SYS ONLINE
SUPPLEMENT_SCHOLAR
evidence · mechanism · dose
Experimental/NeurotrophicResearch peptide

P21

aka Cdk5 activator-derived peptide

CNTF-derived peptide reported to promote neurogenesis in preclinical work.

Educational explainer of a research peptide. Profiles in this section deliberately omit clinical-trial citations, dosing protocols, and purchase links. Not FDA-approved as a supplement; not a recommendation to use.

Overview

P21 is a 21-amino-acid peptide derived from ciliary neurotrophic factor (CNTF) that retains neurogenic activity without CNTF's systemic side effects.

Source
  • Synthesized in research settings
Forms
  • Subcutaneous injection (research)

Mechanism of action

Mimics CNTF-mediated neurogenic signaling, increasing hippocampal neurogenesis and BDNF expression in animal models.

Pathways
  • · CNTF receptor signaling
  • · BDNF induction
  • · Adult hippocampal neurogenesis

How it acts on the body

Native CNTF promotes neurogenesis but causes systemic effects (weight loss, antibody formation) that limited its clinical use. P21 was designed as a minimal active fragment that crosses the blood-brain barrier and reproduces the neurogenic effect without those side effects in rodents.

Reported outcomes include increased BDNF expression, enhanced spatial memory in aged mice, and reversal of cognitive deficits in Alzheimer's models. No published human trials exist.

Hormonal & endocrine impact

How this peptide is reported to shift specific hormones and signaling molecules. Directionality reflects research literature and preclinical models, not clinical prescribing data.

Projected hormonal trajectory
Illustrative curves derived from reported direction of effect. Not measured patient data.

Curves are schematic shapes (sigmoid for increases/decreases, damped oscillation for modulation/stabilization) anchored to a 100% baseline. They communicate direction and tempo of change reported in research literature — not absolute hormone concentrations.

BDNFIncreases
Hippocampal BDNF rises in animal studies.
CNTF pathwayModulates
Partial-agonist-like effect at CNTF receptors.

Effects on the body

Supports
Adult hippocampal neurogenesis in models
Supports
Memory in animal AD models

Organ system effects

Brain & CNS

Hippocampus and cortex.

Endocrine

Minimal systemic involvement reported.

Reported effects

Drawn from preclinical research, anecdote, and small-scale clinical observation. No evidence grades are assigned — most peptides on this page lack rigorous human trials.

  • Targets adult neurogenesis directly
  • Avoids CNTF systemic side effects in animals

Potential side effects

Common
  • · No characterized human profile
Rare
    Serious
    • · Long-term safety unknown

    Drug interactions

    No notable interactions reported.

    Pairing context

    Often combined with
    • Aerobic exercise
      Independently increases BDNF and adult neurogenesis.
    Avoid combining with
    • Active glial tumors
      CNTF-pathway activation in gliomas is under-characterized.
    Important. Research peptides described here are not FDA-approved supplements. Supplement Scholar does not endorse, recommend, or link to any source for purchase. Consult a qualified clinician before considering any peptide therapy.