What it is
P21 (P021) is a small peptidergic compound derived from a fragment of ciliary neurotrophic factor (CNTF), a naturally occurring neurotrophic protein, meaning one that supports the survival and growth of nerve cells. It has been studied preclinically for promoting neurogenesis, the formation of new neurons, and for reducing tau pathology in models of Alzheimer's disease.
In the PeptidesAI encyclopedia it is categorized under cognitive.
How it's thought to work
P21 is proposed to enhance expression of BDNF (brain-derived neurotrophic factor) and adult hippocampal neurogenesis while inhibiting abnormal tau hyperphosphorylation, supporting synaptic plasticity and neuronal survival. In the mouse study that measured it, the increase in BDNF was associated with lower activity of the enzyme GSK3-beta.
What the research says
Studies in a transgenic mouse model of Alzheimer's disease report that P021 lowered abnormal tau phosphorylation and rescued deficits in cognition, neurogenesis and synaptic plasticity. Both the 2014 and 2017 mouse studies came from the same research group. There are no human clinical data, and P21 is not FDA-approved.
Reported side effects
Human safety data is essentially absent. Its long-term effects in humans are unknown.
Reconstitution
P21 (P021) is supplied as a lyophilized (freeze-dried) powder and is typically reconstituted with bacteriostatic (BAC) water before use. It commonly comes in 5 mg and 10 mg vials. The amount of peptide in the vial is fixed; the water added only changes how concentrated the solution is.
Worked example. A 5 mg vial is 5,000 mcg. Reconstituted with 1 mL of BAC water, that works out to 5,000 mcg ÷ 1 mL = 5,000 mcg/mL. On a U-100 insulin syringe, where each unit is 0.01 mL, each unit holds 5,000 × 0.01 = 50 mcg. Use the peptide reconstitution calculator to work out the concentration and units for any vial size and water volume.
Important notes
There are no human clinical data for P21. It is sold only as a research chemical and is not FDA-approved.
Sources
- Disease modifying effect of chronic oral treatment with a neurotrophic peptidergic compound in a triple transgenic mouse model of Alzheimer's disease.. Kazim SF et al. Neurobiology of Disease, 2014. Preclinical
- Prevention of dendritic and synaptic deficits and cognitive impairment with a neurotrophic compound.. Baazaoui N et al. Alzheimer's Research & Therapy, 2017. Preclinical
Frequently asked questions
These questions cover the same ground as the sections above, in a shorter format.
What is P21?
A small peptide derived from a fragment of CNTF, studied in mouse models of Alzheimer's disease for neurogenesis and tau effects.
How is P21 thought to work?
It is proposed to raise BDNF expression and adult hippocampal neurogenesis while inhibiting abnormal tau hyperphosphorylation.
What does the research on P21 say?
Mouse studies report lower tau pathology and rescued cognition and neurogenesis. There are no human clinical data.
What are the reported side effects of P21?
Human safety data is essentially absent.
How much is one unit from a 5 mg P21 (P021) vial?
With 1 mL of BAC water, a 5 mg vial is 5,000 mcg/mL, so one unit on a U-100 syringe (0.01 mL) holds 50 mcg.
The full entry, plus the calculator
The PeptidesAI app has the complete encyclopedia entry for P21 (P021) — one of 70 compounds covered — plus the reconstitution calculator, a dose log and reminders. Free to download on iPhone.
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