Also covered
71/100May 2026 review (v3.0 rubric); v4.1 re-score pending
Starting at $125/mo. PeterMD is one of the providers covered in our editorial directory that dispenses or coordinates P21.
Read review →Cognitive · CNTF Mimetic
P21
Released: Last reviewed:
P21 is a peptide derivative of ciliary neurotrophic factor (CNTF) studied for memory enhancement, neuroprotection, and reversal of cognitive decline.
P21 at a glance
P21 is a peptide derivative of ciliary neurotrophic factor (CNTF) studied for memory enhancement, neuroprotection, and reversal of cognitive decline. Mechanism: CNTF-mimetic peptide. Typical route: Subcutaneous, oral, intranasal. FDA status: Not FDA-approved. Limited compounding-pharmacy availability; most current sources are research-chemical suppliers, which have variable quality controls.
Drug classCNTF-mimetic peptide
Half-life~2 hours
RouteSubcutaneous, oral, intranasal
Common dosing0.5-1 mg/day
FDA statusNot approved
Available throughResearch suppliers (mostly)
Mechanism of action
P21 mimics the neurogenic effects of CNTF by stimulating proliferation and survival of neural progenitor cells in the hippocampus and supporting adult neurogenesis. Preclinical models show enhanced learning and memory.
Dosing reference
Subcutaneous: 0.5-1 mg daily. Cycled 5 days on / 2 days off for 4-8 weeks. Oral and intranasal formulations are also used in some protocols.
Dosing information is provided for educational reference and is not medical advice. Patients should not initiate or modify any peptide regimen without consulting a licensed clinician. See our medical disclaimer.
FDA status & regulatory framework
Not FDA-approved. Limited compounding-pharmacy availability; most current sources are research-chemical suppliers, which have variable quality controls.
U.S. telehealth providers that work with P21
Also covered
85/100May 2026 review (v3.0 rubric); v4.1 re-score pending
Starting at $180/mo. Marek Health is one of the providers covered in our editorial directory that dispenses or coordinates P21.
Read review →Also covered
88/100May 2026 review (v3.0 rubric); v4.1 re-score pending
Starting at $160/mo. Defy Medical is one of the providers covered in our editorial directory that dispenses or coordinates P21.
Read review →Related cognitive enhancement peptides
Frequently asked questions about P21
What is P21 used for?
P21 is used in cognitive-enhancement protocols, particularly by patients interested in adult neurogenesis support, post-concussion recovery, and age-related cognitive decline.
How does P21 differ from Cerebrolysin?
P21 is a single defined peptide acting through CNTF receptor pathways. Cerebrolysin is a cocktail of brain-derived neuropeptides. Cerebrolysin has substantially more clinical-trial evidence; P21 is more of a research-stage compound.
References
- Rescue of cognitive-aging by administration of a neurogenic and/or neurotrophic compound. Neurobiol Aging. 2014;35(9):2134-2146. PMID: 24735831
- Enhancement of dentate gyrus neurogenesis, dendritic and synaptic plasticity and memory by a neurotrophic peptide. Neurobiol Aging. 2011;32(8):1420-1434. PMID: 19767127
Sources are peer-reviewed where available. PubMed (PMID) links resolve to NCBI's PubMed database. FDA links resolve to the U.S. Food and Drug Administration. Citations were last verified 2026-05-11.