Where to Buy PT-141 in 2026: Sizes, Purity Reports and Verification

PT-141 is the research code for the cyclic heptapeptide bremelanotide, CAS 189691-06-3. Pepta Labs lists it as a 10 mg lyophilized powder with reported RP-HPLC purity and identity confirmed by mass spectrometry. This guide covers the chemistry, the listing, how to read the analytical report, how to store the vial, and where the compound's US regulatory status is recorded.

What Is PT-141?

PT-141 is built from seven residues. An acetylated norleucine occupies the N-terminus outside the ring; aspartate at position 2 through lysine at position 7 form a six-residue ring closed by a lactam bond between the Asp side-chain carboxyl and the Lys side-chain amine. There is no cysteine and therefore no disulfide. Position 4 is D-phenylalanine, and the C-terminal lysine carries a free carboxylic acid.

That C-terminus is the only difference from Melanotan-II (CAS 121062-08-6), which ends in a primary amide. Swapping -OH for -NH2 changes the formula from C50H68N14O10 to C50H69N15O9 and the average molecular weight from 1025.17 to 1024.18 Da, a shift of about 1 Da. Because the two share every residue and the same ring, they elute close together on HPLC and are told apart chiefly by mass spectrometry and by the CAS number on the report. Both are listed in the MSH analogue category, together with the linear 13-residue Melanotan-I (CAS 75921-69-6, 1646.85 Da).

How Pepta Labs Lists PT-141

PT-141 is supplied as a lyophilized powder in a sealed glass vial, 10 mg per vial. The 99.1% figure is the reversed-phase HPLC purity measured on the production run Pepta Labs sourced; identity was confirmed by mass spectrometry on the same run. Pepta Labs does not test in-house. The report is produced by an independent laboratory commissioned through a cooperative purchasing group and is available by email request before you order. The salt form supplied is stated on the report. Our quality page describes how reports are obtained.

How to Verify a PT-141 Listing

1. HPLC purity: what 99.1% means

The chromatogram shows the fraction of UV-absorbing material that eluted as the main peak. 99.1% is a purity of the peptide fraction, not a statement of net peptide weight: water, counter-ion and residual salts are invisible to this measurement. Nor does it identify the peak; a 99% pure vial of the wrong peptide is still 99% pure. See HPLC vs mass spectrometry.

2. Mass spectrometry: the number that identifies PT-141

For C50H68N14O10 the monoisotopic mass is 1024.52 Da. Expect [M+H]+ near m/z 1025.5 and [M+2H]2+ near m/z 513.3. If the report shows [M+H]+ near 1024.5, the material is the amide, Melanotan-II, not PT-141. A report that quotes only the theoretical molecular weight without an observed m/z value has not confirmed identity. Values for all catalog compounds are in the expected-mass table.

3. Production-run report or lot-specific COA

A production-run report records results measured on the run the vendor sourced and is matched to the compound and quantity; a lot-specific COA is matched to a lot number on the vial. Pepta Labs provides production-run reports. Ask which you are being sent, and check that the compound name, formula and mass on the document belong to PT-141 rather than a generic template. The COA verification guide covers each section.

4. CAS and identifier check

CAS 189691-06-3 identifies the free PT-141 peptide. Bremelanotide acetate, the salt in the approved drug product, is registered separately. A listing that quotes 121062-08-6 (Melanotan-II) or 75921-69-6 (Melanotan-I) for a PT-141 product is mislabelled. See CAS numbers and molecular weights.

Storage and Shipping

• Shipped at ambient temperature as a sealed lyophilized powder; no cold chain is required for the dry solid.
• Refrigerate at 2-8 C on arrival; store at -20 C for long-term holding.
• Keep the vial sealed and protected from light and moisture.

See the peptide storage guide for handling details.

US Regulatory Status

Bremelanotide is the INN and USAN for PT-141. Drugs@FDA lists bremelanotide acetate as the active ingredient of VYLEESI, NDA 210557, approved on June 21, 2019 and marketed as a prescription product. That approval covers the sponsor's finished drug product. It does not extend to research-grade PT-141 supplied as a chemical reference material, which is how Pepta Labs lists it: for laboratory research only, not as a drug. For how research peptides are regulated in the United States in 2026, see peptide legal status 2026.

Frequently Asked Questions

Is PT-141 the same as bremelanotide?

Yes. Bremelanotide is the INN/USAN for the cyclic heptapeptide Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH (C50H68N14O10, 1025.17 Da, CAS 189691-06-3, UNII 6Y24O4F92S). PT-141 is the original research code and the name used on research listings.

How is PT-141 different from Melanotan-II?

Only at the C-terminus: a free carboxylic acid in PT-141, a primary amide in Melanotan-II. The formulas differ by one nitrogen and one oxygen, the masses by about 1 Da, and the CAS numbers are 189691-06-3 and 121062-08-6.

Why does the report say acetate or TFA when the CAS is for the free peptide?

The CAS registry number identifies the peptide structure. The counter-ion is a property of the batch as synthesised and purified, so it is reported separately.

Can I see the report before I order?

Yes. Email support@peptalabs.com and ask for the PT-141 10mg analytical report; no account is needed.

Where to Buy PT-141

All products are supplied for laboratory research use only and are not for human or animal use.