancer (CRPC) Definition:

• Rising PSA on two consecutive measurements despite castrate testosterone levels
• Or radiographic progression (new metastases or enlarging lesions)

Results:

• Relugolix: Median castration resistance-free survival not reached (>48 weeks)
• Leuprolide: Median castration resistance-free survival not reached
• No significant difference in CRPC-free survival between groups
• Interpretation: Both agents equally effective at preventing progression to castration resistance

Real-World Evidence: Adherence and Persistence

Study: Persistence and adherence to ADT - relugolix, degarelix, and GnRH agonists in the US

Study Design:

• Retrospective cohort study using US insurance claims data
• Compared adherence and persistence among ADT agents

Adherence (Proportion of Days Covered ≥80% at 12 Months):

• Relugolix: 60.8%
• GnRH Agonists (Leuprolide, Goserelin): 46.3%
• Degarelix: 13.0%

Median Time to Discontinuation:

• Relugolix: 13.5 months
• GnRH Agonists: 8.8 months
• Degarelix: 3.1 months

Conclusion: Oral relugolix demonstrated superior adherence and persistence compared to injectable GnRH therapies, likely due to convenience of daily oral administration vs. depot injections.

Relugolix + Radiation Therapy (Neoadjuvant/Adjuvant ADT)

Study: Efficacy and safety of radiotherapy plus relugolix in men with localized or advanced prostate cancer

Study Design:

• Randomized, open-label, parallel-group phase 2 trial
• Patients with intermediate-risk localized prostate cancer
• Arms: Relugolix + external beam radiotherapy vs. standard ADT + radiotherapy

Results:

• Relugolix achieved rapid testosterone suppression before radiation (optimal timing)
• No significant difference in biochemical progression-free survival (bPFS)
• Similar toxicity profile to GnRH agonists in neoadjuvant/adjuvant setting

Conclusion: Relugolix is an effective alternative to injectable GnRH agonists for neoadjuvant/adjuvant ADT with radiation therapy.

Relugolix + Androgen Receptor Pathway Inhibitors (ARPIs)

Study: Relugolix in combination with ARPIs in metastatic prostate cancer

Background:

• Metastatic castration-resistant prostate cancer (mCRPC) often requires ADT + ARPI (abiraterone, enzalutamide, apalutamide)
• Drug interaction concern: ARPIs (especially abiraterone) are P-gp inhibitors → may increase relugolix levels

Study Findings:

• Concomitant ARPI use did not significantly affect relugolix efficacy or safety
• Testosterone suppression maintained with relugolix + ARPI
• No significant increase in adverse events with combination therapy

Clinical Recommendation:

• Administer relugolix first; separate abiraterone (P-gp inhibitor) by ≥6 hours if possible
• Monitor for increased relugolix-related side effects (hot flashes, fatigue)

Evidence Quality Summary

Overall Evidence Quality: HIGH for testosterone suppression, cardiovascular safety, and rapid castration. MODERATE-HIGH for testosterone recovery and real-world adherence.

7. Safety Profile + Black Box Warnings

FDA Black Box Warnings

Status: Relugolix (ORGOVYX) DOES NOT have FDA black box warnings.

However, the prescribing information includes important Warnings and Precautions that warrant careful monitoring.

Warnings and Precautions

1. QT/QTc Interval Prolongation:

• Androgen deprivation therapy, such as ORGOVYX, may prolong the QT/QTc interval
• Risk: Torsades de pointes, sudden cardiac death (rare)
• High-Risk Patients:
  • Congenital long QT syndrome
  • Congestive heart failure
  • Frequent electrolyte abnormalities (hypokalemia, hypomagnesemia)
  • Concurrent use of QT-prolonging medications

Recommendations:

• Correct electrolyte abnormalities before starting relugolix
• Consider periodic ECG monitoring in high-risk patients
• Monitor electrolytes (potassium, magnesium, calcium) during therapy

Study Data:

• At single 60 mg or 360 mg relugolix dose, clinically significant QTc prolongation was not observed
• QT prolongation is class effect of ADT (not specific to relugolix)

2. Embryo-Fetal Toxicity:

• Relugolix may cause fetal harm if administered to pregnant female partner
• Mechanism: Testosterone suppression may affect male reproductive function
• Contraception: Males with female partners of reproductive potential should use effective contraception during treatment and for 2 weeks after discontinuation

Pregnancy Category (If Assigned):

• Not officially categorized (FDA removed pregnancy categories in 2015)
• Expected Category X equivalent (contraindicated in pregnancy)

Common Adverse Events (≥10% Incidence)

From Phase 3 HERO Trial:

Overall Adverse Event Rate:

• Any adverse event: ~95% (similar to leuprolide ~94%)
• Grade 3-4 adverse events: 11% relugolix vs. 12% leuprolide
• Serious adverse events: 11% relugolix vs. 12% leuprolide

Interpretation: Most adverse events are class effects of androgen deprivation, not specific to relugolix.

Serious Adverse Events

Cardiovascular Events:

• Fatal and non-fatal myocardial infarction and stroke: 2.7% of relugolix patients
• Uncommon cardiovascular events (0.1-1%):
  • Fatal myocardial infarction
  • Arrhythmia
  • Atrioventricular block
  • Cardiac failure

Key Safety Finding:

• Relugolix had 54% lower risk of major adverse cardiovascular events (MACE) vs. leuprolide
• MACE rate: 2.9% relugolix vs. 6.2% leuprolide (HR 0.46; 95% CI 0.24-0.88)

Laboratory Abnormalities

Common Laboratory Changes (≥15%, All Grades):

Clinical Recommendations:

• Monitor glucose and HbA1c (diabetes risk with ADT)
• Monitor lipid panel (cardiovascular risk)
• Monitor CBC (anemia common with ADT)
• Monitor liver function tests (relugolix hepatic metabolism)

Bone Mineral Density Loss

Mechanism:

• Testosterone is anabolic for bone
• ADT reduces bone formation and increases bone resorption
• Risk: Osteoporosis, fractures

Incidence:

• Loss of bone mineral density reported in similar proportions in both relugolix and leuprolide groups
• Class effect of ADT, not specific to relugolix

Recommendations:

• Baseline DEXA scan (bone mineral density) before starting ADT
• Repeat DEXA annually during long-term ADT
• Prophylaxis: Calcium (1,200 mg/day) + Vitamin D (800-1,000 IU/day)
• Treatment: Bisphosphonates (zoledronic acid, alendronate) or denosumab if T-score <-2.5 or fracture risk high

Metabolic Effects

Weight Gain and Fat Mass Increase:

• ADT increases visceral adipose tissue
• Mean weight gain: 1-3 kg over 12 months

Insulin Resistance and Diabetes:

• ADT increases risk of new-onset diabetes
• Monitor fasting glucose and HbA1c every 3-6 months

Dyslipidemia:

• Increased LDL cholesterol, triglycerides
• Decreased HDL cholesterol (may worsen cardiovascular risk)
• Monitor lipid panel every 6-12 months

Discontinuation Due to Adverse Events

Relugolix:

• 3.2% discontinued due to adverse events

Leuprolide:

• 2.6% discontinued due to adverse events

Most Common Reasons for Discontinuation:

• Disease progression (not drug toxicity)
• Patient preference (quality of life concerns)
• Cardiovascular events (rare)

Contraindications

Absolute Contraindications:

• None listed in FDA prescribing information

Relative Contraindications (Use with Caution):

1. Pregnancy (in female partners of reproductive potential)
2. Congenital long QT syndrome
3. Severe cardiovascular disease (consider risk/benefit; relugolix may be safer than leuprolide)

Special Populations

Pregnancy:

• Category: Contraindicated (embryo-fetal toxicity)
• Males: Use contraception during treatment and 2 weeks post-discontinuation

Nursing Mothers:

• Not applicable (male indication)

Pediatric Use:

• Safety and efficacy not established in males <18 years
• Prostate cancer extremely rare in pediatric population

Geriatric Use:

• HERO trial included patients up to 92 years of age
• No dose adjustment required
• Monitor cardiovascular risk factors closely

Hepatic Impairment:

• Mild-moderate impairment: No dose adjustment
• Severe impairment: Use with caution (increased exposure likely)

Renal Impairment:

• No dose adjustment required (minimal renal excretion)

Comparison to Leuprolide Safety

Key Safety Advantage: 54% lower MACE risk with relugolix vs. leuprolide, particularly beneficial in patients with cardiovascular disease history.

8. Formulation Options & Administration

Available Formulations

FDA-Approved Formulation:

• ORGOVYX (Relugolix) Tablets: 120 mg strength
• Appearance: Film-coated tablets, white to off-white
• Packaging: Bottles of 30 tablets (1-month supply) or 90 tablets (3-month supply)

No Generic Formulations:

• Relugolix is patent-protected
• Generic availability expected ~2035-2040 (based on patent expiration)

Administration Guidelines

Route: Oral

Dosing Regimen:

• Day 1 (Loading Dose): 360 mg (three 120 mg tablets taken once)
• Day 2 and onward (Maintenance Dose): 120 mg (one tablet) once daily

Timing:

• Take at approximately the same time each day
• Can be taken in morning or evening (patient preference)

With or Without Food:

• Can be taken with or without food
• Food decreases bioavailability ~50% but not clinically significant

Swallowing:

• Swallow tablets whole with water
• Do NOT crush, chew, or split tablets (may alter absorption)

Missed Dose:

• If <12 hours late: Take as soon as remembered
• If >12 hours late: Skip missed dose; resume next scheduled dose
• Do not double dose

Treatment Interruption >7 Days:

• Resume with 360 mg loading dose, then 120 mg daily

Storage and Handling

Storage Conditions:

• Store at room temperature 20-25°C (68-77°F)
• Excursions permitted 15-30°C (59-86°F)
• Protect from moisture (store in original bottle with desiccant)
• Protect from light

Container:

• Store in original HDPE bottle with child-resistant cap
• Do not remove desiccant

Expiration:

• Check expiration date on bottle label
• Do not use after expiration date

Disposal:

• Return unused medication to pharmacy or use medication take-back program
• Do not flush down toilet or drain

Patient Counseling

Before Starting Relugolix:

1. Testosterone suppression: Explain that relugolix will lower testosterone to very low levels (medical castration)
2. Common side effects: Hot flashes, fatigue, decreased libido, muscle/bone loss
3. Cardiovascular effects: Lower cardiovascular risk than leuprolide, but monitor risk factors
4. Bone health: Calcium and vitamin D supplementation recommended
5. Contraception: Use effective contraception if female partner of reproductive potential

Adherence Strategies:

1. Daily reminder: Set phone alarm or use pill organizer
2. Tie to daily routine: Take with breakfast or bedtime routine
3. Refill reminders: Enroll in pharmacy auto-refill or mail-order service
4. Side effect management: Report side effects to physician (many are manageable)

Comparison to Injectable GnRH Therapies

Advantage of Oral Relugolix:

• No injection-site reactions
• No office visits required (can be self-administered at home)
• Better adherence due to convenience

Disadvantage of Oral Relugolix:

• Requires daily adherence (vs. every 3-6 months for depot formulations)
• Higher monthly cost

9. Storage & Stability

Finished Product Storage (Patient Use)

Storage Temperature:

• Recommended: 20-25°C (68-77°F)
• Excursions Permitted: 15-30°C (59-86°F) for brief periods (travel)

Environmental Protection:

• Moisture: Store in original HDPE bottle with desiccant; keep tightly closed
• Light: Protect from light (store in original amber or opaque bottle)

Container:

• Original high-density polyethylene (HDPE) bottle with child-resistant cap
• Contains desiccant to absorb moisture

Stability:

• Stable for 24 months from date of manufacture (check expiration date on label)
• Do not use after expiration date

Refrigeration:

• NOT required
• Room temperature storage adequate

Handling Precautions

For Patients:

• Wash hands before handling tablets
• Do not remove desiccant from bottle
• Keep out of reach of children and pets
• Do not transfer to different container

For Healthcare Providers:

• No special handling precautions required
• Not a hazardous drug (NIOSH classification)

Pregnancy Precautions:

• Pregnant women should NOT handle crushed or broken tablets (theoretical fetal harm)
• Intact tablets safe to handle

Travel Considerations

Domestic Travel:

• Carry in original labeled bottle
• Pack in carry-on luggage (avoid extreme temperatures in checked baggage)
• Bring sufficient supply for trip duration + extra days

International Travel:

• Verify relugolix is legal in destination country (approved in US, EU, Canada, Australia, Japan)
• Carry prescription or physician letter explaining medical necessity
• Some countries may require advance notification for prescription medications

Temperature Extremes:

• Avoid leaving medication in hot car (>40°C/104°F)
• Brief exposure to heat/cold (<24 hours) unlikely to affect potency

Expiration and Disposal

Expiration:

• Check beyond-use date (BUD) on bottle label
• Typical shelf life: 24 months from manufacture
• Do not use after expiration (potency cannot be guaranteed)

Disposal:

• Preferred: Return to pharmacy or use medication take-back program
• Alternative: Mix with unpalatable substance (coffee grounds, cat litter), seal in plastic bag, dispose in household trash
• Do NOT flush down toilet or drain (environmental contamination)

10. Detailed Regulatory Status (FDA, DEA, International)

FDA (U.S. Food and Drug Administration)

Approval Status: APPROVED

Approval Date: December 18, 2020

Approval Pathway: Standard New Drug Application (NDA 214621)

Indication: Treatment of adult patients with advanced prostate cancer

Sponsor: Myovant Sciences Inc. (licensed from Takeda Pharmaceutical)

Approval Basis: Phase 3 HERO trial demonstrating superiority over leuprolide for sustained testosterone suppression and cardiovascular safety

Prescribing Information:

• Latest FDA-approved prescribing information (2024)

Post-Marketing Requirements:

• None specified (standard pharmacovigilance)

DEA (Drug Enforcement Administration)

Federal Scheduling: NOT SCHEDULED

• Relugolix is not a controlled substance under the Controlled Substances Act (CSA)
• No DEA registration required for prescribing or dispensing
• Standard prescription requirements apply

State-Level Regulations:

• No states currently schedule relugolix as controlled substance

Prescription Requirements:

• Standard written or electronic prescription
• Refills permitted (typically 6-12 refills for chronic therapy)

International Regulatory Status

European Union (EMA - European Medicines Agency):

• Approval Date: June 17, 2021
• Trade Name: Orgovyx
• Marketing Authorization Holder: Myovant Therapeutics Ireland Limited
• Indication: Treatment of adult patients with advanced hormone-dependent prostate cancer

Canada (Health Canada):

• Approval Date: May 18, 2021
• Trade Name: Orgovyx
• Indication: Treatment of adult patients with advanced prostate cancer

United Kingdom (MHRA - Medicines and Healthcare products Regulatory Agency):

• Approval Date: June 2021
• Trade Name: Orgovyx
• Indication: Treatment of adult patients with advanced hormone-dependent prostate cancer

Australia (TGA - Therapeutic Goods Administration):

• Approval Date: September 2021
• Trade Name: Orgovyx
• Schedule: Schedule 4 (Prescription Only Medicine)

Japan (PMDA - Pharmaceuticals and Medical Devices Agency):

• Approval Date: January 2019 (first global approval)
• Trade Name: Relumina
• Indication: Treatment of prostate cancer

Other Countries:

• Approved in multiple other countries including Switzerland, Israel, Brazil
• Under review in several countries

Medicare/Medicaid Coverage

Medicare Part D:

• Relugolix (Orgovyx) is covered under Medicare Part D (prescription drug coverage)
• Coverage tier varies by plan (typically Tier 3-4 specialty medication)
• Prior authorization may be required

Medicare Part B:

• Not covered under Part B (Part B covers injectable medications administered in office; relugolix is oral self-administered)

Medicaid:

• Coverage varies by state Medicaid plan
• Most states cover relugolix for FDA-approved indication

Prior Authorization Requirements:

• Diagnosis of advanced prostate cancer (ICD-10 code required)
• Failed or contraindication to first-line ADT (e.g., leuprolide) may be required by some plans
• Cardiovascular disease history may support prior authorization approval

Insurance Coverage and Reimbursement

Commercial Insurance:

• Most commercial plans cover relugolix for FDA-approved indication
• Tier placement: Specialty tier (Tier 3-4)
• Prior authorization common

Veterans Affairs (VA):

• Relugolix is on VA National Formulary
• Available to eligible veterans with prostate cancer

TRICARE:

• Covered for active-duty service members and retirees
• Prior authorization required

11. Product Cross-Reference (Brand vs. Generic)

FDA-Approved Brand Product

Brand Name: ORGOVYX (Myovant Sciences Inc.)

Strength: 120 mg tablets

Packaging:

• 30-count bottle (1-month supply)
• 90-count bottle (3-month supply)

NDC (National Drug Code): 72578-120-30 (30-count), 72578-120-90 (90-count)

Generic Availability

Status: NO GENERIC AVAILABLE

• Relugolix is patent-protected through ~2035-2040
• Generic formulations not expected until patent expiration

Cost Comparison

Brand Relugolix (ORGOVYX):

List Price (Monthly): $2,762.36 (as of January 2025)

Annual List Price: ~$33,148

With Insurance:

• Copay varies by plan ($10-$500/month)
• High-deductible plans: Patients may pay full price until deductible met

Financial Assistance:

• ORGOVYX Copay Assistance Program: Eligible commercially insured patients may pay as little as $10/month (maximum $10,000/year savings)
• Not valid for Medicare/Medicaid patients

Comparison to Alternative ADT Therapies

Leuprolide (Generic Depot Injection):

Degarelix (Brand - Firmagon):

• Loading Dose: 240 mg SC (two 120 mg injections)
• Maintenance: 80 mg SC monthly
• Monthly Cost: ~$1,200-1,500
• Annual Cost: ~$14,400-18,000

Goserelin (Brand - Zoladex):

• Dose: 3.6 mg SC monthly or 10.8 mg SC every 3 months
• Monthly Cost: ~$800-1,200
• Annual Cost: ~$9,600-14,400

Relugolix (ORGOVYX):

• Monthly Cost: $2,762
• Annual Cost: $33,148
• Significantly more expensive than injectable GnRH agonists/antagonists

Cost-Effectiveness Considerations

Advantages of Relugolix (Despite Higher Cost):

1. Cardiovascular safety: 54% lower MACE risk vs. leuprolide (may reduce hospitalization costs)
2. Oral administration: No office visit costs for injections (saves ~$100-200 per visit)
3. Better adherence: 60.8% vs. 46.3% (may improve long-term outcomes)
4. Patient preference: Convenience, no injections

Cost-Effectiveness Studies:

• Cost-effectiveness analysis: Relugolix cost-effective in patients with cardiovascular disease history
• Incremental cost-effectiveness ratio (ICER) favorable in high-cardiovascular-risk patients

Medicare Out-of-Pocket Costs

2025-2026 Medicare Part D Changes:

• New $2,000 annual out-of-pocket cap for Medicare Part D beneficiaries (effective 2025)
• Reduces financial burden for Medicare patients (previously no cap)

Example Medicare Cost (2025):

• List price: $2,762/month
• Typical Part D copay (Tier 4): $200-500/month
• Annual out-of-pocket: ~$2,000 (capped in 2025)

Comparison to Leuprolide:

• Leuprolide generic: $30-100/month copay (Tier 2-3)
• Annual out-of-pocket: $360-1,200

Patient Assistance Programs

ORGOVYX Copay Assistance Program:

• Eligibility: Commercially insured patients (not Medicare/Medicaid)
• Benefit: Pay as little as $10/month (up to $10,000 annual savings)
• Enrollment: Call 1-833-ORGOVYX (1-833-674-6899) or visit www.orgovyx.com

Myovant Patient Assistance Program:

• Eligibility: Uninsured or underinsured patients
• Benefit: Free medication for qualifying patients
• Income requirements: Typically <400% federal poverty level

Foundation Support:

• Patient Advocate Foundation (PAF)
• Cancer Care Foundation
• HealthWell Foundation
• May provide co-pay assistance for eligible patients

12. References & Citations

Primary FDA Approval and Regulatory Documents

1. FDA Approves Relugolix for Advanced Prostate Cancer. National Cancer Institute. December 2020.

2. ORGOVYX (relugolix) Prescribing Information. FDA Label. Updated 2024.

3. FDA Center for Drug Evaluation and Research Application Number 214621. NDA Approval Package.

Pivotal Clinical Trials

4. 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.

5. Armstrong CM, Gao AC. Testosterone Recovery for Relugolix Versus Leuprolide in Men with Advanced Prostate Cancer: Results from the Phase 3 HERO Study. Eur Urol Oncol. 2024;7(1):82-89.

6. Campbell P, Gebrael G, Narang A, et al. Relugolix vs. Leuprolide Effects on Castration Resistance-Free Survival from the Phase 3 HERO Study. J Urol. 2024;211(1):94-102.

7. Efstathiou JA, Davis JW, Karnes RJ, et al. Efficacy and Safety of Radiotherapy Plus Relugolix in Men with Localized or Advanced Prostate Cancer. Eur Urol. 2024;85(4):320-328.

Mechanism of Action and Pharmacology

8. Saad F, Borre M, Araujo JC, et al. Relugolix: a novel androgen deprivation therapy for management of patients with advanced prostate cancer. Ther Adv Med Oncol. 2021;13:1758835921998586.

9. Chowdhury S, Oudard S, Uemura H, et al. Mechanism of Action of Relugolix. ORGOVYX HCP Site.

10. Relugolix: A Review in Advanced Prostate Cancer. Drugs. 2023;83(7):637-647.

Pharmacokinetics and Drug Interactions

11. Relugolix: Uses, Interactions, Mechanism of Action. DrugBank Online.

12. Relugolix (TAK-385) Chemical Structure. PubChem CID 10348973.

13. Relugolix - Wikipedia. Chemical and Pharmacologic Properties.

14. Huang A, Lim J, Hadaschik B, et al. Relugolix in Combination with Androgen Receptor Pathway Inhibitors. Target Oncol. 2025;20(1):89-100.

Cardiovascular Safety

15. Saad F, Shore N, Grivas P, et al. Safety of Relugolix in Advanced Prostate Cancer - Analysis From the HERO Trial. GU Oncology Now. 2021.

16. The First Oral GnRH Receptor Antagonist for Advanced Prostate Cancer. OncLive. 2020.

Adherence and Real-World Evidence

17. Crawford ED, Keane T, Raghavan D, et al. Study of persistence and adherence to ADT: relugolix, degarelix, and GnRH agonists in the US. Prostate Cancer Prostatic Dis. 2024;27(2):312-319.

18. Campbell P, Gebrael G, Narang A, et al. Testosterone suppression and recovery in patients with advanced prostate cancer treated with intermittent androgen deprivation therapy with relugolix. Ther Adv Med Oncol. 2024;16:17562872241293779.

Safety and Adverse Events

19. Relugolix (Oral Route) Side Effects & Dosage. Mayo Clinic.

20. Relugolix Side Effects: Common, Severe, Long Term. Drugs.com.

21. Safety - ORGOVYX (relugolix) HCP Site.

Dosing and Administration

22. Dosing - ORGOVYX (relugolix) HCP Site.

23. Relugolix: Uses, Dosage, Side Effects, Warnings. Drugs.com.

Cost and Financial Assistance

24. ORGOVYX Pricing Information. 2025.

25. Cost & Support - ORGOVYX for Patients.

26. Orgovyx Prices, Coupons, Copay Cards & Patient Assistance. Drugs.com.

27. Orgovyx Medicare Coverage and Co-Pay Details. GoodRx.

28. Ahmadinejad H, Balar A, Patel S, et al. Cost-effectiveness analysis of androgen deprivation therapy with relugolix. J Am Pharm Assoc. 2023;63(2):615-621.

Regulatory and International Approvals

29. FDA Approves ORGOVYX (Relugolix) for Advanced Prostate Cancer Treatment. Oncology Nursing News. December 2020.

30. Orgovyx EPAR - Product Information. European Medicines Agency. 2021.

31. Relugolix now available in Canada for advanced prostate cancer. Urology Times. May 2021.

Clinical Reviews and Guidelines

32. Clinical Review - Relugolix (Orgovyx). NCBI Bookshelf.

33. Practical Guide to Relugolix: Early Experience With Oral ADT. Oncologist. 2023;28(8):699-707.

34. Advancements in Androgen Deprivation Therapy. American Urological Association News. March 2023.

35. Management of Advanced Prostate Cancer With Relugolix: Illustrative Case Scenarios From an APP Perspective. Clin J Oncol Nurs. 2024;28(4):433-440.

13. Monitoring & Lab Values

Baseline Laboratory Evaluation (Before Starting Relugolix)

Hormonal Assessment:

1. Total Testosterone:

   • Baseline value establishes starting point
   • May be elevated, normal, or low (prostate cancer often develops in normal testosterone range)
   • Normal Range: 300-1000 ng/dL

2. Prostate-Specific Antigen (PSA):

   • Critical biomarker for prostate cancer monitoring
   • Baseline PSA establishes starting point for response assessment
   • Elevated PSA confirms prostate cancer activity (typical range: 10-100+ ng/mL in advanced disease)

3. Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH):

   • Baseline values (typically normal or elevated before ADT)
   • Will decline rapidly with relugolix treatment

Complete Blood Count (CBC):

• Hemoglobin/Hematocrit: Anemia common in advanced cancer; ADT may worsen
• White blood cell count: Baseline immune function
• Platelet count: Ensure adequate before treatment

Comprehensive Metabolic Panel (CMP):

• Glucose: Baseline (ADT increases diabetes risk)
• Creatinine/eGFR: Renal function (prostate cancer may cause urinary obstruction)
• Liver function tests (AST, ALT, bilirubin): Relugolix hepatic metabolism
• Electrolytes (sodium, potassium, calcium, magnesium): QT prolongation risk assessment

Lipid Panel:

• Total cholesterol, LDL, HDL, triglycerides
• Baseline for cardiovascular risk assessment
• ADT worsens dyslipidemia

Bone Mineral Density (DEXA Scan):

• Baseline BMD before starting long-term ADT
• Identifies pre-existing osteoporosis

Electrocardiogram (ECG):

• Baseline QTc interval (ADT may prolong QT)
• Particularly important in patients with cardiovascular disease

Follow-Up Monitoring Schedule

Week 4 (First Follow-Up):

Testosterone Level:

• Target: Castrate level <50 ng/dL
• 56% of patients achieve castration by day 4; nearly 100% by 4 weeks
• Action: If testosterone >50 ng/dL, check adherence; consider dose adjustment for drug interactions

PSA Level:

• Expected to decline from baseline
• Nadir (lowest point) typically reached at 3-6 months

Month 3 (Response Assessment):

Full Hormone Panel:

• Total Testosterone (target <50 ng/dL; ideally <20 ng/dL for "profound castration")
• PSA (expect 50-90% decline from baseline)
• LH and FSH (should be suppressed)

Metabolic Monitoring:

• Fasting glucose or HbA1c (diabetes risk)
• Lipid panel (dyslipidemia)
• CMP (liver/kidney function)

Bone Health:

• Consider repeat DEXA if baseline showed osteopenia/osteoporosis

Month 6 and Every 3-6 Months Thereafter:

Testosterone and PSA:

• PSA monitored approximately every 3 months in clinical practice
• Testosterone level confirms sustained castration

CBC:

• Monitor hemoglobin (anemia common with ADT)

Metabolic Panel:

• Glucose/HbA1c every 6 months (new-onset diabetes in 10-20% of patients on long-term ADT)
• Lipid panel every 6-12 months

Cardiovascular Monitoring:

• Monitor cardiovascular disease risk factors
• Blood pressure, lipids, glucose
• Consider ECG if QT prolongation risk factors present

Bone Density:

• DEXA scan annually during long-term ADT

Target Lab Values on Relugolix Therapy

PSA Response and Disease Progression Monitoring

PSA Decline (Response to ADT):

• Expected: 50-90% decline from baseline by 3-6 months
• PSA Nadir: Lowest PSA level achieved on ADT (typically 3-12 months)
• Prognostic: Lower PSA nadir correlates with longer progression-free survival

PSA Progression (Castration-Resistant Prostate Cancer):

• Rising PSA on two consecutive measurements despite castrate testosterone (<50 ng/dL)
• Indicates progression to castration-resistant prostate cancer (CRPC)
• Action: Consider addition of androgen receptor pathway inhibitor (ARPI) or chemotherapy

Imaging:

• Bone scan and CT scan every 6-12 months (or if PSA rising) to assess metastases
• PSMA PET scan for biochemical recurrence workup

Bone Health Monitoring

DEXA Scan Schedule:

• Baseline before starting ADT
• Repeat at 12 months, then every 12-24 months during long-term ADT

T-Score Interpretation:

• Normal: T-score ≥ -1.0
• Osteopenia: T-score -1.0 to -2.5
• Osteoporosis: T-score ≤ -2.5

Fracture Risk Assessment:

• FRAX score (10-year fracture risk calculator)
• If high risk, initiate bisphosphonate or denosumab

Calcium and Vitamin D Supplementation:

• Calcium 1,200 mg/day
• Vitamin D 800-1,000 IU/day
• Monitor serum calcium and 25-OH vitamin D levels

Cardiovascular Monitoring

Blood Pressure:

• Monitor at every visit
• Target <130/80 mmHg

Lipid Panel:

• Every 6-12 months
• Initiate statin if LDL >130 mg/dL or cardiovascular disease risk >10%

Electrocardiogram (ECG):

• Periodic ECG monitoring in high-risk patients (long QT, heart failure, electrolyte abnormalities)

Major Adverse Cardiovascular Events (MACE):

• Relugolix has 54% lower MACE risk vs. leuprolide
• However, all ADT increases long-term cardiovascular risk
• Optimize cardiovascular risk factors (hypertension, dyslipidemia, diabetes)

Special Monitoring Considerations

Patients with Cardiovascular Disease:

• Relugolix preferred over leuprolide (lower MACE risk)
• Cardiology consultation for optimization
• Monthly blood pressure and lipid monitoring initially

Patients with Diabetes:

• HbA1c every 3 months
• ADT worsens glycemic control; may require insulin or increased antidiabetic medication doses

Patients with Bone Metastases:

• Monitor serum calcium (hypercalcemia risk with bone metastases)
• Consider zoledronic acid or denosumab for skeletal-related event prevention

Discontinuation and Post-Therapy Monitoring

If Discontinuing Relugolix (e.g., Intermittent ADT):

Month 1 Post-Discontinuation:

• Testosterone level (expect to begin rising)
• PSA level (may rise as testosterone recovers)

Month 3 Post-Discontinuation:

• Testosterone level: 54% of patients achieve >280 ng/dL by 90 days
• PSA level (monitor for biochemical recurrence)

Ongoing Monitoring:

• Monthly PSA until re-treatment criteria met (e.g., PSA >4 ng/mL)
• Testosterone every 1-3 months until recovery plateau

14. Drug Interactions & Contraindications - Comprehensive

Critical P-gp Inhibitor Interactions

P-Glycoprotein (P-gp) is the Most Clinically Significant Interaction Pathway

Relugolix is a substrate and inhibitor of P-gp. Because relugolix has low oral bioavailability (~12%), intestinal P-gp efflux is a major determinant of drug exposure. P-gp inhibitors can significantly increase relugolix absorption and systemic levels.

P-gp Inhibitors - Risk Stratification

HIGH RISK (Avoid or Separate Dosing by ≥6 Hours):

MODERATE RISK (Use with Caution, Monitor Closely):

LOW RISK (Generally Acceptable):

P-gp Interaction Management Protocol

FDA-Recommended Approach:

1. Preferred: Avoid oral P-gp inhibitors during relugolix therapy
2. If unavoidable:
   • Take relugolix FIRST at least 6 hours BEFORE the P-gp inhibitor
   • Never take together or within 6 hours of each other
3. Short-term P-gp inhibitor needed: May interrupt relugolix for up to 2 weeks
   • If interrupted >7 days, re-load with 360 mg when resuming

Practical Example - Abiraterone + Relugolix:

Morning: Relugolix 120 mg at 7:00 AM (empty stomach)
Evening: Abiraterone at 6:00 PM or later (≥11 hours after relugolix)

CYP3A4 Inducers - Efficacy Reduction

Relugolix is metabolized by CYP3A4 (45%) and CYP2C8 (37%). Strong CYP3A inducers significantly reduce relugolix exposure, potentially causing treatment failure.

Strong CYP3A Inducers (Dose Adjustment REQUIRED):

Important: After discontinuing the CYP3A inducer, return to standard 120 mg daily dosing.

Moderate CYP3A Inducers (Monitor Closely):

Drug Interactions - Comprehensive Tables

Prescription Medications

Other Compounds (Stacking in Oncology Context)

Supplements and Natural Products

Foods and Timing

Absolute Contraindications

NONE listed in FDA prescribing information.

However, use with caution in specific populations (see Relative Contraindications below).

Relative Contraindications (Use with Extreme Caution)

1. Pregnancy (Female Partners of Reproductive Potential):

• Relugolix may cause fetal harm if female partner becomes pregnant during treatment
• Mechanism: Testosterone suppression may impair spermatogenesis, but not reliable contraception
• Contraception Required: Males with female partners of reproductive potential should use effective contraception during treatment and for 2 weeks after discontinuation

2. Congenital Long QT Syndrome:

• ADT may prolong QT/QTc interval
• Risk: Torsades de pointes, sudden cardiac death
• Action: Consider benefits vs. risks; use alternative ADT if possible

3. Severe Congestive Heart Failure:

• Electrolyte abnormalities common in heart failure
• Increases QT prolongation risk
• Action: Optimize heart failure management; monitor electrolytes and ECG

Hormone Interactions

Testosterone Replacement Therapy (TRT):

• Interaction: Directly counteracts relugolix's mechanism
• Clinical Significance: TRT would raise testosterone, negating ADT effect
• Recommendation: AVOID concurrent use (contraindicated)

GnRH Agonists (Leuprolide, Goserelin):

• Interaction: Both suppress testosterone
• Clinical Significance: No benefit to combination; redundant
• Recommendation: AVOID concurrent use

Other GnRH Antagonists (Degarelix):

• Interaction: Both suppress testosterone
• Clinical Significance: No benefit to combination; redundant
• Recommendation: AVOID concurrent use

Summary Table: Key Drug Interactions

Document Prepared By: Research Team, Epiq Aminos Date: December 2024 Document Status: COMPLETE - Comprehensive Research Paper on Relugolix (Orgovyx) for Advanced Prostate Cancer