Cognitive & Mood Synthetic CNTF-derived peptideNot FDA-approved · research compound

P-21

P21 · P-21 Peptide

Evidence: Preclinical / animal. Example dose: finalize with a provider. Not a fact-check stamp.

500 mcg to 1 mg daily – 1-2 mg SubQ Daily during 4-6 week cycles

Neurogenesis promoterHippocampal neural stem cell activatorCognitive enhancement peptide

P-21 is a synthetic 21-amino acid peptide derived from the active region of ciliary neurotrophic factor (CNTF) that promotes hippocampal neurogenesis. Unlike full-length CNTF, P-21 crosses the blood-brain barrier and does not produce the appetite suppression and weight loss associated with CNTF, making it suitable for targeted cognitive enhancement without metabolic side effects. P-21 stimulates the differentiation of neural progenitor cells into mature neurons in the hippocampus, the brain region critical for memory consolidation and spatial navigation. It is used in short intensive cycles (4-6 weeks) 2-3 times per year rather than continuously.

Quick Start

Route

SubQ injection

Start low

500 mcg to 1 mg SubQ

Frequency

Daily during 4-6 week cycles

Timing

No fasting required. Morning preferred.

Can be taken any time. No fasting required. 4-8 week cycles.

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Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.

Tiered Protocols · lowest first

Conservative start

500 mcg to 1 mg daily · SubQ injection · Daily during 4-6 week cycles

conservative starter

500 mcg to 1 mg daily

Daily during 4-6 week cycles

Intermediate

Neurogenesis & Synaptic Plasticity

1-2 mg · SubQ · Daily

animal study · Bolognin et al. 2014 (Neurobiol Aging)

Competes with Cerebrolysin in terms of neuro-regeneration goals but is a synthetic small peptide requiring much smaller volumes. No human trial has been conducted. This dose is extrapolated from animal research and has not been tested for safety or effect in people.

1-2 mg

Daily

Reconstitution CalculatorU-100

Vial strength

BAC water

Vials in this mix

Syringe size

Target dose

050100u

Draw to

— units

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I will split this dose across more than one syringe

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How it works

P-21 promotes differentiation of hippocampal neural progenitor cells into mature, functional neurons through CNTF receptor-independent mechanisms. It increases expression of BDNF and other neurotrophic factors in the hippocampus, enhances synaptic plasticity and long-term potentiation (LTP), and supports the survival and integration of newly generated neurons into existing neural circuits. Unlike full-length CNTF, P-21 does not activate the CNTF receptor complex (CNTFRalpha/LIFRbeta/gp130), which is responsible for the appetite suppression and cachexia associated with systemic CNTF. This selectivity makes P-21 a targeted neurogenesis agent without metabolic side effects.

What to expect

Early

Days 1–7

Days 1-14: Minimal perceptible changes. Neurogenesis is a slow process.

Mid

Weeks 2–4

Weeks 2-4: Subtle cognitive improvements may emerge. Memory consolidation improves.

Later

Weeks 4–12

Weeks 4-6+: New neurons integrate into hippocampal circuits. Benefits may persist for months after cycle ends.

Evidence

HumanNo published trials

AnimalPresent

In-vitroPresent

Each reference below was re-fetched from its PubMed record, and the quoted sentence was confirmed to appear in that abstract and to support the claim it sits under. Follow any of them to read the source.

We investigated for the first time the effect of oral treatment during prenatal to early postnatal development with a neurotrophic compound, P021 (Ac-DGGLAG-NH2), on neurobehavior and AD-like pathology in 3xTg-AD, a transgenic mouse model of AD.

We investigated for the first time the effect of oral treatment during prenatal to early postnatal development with a neurotrophic compound, P021 (Ac-DGGLAG-NH2), on neurobehavior and AD-like pathology in 3xTg-AD, a transgenic mouse model of AD.

Prenatal to early postnatal neurotrophic treatment prevents Alzheimer-like behavior and pathology in mice. Alzheimer's research & therapy · 2020 · PMID 32854771

Evidence scope. Transgenic mouse model; oral developmental treatment, not the card's subcutaneous adult regimen.

Claims we could not support

No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.

Complete regimen: 500 mcg to 1 mg daily via SubQ injection, Daily during 4-6 week cycles. The verified row supports only the narrower dose/route boundary stated above, not every element of the displayed regimen.

Mechanism: P-21 promotes differentiation of hippocampal neural progenitor cells into mature, functional neurons through CNTF receptor-independent mechanisms. It increases expression of BDNF and other neurotrophic factors in the hip. No checked live abstract supported this full mechanistic claim at the card's formulation/route without extrapolation.

Primary safety claim: Generally well tolerated. No checked live abstract directly established this as the primary concern for the card's exact formulation and regimen.

The honest take

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Hippocampal neurogenesis

Animal data supports increased neurogenesis. Mechanism is distinct from BDNF upregulation (Semax) and is additive when combined. Limited human validation.

No appetite/weight effects

P-21 was specifically designed to retain CNTF's neurogenic properties without the metabolic cachexia. Animal data confirms this selectivity.

Interactions & stacking

Two different questions: what is documented about running these together, and what is documented about drawing them into the same syringe. A good pharmacological partner can still have to be pinned separately.

Documented together

BPC-157Non-overlapping (brain vs tissue repair)

GHK-CuNon-overlapping mechanisms

AOD-9604Non-overlapping mechanisms

5-Amino-1MQNon-overlapping mechanisms

Keep separate

CJC-1295 with DACDAC maleimide reactivity concern.

Check any specific pair in the Stack & Interaction Checker, which answers both questions separately. Absence of a documented conflict is not evidence of safety.

Side effects & safety

Commonly reported

Generally well tolerated
Mild injection site irritation

Less common & notes

Limited safety data.
P-21 is designed to avoid CNTF's appetite suppression and weight loss.
No significant adverse events reported in community use.
Long-term data not available.

Pharmacokinetics

Illustrative plasma concentration · 19 h

Half-life

4.5h

Peak · Tmax

0.5h

Elimination

22.5h

Bioavailability

~100%

SubQ

Duration of action

24+ hours (neurogenesis signaling persists; new neuron integration takes weeks)

Clearance

Enzymatic degradation (peptidases) and renal

Storage. Limited published stability data. Conservative 28-day estimate after reconstitution. BAC water 2-8C. Protect from light.

Regulatory status

Not FDA-approved. Available as research peptide. WADA status not specifically listed.

Put it to work

Calculate, log & track

Open P-21 straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.

Open P-21 in the app →

Go deeper

The guide & community

The complete P-21 walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.

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