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Nootropics & cognitive

P21

CNTF-derived peptide with claimed neurogenic potential; adamantane-conjugated variant designed for blood-brain barrier penetration.

Investigational research compound Nootropics & cognitive Longevity

Reviewed 2026-09-12
Full name
P21 neurogenic peptide (CNTF-derived)
Also known as
P-21
Regulatory status
Investigational research compound; adamantane variant not approved for human use
Variant note
The adamantane-conjugated form (sometimes marketed as 'Adamax') is a blood-brain-barrier-penetration modification of the same peptide, with essentially no published pharmacology or safety data beyond community discussion.

Origin

Proposed to derive from or mimic the activity domain of ciliary neurotrophic factor (CNTF). The adamantane-conjugated variant was engineered for better blood-brain-barrier penetration via the adamantane cage structure.

Mechanism

Proposed as a CNTF mimetic, activating CNTF receptor signaling (gp130/STAT3, PI3K/Akt) to support neuronal survival, differentiation, and neurogenesis. The adamantane conjugate adds lipophilicity to improve CNS delivery.

Research summary

Evidence

Primary literature on P21 as a therapeutic peptide is very thin; most PubMed hits are for the unrelated cyclin-dependent kinase inhibitor p21 protein. No peer-reviewed clinical trials or systematic preclinical reports exist. Evidence quality is very low.

Evidence tier: Investigational research compound — see the methodology note for how this is assessed.

Citations

Reported benefits

  • neurogenesis stimulation (theoretical)
  • neuroprotection (theoretical)
  • appetite stimulation (anecdotal)

Dosing protocols reported in the literature & community

These are protocols reported by compounding pharmacies, published trials, or self-experimentation communities — not a prescription. Start low, especially for anything new.

Reported dosing protocols
RouteReported protocol
Subcutaneous injection (research; no human standard)No validated human dose exists for either form.

Side effects

  • insufficient human data

Safety notes

Safety: Essentially unevaluated in humans. CNTF itself has mixed effects, neuroprotective at some doses, neurotoxic at high ones, and P21 may carry similar risks. Not recommended outside formal research.
Community & reddit notes (anecdotal — not clinical evidence)

Occasionally mentioned in nootropic forums with anecdotal cognitive and appetite claims. Use is rare, evidence speculative.

Mixing compatibility

Pulled from a community-charted mixing-compatibility reference (anecdotal, clinic-use, and community-reported signals) — not a safety guarantee. Verify independently before combining anything.

Anecdotally combined (outside clinic protocols)

Reported as a combination to avoid