Cognitive & Nootropic

P21

P021 · CNTF-derived peptide · Ciliary Neurotrophic Peptide

CNTF C-terminal fragment, not FGL, not Semax. Animal neurogenesis and metabolic papers are not a human TBI or amyloid protocol.

Not FDA-approved - research chemical

Quick answer

What it is: CNTF C-terminal fragment, not FGL, not Semax.

Typical research dose: 500-2000 mcg/day (SC or intranasal)

Reconstitution calculator ↓

Research summary, not medical advice.

Reviewed by Kymata Health Editorial Team
Last updated: August 2026Evidence: Low
Typical research dose
500-2000 mcg/day (SC or intranasal)
Frequency
1× daily
Half-life
Short (peptide)
Common vials
5 mg / 10 mg
CAS
N/A
Molecular weight
~2.3 kDa

Use-case scores

0–10 against the evidence we have, not a gym ranking. Hidden domains do not apply here.

  • Cognition3/10

    Neurotrophic fragment in animal models. Not a human nootropic RCT.

  • Metabolic / weight3/10

    Hypothalamic energy-expenditure animal data. Not a GLP-1 and not a fat-loss label.

Compound card

Sequence
CNTF C-terminal fragment (21 aa)
Class
Preclinical CNTF-derived peptide (not FGL)
Formula
C-terminal CNTF fragment (21 AA)
Status
Not FDA-approved · research use
Dose it
5 mg + 2.5 mL BAC water → 2 mg/mL · 500 mcg ≈ 25 units (U-100)
Open in calculator

How it works

P21 is a 21-amino-acid fragment (C-terminal portion) of ciliary neurotrophic factor (CNTF). It was identified through structure-activity relationship studies on CNTF to isolate the neurotrophic and metabolic activity without receptor coupling to the JAK/STAT pathway.

P21 promotes neurogenesis, axonal regeneration, and optic nerve repair in preclinical models. It also has significant effects on hypothalamic energy regulation - animal studies showed marked fat mass reduction, improved insulin sensitivity, and increased energy expenditure without reducing food intake or causing cachexia. The metabolic mechanism involves direct activation of hypothalamic AMPK and changes in neuropeptide Y (NPY) / proopiomelanocortin (POMC) signaling.

Source: PMID: 23877024

Background & History

P21 is a CNTF C-terminal fragment, not FGL, not Semax. Animal neurogenesis and metabolic papers are not a human TBI or amyloid protocol.

Research Use Cases

  • ✓CNTF-fragment identity vs FGL vs Semax
  • ✓Preclinical Alzheimer-model papers as animal work, not a human indication
  • ✓Not a TBI or Parkinson treatment page

Dosing

PhaseDoseFrequencyNotes
Research Protocol1 - 5 mg3x per week SC (research dosing)Based on preclinical scaling. No established human dosing. Very limited human data.

Administration

Route / form
Subcutaneous injection
Timing
Varies. Research compound with no established protocol.
Empty stomach?
No - Food timing is not critical.

Timeline

Preclinical timeline
Animal studies: fat mass reduction, improved insulin sensitivity, neurogenesis markers.

Who it is for

Neuroprotection / Neural Repair

Low

Strong preclinical data for axonal regeneration and optic nerve repair. Human data lacking.

Metabolic / Fat Loss

Low

Hypothalamic energy regulation effects in animals. No human clinical data.

Reconstitution

Vial
5 mg
Diluent
2.5 mL
Concentration
2 mg/mL
Per Unit (100u syringe)
20 mcg
Dose of 500 mcg = 25 units on a 100-unit insulin syringe

Safety & Considerations

Research compound. No established human safety data. Use only under medical supervision. Preclinical studies show favorable profile.

Regulatory & Legal Status

FDA Status (US)
Research Only
WADA Status (2026)
Not Listed

Not currently on the WADA 2026 Prohibited List. Policies may change - verify before competition.

Classification

Research Chemical

US Compounding: Not eligible / not available

⚠️ This information is for educational purposes only and may not reflect the most current regulatory updates. Always verify with official FDA, WADA, and jurisdiction-specific sources before use.

Limits of current evidence

  • Different molecule from FGL (NCAM FG loop).
  • This site will not treat obesity or neurodegeneration from this leaf.

Verdict

P21 is a CNTF fragment, not FGL, not Semax. Animal neurogenesis and metabolic papers are not a human protocol. Do not treat optic-nerve animal work as an eye drug.

Interactions & Contraindications

Research compound, thin human file. This site will not treat Alzheimer disease from a peptide page.

Synergies & Common Stacks

+ Semax →

Different molecules. Complementary neurogenesis marketing is not a combo RCT.

Frequently Asked Questions

What does P21 do?▼
P21 is a fragment of CNTF with neuroprotective and metabolic effects. In animals, it promotes neurogenesis, axonal repair, and fat mass reduction via hypothalamic mechanisms. Human data is very limited.

Prescription options: compare licensed telehealth providers

Some peptide therapies are available only by prescription after a consult with a licensed clinician.

Compare telehealth →
← Back to Peptide Library