P21
Synthetic hexapeptide derived from CNTF (ciliary neurotrophic factor)
- Class
- Nootropic peptide
- Half-life
- ~10 min
- Route
- Intranasal
- Cadence
- Daily
- Evidence
- Animal data primarily
Overview
P21 is a synthetic six-amino-acid peptide (Ac-DGGL(A)G-NH2) designed as a short, stable fragment derived from ciliary neurotrophic factor (CNTF). The original rationale: CNTF promotes neuron survival and synaptic plasticity in animal models, but it's a large protein that doesn't cross the blood-brain barrier well and triggers harsh side effects when given systemically. P21 was engineered to retain some of CNTF's neurotrophic effects in a smaller, intranasal-deliverable package.
The peptide appears in research-market catalogues as a nootropic, with sellers claiming it enhances memory, learning, and neuroplasticity. The evidence base is almost entirely rodent studies — mostly Russian-language publications from the 2000s-2010s showing improved performance in Morris water maze and passive avoidance tests after intranasal dosing. There are no published human trials, no FDA/EMA regulatory filings, and no independent Western replications of the original Russian data.
Bottom line: P21 is a real peptide sequence with some published animal data supporting a cognitive effect, but the human evidence is zero and the animal data comes from a narrow source base. It's in a grey zone between 'legitimate research peptide with thin data' and 'research-market product with no real clinical grounding.'
Safety considerations
A few of the safety signals worth knowing — the full list, with dosing context and what to monitor, is inside AIx Core.
- Not approved for human use by any regulator. No human safety trials published. All efficacy data are rodent-only.
- No long-term toxicity studies in any species. The safety profile beyond 2-4 weeks of daily dosing is completely unknown.
- Intranasal delivery bypasses the blood-brain barrier — this is the intended mechanism, but it also means systemic safety checks (liver metabolism, renal clearance) don't apply in the usual way. Unknown CNS accumulation risk.
+ 3 more safety notes inside AIx Core →
Commonly monitored
Markers and signals people track when researching P21.
- Subjective cognitive changes — memory, focus, learning speed
- Sleep quality (some users report vivid dreams or disrupted sleep)
- Mood — irritability or anxiety if dosing too high
- Nasal irritation or congestion from intranasal delivery
- Neurological symptoms — headache, dizziness, any unusual sensory changes
Frequently asked questions
What is P21?
Synthetic hexapeptide derived from CNTF (ciliary neurotrophic factor). P21 is a synthetic six-amino-acid peptide (Ac-DGGL(A)G-NH2) designed as a short, stable fragment derived from ciliary neurotrophic factor (CNTF). The original rationale: CNTF promotes neuron survival and synaptic plasticity in animal models, but it's a large protein that doesn't cross the blood-brain barrier well and triggers harsh side effects when given systemically. P21 was engineered to retain some of CNTF's neurotrophic effects in a smaller, intranasal-deliverable package.
How is P21 administered?
Intranasal, typically daily.
What is the half-life of P21?
~10 min — Short plasma half-life; intranasal delivery targets CNS directly.
Is P21 approved for human use?
P21 is investigational — not approved by the FDA, EMA, or MHRA for human use at the time of writing.
What does the evidence show for P21?
Evidence tier: Animal data primarily. Shadurskaya 2006 (Russian) dosed 50-500 μg/kg intranasal in rats for 7 days; Morris water maze latency improved ~25-30% vs control. No Western replication.
What is commonly monitored when researching P21?
Commonly tracked markers + signals: Subjective cognitive changes — memory, focus, learning speed, Sleep quality (some users report vivid dreams or disrupted sleep), Mood — irritability or anxiety if dosing too high, Nasal irritation or congestion from intranasal delivery, Neurological symptoms — headache, dizziness, any unusual sensory changes.
Open this in AIx Core for the full picture
Mechanism breakdown, receptor pathway diagram, full safety list, monitored items, source citations, and one-tap add-to-protocol. Free with any account.