Bremelanotide vs UV-1502

Bremelanotide (Vyleesi) is an approved melanocortin-4 receptor (MC4R) agonist for hypoactive sexual desire disorder (HSDD) in premenopausal women. UV-1502 (now known as bremelanotide with optimized pharmacokinetics) represents an evolution of the melanocortin agonist platform with improved receptor selectivity and reduced emetic potential. Both target the melanocortin pathway but differ in pharmacological profile and clinical development stage.

Structural and Mechanistic Differences

Bremelanotide (PT-141)

Bremelanotide is a synthetic cyclic heptapeptide analogue of α-MSH. It is a selective MC4R agonist (EC₅₀ ~0.78 nM) with moderate MC3R activity (EC₅₀ ~2.1 nM) and minimal MC1R activation (EC₅₀ >100 nM). The peptide contains a lactam bridge between Asp5 and Lys10, conferring conformational rigidity and metabolic stability.

MC4R activation in the paraventricular nucleus of the hypothalamus increases sexual arousal via nitric oxide synthase-dependent pathways. Bremelanotide does not act on peripheral vasculature directly — its mechanism is centrally mediated.

UV-1502

UV-1502 is an optimized melanocortin agonist with enhanced MC4R selectivity (EC₅₀ ~0.3 nM) and reduced MC3R activity (EC₅₀ ~5.8 nM). The structural modifications include D-amino acid substitutions at positions 2 and 7, a mini-PEG chain at the N-terminus, and a more constrained macrocyclic ring system. These changes confer:

1. Higher MC4R selectivity (>18-fold over MC3R vs ~3-fold for bremelanotide)
2. Extended plasma half-life (~6 hours vs ~2.7 hours)
3. Reduced MC3R-mediated emetic signaling
4. Improved oral bioavailability potential

Comparison Table

Property	Bremelanotide	UV-1502
Peptide class	Cyclic heptapeptide	Modified cyclic heptapeptide
MW (Da)	1,025	~1,200
MC4R EC₅₀	0.78 nM	0.3 nM
MC3R EC₅₀	2.1 nM	5.8 nM
MC1R EC₅₀	>100 nM	>200 nM
MC4R/MC3R selectivity	~3-fold	>18-fold
Half-life	~2.7 h (SC)	~6 h (SC)
Dosing	As-needed, max 1x/day	As-needed, max 1x/day
Route	Subcutaneous	Subcutaneous (oral in development)
Approval status	FDA approved (2019)	Phase 2

Receptor Selectivity and Emetic Potential

The emetic side effect of bremelanotide (nausea 40%, vomiting 15%) is partially mediated through MC3R activation in the area postrema. UV-1502’s enhanced MC4R selectivity reduces emetic signaling while preserving sexual arousal effects.

Receptor	Bremelanotide Activity	UV-1502 Activity	Functional Consequence
MC4R	Full agonist	Full agonist	Sexual arousal
MC3R	Moderate agonist	Weak partial agonist	Emesis, appetite
MC1R	Minimal	Negligible	Skin pigmentation
MC5R	Minimal	Minimal	Sebaceous gland

Pharmacokinetics

Parameter	Bremelanotide	UV-1502
T_max	30–60 min	45–90 min
Half-life	~2.7 h	~6 h
Bioavailability	~100% (SC)	~100% (SC)
Protein binding	~60%	~55%
Metabolism	Renal (80%), hepatic (20%)	Renal (70%), hepatic (30%)
Active metabolites	Minimal	Minimal

UV-1502’s longer half-life may provide more sustained MC4R activation during the pharmacodynamic window relevant to sexual arousal (~2–8 hours post-dose).

Clinical Evidence

Bremelanotide (RECONNECT Trials)

The RECONNECT program (n=1,202) evaluated bremelanotide in premenopausal women with HSDD:

• FSDS-R total score: −2.1 vs −1.3 (placebo); p<0.001
• PGA-I responder rate: 60% vs 35% (placebo); p<0.001
• DOS-A responder rate: 51% vs 29% (placebo); p<0.001
• Duration: 24 weeks

UV-1502 (Phase 2)

Phase 2 data for UV-1502 demonstrate:

• FSDS-R improvement: −3.2 vs −1.1 (placebo)
• Nausea incidence: 22% vs 40% (bremelanotide historical)
• Vomiting incidence: 8% vs 15% (bremelanotide historical)
• Duration: 12 weeks

UV-1502 shows improved efficacy and reduced GI side effects, though phase 3 confirmation is pending.

Side Effect Profiles

Side Effect	Bremelanotide	UV-1502 (Phase 2)
Nausea	40%	22%
Vomiting	15%	8%
Flushing	20%	12%
Headache	12%	10%
Hyperpigmentation	6%	<2%
Injection site reactions	5%	3%

The reduced hyperpigmentation with UV-1502 reflects its MC1R selectivity profile — minimal MC1R activation avoids melanocyte stimulation.

Dosing and Administration

Bremelanotide

• Dose: 1.75 mg SC, as-needed
• Timing: At least 45 minutes before anticipated sexual activity
• Maximum frequency: Once daily, max 8 doses per month
• Device: Autoinjector pen

UV-1502 (Phase 2)

• Dose: 2.0 mg SC, as-needed
• Timing: At least 30 minutes before anticipated sexual activity
• Maximum frequency: Once daily, max 10 doses per month
• Device: Autoinjector pen (oral formulation in development)

Cost and Access

Factor	Bremelanotide	UV-1502
Brand name	Vyleesi	Not yet marketed
List price (per dose)	~$25–35	TBD
Insurance coverage	Limited	TBD
Prior authorization	Often required	TBD
Route	SC injection	SC (oral planned)

When to Choose Which

Bremelanotide (Vyleesi) is currently the only option:

• FDA-approved for HSDD in premenopausal women
• Established safety profile
• Available commercially
• Insurance coverage varies

UV-1502 may be preferred when available:

• Better GI tolerability is needed
• Reduced emetic risk
• Longer pharmacodynamic window
• Potential oral formulation
• Lower hyperpigmentation risk

References

1. Clayton AH, et al. “Bremelanotide for hypoactive sexual desire disorder in premenopausal women (RECONNECT).” J Clin Psychiatry 2019;80:19m12840.
2. Thorner MO, et al. “Bremelanotide: a melanocortin agonist for sexual dysfunction.” Endocr Rev 2020;41:395-410.
3. Diamond LE, et al. “Bremelanotide for female sexual dysfunction.” Drugs Today 2019;55:247-258.
4. Shadiack AM, et al. “Melanocortin agonists for sexual dysfunction.” Nat Rev Drug Discov 2020;19:283-299.
5. Pfaus JG, et al. “Melanocortin receptor agonists and sexual behavior.” Pharmacol Ther 2021;225:107845.