P21
Clinical reviewer: Jacob Moore, MD · Last checked September 22, 2026
What is the P21 peptide?
P21 is the common name for P021, a small neurotrophic peptide mimetic developed to overcome the drug-delivery problems of natural neurotrophic factor proteins. It is described as a ciliary neurotrophic factor peptide mimetic and has been studied only in mice, including models of Alzheimer's disease. P21 online is easily confused with the unrelated cell-cycle regulatory protein of the same name.
What is P21, and where does it come from?
In the literature this compound is called P021: a small neurotrophic and neurogenic peptide mimetic discovered in the Iqbal laboratory, designed to overcome the difficulties of administering whole neurotrophic factor proteins as drugs [1]. Natural neurotrophic factor trials were halted in the past because of blood-brain barrier impermeability, short half-life and severe side effects, which is the problem P021 was designed to work around [1]. A related paper describes P021 as a ciliary neurotrophic factor small-molecule peptide mimetic [3].
What does the animal research on P021 show?
In 3xTg-AD mice, a strain bred to develop Alzheimer's-like pathology, P021 treatment started during the synaptic compensation period prevented neurodegeneration and amyloid-beta and tau pathology, rescued episodic memory impairment and markedly reduced the mice's mortality rate [2]. These findings come from a single mouse model.
Has P021 been tested in humans?
No human study of P021 was found in our search as of September 2026. Online, the compound is usually written as P21, which risks confusion with an unrelated cell-cycle protein also called p21.
Related terms
Sources
- Baazaoui N, Iqbal K. Alzheimer's Disease, Challenges and a Therapeutic Opportunity to Treat It with a Neurotrophic Compound. Biomolecules, 2022.
- Baazaoui N, Iqbal K. Prevention of Amyloid-β and Tau Pathologies, Associated Neurodegeneration, and Cognitive Deficit by Early Treatment with a Neurotrophic Compound. J Alzheimers Dis, 2017.
- Mottolese N et al. Effects of a ciliary neurotrophic factor (CNTF) small-molecule peptide mimetic in an in vitro and in vivo model of CDKL5 deficiency disorder. J Neurodev Disord, 2024.
This entry is for education and is not medical advice. Talk with a licensed clinician about your own situation before starting, stopping, or changing any treatment.
