P21
CNTF-Derived Neurogenic Peptide | Cognitive Enhancement & Neuroprotection
P21 (also known as P021) is a synthetic tetrapeptide derived from the biologically active region of human ciliary neurotrophic factor (CNTF). Featuring an adamantylated glycine modification for enhanced blood-brain barrier penetration and metabolic stability, P21 promotes neurogenesis, enhances synaptic plasticity, and has shown significant cognitive benefits in preclinical models of Alzheimer's disease, traumatic brain injury, and age-related cognitive decline.
Daily dose
500mcg-2mg IN / 100-500mcg SubQ
Frequency
1x daily
Cycle length
4-6 weeks
Storage
2-8°C
Key benefits
Neurogenesis enhancement, memory and learning improvement, synaptic plasticity, neuroprotection against tau pathology, BDNF upregulation, potential disease modification in Alzheimer's, reduced anxiety. Superior safety profile compared to full-length CNTF.
How it works
P21 inhibits the LIF/STAT3 signaling pathway that suppresses adult neurogenesis. It upregulates BDNF expression, activates the TrkB/PI3K/AKT pathway, and inhibits GSK3β activity. This promotes hippocampal neurogenesis, increases synaptic proteins (synaptophysin, synapsin I), enhances glutamate receptor expression, and reduces tau hyperphosphorylation. The adamantane modification provides BBB penetration and metabolic stability.
Dosage protocols
Goal
Cognitive enhancement (SubQ)
Dose
100-300mcg · 1x daily
Route
SubQ
Goal
Cognitive enhancement (IN)
Dose
500mcg-1mg · 1x daily
Route
Intranasal
Goal
Neuroprotection
Dose
300-500mcg · 1x daily
Route
SubQ
Goal
Acute cognitive boost
Dose
1-2mg · As needed
Route
Intranasal
Goal
Initial assessment
Dose
100mcg · 1x daily
Route
SubQ
Research indications
cognitive
neuroprotection
synaptic
Administration
Interactions
Safety notes
No human clinical trials conducted - all data is preclinical
18-month rodent studies showed no adverse effects
No weight loss (unlike full-length CNTF)
No tumor formation in long-term studies
Start with lower doses to assess individual response
Not recommended during pregnancy or breastfeeding
Consult healthcare provider before use
Research studies
Original P21 Discovery Study - Neurogenesis and Memory Enhancement (2010)
Mice | C57Bl6 | IP administration | 4 weeks | Enhanced learning, memory, and neurogenesis
Original study demonstrating P21 (Ac-DGGLAG-NH2) enhanced learning and both short-term and spatial reference memories in normal adult mice. P21 induced enhancement of neurogenesis and maturation of newly born neurons in the dentate gyrus, increased synaptophysin and synapsin I expression.
View study →3xTg-AD Alzheimer's Model - Long-term Efficacy (2014)
Mice | 3xTg-AD | 60 nmol/g feed oral | 6-12 months | Tau reduction, BDNF increase, cognitive rescue
P021 treatment significantly reduced abnormal tau hyperphosphorylation, increased BDNF expression, rescued neurogenesis deficits, and improved cognitive function in triple-transgenic Alzheimer's mice. Effects mediated via BDNF/TrkB/PI3K/AKT/GSK3β pathway.
View study →Traumatic Brain Injury Enhancement Study
Mice | C57Bl6 | CCI model | 50 nmol/animal/day | 30 days | Neurogenesis and memory recovery
In controlled cortical impact TBI model, Peptide 6 (P21 parent) increased newborn neurons in dentate gyrus by 80%, reversed TBI-induced dendritic and synaptic density loss, and improved memory recall on behavioral testing.
View study →18-Month Chronic Safety and Efficacy Study
Mice | 3xTg-AD and wild-type | Oral | 18 months | Prevention of neurodegeneration
Long-term P021 treatment starting at 3 months prevented neurodegeneration, Aβ and tau pathologies, rescued episodic memory impairment, and markedly reduced mortality rate in 3xTg-AD mice. No adverse effects observed.
View study →CDKL5 Deficiency Disorder Study (2024)
Mice and cell culture | CDKL5 KO | Various doses | In vitro efficacy, limited in vivo benefit
P021 restored neuronal proliferation, survival, and maturation in human CDKL5-deficient cell models via GSK3β pathway normalization. However, in vivo treatment in CDKL5 KO mice showed limited benefit, suggesting disease-specific limitations.
View study →Synaptic Protein and Glutamate Receptor Enhancement
Mice | 3xTg-AD | Oral P021 | Enhanced NMDA/AMPA receptor expression
P021 treatment significantly increased levels of GluN2A, GluA1, GluA2+3 subunits of NMDA and AMPA receptors in hippocampus, contributing to enhanced synaptic plasticity and learning capacity.
View study →