Leuprolide

A synthetic nonapeptide GnRH superagonist that initially stimulates and then durably suppresses gonadotropin secretion, FDA-approved since 1985 in daily and long-acting depot formulations for advanced prostate cancer, endometriosis, uterine fibroids, and central precocious puberty.

Also referenced as: Leuprorelin, Leuprolide Acetate, Leuprolide Mesylate, Lupron, Lupron Depot, Eligard, Fensolvi, Camcevi, TAP-144

What is Leuprolide?

Leuprolide (leuprorelin outside the U.S.) is a synthetic nonapeptide analog of gonadotropin-releasing hormone with the sequence 5-oxo-Pro-His-Trp-Ser-Tyr-D-Leu-Leu-Arg-Pro-NHEt — native GnRH with a D-leucine swapped in at position 6 and an ethylamide replacing the C-terminal glycinamide. Those two changes make it a longer-lived, higher-affinity “superagonist” of the GnRH receptor, and it became one of the earliest synthetic peptides to reach large-scale clinical use when FDA approved the daily injection (Lupron) on April 9, 1985 as a Type 1 new molecular entity for palliative treatment of advanced prostatic cancer.

Unlike most compounds in this library, leuprolide is close to absent from the retail research-peptide market: it carries no listings anywhere in PeptideBenchmark’s vendor pricing data. Where it circulates outside pharmacies is the analytical-reagent and bulk-API channel — supplied as a reference standard rather than as a consumer research vial. The GnRH agonist that actually occupies the retail research niche is triptorelin, a chemically distinct decapeptide that carries D-Trp at position 6 and keeps the C-terminal glycinamide native GnRH has. The two are routinely discussed as if interchangeable. They are not the same molecule, and only one of them is what a research catalog is usually selling.

How it works

• GnRH receptor superagonism — the D-Leu6 substitution and C-terminal ethylamide increase receptor binding and resistance to enzymatic degradation; FDA labeling states plainly that the analog “possesses greater potency than the natural hormone” at the pituitary GnRH receptor (FDA Lupron Injection labeling, NDA 019010; Conn & Crowley, New England Journal of Medicine, 1991, 324(2):93–103)
• Pulsatility is the switch — the pituitary requires pulsatile GnRH exposure; in rhesus monkeys with hypothalamic lesions that abolished gonadotropin release, hourly GnRH delivery reestablished gonadotropin secretion while continuous infusion failed to. The authors showed the effect was attributable to the pattern of delivery rather than the amount of hormone, and that switching a restored animal to continuous infusion produced desensitization and downregulation (Belchetz et al., Science, 1978, 202(4368):631–633). Leuprolide’s clinical formulations are engineered to deliver exactly that suppressive continuous exposure
• Flare first, then downregulation — dosing initially raises LH and FSH, transiently increasing testosterone and dihydrotestosterone in men or estrone and estradiol in premenopausal women; sustained exposure then downregulates and desensitizes pituitary GnRH receptors. Labeling states these decreases occur within two to four weeks of initiation, with castrate testosterone demonstrated for up to five years (FDA Lupron labeling; Conn & Crowley, 1991)
• The therapeutic effect is downstream sex-steroid deprivation — leuprolide has no direct cytotoxic action; suppression of gonadal steroids drives regression or quiescence of hormone-dependent tissue, which is why its pivotal prostate-cancer trial measured testosterone suppression and objective response against estrogen therapy rather than a tumor-kill endpoint (The Leuprolide Study Group, New England Journal of Medicine, 1984, 311(20):1281–1286)

Research status

Leuprolide is among the most thoroughly characterized peptide drugs in existence, with an evidence base built across oncology, gynecology, and pediatric endocrinology — plus documented failures outside the hormonal axis.

Approved indications. The 1985 daily injection was followed by long-acting depot and implant formulations spanning 1- to 6-month dosing intervals, beginning with Lupron Depot 7.5 mg in January 1989. Current U.S. labeling covers palliative treatment of advanced prostate cancer (Lupron Depot, Eligard, Camcevi), management of endometriosis including pain relief and lesion reduction, preoperative hematologic improvement in anemic women with uterine fibroids given concomitantly with iron, and central precocious puberty (Lupron Depot-PED; Fensolvi, approved May 1, 2020, as a 45 mg subcutaneous 6-month option for patients aged 2 and older). Camcevi, a ready-to-use leuprolide mesylate emulsion, was approved May 25, 2021 as a 6-month 42 mg depot, with a 3-month 21 mg strength (Camcevi ETM) following on August 25, 2025. The Lupaneta Pack, which co-packaged leuprolide depot with norethindrone acetate tablets for endometriosis add-back, was approved in December 2012 but is now listed as discontinued.

Pivotal prostate-cancer evidence. The Leuprolide Study Group randomized 199 men with previously untreated stage D2 prostate cancer — 98 to leuprolide 1 mg subcutaneously daily, 101 to diethylstilbestrol 3 mg orally daily. Objective response was 86% versus 85%, with comparable suppression of testosterone and dihydrotestosterone. The DES arm had significantly more painful gynecomastia, nausea and vomiting, and edema, plus a non-significant excess of thromboembolism (P = 0.065); the leuprolide arm reported more hot flashes. One-year survival was 87% versus 78%, a difference that did not reach significance (P = 0.17) (New England Journal of Medicine, 1984, 311(20):1281–1286). This trial established androgen deprivation without estrogens or orchiectomy and anchored the 1985 approval.

Endometriosis and add-back therapy. Hornstein et al. enrolled 201 women, all receiving leuprolide depot 3.75 mg every 4 weeks, and randomized them across four arms for 12 months: placebo add-back, norethindrone acetate 5 mg alone, or norethindrone plus conjugated equine estrogens at 0.625 mg or 1.25 mg. All four groups improved on pelvic pain by week 8. The agonist-alone group lost 6.3% of bone density at 52 weeks, while bone density was preserved in all three add-back arms; the 1.25 mg estrogen arm had more early withdrawals for lack of symptom improvement, which is why the conclusion endorsed norethindrone alone or with the lower estrogen dose (Obstetrics & Gynecology, 1998, 91(1):16–24). This is the basis of modern add-back practice.

Central precocious puberty. GnRH agonists are standard of care, but an international consensus statement concluded that efficacy for increasing adult height is undisputed only in early-onset central precocious puberty (girls under 6), and that use for conditions other than central precocious puberty requires additional investigation and cannot be suggested routinely. The same statement noted that few controlled prospective studies exist in children and that many of its conclusions rest partly on expert opinion — while declining to endorse common concerns about weight gain or long-term bone-density loss (Carel et al., Pediatrics, 2009, 123(4):e752–e762).

Failures and unresolved questions. Voyager Pharmaceutical’s leuprolide implant program for Alzheimer’s disease ran two 90-participant Phase 2 ALADDIN studies (NCT00063310, completed February 2006; NCT00076440, completed March 2007) and a 555-participant Phase 3, VP-AD-301 (NCT00231946, registered intervention VP4896, started September 2005). None led to approval and the program was abandoned. A successor academic Phase 2 — LUCINDA (NCT03649724), run by Weill Cornell in postmenopausal women aged 60 and over with mild cognitive impairment or Alzheimer’s disease already on a stable cholinesterase inhibitor, testing Eligard 22.5 mg every 12 weeks against placebo over 48 weeks in a planned 180 participants — is listed as active but not recruiting, with a July 2026 completion date and no results posted as of August 2026.

Separately, PRONOUNCE (NCT02663908) was the first trial designed to compare the cardiovascular safety of a GnRH antagonist against an agonist prospectively and at random. It enrolled a specific population: men who had prostate cancer and established atherosclerotic cardiovascular disease, assigned to degarelix or leuprolide for 12 months. Enrollment stopped in April 2020 at 545 of a planned 900 patients, for slow recruitment and a lower-than-anticipated cardiovascular event rate — the sponsor stated the decision was not based on safety concerns, knowledge of the results, or the COVID-19 pandemic. Major adverse cardiovascular events occurred in 5.5% of the degarelix arm and 4.1% of the leuprolide arm (hazard ratio 1.28, 95% CI 0.59–2.79; P = 0.53). That null came from an underpowered trial, which is why the authors themselves concluded the relative cardiovascular safety of the two classes remains unresolved (Lopes et al., Circulation, 2021, 144(16):1295–1307).

Trial registry picture. ClinicalTrials.gov lists roughly 515 studies naming leuprolide as an intervention (August 2026), including 124 Phase 3 and 59 Phase 4 records. The distribution mirrors clinical practice: about 275 in prostate cancer, 60 in breast cancer (largely ovarian suppression in premenopausal hormone-receptor-positive disease), 29 in endometriosis, 23 in precocious puberty, 20 in infertility (pituitary downregulation and trigger protocols in assisted reproduction, an off-label but entrenched use), and 11 in uterine fibroids. Only four touch Alzheimer’s disease.

Common dosage forms

• Daily subcutaneous injection — leuprolide acetate multi-dose vial, 14 mg/2.8 mL (5 mg/mL), the original 1985 presentation. The Lupron brand of this form is now listed as discontinued in Drugs@FDA; the daily injection survives as generic, with eight abbreviated applications currently marketed and new ones still being approved
• Intramuscular depot microspheres — Lupron Depot and Lupron Depot-PED kits in strengths from 3.75 mg to 45 mg for 1-, 3-, 4-, or 6-month dosing intervals
• Subcutaneous in-situ-forming polymer depots — Eligard (7.5, 22.5, 30, and 45 mg) and the pediatric Fensolvi (45 mg, 6-month), which gel after injection and release drug continuously
• Ready-to-use emulsion — Camcevi (leuprolide mesylate, supplied as leuprolide base equivalent), a subcutaneous depot requiring no reconstitution, in a 42 mg 6-month and a 21 mg 3-month presentation
• Discontinued formats — the Lupaneta Pack co-packaged leuprolide depot with norethindrone acetate tablets for endometriosis add-back; Viadur, a 12-month osmotic (DUROS) implant for prostate cancer, was withdrawn by Bayer in 2007–2008 for commercial rather than safety reasons
• Research-market vials — largely absent. PeptideBenchmark’s vendor pricing data carries no leuprolide listings at all; where the compound is sold outside a pharmacy it is generally as an analytical reference standard or bulk API. Any such material is a plain aqueous presentation on reconstitution — none of the depot release technology that defines the clinical products is present

Key considerations

• This is a fully approved, widely available prescription drug. Leuprolide has held FDA approval since 1985 and the daily injection exists in multiple marketed generics. Material offered “for research use only” is a gray-market presentation of a medicine dispensed through ordinary pharmacies, without the release testing or the engineered delivery systems of the licensed products — and unlike most compounds profiled here, it is not something our vendor tracking actually finds on retail shelves.
• The formulation is inseparable from the pharmacology. Suppression depends on continuous receptor exposure from depot release; intermittent exposure to a GnRH agonist stimulates rather than suppresses the axis, which is the direct lesson of the Belchetz experiment (Science, 1978). A reconstituted vial dosed intermittently does not reproduce the exposure profile the clinical literature describes — it can reproduce the opposite one.
• The flare is a real safety signal, not a footnote. Labeling warns that the initial testosterone surge can transiently worsen prostate-cancer symptoms, including temporary increases in bone pain, and that ureteral obstruction and spinal cord compression have been observed with LH-RH agonists, potentially contributing to paralysis with or without fatal complications. The same biphasic response raises estradiol in women before suppression sets in.
• Class-wide metabolic and cardiovascular warnings apply. In October 2010, FDA required GnRH-agonist labels to add warnings about increased risk of diabetes, myocardial infarction, sudden cardiac death, and stroke in men treated for prostate cancer. The labeling itself calibrates this — the risk “appears low based on the reported odds ratios” and is meant to be weighed against a patient’s other cardiovascular risk factors. Prolonged use also reduces bone mineral density (the reason add-back regimens exist), and labeling notes that androgen deprivation may prolong the QT/QTc interval. PRONOUNCE’s early stop means the agonist-versus-antagonist question remains open.
• Naming confusion is pervasive, and it has a pricing consequence. Leuprolide (U.S. adopted name) and leuprorelin (international name) are the same molecule. Triptorelin, goserelin, and nafarelin are different GnRH agonists with different substitutions and formulations, and “Lupron” is often used loosely as shorthand for the entire class. This matters here specifically: our pricing data contains triptorelin listings and zero leuprolide listings, so a shopper who searched for one and found the other has changed molecules, not brands. GnRH antagonists (degarelix, relugolix) suppress the axis immediately without a flare — the opposite initial effect from leuprolide.