A 7-amino-acid cyclic melanocortin peptide and the first FDA-approved treatment for hypoactive sexual desire disorder (HSDD) in premenopausal women. Acts centrally in the brain on MC4 receptors rather than peripherally like PDE5 inhibitors (Viagra).
PT-141 (Bremelanotide) is a cyclic 7-amino-acid peptide that activates melanocortin-4 receptors (MC4R) in the brain. Marketed as Vyleesi, it is the first and only FDA-approved treatment for hypoactive sexual desire disorder (HSDD) in premenopausal women.
PT-141 was originally developed from the tanning peptide melanotan II (which activates multiple melanocortin receptors). During clinical trials for melanotan II, researchers noticed an unexpected side effect — increased sexual arousal. This led to the development of PT-141 as a more selective MC4R agonist targeting sexual desire specifically.
PT-141 (bremelanotide, marketed as Vyleesi) is the only FDA-approved peptide drug specifically indicated for sexual dysfunction. Approved in June 2019 for hypoactive sexual desire disorder (HSDD) in premenopausal women, it works through a completely different mechanism than PDE5 inhibitors like sildenafil (Viagra) — it acts centrally in the brain rather than peripherally on blood flow.
PT-141 was derived from Melanotan II, a synthetic melanocortin peptide originally developed for tanning. During clinical trials, researchers noticed that Melanotan II produced unexpected sexual arousal as a side effect. PT-141 was developed as a refined version that retained the sexual effects while reducing the tanning and nausea side effects. It is a cyclic heptapeptide that activates melanocortin-4 receptors (MC4R) in the hypothalamus, modulating neural pathways involved in sexual desire and arousal.
Despite being FDA-approved, Vyleesi has had limited commercial success, partly due to its injection-based administration (subcutaneous auto-injector), the requirement to use it at least 45 minutes before anticipated sexual activity, and nausea as a common side effect. It remains the only FDA-approved on-demand treatment for female HSDD.
PT-141 binds to the melanocortin-4 receptor (MC4R), a Gs-coupled GPCR expressed in the hypothalamus (paraventricular nucleus), amygdala, and other limbic structures involved in sexual behavior. MC4R activation increases dopaminergic signaling in the mesolimbic reward pathway, modulating the neural circuits that generate sexual desire. This central mechanism is why PT-141 works regardless of the physical cause of low desire — it targets the brain's desire circuits directly.
| Pathway | Effect | Significance |
|---|---|---|
| MC4R activation | Agonist binding in hypothalamic nuclei | Stimulates neural pathways underlying sexual desire and arousal |
| Dopamine modulation | Enhances dopaminergic signaling in reward circuits | Increases motivation and desire components of sexual behavior |
| Oxytocin release | MC4R activation promotes oxytocin release | May contribute to bonding and arousal aspects |
| Melanocortin effects | Some residual MC1R activity | Can cause transient skin darkening and facial flushing |
| Study | Design | Findings | Level |
|---|---|---|---|
| RECONNECT (Phase III) | RCT, n=1,247 premenopausal women with HSDD | Statistically significant increase in desire and decrease in distress vs placebo over 24 weeks | Level I |
| Male ED | Phase II trials | Some efficacy in erectile dysfunction, but development focused on female HSDD | Level II |
| Duration of effect | Clinical data | Single SC injection provides effect for ~24 hours; not a daily medication | Level I-II |
Nausea: The most common adverse effect, occurring in approximately 40% of patients. Nausea is typically mild-to-moderate and transient (resolving within hours), but it is significant enough to limit patient acceptance. The FDA label recommends no more than one dose per 24 hours and no more than 8 doses per month.
Blood pressure: Transient blood pressure increases (average 2-3 mmHg systolic) have been observed after injection. Vyleesi is not recommended for patients with uncontrolled hypertension or cardiovascular disease.
Skin hyperpigmentation: Due to PT-141's melanocortin activity, darkening of the skin (particularly gums, face, and breasts) has been reported with repeated use. The FDA label specifically warns about this effect, which may be persistent.
Focal hyperpigmentation: PT-141 should not be used in patients with a history of skin conditions sensitive to melanocyte activation, as it could theoretically affect nevi (moles) or other pigmented lesions.
| Jurisdiction | Status |
|---|---|
| FDA | Approved: Vyleesi (bremelanotide) for HSDD in premenopausal women (2019). SC autoinjector. |
| EMA | Not approved in EU |
| WADA | Not specifically banned |