Kisspeptin-54

The 54-residue kisspeptin isoform, also called metastin, that activates the KISS1R receptor to drive hypothalamic GnRH release; it is the form used in most human reproductive-endocrinology trials, including IVF oocyte-maturation triggering.

Also referenced as: KP-54, Kisspeptin 54, Metastin, Kisspeptin-54 (human), KiSS-1 (68-121)

What is Kisspeptin-54?

Kisspeptin-54 is a 54-residue, C-terminally amidated peptide cleaved from the KiSS-1 precursor protein — residues 68–121 of the human sequence in UniProt entry Q15726, with a molecular weight near 5.8 kDa. Two groups isolated it from human placenta in 2001: one named it metastin after its effect on tumor cell migration (Ohtaki et al., Nature, 2001, 411(6837):613–617), the other named the whole peptide family kisspeptins after the KiSS-1 metastasis-suppressor gene they derive from (Kotani et al., Journal of Biological Chemistry, 2001, 276(37):34631–34636).

It is the major circulating kisspeptin isoform in humans, and it is the isoform used in almost all of the human reproductive-endocrinology work on this pathway — a body of research concentrated in the group of Waljit Dhillo at Imperial College London. That clinical literature is why the compound appears in reference entries at all. It is worth separating from its shorter relative at the outset: listings and reference entries that say only “kisspeptin” usually mean kisspeptin-10, the C-terminal decapeptide (KiSS-1 residues 112–121) that kisspeptin-54 contains but is not identical to.

How it works

• KISS1R agonism upstream of GnRH — kisspeptins bind the G protein–coupled receptor KISS1R (originally GPR54 / hOT7T175) with low-nanomolar affinity and signal through Gq, driving PIP2 hydrolysis, calcium mobilization, and MAP kinase phosphorylation (Kotani et al., Journal of Biological Chemistry, 2001, 276(37):34631–34636; Ohtaki et al., Nature, 2001, 411(6837):613–617). In vivo the relevant receptor population sits on hypothalamic GnRH neurons, so the peptide acts one step above the pituitary rather than on it.
• Human genetics validate the target — loss-of-function mutations in GPR54 cause normosmic idiopathic hypogonadotropic hypogonadism and failure of pubertal onset, established independently in two 2003 reports (de Roux et al., PNAS, 2003, 100(19):10972–10976; Seminara et al., New England Journal of Medicine, 2003, 349(17):1614–1627). This is unusually strong target validation for a peptide at this stage of development: the pathway is required for normal human reproduction, not merely correlated with it.
• Measured human pharmacology — in a double-blind, placebo-controlled crossover study, a 90-minute intravenous infusion of kisspeptin-54 at 4 pmol/kg/min in six male volunteers significantly raised plasma LH (10.8 ± 1.5 vs. 4.2 ± 0.5 U/L), FSH, and testosterone (24.9 ± 1.7 vs. 21.7 ± 2.2 nmol/L over 180 minutes) against saline. The same study calculated a plasma half-life of 27.6 ± 1.1 minutes and a metabolic clearance rate of 3.2 ± 0.2 mL/kg/min (Dhillo et al., Journal of Clinical Endocrinology & Metabolism, 2005, 90(12):6609–6615).
• Response depends on endogenous hormonal state, not just dose — a subcutaneous bolus of 0.4 nmol/kg raised LH in every phase of the menstrual cycle but by wildly different magnitudes: a mean increase over baseline of 0.12 ± 0.17 IU/L in the follicular phase against 20.64 ± 2.91 IU/L preovulatory (Dhillo et al., Journal of Clinical Endocrinology & Metabolism, 2007, 92(10):3958–3966). Because the peptide releases an endogenous GnRH pool rather than stimulating the pituitary directly, its effect is gated by the state of the axis it acts on.

Research status

There is no approved kisspeptin product in any jurisdiction. Every human exposure to kisspeptin-54 on record comes from investigator-led or industry trials, and no registrational program has advanced past Phase 2.

Healthy-volunteer physiology. Beyond Dhillo et al. (2005, 2007), Comninos et al. administered intravenous kisspeptin-54 at 1 nmol/kg/h to 29 healthy young men in a randomized, double-blind, placebo-controlled two-way crossover fMRI study and reported enhanced limbic activation to sexual and couple-bonding stimuli plus attenuated negative mood (The Journal of Clinical Investigation, 2017, 127(2):709–719). Abbara et al. showed the hypothalamic response to kisspeptin-54 is preserved in healthy older men (Neuroendocrinology, 2018, 106(4):401–410).

IVF oocyte-maturation trigger — the deepest evidence. Jayasena et al. gave a single subcutaneous injection of kisspeptin-54 (1.6 to 12.8 nmol/kg) to 53 women after controlled ovarian stimulation; egg maturation occurred at every dose, embryos were transferred in 92% (49/53), and biochemical and clinical pregnancy rates were 40% (21/53) and 23% (12/53) (The Journal of Clinical Investigation, 2014, 124(8):3667–3677; NCT01667406). Abbara et al. then ran a Phase 2, multi-dose, open-label trial in 60 women at high risk of ovarian hyperstimulation syndrome, randomizing patients across four kisspeptin-54 doses under an adaptive allocation design: oocyte maturation occurred in 95%, live birth per transfer was 45% across doses (51 transfers), and no woman developed moderate, severe, or critical OHSS (Journal of Clinical Endocrinology & Metabolism, 2015, 100(9):3322–3331). Note what that randomization was and was not — patients were allocated between kisspeptin doses, and the trial carried no non-kisspeptin comparator arm. A follow-on Phase 2 randomized, placebo-controlled trial in 62 high-risk women found that a second dose 10 hours after the first raised the proportion achieving an oocyte yield of at least 60% from 45% (14/31) to 71% (21/31), an absolute difference of 26% (CI 2–50%, P = 0.042) (Abbara et al., Human Reproduction, 2017, 32(9):1915–1924). The authors state plainly that further studies are needed to compare kisspeptin-54 directly with established triggers; no such head-to-head trial has been published, and no Phase 3 program exists.

Negative and cautionary findings. In a randomized, double-blind, parallel-design study, women with hypothalamic amenorrhea given twice-daily subcutaneous kisspeptin-54 (6.4 nmol/kg) for two weeks showed a potent day-one response (mean maximal LH increment 24.0 ± 3.5 IU/L) that collapsed to 2.5 ± 2.2 IU/L by the fourteenth injection day, with FSH following the same pattern — clear tachyphylaxis, in five women per arm. Response to GnRH was retained, locating the desensitization upstream of the pituitary (Jayasena et al., Journal of Clinical Endocrinology & Metabolism, 2009, 94(11):4315–4323). Lowering the frequency helps: twice-weekly dosing for 8 weeks in the same population still stimulated reproductive hormone release (Jayasena et al., Clinical Pharmacology & Therapeutics, 2010, 88(6):840–847), and twice-daily dosing did not abolish menstrual cyclicity in healthy volunteers (Jayasena et al., Journal of Clinical Endocrinology & Metabolism, 2013, 98(11):4464–4474). Sustained receptor agonism inverts the effect entirely: continuous exposure to TAK-448 — an investigational analog not of kisspeptin-54 but of its 10-residue C-terminus — drove testosterone into the castration range in healthy men and in prostate cancer patients across two Phase 1 studies (MacLean et al., Journal of Clinical Endocrinology & Metabolism, 2014, 99(8):E1445–E1453). That development line has since stopped: all three registered TAK-448 trials on ClinicalTrials.gov were terminated, though for different reasons — NCT01132404 in prostate cancer (registered Phase 1/Phase 2) was halted to develop a new formulation under a new protocol, while NCT02381288 in middle-aged and older men with low testosterone and NCT02369796 in hypogonadotropic hypogonadism were each stopped after missing their primary endpoint.

Head-to-head potency. A single-blind, placebo-controlled study infused vehicle, kisspeptin-10, kisspeptin-54, and GnRH intravenously in healthy men at matched doses (0.1, 0.3, 1.0 nmol/kg/h). The two kisspeptin isoforms produced similar gonadotropin responses, and GnRH outperformed both — roughly three-fold over kisspeptin-10 and roughly two-fold over kisspeptin-54 (mean AUC serum LH at 1.0 nmol/kg/h: 10.81 ± 1.73 h·IU/L for kisspeptin-10, 14.43 ± 1.27 for kisspeptin-54, 34.06 ± 5.18 for GnRH). The study had five subjects per group (Jayasena et al., Human Reproduction, 2015, 30(8):1934–1941).

Where development actually went. Attention has shifted from native kisspeptin-54 to longer-acting KISS1R agonists. MVT-602 produced an LH rise of similar amplitude to kisspeptin-54 but peaking at 21.4 versus 4.7 hours, with correspondingly greater LH exposure, and sustained GnRH neuron firing for 115 versus 55 minutes (Abbara et al., The Journal of Clinical Investigation, 2020, 130(12):6739–6753), with further randomized placebo-controlled data in Fertility and Sterility, 2024, 121(1):95–106.

Registry picture. ClinicalTrials.gov returns 19 studies matching kisspeptin-54 as of August 2026, weighted toward Phase 1 and Phase 2 — 16 of the 19. That count overstates isoform-specific activity in two ways. Several of the U.S. records — including the Massachusetts General Hospital series — register their intervention as “kisspeptin 112-121,” which is kisspeptin-10, not kisspeptin-54. And the three records tagged Phase 3 are small investigator-run physiology studies rather than registrational trials, two of them explicitly studying KP-10.

The oncology origin story remains preclinical. KiSS-1 was identified as a melanoma metastasis-suppressor gene (Lee et al., Journal of the National Cancer Institute, 1996, 88(23):1731–1737), and metastin inhibited chemotaxis, invasion, and pulmonary metastasis of receptor-transfected melanoma cells in mice (Ohtaki et al., 2001). No human oncology trial of kisspeptin-54 has been conducted.

Common dosage forms

• Research-grade lyophilized powder — where the 54-mer is offered at all, the format is a milligram-scale vial of synthetic peptide reconstituted before use. Published human studies used commercially synthesized material; the Imperial infusion protocols made it up in gelofusine, a gelatin-based colloid, rather than plain water for injection (Comninos et al., 2017).
• Trial routes — published human work used two routes only: intravenous infusion and subcutaneous bolus injection, with quantities expressed per unit body weight rather than as fixed vial strengths. No fixed-dose, ready-to-use commercial presentation of kisspeptin-54 exists anywhere.
• What retail research listings actually contain — vials labeled “kisspeptin” are predominantly kisspeptin-10, commonly in 5 mg or 10 mg lyophilized presentations. Kisspeptin-54 is scarce to the point of absence: across the vendor catalogs PeptideBenchmark tracks, every kisspeptin listing resolves to the decapeptide and none offers the 54-residue peptide. Part of the reason is synthetic — a 54-residue solid-phase build is a substantially harder and lower-yielding job than a decapeptide.
• No validated alternative formats — there is no oral, sublingual, intranasal, or topical kisspeptin-54 format with human data behind it.

Key considerations

• Regulatory status is “unapproved,” and the FDA listing you may see refers to a different molecule. No kisspeptin product is approved by the FDA or any comparable regulator. Kisspeptin-10 — not kisspeptin-54 — is the entry on the FDA’s interim 503A list of bulk drug substances that may present significant safety risks (Category 2, added September 29, 2023), cited for immunogenicity risk by certain routes of administration and complexities around peptide-related impurities and API characterization. That entry was still in place as of August 2026. Kisspeptin-54 does not appear on that list at all, and absence from a Category 2 entry is not clearance — it means the substance was never taken through that nomination process.
• Isoform confusion is the single biggest naming hazard here. Kisspeptin-54 (metastin, KiSS-1 68–121), kisspeptin-14 (108–121), kisspeptin-13 (109–121), and kisspeptin-10 (112–121) all share the same C-terminal RF-amide decapeptide and all activate the same receptor, but they are distinct molecules with distinct pharmacokinetics. The mouse ortholog of metastin is 52 residues, not 54 (UniProt Q6Y4S4, residues 68–119), so rodent papers writing “KP-52” or “kisspeptin-52” are describing the species equivalent rather than a separate compound. A certificate of analysis headed only “kisspeptin” does not establish which isoform is in the vial, and for a 54-residue synthesis the identity and purity questions carry more weight than they do for a short fragment.
• The “kisspeptin-54 is more potent” claim is rodent data that did not replicate in humans. In mice, kisspeptin-54 sustained LH release far longer than kisspeptin-10, with plasma half-lives of about 32 versus 4 minutes, and only kisspeptin-54 activated c-FOS in GnRH neurons behind the blood-brain barrier (d’Anglemont de Tassigny et al., PLoS ONE, 2017, 12(5):e0176821). In the direct human intravenous comparison, the two isoforms performed similarly and GnRH outperformed both (Jayasena et al., 2015).
• Chronic exposure works against the axis, not for it. The dominant repeat-dosing finding in humans is desensitization, and sustained KISS1R agonism with a decapeptide analog produced castrate-range testosterone. Any framing of this compound as a durable testosterone or fertility “booster” contradicts the human dataset; the only setting where the evidence is genuinely encouraging is single-dose use as an ovulation trigger under clinical supervision.
• Human safety data are short-duration and narrow. Exposure on record is overwhelmingly single-dose or few-week, in supervised research settings, and heavily weighted toward women undergoing IVF plus small healthy-volunteer cohorts. The most direct off-target safety check found no significant change in GH, prolactin, or TSH over seven days of twice-daily kisspeptin-54, but in only five women (Jayasena et al., Clinical Endocrinology, 2014, 81(6):891–898). There is no long-term safety dataset, no pediatric data, and no data in men using exogenous androgens.