Cognitive · Research Phase
P21 (Peptide)
No lawful US pathway
01 · Overview
A small synthetic peptide (P021) derived from the most active region of ciliary neurotrophic factor (CNTF), with an adamantylated glycine added to improve blood-brain barrier permeability and resistance to degradation (PMID 28655344). In aged rats, P021 increased BDNF expression, reduced neurogenesis deficits, and restored synaptic markers (PMID 24702821).
All available evidence is from animal studies.
02 · Research summary & key findings
In aged rats, oral P021 reduced age-related decline in learning and memory (Bolognin et al., Neurobiol Aging, 2014) (PMID 24702821). In 3xTg Alzheimer mice, chronic oral P021 reduced tau hyperphosphorylation and soluble amyloid-beta, likely via increased BDNF and reduced GSK-3beta activity, and rescued cognition, neurogenesis, and synaptic plasticity (PMID 25046994). Started early, P021 prevented dendritic and synaptic deficits and cognitive impairment in 3xTg mice (PMID 28655344). No human clinical trials have been reported.
03 · Regulatory status
P21 (Peptide) is in the research phase with limited clinical data in humans. Current evidence is primarily derived from preclinical (animal or in vitro) studies.
No lawful pathway today
P21 (Peptide) is not FDA-approved and does not currently have a lawful prescription or compounding pathway in the United States, so we do not sell it and will not book a consultation for it. That can change: in 2026 FDA began reviewing several peptides for compounding. If you are working on the goal it is studied for, a licensed clinician can tell you what is lawfully available, which may be something else.
Tell me if the status changes
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Looking for a lawful, clinician-prescribed option for cognitive support?
P21 (Peptide) is a research compound, is not FDA-approved, and has no lawful US compounding pathway, so we do not offer it and no clinician we work with will prescribe it. Products sold online as “research chemicals” are not made or tested to the standards required of medicines. If you are working on cognitive support, a licensed clinician can tell you at a free consultation whether an FDA-approved or lawfully compounded treatment fits you, or whether nothing does.
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04 · Administration routes
- Subcutaneous injection
- Intranasal
References
- [1]Rescue of cognitive-aging by administration of a neurogenic and/or neurotrophic compound Neurobiol Aging, 2014. PMID 24702821
- [2]Disease modifying effect of chronic oral treatment with a neurotrophic peptidergic compound in a triple transgenic mouse model of Alzheimer's disease Neurobiol Dis, 2014. PMID 25046994
- [3]Prevention of dendritic and synaptic deficits and cognitive impairment with a neurotrophic compound Alzheimers Res Ther, 2017. PMID 28655344
Primary literature
- PubMed: "P21"
Peer-reviewed literature indexed by the National Library of Medicine.
- ClinicalTrials.gov: "P21"
Registered interventional and observational studies, including status and phase.
- PubChem: "P21"
Chemical structure, molecular properties, and bioactivity data.
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Disclaimer: This information is provided for educational and research purposes only. It is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any peptide therapy. The Peptide Association does not endorse or recommend any specific treatment protocol. See our editorial policy for how this content is produced and reviewed. Clinicians: join the network.