P21, more often written P021 in the literature, is a synthetic peptide designed in an academic Alzheimer's lab, not a marketed drug. It was built from a short active stretch of ciliary neurotrophic factor (CNTF), one of the body's own nerve-growth proteins. The idea was to keep the useful signaling part of CNTF while shedding the size and instability that make the full protein impractical as a medicine.
The work comes almost entirely from Khalid Iqbal, Faraz Kazim and colleagues at the New York State Institute for Basic Research in Developmental Disabilities. Their published structure is Ac-DGGLAG-NH2, a pentapeptide with a molecular weight around 578, corresponding to residues 148–151 of human CNTF with an adamantylated glycine added at the end. That adamantane group is the design trick: the team reported it raises blood-brain-barrier permeability and slows breakdown by carboxypeptidases, which let them dose mice orally by mixing the compound into food (Kazim et al., *Mol Neurodegener*, 2017).
What the research says it does
In rodent studies, P021 is described as neurogenic and neurotrophic. The proposed mechanism, as reported by the originating group, runs through a few linked steps:
- It raises expression of brain-derived neurotrophic factor (BDNF), partly by inhibiting leukemia inhibitory factor (LIF) signaling.
- Higher BDNF is associated with reduced activity of GSK-3β, an enzyme that drives abnormal tau phosphorylation.
- The net effect in the animal models is more new neurons in the hippocampal dentate gyrus, better dendritic and synaptic measures, and less tau pathology.
Most of this rests on transgenic Alzheimer's mouse models. In one long study, female 3×Tg-AD mice fed P021 starting at three months of age showed rescued dendritic and synaptic deficits and reversal of cognitive impairment (Kazim et al., *Mol Neurodegener*, 2017, PMC5488423). The compound has also been examined in a Down syndrome mouse model (Ts65Dn) and, more recently, in cell and animal models of CDKL5 deficiency disorder (Trazzi et al., *J Neurodev Disord*, 2024). A 2025 imaging study tracked brain microstructure changes from early P021 treatment in the same Alzheimer's mouse model (*PMC12993872*).
State of the evidence
This is preclinical. As of mid-2025, the Alzheimer's Drug Discovery Foundation's review noted no human clinical trials of P021 on ClinicalTrials.gov, and a worldwide development license held by Phanes Biotech. Every efficacy claim above comes from animals or cell culture. None of it has been confirmed in people, and there are no human safety, dosing, or effectiveness data. The literature is also narrow: the great majority of papers share the same originating research group, which is normal for an early academic compound but worth keeping in mind.
P021 is not approved by the FDA or any comparable regulator. It is a research compound, sold (where sold at all) for laboratory use only and explicitly not for human consumption. WADA does not list it by name; that absence is not a clearance, and the broader category of growth-factor and neurotrophic signaling agents draws anti-doping scrutiny.
The buyer / quality angle
Because P021 only exists as a research chemical, there is no pharmaceutical-grade supply chain behind it. Anything sold under the name "P21" or "P021" depends entirely on the vendor's own synthesis and testing. The original peptide was purified to greater than 96% by reverse-phase HPLC with identity confirmed by mass spectrometry; a research-chemical vial may or may not match that. If you are evaluating a seller, the facts that matter are a recent, batch-specific certificate of analysis showing identity (mass spec) and purity (HPLC), and whether an independent lab, not the seller, ran it. peptideone aggregates the third-party rater signals that exist, but for an obscure compound like this, published COA coverage is thin.
Nothing here is medical, dosing, or efficacy advice. It is a summary of what the published research records, with attribution.