P21

A lab-made peptide built from the most active stretch of ciliary neurotrophic factor (CNTF), with an adamantane group added so it reaches the brain. It was first described in 2010 by Khalid Iqbal's group in New York, which named it P21 and later P021. It is a research chemical with no approved use.

No. The cell-cycle protein p21 (CDKN1A) is a tumor suppressor and a different molecule. In peptide and nootropic circles, P21 means the CNTF peptide P021.

There is no tested human dose. Guides and forums cluster at 500 mcg to 1 mg once a day, with a wider spread of 100 mcg to 2 mg. Ceretropic, the first seller, advised 1 mg a day by nose, rising to 2 to 4 mg. Injection guides start at 100 to 300 mcg.

Both are used. Ceretropic's chemist preferred the nose because he felt nothing from injections, and one vendor says most of its customers use sprays. Some users report the reverse. The rodent studies mostly gave it in food, so neither human route has data behind it.

One guide adds 2 mL of bacteriostatic water to a 10 mg vial for 5 mg/mL, so 500 mcg is 10 units on a U-100 insulin syringe. Our calculator does the math for any vial and volume.

No human timeline exists. One forum view is that the full effect builds over about a month of steady use, and a blog suggests testing for at least 4 to 6 weeks. In rodents the benefits showed only after weeks to months of dosing.

Morning. The most common complaint is overstimulation or poor sleep with evening doses.

Most studies mixed P021 into mouse or rat food. In one long mouse study the chow held 60 nmol per gram, about 162 nmol per mouse per day, for up to 18 months. A brain-injury study gave the parent peptide at 50 nmol a day for 30 days.

In rodents, yes: oral in-diet dosing worked and the compound crossed the blood-brain barrier. No oral human product or dose is in circulation.

No. ClinicalTrials.gov lists no P021 trial, and every published result is from cells, mice or rats.

No. It has never been reviewed for approval and is not on FDA's 503A compounding category lists, so pharmacies have no pathway to compound it.

WADA's 2026 List does not name it, and CNTF is not among the growth factors listed in S2. The S0 class bans substances with no human therapeutic approval, including drugs still in pre-clinical development, and P21 has no approval anywhere, but WADA has not ruled on it. Tested athletes should ask their anti-doping agency before using it.

No human safety data exist. Users most often report poor sleep or overstimulation with late doses, then headache, irritability, nasal irritation, lethargy and vivid dreams. Single reports include a panic episode and vision problems after months of nasal use.

Powder: room temperature or fridge, away from light, or -20 C for the long term. Mixed: fridge at 2 to 8 C and use within 28 to 30 days.

Not published. The adamantane group was added to slow breakdown by enzymes, but no study reports a half-life in animals or people.

P21 came from mapping which part of Cerebrolysin's effect works through CNTF, then shrinking that region to a few amino acids. Users often treat it as a simpler substitute.