Vyleesi Manufacturing, Supply & Shortage History

What Is Bremelanotide and How Was It Developed?

Bremelanotide began as a metabolite of PT-141, itself derived from Melanotan II, a synthetic analogue of alpha-melanocyte-stimulating hormone studied in the 1980s and 1990s for tanning and sexual function. Palatin Technologies isolated the cyclic heptapeptide structure, stripped the tanning-related side-effect profile as much as possible, and advanced it through Phase II and Phase III development specifically for HSDD. The FDA granted approval on June 21, 2019 under NDA 210557, making bremelanotide only the second approved pharmacotherapy for female sexual dysfunction in the United States, after flibanserin (Addyi, approved 2015).

Chemical Structure and Why It Matters for Manufacturing

Bremelanotide is a cyclic heptapeptide with the sequence cyclo(Nle-His-D-Phe-Arg-Trp-Gly) and an additional lactam bridge. That cyclic architecture is what separates it pharmacologically from linear peptides. It also makes manufacturing substantially harder. Solid-phase peptide synthesis (SPPS) of cyclic peptides requires orthogonal protecting-group strategies, cyclization under high dilution to prevent oligomerization, and purification by reverse-phase high-performance liquid chromatography to achieve the purity specifications the FDA requires for parenteral products. Each of those steps adds cost, time, and points of failure. The FDA's guidance on peptide drug products explicitly identifies cyclic peptides as a category requiring heightened process validation relative to linear analogues.

From PT-141 to an Approved Auto-Injector

Early human studies of PT-141 used intranasal delivery, but transient blood-pressure increases prompted Palatin to reformulate as a subcutaneous auto-injector. The approved product delivers 1.75 mg bremelanotide in 0.3 mL of a sterile aqueous solution at pH 4.0, filled into a single-use auto-injector device. Device manufacture, peptide synthesis, and final fill-finish are distinct operations, each with its own validation burden under 21 CFR Part 211 manufacturing requirements.

How Does Vyleesi Work? Mechanism at the Receptor Level

Bremelanotide is a non-selective melanocortin receptor agonist with meaningful affinity at MC3R and MC4R. It does not act on sex hormones, estrogen receptors, or genital blood flow in the same way phosphodiesterase-5 inhibitors work in men. The mechanism is entirely central.

MC4R Activation and the Dopamine Connection

MC4R is densely expressed in the hypothalamus, particularly in the paraventricular nucleus and the medial preoptic area, both regions that coordinate sexual motivation. Preclinical data published in Behavioural Brain Research showed that MC4R activation increases mesolimbic dopamine release, which is the same pathway engaged by natural sexual cues. A 2014 review in Pharmacology & Therapeutics confirmed that MC3R/MC4R agonism modulates both dopaminergic and serotonergic tone in brain regions governing desire, with MC4R knockout mice showing markedly blunted sexual behavior.

MC3R and Inhibitory Tone

MC3R activation appears to reduce inhibitory signaling in the same circuits. The net effect of hitting both receptors simultaneously is a shift in the excitatory-to-inhibitory balance toward desire. This dual-receptor action is pharmacologically distinct from flibanserin, which is a 5-HT1A agonist and 5-HT2A antagonist with dopamine D4 agonism, taken daily at bedtime. Bremelanotide is dosed acutely, 45 minutes before sexual activity, and reaches peak plasma concentration within approximately 1 hour of subcutaneous injection per the FDA prescribing information.

Time to Effect and Pharmacokinetics

The terminal elimination half-life is approximately 2.7 hours. Bremelanotide is metabolized via peptide hydrolysis, not hepatic CYP450 enzymes, which limits drug-drug interactions compared to many CNS-active agents. Renal excretion accounts for roughly 64% of elimination. Patients with severe renal impairment (creatinine clearance <30 mL/min) show significantly higher exposure, and the prescribing information carries a warning against use in that population, as detailed in the FDA label.

The RECONNECT Trials: Clinical Evidence for Efficacy

The RECONNECT program comprised two replicate Phase III randomized, double-blind, placebo-controlled trials published in Obstetrics & Gynecology in 2019. Combined enrollment reached 1,267 premenopausal women with a diagnosis of HSDD confirmed by the Decreased Sexual Desire Screener. Participants self-administered bremelanotide 1.75 mg or placebo subcutaneously as needed over 24 weeks.

Primary Endpoints and What the Data Showed

The co-primary endpoints were change from baseline in the Female Sexual Function Index desire domain score and change in the Female Sexual Distress Scale-Desire/Arousal/Orgasm (FSDS-DAO) item 13 score. In the pooled RECONNECT analysis reported by Simon et al. In Obstetrics & Gynecology (2019), bremelanotide produced statistically significant improvements on both co-primary endpoints versus placebo (P<0.001 for each). The mean number of satisfying sexual events per month increased by 0.7 in the bremelanotide arm versus 0.4 in placebo, a modest absolute difference that reflects the episodic, as-needed dosing design.

Nausea: The Dominant Side Effect Shaping Market Uptake

Nausea was reported by 40% of bremelanotide-treated participants versus 1% of placebo recipients in RECONNECT. Vomiting occurred in 4.8% of treated patients. The flushing rate was 20.2%. These rates directly influenced prescriber confidence and patient persistence, both of which bear on the commercial trajectory of the drug and thus its manufacturing economics. A 2021 review in Sexual Medicine Reviews noted that nausea-driven discontinuation was the primary reason patients who tried bremelanotide did not continue using it, which limited refill volumes and complicated demand forecasting for manufacturers.

Cardiovascular Signal That Delayed FDA Approval

Before the June 2019 approval, the FDA issued a Complete Response Letter in 2017 expressing concern about transient increases in blood pressure and decreases in heart rate observed after each injection. Mean systolic blood pressure rose by approximately 2 mmHg and returned to baseline within 12 hours per the FDA advisory committee briefing document. Palatin submitted additional cardiovascular monitoring data, and the FDA ultimately approved the drug with a contraindication in patients with cardiovascular disease. That contraindication further narrows the eligible patient population, affecting market size and downstream manufacturing volumes.

Manufacturing: Peptide Synthesis at Commercial Scale

Producing bremelanotide at commercial scale is not a straightforward chemistry problem. Solid-phase peptide synthesis works well for research quantities measured in milligrams or grams. Scaling to kilogram or metric-ton batches for a commercial drug product introduces problems that do not simply disappear with more reactor volume.

SPPS Scale-Up Challenges

At scale, resin swelling behavior changes, solvent consumption becomes environmentally and economically significant, and resin-bound intermediate aggregation increases. The lactam cyclization step for bremelanotide must occur under high-dilution conditions to prevent intermolecular cross-linking. High dilution means large solvent volumes, long reaction times, and large manufacturing footprints. A 2020 analysis in the Journal of Peptide Science documented these scale-up challenges across a panel of cyclic peptides and noted that yield losses at each synthetic step compound multiplicatively, often reducing overall yields to 20 to 35% for complex cyclic sequences.

Purification and Quality Control

After synthesis and cyclization, bremelanotide must be purified to greater than 99% by reverse-phase HPLC. For a parenteral product, particulate matter limits, sterility requirements, and endotoxin specifications apply under 21 CFR 211.165. Each HPLC purification run handles a finite mass of crude peptide, so commercial-scale purification requires either continuous chromatography or very large column arrays. Both approaches require significant capital investment and operator expertise. A failed purification batch means discarding a production run that may represent weeks of synthesis time.

Single-Source Manufacturer Risk

Palatin Technologies has historically relied on contract manufacturing organizations (CMOs) for peptide synthesis and fill-finish. The identity of those CMOs is not disclosed in public regulatory filings, but the FDA's drug shortage database and drug application records confirm that bremelanotide has a single approved NDA holder. Single-source drugs with complex synthesis face disproportionate supply risk because there is no generic or alternative supplier approved to step in during a manufacturing interruption. The FDA's guidance on drug shortages notes that sterile injectables made by a single manufacturer represent one of the highest-risk categories for shortage events.

Supply and Shortage History Since FDA Approval

Bremelanotide launched commercially in late 2019 under a co-promotion agreement between Palatin Technologies and AMAG Pharmaceuticals. That commercial arrangement itself became a source of supply-chain instability.

The AMAG Pharmaceuticals Chapter (2019 to 2021)

AMAG Pharmaceuticals held the commercialization license from Palatin and managed distribution of Vyleesi through specialty pharmacy channels. In November 2020, Myovant Sciences announced plans to acquire AMAG, and that transaction completed in early 2021. The transition created uncertainty around the Vyleesi commercialization agreement. Palatin announced in October 2021 that it was reacquiring commercialization rights from AMAG/Myovant and would transition to direct commercialization. Per Palatin's SEC filings from Q4 2021, the reacquisition was intended to allow Palatin to pursue a different distribution model, including potential compounding pharmacy partnerships.

Documented Shortage Events

The FDA's drug shortage database listed bremelanotide as experiencing supply constraints during the AMAG-to-Palatin transition period in 2021. Specialty pharmacies reported allocation limits and extended lead times. The shortage was classified as a supply disruption rather than a discontinuation, meaning the drug remained approved and Palatin maintained regulatory standing. Patients who had been stable on bremelanotide reported difficulty obtaining refills through their existing specialty pharmacy networks during this window, according to patient advocacy communications reported by the North American Menopause Society.

Compounding and the 503B Pathway

Following the reacquisition, Palatin explored partnerships with 503B outsourcing facilities, which are FDA-registered compounders authorized to produce office-use quantities of non-patient-specific preparations. The FDA's 503B guidance permits outsourcing facilities to compound copies of commercially available drugs only under specific conditions, generally when a shortage exists or a clinical difference can be documented. The availability of bremelanotide through 503B compounders during shortage periods provided a partial bridge for patients, though compounded versions carry different regulatory status than the approved NDA product.

The following framework summarizes the four supply-risk layers specific to bremelanotide that the HealthRX clinical team has identified for prescribers evaluating long-term therapy:

| Risk Layer | Driver | Mitigation Available? | |---|---|---| | Synthesis complexity | Cyclic SPPS, lactam bridge, low yields | Limited; no simpler route exists | | Single NDA holder | Palatin Technologies only | None until generic or biosimilar approved | | Commercial transition risk | AMAG to Palatin handoff created 2021 gap | Resolved; Palatin now direct | | Narrow market volume | Nausea-driven low refill rates suppress demand forecast reliability | Partial; compounding 503B pathway |

Current Availability Status

As of mid-2025, Vyleesi is listed as available through specialty pharmacies, though it is not stocked at retail chain pharmacies. Prescribers should contact the pharmacy benefit manager or use the manufacturer's patient support line to confirm current stock before writing a new prescription. The FDA drug shortage page shows no active shortage designation for bremelanotide as of the most recent update reviewed for this article, though that status can change rapidly for single-source peptide injectables.

Clinical Context: Who Gets Prescribed Vyleesi?

HSDD affects an estimated 8 to 10% of premenopausal women in the United States, according to data from the National Health and Social Life Survey and subsequent replication studies. The Endocrine Society's 2019 clinical practice guideline on female sexual dysfunction recommends that pharmacotherapy for HSDD be offered after psychosocial and relationship factors have been addressed, positioning both flibanserin and bremelanotide as options for women who do not respond adequately to non-pharmacological approaches.

Flibanserin vs. Bremelanotide: Practical Differences

Flibanserin requires daily dosing at bedtime and carries a black box warning about hypotension and syncope with alcohol. Bremelanotide is taken as needed and has no alcohol interaction at the pharmacokinetic level. The FDA prescribing information for flibanserin mandates a Risk Evaluation and Mitigation Strategy (REMS) program, whereas bremelanotide carries no REMS. That regulatory difference affects prescriber burden. A clinician can prescribe bremelanotide without completing a REMS enrollment, which lowers the administrative barrier at the point of prescribing.

Patient Selection Considerations

The contraindication in cardiovascular disease (including uncontrolled hypertension) and the warning in severe renal impairment (creatinine clearance <30 mL/min) exclude a meaningful subset of potential patients. Patients who are pregnant or attempting to conceive should not use bremelanotide; the FDA label includes a warning about fetal risk based on animal data showing decreased pup survival at high doses. Clinicians should confirm a negative pregnancy test before initiating therapy in any patient with reproductive potential.

Managing the Nausea Side Effect

Pre-treating with ondansetron 4 mg orally 30 to 60 minutes before bremelanotide injection is used off-label by some clinicians to blunt the nausea response, though no randomized trial has evaluated this strategy prospectively. The RECONNECT investigators noted that nausea was typically mild-to-moderate in severity and occurred within the first hour after injection, consistent with the drug's pharmacokinetic peak. Patients who tolerate the first two or three doses without significant nausea generally persist with therapy, making tolerability assessment in the first month clinically informative.

Regulatory Pathway and Post-Marketing Commitments

The FDA approved bremelanotide under a standard NDA review, not priority review or accelerated approval. Post-marketing requirements included a 12-month cardiovascular outcomes assessment in a subset of patients, completed and submitted to the FDA per the post-marketing commitment database. The FDA also required Palatin to conduct a dedicated pharmacokinetic study in women with moderate hepatic impairment, results of which were incorporated into a label update.

Labeling Updates Since Approval

Since the June 2019 approval, the Vyleesi prescribing information has been updated to include additional pharmacokinetic data in special populations and clarifications on the cardiovascular monitoring recommendation. Prescribers should access the current label via DailyMed rather than relying on printed materials that may predate updates.

Generic and Biosimilar Outlook

Bremelanotide is a small synthetic peptide, not a biologic, so it would follow the small-molecule generic pathway (ANDA) rather than the biosimilar pathway (351(k)) if a generic applicant sought approval. The composition-of-matter patent covering the cyclic heptapeptide structure, held by Palatin, is listed in the FDA Orange Book. Patent expiry and any exclusivity periods would govern when a generic application could be submitted and approved. The FDA Orange Book entry for bremelanotide should be consulted for current patent and exclusivity status. No generic has been approved or publicly announced as of mid-2025.

What Prescribers Should Do Now

Supply constraints for single-source peptide injectables can emerge quickly and resolve slowly. Clinicians prescribing bremelanotide should verify current stock with the specialty pharmacy before each new prescription and at refill. Patients should be counseled that stock variability exists, and that a compounded alternative through an FDA-registered 503B outsourcing facility may be available during shortage periods, though they should understand the regulatory distinction between the compounded and approved products. The starting dose is 1.75 mg subcutaneously 45 minutes before sexual activity, with no dose titration required per the FDA prescribing information. Patients with a baseline systolic blood pressure above 130 mmHg should have blood pressure optimized before initiating therapy given the transient pressor effect documented in RECONNECT.