Peptide Sciences Closed: How to Vet a Replacement Research Peptide Supplier

What happened to Peptide Sciences?

On March 6, 2026, Peptide Sciences stopped selling research products. Its website was replaced with a brief notice saying the company had voluntarily ended operations; no reason, transition plan or successor was announced. As of October 26, 2026, the company's old product and article addresses redirect to that notice, so links to its pages around the web no longer lead to any product, certificate or article.

We make no claim about why it closed. What matters for a lab is practical: an established source is gone, past documentation is no longer available from the supplier, and new orders have to come from somewhere else.

What to keep from your past orders

If your work used Peptide Sciences material, your own records are now the only record. Before anything else, gather what you have for each compound still in use.

• Certificates of analysis for every lot you received, saved as files rather than links to the old site.
• Lot numbers as printed on the vials, and the dates each lot was received, opened and used.
• The purity, identity (mass) and, where reported, net peptide content stated on each certificate: these are the figures a new supplier's certificate will be compared with.
• Any of your own analytical results, such as in-house HPLC or mass spectrometry of incoming material.

Be wary of sites using the old name

When a well-known name disappears, lookalike sites and listings often appear to capture its search traffic. The company itself announced that it had stopped selling, so a site still taking orders under that name deserves close scrutiny: check the domain, check who operates it, and ask which independent laboratory tested the lot you would receive.

Regulatory laboratories have documented a steady flow of counterfeit and illegal peptide preparations, including products whose contents did not match their labels^1,2. That is the baseline risk with any unfamiliar source, and it is higher when a seller trades on a name it may not own.

How to vet a replacement supplier

The questions are the same ones that should be asked of any supplier, but a forced switch is the moment to ask them all. The full checklist is in how to choose a research peptide supplier; the essentials are below.

Switching lots: compare before you rely on new material

Synthetic peptides carry process-related impurities, such as deletion and truncated sequences, that differ from one manufacturing route to another³. Two lots of the same compound from different suppliers can therefore both meet a purity specification and still not be identical. For work that depends on continuity, compare the new lot's certificate with your old records: the observed mass should match the expected mass, the purity should meet your specification, and the net content, where reported, should be in line with what you used before.

How to read a peptide COA explains each field on a certificate and the red flags to look for, including certificates that never change between lots and purity figures with no chromatogram.

Where to find specific compounds

If your work used any of these widely studied research peptides, each page below has a cited summary of the published research and the certificates for current lots: BPC-157, TB-500, GHK-Cu, KPV, CJC-1295 (no DAC), CJC-1295 (with DAC), Ipamorelin, Sermorelin, Tesamorelin, Semax, Selank, Epitalon, MOTS-c, NAD+, Thymosin Alpha-1, PT-141 and DSIP. The full range is in the shop.

How Peptides Only documents each lot

Every lot Peptides Only sells is tested by an independent laboratory before release, for identity by mass spectrometry and purity by HPLC. The certificate for each lot, with the laboratory's name and the test date, is published in the COA library before you buy, and the lot number on the vial matches it. Products are sold for laboratory research only, under the research use policy, and ship from the USA.