Kisspeptin-54

Kisspeptin-54 shares the same active C-terminal decapeptide as kisspeptin-10 but with a longer N-terminal extension that gives it a substantially longer circulating half-life, around 28 minutes versus roughly 4. In IVF, the standard trigger is hCG, whose ~30-hour half-life keeps stimulating the corpora lutea long after ovulation and is the main driver of ovarian hyperstimulation syndrome. Kisspeptin-54 instead evokes the woman's own LH surge, which is short and self-limiting, so oocytes mature without the prolonged luteal overstimulation. Imperial College trials have shown effective oocyte maturation with very low OHSS rates even in women at high risk.

Targets: KISS1R (GPR54), GnRH neurons, Endogenous LH surge

• · Trials used 3.2 to 12.8 nmol/kg, which works out to roughly 1.3 to 5.2 mg for a 70 kg woman. A second dose 10 hours after the first has been used in high-risk patients to improve maturation rates. This is a clinical-trial procedure, not something to replicate outside a fertility unit.

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• very commonNo significant adverse effects reported in trial populations— Tolerability has been the headline finding across the Imperial College IVF programme.
• uncommonInjection-site reaction
• uncommonHeadache
• rareOvarian hyperstimulation syndrome— Markedly less frequent than with hCG triggering, but not zero.

• Hormone-sensitive malignancy.
• Use outside a monitored fertility protocol - a mistimed trigger in a stimulated cycle wastes the cycle and can be dangerous.

• conflicthcg — They are alternative triggers. Using both defeats the entire OHSS-reduction rationale for kisspeptin.
• redundantkisspeptin-10 — Same receptor, same active C-terminus; KP-54 simply lasts longer.
• synergycetrorelix — Antagonist-based IVF cycles are exactly where kisspeptin triggering has been studied.

• · Serum LH at 4 to 12 hours post-trigger to confirm the surge occurred.
• · Oestradiol and follicle count as part of standard IVF cycle monitoring.
• · Symptoms of OHSS - abdominal distension, rapid weight gain, breathlessness.

Investigational only; not approved in any jurisdiction. Rarely available even as a research chemical because of the cost of synthesising a 54-mer.

• Jayasena et al. 2014, kisspeptin-54 triggers egg maturation in women undergoing IVF, Journal of Clinical Investigation (trial)
• Abbara et al. 2015, efficacy of kisspeptin-54 to trigger oocyte maturation in women at high risk of OHSS, JCEM (trial)
• Jayasena et al. 2015, direct comparison of the effects of intravenous kisspeptin-10, kisspeptin-54 and GnRH on gonadotrophin secretion in healthy men, Human Reproduction 30(8):1934-41 (trial)

The receptor pharmacology is identical to kisspeptin-10 because the business end of the molecule is identical: Gq/11 coupling at KISS1R, phospholipase C, IP3 and DAG, calcium release, GnRH neuron depolarisation and a physiological GnRH pulse. What differs is duration, and in the IVF context duration is the entire therapeutic argument. Standard hCG triggering works because hCG is a long-acting LH surrogate, but its roughly 30-hour terminal half-life means it keeps flogging the corpora lutea for days after ovulation, driving VEGF release and the vascular permeability that becomes ovarian hyperstimulation syndrome. Kisspeptin-54 instead evokes the woman's own endogenous LH surge, which is generated by her own pituitary and is therefore self-limiting in exactly the way a natural surge is - it rises, it peaks, it terminates. Oocytes mature; the luteal overdrive does not happen. That is why the OHSS rates in the Imperial trials are so low even in deliberately high-risk women with high antral follicle counts, and it is a genuinely elegant piece of physiology rather than a marketing claim. The 28-minute half-life is the reason kisspeptin-54 rather than kisspeptin-10 is used: a four-minute peptide cannot sustain a GnRH stimulus long enough to produce a full surge from a single subcutaneous injection, which is also why a second dose ten hours after the first was tested in high-risk patients to improve maturation rates.

The dominant failure mode is not a side effect, it is a wasted cycle. Trigger timing in IVF is measured in hours, retrieval is scheduled 36 hours out, and a trigger that fails to produce a surge means no mature oocytes from a cycle that cost thousands and weeks of injections. That is precisely why this compound has no meaningful grey-market use and should not acquire one. Beyond that, OHSS is markedly less frequent than with hCG but it is not zero, so distension, rapid weight gain and breathlessness in the days after retrieval still need to be taken seriously. On the supply side, a 54-residue peptide is expensive and difficult to synthesise correctly, and anything sold cheaply under this name is far more likely to be kisspeptin-10 or nothing at all.

• KISS1R (GPR54) — Comparable to kisspeptin-10, since the receptor-binding C-terminal decapeptide is identical. Specific values were not resolved here.

  Gq/11 signalling on hypothalamic GnRH neurons, producing a sustained enough GnRH stimulus to generate a complete endogenous LH surge from a single subcutaneous dose.

• Endogenous pituitary LH surge

  The therapeutic endpoint in IVF. Self-limiting by design, which is what separates it from hCG triggering and is the entire basis of the OHSS-reduction claim.

• Kisspeptin-54 to trigger oocyte maturation in women undergoing IVF 2 · 2014

  Oocyte maturation after a single subcutaneous kisspeptin-54 trigger in place of hCG, across escalating dose cohorts. Demonstrated that an endogenous LH surge sufficient for oocyte maturation can be evoked pharmacologically, with live births resulting.

• Kisspeptin-54 trigger in women at high risk of ovarian hyperstimulation syndrome 2 · 2015

  Oocyte maturation and OHSS incidence in women at high risk, including the two-dose regimen with a second injection ten hours after the first. This is the trial that supports the central claim - effective maturation with markedly low OHSS in exactly the population that gets OHSS.

• Direct comparison of intravenous kisspeptin-10, kisspeptin-54 and GnRH in healthy men 1 · 2015

  Head-to-head gonadotropin response to all three peptides in the same subjects, which is the study that quantifies what the longer isoform actually buys you.

The endogenous LH surge begins within about four hours of a subcutaneous trigger dose and peaks in the following hours, with oocyte retrieval scheduled 36 hours after the injection. In the high-risk two-dose protocol the second injection goes in ten hours after the first to extend the surge and improve maturation rates. Everything about this compound is measured in hours, not days, and there is no chronic dosing timeline because there is no chronic use.

Kisspeptin-54 and hCG are alternative triggers, not partners - giving both reintroduces exactly the prolonged luteal stimulation that the kisspeptin trigger exists to avoid, and throws away the whole point. The coherent pairing is with a GnRH antagonist cycle, since cetrorelix or ganirelix protocols are the setting in which kisspeptin triggering has actually been studied. Luteal phase support matters more after a kisspeptin trigger than after an hCG trigger, because there is no long-acting exogenous luteotrophin propping up the corpus luteum afterwards; that is handled as part of the clinical protocol and is not something to improvise. Combining with kisspeptin-10 is meaningless duplication.

Against hCG as an IVF trigger, kisspeptin-54 is the physiologically cleverer option and the one with far lower OHSS rates in the trials, but hCG has decades of use, universal availability and licensing behind it, while kisspeptin-54 has phase 2 data from essentially one group and no licence anywhere. Against a GnRH agonist trigger such as leuprolide, which is the established low-OHSS alternative in antagonist cycles, kisspeptin-54 is a similar idea executed one level higher in the axis - the agonist trigger flogs the pituitary with a supraphysiological GnRH signal, kisspeptin asks the hypothalamus to do it properly. Whether that translates into better outcomes than an agonist trigger is not established, and that is the trial that has not been done. Against kisspeptin-10, the longer isoform is the only one that can produce a full surge from one injection.

There is no meaningful consumer market for kisspeptin-54. It is an investigational compound supplied for trials, a 54-residue peptide is expensive to make correctly, and per-cycle costs in a research setting are not published. Anything advertised as cheap kisspeptin-54 online should be treated as mislabelled.

• ?The full 54-residue sequence is published but I did not verify it against a primary source in this session, so the sequence fields are deliberately left blank rather than filled from memory.
• ?Volume of distribution, clearance and protein binding are not published.
• ?The 28-minute half-life is the widely cited figure and is consistent with the comparative study, but I did not confirm the specific value from a primary pharmacokinetic paper here.
• ?Participant numbers for the two IVF trials are not recorded here because I did not resolve them from the abstracts in this session.
• ?There is no phase 3 evidence and no head-to-head trial against a GnRH agonist trigger, which is the comparison that would actually matter clinically.
• ?Long-term outcomes for children conceived after kisspeptin triggering are not characterised, simply because the numbers are small and recent.

• Kisspeptin-54 triggers egg maturation in women undergoing in vitro fertilization Jayasena CN, Abbara A, Comninos AN, Nijher GM, Christopoulos G, Narayanaswamy S, Izzi-Engbeaya C, Sridharan M, Mason AJ, Warwick J, Ashby D, Ghatei MA, Bloom SR, Carby A, Trew GH, Dhillo WS, Journal of Clinical Investigation, 2014 · PMID 25036713

  The proof-of-concept trial. Worth reading for how carefully the dose escalation was done, because triggering is a one-shot procedure with no second chance in a given cycle.

• Efficacy of Kisspeptin-54 to Trigger Oocyte Maturation in Women at High Risk of Ovarian Hyperstimulation Syndrome (OHSS) During In Vitro Fertilization (IVF) Therapy Abbara A, Jayasena CN, Christopoulos G, Narayanaswamy S, Izzi-Engbeaya C, Nijher GM, Comninos AN, Peters D, Buckley A, Ratnasabapathy R, Prague JK, Salim R, Lavery SA, Bloom SR, Szigeti M, Ashby DA, Trew GH, Dhillo WS, Journal of Clinical Endocrinology and Metabolism, 2015 · PMID 26192876

  The high-risk population study, and the source of the two-dose regimen. This is the paper that makes the OHSS argument rather than just asserting it.

• Direct comparison of the effects of intravenous kisspeptin-10, kisspeptin-54 and GnRH on gonadotrophin secretion in healthy men Jayasena CN, Abbara A, Narayanaswamy S, Comninos AN, Ratnasabapathy R, Bassett P, Mogford JT, Malik Z, Calley J, Ghatei MA, Bloom SR, Dhillo WS, Human Reproduction, 2015 · PMID 26089302

  Quantifies the difference between the two kisspeptin isoforms in the same men, which is the cleanest justification for why IVF work uses the 54-mer.