Relugolix

Relugolix is an oral gonadotropin-releasing hormone (GnRH) receptor antagonist that reduces the production of sex hormones by blocking GnRH receptors in the pituitary gland. In men, this lowers luteinising hormone and follicle-stimulating hormone levels, reducing testosterone production and supporting androgen deprivation therapy for advanced prostate cancer. In women, relugolix can be used in combination with estradiol and norethindrone acetate to manage selected gynaecological conditions, including heavy menstrual bleeding associated with uterine fibroids and moderate to severe pain associated with endometriosis. These formulations have different compositions, indications, and safety considerations and should not be considered interchangeable. Relugolix is supplied as an oral tablet and is generally taken once daily according to the relevant product instructions. By suppressing hormone signalling, it can help control hormone-sensitive disease or reduce symptoms associated with excess hormonal stimulation. Treatment requires assessment of the patient's medical history, concomitant medicines, and relevant laboratory or clinical parameters. Important considerations include cardiovascular risk, potential changes in heart rhythm, liver-related laboratory abnormalities, and bone mineral density. Combination therapy containing estradiol and norethindrone acetate also carries risks associated with oestrogen and progestin exposure, including thromboembolic events. The appropriate formulation and duration depend on the condition being treated and the applicable prescribing information.

Relugolix was developed as an orally active, non-peptide GnRH receptor antagonist. Unlike GnRH agonists, which can initially stimulate hormone release before suppressing it, relugolix blocks the receptor directly and reduces gonadotropin secretion. In the United States, the FDA approved relugolix as ORGOVYX in December 2020 for adults with advanced prostate cancer. The FDA subsequently approved MYFEMBREE in 2021, a combination of relugolix, estradiol, and norethindrone acetate, initially for heavy menstrual bleeding associated with uterine fibroids; its indication was expanded in 2022 to include moderate to severe pain associated with endometriosis in premenopausal women. The prostate cancer indication was supported by the HERO phase III clinical trial, which evaluated sustained testosterone suppression compared with leuprolide. The LIBERTY phase III clinical programme evaluated relugolix combination therapy for heavy menstrual bleeding associated with uterine fibroids, while the SPIRIT phase III trials evaluated its use for endometriosis-associated pain. Regulatory authorisations and product availability vary between countries. Indian Central Drugs Standard Control Organisation (CDSCO) committee records have discussed proposed relugolix products and indications; such committee recommendations or permissions to conduct clinical trials should not be interpreted as proof of final marketing approval. The approved status of a particular formulation should therefore be verified against current local regulatory information.

Relugolix as a single-agent tablet is approved in the United States for the treatment of adult patients with advanced prostate cancer. It suppresses testosterone production and may be used as part of long-term androgen deprivation therapy, according to the patient's clinical condition and oncology treatment plan. Relugolix in combination with estradiol and norethindrone acetate is approved in the United States for the management of heavy menstrual bleeding associated with uterine leiomyomas, commonly known as uterine fibroids, and moderate to severe pain associated with endometriosis in premenopausal women. The added hormones help mitigate some consequences of ovarian hormone suppression, particularly bone loss and vasomotor symptoms, but introduce additional oestrogen- and progestin-related risks. The single-agent and combination formulations have different indications, contraindications, and dosing instructions. Approval for one formulation does not establish approval for another condition or formulation. Uses in other gynaecological conditions, fertility treatment, or other hormone-sensitive disorders should not be assumed to be approved unless supported by the relevant local product information and clinical guidance.

Relugolix dosing depends on the formulation and indication. For adults receiving single-agent relugolix for advanced prostate cancer under US prescribing information, treatment begins with a 360 mg oral loading dose on the first day, followed by 120 mg orally once daily at approximately the same time each day. Tablets may be taken with or without food and should be swallowed whole. If treatment is interrupted for more than seven days, the prescribing information directs restarting with the loading dose. For the relugolix, estradiol, and norethindrone acetate combination used for uterine fibroids or endometriosis, the usual US regimen is one tablet orally once daily, with treatment initiated according to the product's menstrual-cycle instructions. Pregnancy must be excluded before starting the combination, and hormonal contraceptives should be discontinued as directed by the prescribing information. The recommended duration of the combination is limited to 24 months because continued bone loss may not be reversible. Treatment duration for single-agent relugolix in prostate cancer depends on disease status, treatment goals, tolerability, and the oncology plan. Clinicians should follow the specific product label for missed doses, interactions, interruptions, and monitoring requirements.

Common adverse effects of single-agent relugolix include hot flushes, fatigue, musculoskeletal pain, constipation, diarrhoea, and changes in laboratory measurements such as glucose, triglycerides, liver enzymes, and haemoglobin. Suppression of testosterone can also contribute to reduced libido, erectile dysfunction, and other effects associated with androgen deprivation. Patients taking the relugolix combination for gynaecological conditions may experience hot flushes, headache, sweating, mood changes, irregular uterine bleeding, or reduced menstrual bleeding. The combination may also affect bone mineral density and can produce adverse effects associated with estradiol and norethindrone acetate. Side effects vary with the formulation, treatment duration, individual health status, and concomitant medicines. Some symptoms improve with continued treatment, while persistent or troublesome effects may require clinical review. Patients should not alter or discontinue treatment without consulting their prescriber, particularly when relugolix is being used as part of prostate cancer treatment.

Relugolix may contribute to QT/QTc interval prolongation, a change in the heart's electrical activity that can increase the risk of serious rhythm disturbances in susceptible patients. Androgen deprivation therapy is also associated with metabolic changes and potential cardiovascular risk; patients with relevant cardiac conditions or risk factors require appropriate assessment. Single-agent relugolix can cause hypersensitivity reactions, including angioedema, and is contraindicated in patients with known severe hypersensitivity to the product. The medicine may cause fetal harm through its mechanism of action, and appropriate contraception counselling is necessary when pregnancy is possible. The relugolix combination carries a boxed warning in US prescribing information for thromboembolic and vascular events, including deep vein thrombosis, pulmonary embolism, stroke, and myocardial infarction. It is contraindicated in certain patients with current or previous thromboembolic disease or substantial cardiovascular risk. The combination may also cause bone mineral density loss, which can persist or may not be fully reversible; treatment is limited to 24 months under US prescribing information. Pregnancy is a contraindication to the combination. Treatment should be interrupted or discontinued when required by severe hypersensitivity, significant adverse events, suspected pregnancy, or other product-specific safety criteria. Urgent assessment is required for symptoms such as chest pain, sudden breathlessness, one-sided leg swelling, or sudden neurological changes.

Before starting relugolix, assess the indication, current medicines, cardiovascular history, and relevant baseline clinical and laboratory parameters. For single-agent treatment, consider the risk of QT prolongation, electrolyte abnormalities, metabolic changes, and cardiovascular disease. Review other medicines that may prolong the QT interval and correct clinically significant electrolyte disturbances where appropriate. Relugolix is a substrate of P-glycoprotein (P-gp), and interactions can occur with P-gp inhibitors or medicines that combine P-gp and strong CYP3A induction. Under US prescribing information for ORGOVYX, co-administration with oral P-gp inhibitors should generally be avoided; if unavoidable, the prescribed doses should be separated as directed by the label. Combined P-gp and strong CYP3A inducers should also generally be avoided, with dose modification considered only according to product-specific instructions. For the relugolix combination, oral P-gp inhibitors should be avoided when possible, and any unavoidable use requires the label-directed dosing separation. Before starting the combination, exclude pregnancy and assess thromboembolic risk, smoking status, blood pressure, osteoporosis risk, and relevant medical history. Bone mineral density assessment should be considered according to individual risk and product guidance. Hormonal contraceptives should not be used concomitantly with the combination unless specifically directed by the applicable prescribing information. Vaccination considerations are not a principal relugolix-specific precaution, but routine preventive care should be maintained according to the patient's clinical circumstances.

Confirm whether the prescription is for single-agent relugolix for prostate cancer or the combination product containing estradiol and norethindrone acetate for a gynaecological indication. These formulations are not interchangeable. Review the current product label before prescribing, particularly for dosing interruptions, drug interactions, contraindications, and treatment-duration limits. For prostate cancer, establish a baseline clinical assessment and monitor treatment response, testosterone suppression where indicated, cardiovascular and metabolic risk factors, liver enzymes, haemoglobin, and adverse effects according to the oncology plan. Reinforce daily adherence and explain the need for a loading dose when starting single-agent treatment. For the combination product, confirm that pregnancy has been excluded, review thromboembolic risk and contraindications, assess bone health, and counsel patients about the 24-month treatment limit under US prescribing information. Explain that reduced or absent menstrual bleeding does not reliably exclude pregnancy. Ask patients to report chest pain, sudden breathlessness, severe headache, leg swelling, jaundice, or signs of a serious allergic reaction promptly. Pharmacists should verify the exact formulation and strength, check for P-gp and CYP3A-related interactions, and provide clear instructions for missed doses and storage. Coordination among oncology, gynaecology, primary care, and pharmacy teams can support safe long-term treatment and appropriate monitoring.