P21
CNTF-derived neuroprotective peptide — promotes neurogenesis and adult neural stem cell proliferation.
Research facts
| Half-life | ~4–6h |
|---|---|
| Route | SubQ / Nasal |
| Typical dose | 100–200 mcg/day |
| Frequency | Once daily |
| Solvent | Bacteriostatic water |
| pH | 5.5–7.5 |
| Stability | 30 days at +4°C |
Mechanism of action
P21 is a synthetic peptide derived from CNTF (Ciliary Neurotrophic Factor) that activates LIF/CNTF receptor signalling to promote the proliferation of adult neural stem cells (NSCs) in the subventricular zone and hippocampus. Unlike CNTF itself (which causes weight loss and muscle wasting via systemic cytokine effects), P21 appears to act predominantly on neural tissue without significant systemic side effects. It also upregulates CNTF endogenously and activates JAK/STAT3 signalling in neural progenitor cells, driving neurogenesis. Preliminary studies suggest it improves memory and cognitive function in ageing rodent models via increased hippocampal neurogenesis.
Documented effects (research-model)
- Neural stem cell proliferation and neurogenesis
- Hippocampal neurogenesis support
- Memory consolidation improvement in animal models
- Neuroprotection via CNTF receptor signalling
- Potential Alzheimer's/neurodegeneration research application
Research protocols
| Protocol | Dose | Frequency | Cycle | Vial |
|---|---|---|---|---|
| Standard | 100–200 mcg/day | Once daily SubQ or nasal | 4–8 weeks | 2mg / 2mL BAC water |
Research context only. Not medical advice. Consult a qualified healthcare professional before any protocol decision.
Synergies
- Semax MODERATE
P21 (neurogenesis via CNTF) + Semax (neuroplasticity via BDNF). Complementary neurogenesis and plasticity stack.
Myths & misconceptions
Evidence gaps
- Almost entirely preclinical data — very few published studies beyond cell culture and rodent work.
- Human pharmacokinetics completely unknown.
- Whether intranasal/SubQ P21 meaningfully activates CNS neural stem cells in humans is unestablished.
Safety notes
Very limited human safety data. Among the most experimental compounds in this library. Proceed with significant caution. Research context strictly maintained.
Biomarkers to monitor
Primary-source citations
- PMID 22120630 — CNTF peptide P21 promotes neural stem cell proliferation in the adult rodent brain (Neuropharmacology. 2012)
Frequently asked
What is P21?
P21 (P21 — CNTF-Derived Neuroprotective Peptide) is a research compound classified in our library as Tier D — Animal or in-vitro data only.. CNTF-derived neuroprotective peptide — promotes neurogenesis and adult neural stem cell proliferation.
What is the evidence tier for P21?
We classify P21 as Tier D: Animal or in-vitro data only. See our full peptide evidence tiers explainer for how we assign S/A/B/C/D.
What is the research dose of P21?
For P21, typical research dose is 100–200 mcg/day, route is SubQ / Nasal, half-life is ~4–6h. Protocols vary by research goal — see the protocols section on this page for standard and advanced dosing schedules. Research use only, not medical advice.
Is P21 safe?
Very limited human safety data. Among the most experimental compounds in this library. Research context only — no compound on this site is approved for human therapeutic use unless explicitly noted.