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P21, also written P021, is an experimental peptide compound derived from ciliary neurotrophic factor (CNTF), a natural protein that supports nerve cells. It is not FDA-approved, it has not been tested in people, and no approved medicine in the United States contains it.
The name can cause confusion. p21 is also the name of a well-known human protein involved in cell division, which is unrelated to this compound.
P021 is based on a four-amino-acid stretch of CNTF (amino acids 148 to 151) that researchers identified as biologically active. A bulky, fat-soluble chemical group, an adamantylated glycine, was added at one end. According to the researchers, this was meant to help it cross the blood-brain barrier and resist breakdown.
Full-length CNTF had been tested in human trials in earlier decades and caused side effects such as loss of appetite, cramps and muscle pain. P021 was designed in part to avoid those problems. In laboratory studies it is reported to block signaling by a protein called leukemia inhibitory factor (LIF) and to raise levels of BDNF, a brain growth factor.
P021 was developed by researchers led by Khalid Iqbal at the New York State Institute for Basic Research in Developmental Disabilities, with early work published around 2010. Studies have used mouse models of Alzheimer's disease (3xTg-AD mice) and of Down syndrome (Ts65Dn mice), measuring learning and memory, the formation of new nerve cells, and markers such as tau and amyloid.
A May 2025 report by the Alzheimer's Drug Discovery Foundation found that no studies have tested P021 in humans and that its safety in humans has not been assessed. It noted rodent studies lasting up to 18 months without the weight loss seen with full-length CNTF, and listed P021 as under development by a company called Phanes Biotech, with no clinical trials registered.
Mouse models do not fully reproduce human disease, so these results cannot show whether P021 would be safe or useful for people.
Current status: Not FDA-approved.
P21 has not gone through the FDA review that a drug must pass before it can be marketed for use in people. It does not appear in any category of the FDA's 503A nomination lists (as updated May 14, 2026) and is not on the 503A bulks list, so it does not meet the conditions for 503A compounding.
It is also not a dietary supplement. Products labeled "for research purposes only" or "not for human consumption" are not approved medicines, and the FDA has not reviewed their contents, purity or quality.
No human safety data exist for P021, and the FDA has not published a safety assessment of it. Findings in rodents do not establish safety in people.
P21 is not named on the World Anti-Doping Agency (WADA) 2026 Prohibited List. The list's S0 class covers any pharmacological substance not addressed elsewhere on the list that has no current approval by any government health authority for human therapeutic use. Athletes should confirm the status of any substance with their anti-doping organization.
Peptide Labs does not sell this compound. This page is general information, not medical advice. We do not supply, prepare or distribute P21 in any form, and nothing on this page should be read as an offer.
For personal medical questions, including concerns about memory or thinking, the right person to ask is a licensed healthcare provider.
See the full list of compound profiles in the Peptide Guide. Other compounds discussed in brain research include dihexa, Semax and Cerebrolysin. You can also read what peptides are.
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