PT-141 (Bremelanotide) vs Melanotan II

PT-141 and Melanotan II are closely related cyclic peptides that act on the melanocortin receptor system. Melanotan II came first, as a synthetic analogue of alpha-melanocyte-stimulating hormone (alpha-MSH), and was originally studied in pigmentation research. Observations made during that research led to the development of PT-141, known by its drug name bremelanotide, which was taken forward with a focus on central melanocortin signalling.

The practical difference for researchers is receptor profile and research context. Melanotan II acts broadly across several melanocortin receptors, including the MC1 receptor that drives melanin production, while PT-141 has been characterised mainly through its activity at MC4 and MC3 receptors in the brain. Their regulatory status also differs: bremelanotide is FDA-approved as Vyleesi, while Melanotan II is a research compound. PRIME supplies both for laboratory research use only.

PT-141 (bremelanotide): a centrally focused melanocortin agonist

PT-141 is a synthetic cyclic heptapeptide and the research code for bremelanotide. It was developed from the Melanotan II line of research and shares much of its core structure, but it was taken forward with attention on melanocortin signalling in the central nervous system rather than on skin pigmentation.

In research, PT-141 has been characterised mainly as an agonist at the MC4 and MC3 melanocortin receptors, which are expressed in brain regions involved in motivation, appetite and sexual behaviour. Preclinical studies have used it to explore how melanocortin pathways in the hypothalamus and related regions influence behaviour, and it has been investigated in human clinical trials. Bremelanotide is FDA-approved under the brand name Vyleesi.

That approval applies to the licensed pharmaceutical product. The PT-141 supplied by PRIME is a research-grade peptide sold for laboratory use only, not a medicine, and it carries no guidance for use in people.

For researchers, PT-141 is useful as a melanocortin agonist with a better-defined central focus than its parent compound, which makes it a common reference point in receptor selectivity work. PRIME offers PT-141 research peptide as a lyophilized powder, with batch testing published for each lot.

Melanotan II: a broad-acting alpha-MSH analogue

Melanotan II, often shortened to MT-2 or MT-II, is a synthetic cyclic heptapeptide based on alpha-melanocyte-stimulating hormone. It was designed to be more stable than the natural hormone and was originally studied for its ability to stimulate melanogenesis, the production of melanin pigment in the skin. Melanotan II is a research compound and is not an approved medicine in the US.

Unlike PT-141, Melanotan II acts across several melanocortin receptor subtypes. Its activity at the MC1 receptor on melanocytes is the basis of its pigmentation research, while its activity at MC3 and MC4 receptors links it to studies of appetite, energy balance and sexual behaviour in animal models. Activity at the MC5 receptor has also been described. This broad profile makes it a useful tool for studying the melanocortin system as a whole, but it also means effects in a model can be harder to attribute to a single receptor.

Early research observations on Melanotan II are what prompted the development of PT-141, so the two are often studied side by side in structure-activity work.

PRIME supplies Melanotan II research peptide as a lyophilized powder for laboratory use, with a published lab report for each batch.

The choice usually comes down to receptor selectivity. If a study needs to probe central melanocortin signalling, particularly MC4 and MC3 receptor pathways linked to behaviour, PT-141 is the more targeted tool, and its clinical history as bremelanotide provides a large body of background literature. If a study concerns melanogenesis, MC1 receptor biology or the melanocortin system as a whole, Melanotan II is the more appropriate choice because of its broad receptor activity.

Receptor-comparison studies often use both, with PT-141 serving as the more selective comparator. For fuller background, see the PT-141 (bremelanotide) research guide and the Melanotan II research guide. Researchers interested in the smaller alpha-MSH fragment may also want the KPV peptide research guide, since KPV is derived from the same hormone.

Always confirm identity and purity for the specific lot on the PRIME lab results page before starting an experiment.

For laboratory research use only. Not for human consumption.