For most of the modern era, research into sexual function pointed at the periphery: blood flow, vascular smooth muscle, and the PDE5-inhibitor drugs (sildenafil and its relatives) that act on it. A quieter line of work has moved upstream, to the brain circuits that generate desire in the first place. Two peptide systems dominate that literature. One is kisspeptin, the master switch that sits at the very top of the reproductive axis. The other is the melanocortin system, whose central signaling shapes arousal. This roundup collects notable peer-reviewed findings from both — with the standing caveat that most of this work is early, small, and, for the compounds in our catalog, strictly research-use-only.
Kisspeptin: imaging desire in the brain
The most-cited recent kisspeptin work comes from a single group at Imperial College London (the laboratories of Waljit Dhillo and Alexander Comninos), which ran two placebo-controlled crossover trials in people diagnosed with hypoactive sexual desire disorder (HSDD).
The women's study — Thurston, Comninos, Dhillo and colleagues, JAMA Network Open, October 26, 2022 — enrolled 32 premenopausal women who completed both a kisspeptin and a placebo visit. Under functional MRI, kisspeptin activated brain regions tied to sexual arousal while deactivating regions associated with self-monitoring and inhibition, and hippocampal responses to erotic stimuli tracked each participant's baseline sexual distress. No significant adverse events were reported.
The companion men's study — Mills and colleagues, JAMA Network Open, February 3, 2023 — ran 32 men with HSDD through the same crossover design, adding a physiological readout. Kisspeptin again modulated activity across the sexual-processing network, and it increased penile tumescence by up to 56% more than placebo during a sexual-video task.
Two things are worth keeping straight. First, this is investigational work: kisspeptin is not approved anywhere for any sexual-function indication, and the authors themselves frame the results as early signals that need larger and longer studies. Second, both trials used kisspeptin-54, the full-length isoform. The compound in our catalog, kisspeptin-10, is the shorter C-terminal decapeptide; both fragments signal through the same KISS1R receptor, but they are not the same molecule — a naming distinction worth reading carefully (see our peptide nomenclature primer). For the underlying wiring, our HPG axis explainer maps where kisspeptin sits relative to GnRH.
The same peptide, a second job: reproduction
Kisspeptin is not only a desire modulator. Because it sits above GnRH in the hypothalamic-pituitary-gonadal cascade, it is also a lever on the reproductive axis itself — and that is where its longest clinical track record lies.
In an earlier phase 2 study — Abbara and colleagues, Journal of Clinical Endocrinology & Metabolism, 2015 — 60 women at high risk of ovarian hyperstimulation syndrome (OHSS) received a single injection of kisspeptin-54 to trigger oocyte maturation during IVF. Oocyte maturation occurred in the large majority of women, and no participant developed moderate, severe, or critical OHSS. The rationale is mechanistic: kisspeptin triggers an endogenous, self-limiting LH surge, which researchers have proposed may be gentler than a bolus hCG trigger.
A 2025 study sharpened the safety picture. Mills and colleagues, JCEM, November 2025 (volume 110, pages 3133–3141), gave kisspeptin or placebo to 95 participants (63 men, 32 women) and measured mood and stress alongside hormones. Kisspeptin robustly raised luteinizing hormone, confirming it was biologically active — but it produced no significant change in anxiety, cortisol, blood pressure, or heart rate. That is a null result on a hypothesized central effect, and the authors read it as reassurance for anyone developing kisspeptin-based therapeutics: the peptide stimulated the reproductive axis without a detectable anxiety signal. It is a useful reminder that plausible brain effects do not always materialize.
The melanocortin arm: bremelanotide (PT-141)
A different peptide system converges on a similar endpoint. PT-141, or bremelanotide, is a cyclic heptapeptide analog of α-melanocyte-stimulating hormone. It is a nonselective melanocortin agonist (it engages MC1R, MC3R, MC4R, and MC5R), and its pro-sexual effect is attributed to central MC4R/MC3R signaling in the hypothalamus and limbic system — a brain mechanism, which is the conceptual opposite of the peripheral, vascular action of PDE5 inhibitors.
The pivotal evidence is the RECONNECT program: Kingsberg and colleagues, Obstetrics & Gynecology, 2019 (volume 134, pages 899–908) — two Phase 3 randomized trials in roughly 1,267 premenopausal women with HSDD, using a subcutaneous, on-demand regimen over 24 weeks. Both trials showed statistically significant improvements in sexual desire and related distress versus placebo, and bremelanotide (marketed as Vyleesi) was FDA-approved in 2019 for that population. Prespecified subgroup analyses followed in The Journal of Sexual Medicine in 2022.
Tolerability, not efficacy, tends to define the compound in the literature. Pooled data across the clinical development program report nausea in roughly 40% of participants, flushing in about 20%, and headache in about 12%, and the average effect sizes on desire are modest. Interest has continued: a 2023 Journal of Sexual Medicine report described real-world refill patterns in a single sexual-medicine clinic, and a 2024 observational series (Goldstein and Goldstein) described off-label, exploratory use in 21 men. None of that changes the compound's status in our catalog — PT-141 is sold for research use only. It descends from the same melanocortin lineage as Melanotan 2, a relationship we unpack in our Melanotan 1 vs Melanotan 2 comparison.
Melanocortin momentum in 2026: setmelanotide
The melanocortin receptor family is having a broader moment, and it spills past sexual function. Setmelanotide (IMCIVREE) is the MC4R-selective agonist — the clean counterpart to bremelanotide's nonselective profile. Its pivotal Phase 3 TRANSCEND trial enrolled 120 patients with acquired hypothalamic obesity and reported a 19.8% placebo-adjusted reduction in BMI over 52 weeks, results published in The New England Journal of Medicine. In March 2026 the FDA approved setmelanotide for acquired hypothalamic obesity — the first labeled option for that rare, brain-injury-driven form of obesity — and the EMA's CHMP issued a positive opinion the same month.
Why does an obesity drug belong in a sexual-signaling roundup? Because it underscores how pleiotropic the melanocortin system is: the same MC4R node that bremelanotide leans on for arousal is a central regulator of energy balance. One receptor family, two very different endpoints, both moving in 2026. Our melanocortin system explainer walks through how the five receptors divide the labor.
Reading this literature
A single through-line runs across these papers: the drug target for desire is moving into the brain, and kisspeptin and the melanocortins are the two central levers with the most recent data. That is a genuine shift from the vascular, peripheral framing that defined the field for decades.
The caveats are just as important. The kisspeptin sexual-function work is a small set of crossover trials from one research group, and the compound remains investigational for any psychosexual use. Bremelanotide is approved, but with modest efficacy and real tolerability costs. And the 2025 kisspeptin anxiety study is a standing reminder that a hypothesized central effect can simply fail to appear. Where a compound is approved, its trial results are facts about trial participants and product labels — not outcomes any reader should expect or pursue. The catalog compounds discussed here — kisspeptin-10, PT-141, and Melanotan 2 — are research materials, characterized for identity and purity on their certificates of analysis and organized in our reference library, and nothing here is a protocol for use.
FAQ
Is kisspeptin approved to treat low sexual desire? No. The HSDD findings come from early, placebo-controlled crossover trials at a single center; kisspeptin is not approved for any sexual-function indication, and its longer clinical record is in reproductive endocrinology and IVF research.
How does bremelanotide's mechanism differ from a PDE5 inhibitor? Bremelanotide is thought to act centrally, through melanocortin (chiefly MC4R) signaling in the brain, whereas PDE5 inhibitors act peripherally on vascular smooth muscle. That difference in site of action is the core of the "brain as the target" thesis.
Does the catalog's kisspeptin-10 match the trials? Not exactly. The Imperial trials used kisspeptin-54, the full-length isoform; kisspeptin-10 is the shorter C-terminal decapeptide. Both act on the KISS1R receptor, but they are distinct molecules, and both are supplied for research use only.
This article is educational and for the laboratory research community. Trulogic Labs products are sold for laboratory and research use only and are not for human consumption.