P21
Also known as: CNTF-derived peptide · neuropoietin-related peptide
A small peptide derived from a neurotrophic-cytokine framework, characterised in academic research for hippocampal neurogenesis induction and anti-neuroinflammatory effects in models of cognitive ageing and Alzheimer-type pathology.
- Category
- Neurogenesis
- Half-life
- Pharmacodynamic effects on neurogenesis extend across weeks despite shorter plasma exposure
Section 1
Overview
P21 is a small synthetic peptide engineered from a region of the neurotrophic-cytokine family — the same superfamily that includes ciliary neurotrophic factor (CNTF) and the leukaemia inhibitory factor — designed to retain the pro-neurogenic activity of the full protein while losing the broader cytokine effects that would otherwise dominate the systemic response.
The molecule has been characterised in academic research as one of the few peptide candidates capable of measurably inducing hippocampal neurogenesis in adult animals — generating new dentate gyrus neurons from quiescent neural stem cells. The endpoint matters because adult hippocampal neurogenesis is one of the few demonstrated routes by which the adult brain produces structurally new processing capacity, and its rate declines with age and with chronic stress.
P21 also shows anti-neuroinflammatory effects in cell-culture and animal models, attenuating microglial activation in response to amyloid-beta exposure and similar inflammatory triggers. The compound is studied in models of cognitive ageing and Alzheimer-type pathology where neurogenic decline and neuroinflammation are both implicated.
Section 2
Discovery & History
- Developed in academic research as part of a programme to derive smaller, more drug-like fragments from the cytokine-family neurotrophic factors that had themselves proven impractical as therapeutics due to molecular size and pleiotropic effects.
- Subject to a peer-reviewed preclinical literature from the early 2010s onwards, with the strongest data coming from murine models of cognitive ageing and Alzheimer-type pathology.
- Has not progressed to clinical-trial registration in any jurisdiction. No human safety or efficacy data is publicly available.
- Remains a research peptide used as a tool for studying adult neurogenesis and neuroinflammation pharmacology.
Section 3
Mechanism of Action
- 1Promotion of adult hippocampal neurogenesis — induction of neural stem cell proliferation in the dentate gyrus and survival of newly differentiated neurons.
- 2Modulation of the JAK-STAT signalling cascade downstream of the cytokine-receptor framework the peptide derives from, without producing the broader systemic cytokine effects of the parent molecules.
- 3Anti-neuroinflammatory effects via attenuation of microglial activation, reduction of pro-inflammatory cytokine release, and shift of microglia toward the M2 (resolution) phenotype.
- 4Indirect cognitive effects through restoration of neurogenic capacity in aged or pathological brain states where baseline neurogenesis is depressed.
- 5Reported reduction of amyloid-beta-induced neuronal injury in Alzheimer-model preparations, partly via the anti-inflammatory mechanism.
Section 4
Researched Benefits
Findings reported in the published preclinical and clinical literature. Effects in research contexts do not constitute claims of therapeutic benefit in humans.
- 1Induction of measurable adult hippocampal neurogenesis in aged-mouse models in published research.
- 2Improved performance on hippocampus-dependent learning tasks in cognitively impaired animal models.
- 3Anti-neuroinflammatory effects in models of Alzheimer-type pathology.
- 4Restoration of synaptic plasticity markers (LTP magnitude, spine density) in aged-brain preparations.
- 5Distinct mechanism from the BDNF-inducer family — useful as a complementary research tool.
Section 5
Theoretical Dosing & Protocols
| Route | Dosage | Frequency | Duration |
|---|---|---|---|
| Subcutaneous / intraperitoneal (research) | Microgram-range doses in animal protocols | Daily during a study course | Variable; chronic protocols of several weeks have been examined in mouse research |
Note: No validated human protocol exists. No clinical trials are publicly registered.
Section 6
Administration Routes
- Subcutaneous injection — primary route in animal research.
- Intraperitoneal in some rodent studies.
- Oral administration has not been validated in published research.
Section 7
Safety Profile
Commonly reported
- · Limited safety data — preclinical animal research only, no human pharmacovigilance
- · Generally well-tolerated in the reported animal protocols at studied doses
Rare / theoretical
- · Theoretical concerns relating to chronic JAK-STAT modulation, which is implicated in some oncogenic pathways when persistently activated
- · Long-term toxicology data is not publicly available
- · Pleiotropic cytokine-family pharmacology — even with the smaller peptide, off-target signalling cannot be ruled out
Contraindications
- · Not authorised for human use in any jurisdiction
- · Theoretical contraindication in subjects with active or historic malignancy via the JAK-STAT mechanism
- · No data in pregnancy, lactation, or paediatric contexts
Section 8
UK & EU Regulatory Context
United Kingdom
Not a licensed medicine. Research chemical for laboratory and preclinical use only.
European Union
Not approved by the EMA. No clinical authorisation in any major EU jurisdiction.
Section 9
Clinical Studies Summary
P21 induces adult hippocampal neurogenesis in aged mice
Chronic administration produced measurable increases in dentate gyrus BrdU-positive neuron counts in aged mice versus age-matched controls, with corresponding improvements on hippocampus-dependent learning tasks.
P21 attenuates amyloid-beta induced neuroinflammation
Reduction of microglial activation markers and pro-inflammatory cytokine release in Alzheimer-model mouse brains receiving P21 administration during the pathology-progression window.
Cognitive recovery in Alzheimer's mouse models with P21 treatment
Partial restoration of spatial and recognition memory performance in transgenic mouse models of Alzheimer-type pathology following chronic P21 administration.
Section 10
Frequently Asked Questions
Section 11
Sourcing for Laboratory Research
Sourcing P21 for laboratory research
Researchers in the United Kingdom and elsewhere typically obtain P21 from specialist research-chemical suppliers. Purity, third-party testing, and supplier transparency are the principal differentiators worth evaluating before placing an order. The two suppliers below are commonly referenced in UK research contexts.
Reminder: research peptides are sold strictly for in vitro and preclinical laboratory purposes. Importation or supply for human consumption is not permitted under UK medicines legislation.