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Last reviewed: March 2026Sources: PubMed, FDA, WADA Prohibited List

Evidence graded using the PeptideScholar A-D system

P21

DLimited Data
30
Low Credibility
1 cited studyy · Evidence level D

CNTF-derived peptide analog · 15 amino acids

Not FDA Approved

P21 is a synthetic peptide derived from ciliary neurotrophic factor (CNTF), a cytokine with neurotrophic and neuroprotective properties. Developed by Ceregene (now defunct) for Alzheimer's disease, it was designed to mimic CNTF's effects without the side effects of the full protein. No human clinical data exists.

Mechanism of Action

Claimed to activate CNTF receptor signaling pathways, promoting neurogenesis, neuronal survival, and synaptic plasticity. Also proposed to reduce neuroinflammation and amyloid pathology. However, the mechanism is not well-characterized, and most data comes from cell culture studies rather than validated animal models.

Benefits

  • Promotes neurogenesis in cell culture models
  • Mimics CNTF neurotrophic activity without systemic cytokine side effects
  • May enhance synaptic plasticity and memory in preclinical models
Not Medical Advice — Research-Reported Information Only

This content is for informational purposes only and does not constitute medical advice.

P21 — Dosing in Published Research

Reported Routes: Subcutaneous injection, Intranasal
No established human dosing. Originally developed for intracerebroventricular delivery in clinical trials (which never progressed past preclinical stages). Research chemical dosing is entirely speculative.

The dosing information above is sourced from published research literature and clinical trials. These are not recommendations. Individual responses vary. Always consult a healthcare provider before considering any peptide-based therapy.

Side Effects

  • No human safety data exists
  • Unknown long-term effects on the CNS
  • Theoretical risk of inappropriate neurogenesis or gliosis
  • Not approved for human use

Considering Peptide Research?

P21 is not FDA-approved. Always consult a licensed healthcare provider before considering any peptide.

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Research & Evidence

ReviewCochrane Database Syst Rev, 2023

Cerebrolysin for acute ischaemic stroke.

Cochrane review found cerebrolysin (the parent compound from which P21 is derived) may improve functional outcomes in acute ischemic stroke; evidence quality was low to moderate

PMID: 37818733

References

  1. 1. Cerebrolysin for acute ischaemic stroke.. Cochrane Database Syst Rev, 2023. “Cochrane review found cerebrolysin (the parent compound from which P21 is derived) may improve functional outcomes in acute ischemic stroke; evidence quality was low to moderate” [PMID: 37818733]

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P21 FAQ

Medical Disclaimer

This content is for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment recommendations.

Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment. Do not disregard professional medical advice based on information found on this site.

No claims of therapeutic efficacy are made for substances that are not FDA-approved for the discussed indications. Research citations reflect published findings and do not imply endorsement.

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