P21
Also known as: NAPVSIPQ, P021 peptide, Neurotrophic peptide P21
Overview
P21 (also called P021) is a synthetic tetrapeptide derived from the CNTF (ciliary neurotrophic factor) binding interface and designed to mimic neurotrophic signaling without the typical side effects of full CNTF. Research by Iqbal and colleagues at the New York State Institute for Basic Research has shown P21 stimulates BDNF expression, promotes neurogenesis, reduces amyloid-beta deposition, and decreases tau hyperphosphorylation in Alzheimer's disease models. It also supports dendritic architecture and synaptic protein expression.
Mechanism of Action
P21 acts as a compact neurotrophic mimetic by supporting BDNF-TrkB signaling, increasing BDNF mRNA in hippocampal tissue and BDNF protein in cortical samples. This drives phospho-CREB activation and downstream TrkB signaling cascades including PI3K/Akt and GSK3β inhibition. Inhibitory phosphorylation of GSK3β reduces both tau hyperphosphorylation (at AT8 and PHF1 epitopes) and amyloid precursor protein processing/Aβ production. P21 also increases MAP2 (dendritic stability), PSD95 (synaptic scaffolding), and synaptophysin (synaptic vesicle) expression.
Potential Benefits
- BDNF upregulation promoting neuroplasticity
- Reduction in amyloid-beta deposits in transgenic Alzheimer's models
- Decrease in tau hyperphosphorylation at multiple epitopes
- GSK3β inhibition protecting against neurofibrillary tangle formation
- Hippocampal neurogenesis stimulation
- Improved spatial learning and memory in aged animal models
- Dendritic spine density and synaptic protein preservation
Dosage Protocols
The following reflects doses used in published research studies. This is not medical advice. Consult a qualified healthcare professional.
| Beginner | 0.5 mg intranasal once daily |
| Intermediate | 1 mg intranasal daily, split AM/PM |
| Advanced | 1.5-2 mg intranasal daily |
| Cycle Duration | 4-12 weeks |
Derived from CNTF — promotes neurogenesis. Human dosing protocols not well-established; based on rodent-to-human extrapolation.
Use our Reconstitution Calculator to determine exact syringe units for your protocol.
Routes of Administration
Intranasal Moderate — preferred for CNS peptides
Bypasses BBB via olfactory pathway.
Subcutaneous Injection High systemic
Less common; systemic delivery requires higher doses to reach CNS.
Read our full Routes of Administration Guide for detailed comparison of all delivery methods.
Stacking Protocols
Popular research stacks involving P21:
Neurogenesis Stack
Layered cognitive/neurogenic support. P21 for CNTF-mediated neurogenesis, Semax for BDNF, Dihexa for HGF-mediated synaptogenesis.
Explore our complete Peptide Stacking Guide for more combinations and safety considerations.
Reconstitution
| Storage | Refrigerate at 2-8°C after reconstitution |
|---|
For nasal peptides (Semax, Selank, PT-141 nasal), reconstitute in sterile saline and transfer to a metered nasal spray device.
Need exact syringe measurements?
Amino Acid Sequence
Ac-DGGLAG-NH2 (based on CNTF binding domain fragment; specific sequence varies by source)
Side Effects & Safety
- Limited data; generally well-tolerated in preclinical models
- No human safety data
Safety & Contraindications
This information is for educational purposes only. Consult a qualified healthcare provider before using any peptide.
Pregnancy / Lactation
Bleeding Disorders
Active Skin Infection at Injection Site
Pharmacokinetics
| Half-Life | Not well characterized for this peptide; consult primary literature |
|---|---|
| Storage | Store lyophilized peptide at -20°C (long-term) or 2-8°C (short-term, under 30 days). Reconstituted: refrigerate at 2-8°C and use within 28-30 days. Protect from light. Do not freeze reconstituted solution. |
Synergistic Compounds
The following compounds have been studied alongside P21 for potential complementary or synergistic effects:
Learn More
References & Further Reading
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