Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of P21 and Selank — mechanism, dosing, side effects, legal status, and pricing.
P21 (also P021) is a small peptidergic compound — the tetrapeptide core Asp-Gly-Gly-Leu with an N-terminal acetyl and a C-terminal adamantylated glycine amide (Ac-DGGL(A)G-NH2) — derived from an active region (residues ~148–151) of human ciliary neurotrophic factor (CNTF). It was designed and characterized in the Khalid Iqbal laboratory at the New York State Institute for Basic Research in Developmental Disabilities (NYS IBR). It is an experimental, preclinical compound — NOT FDA-approved and NOT tested in humans in published trials. Distinct from the cyclin-dependent kinase inhibitor protein p21/CDKN1A/WAF1 (a completely different gene product; the two share only the name).
Selank is a synthetic heptapeptide analog of the endogenous immunomodulatory tetrapeptide tuftsin, extended with a Pro-Gly-Pro C-terminus for metabolic stability. Developed at the Institute of Molecular Genetics (Russian Academy of Sciences), it is registered as an anxiolytic drug in Russia but is not approved by the FDA or EMA.
P21
Selank
Category
Legal Status
Mechanism
Dose Range
Route
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
P21
Selank
COA corpus from Disclosed Labs — independently tested batches only.
P21
2
COAs
99.1%
Avg purity
1
Labs
Selank
81
COAs
99.6%
Avg purity
18
Labs
Selank is among peptides under FDA review for the Category 1 (503A) list; if added, it would require a prescription to be compounded by registered 503A/503B pharmacies — not yet authorized. P21 remains research-only. In April 2026 the FDA removed 12 peptides from Category 2, which does not place them on the Category 1 list or authorize compounding. The FDA's Pharmacy Compounding Advisory Committee is advisory and meets July 23–24, 2026 to review nominations and make recommendations to the FDA.
Evidence is preclinical (rodent) only. Key publication: Kazim, Blanchard, Dai, Tung, LaFerla, Iqbal & Iqbal, Neurobiology of Disease 2014 (PMID 25046994) reported that chronic oral P021 rescued cognition, boosted dentate-gyrus neurogenesis, and reduced tau hyperphosphorylation in 3xTg-AD mice. Additional preclinical papers from the Iqbal group (and collaborators) have shown dendritic/synaptic rescue in AD and aging rodent models (e.g., Kazim et al., Alzheimer's Res Ther 2017). No Phase 1/2/3 human trials have been published; no human safety or pharmacokinetic data exist. Grey-market vendor material is unvalidated — purity, identity, and dosing are not verifiable.
Selank's clinical evidence base is almost entirely Russian. Zozulia et al. (2008, Zh Nevrol Psikhiatr Im S S Korsakova; PMID 18454096) compared selank to medazepam in 62 patients with generalized anxiety disorder and neurasthenia, reporting comparable anxiolytic efficacy plus antiasthenic/psychostimulant effects, together with changes in serum enkephalin-degrading enzyme activity. Mechanistic work includes Inozemtseva et al. (2008, Dokl Biol Sci; PMID 18841804) showing intranasal Selank increases hippocampal BDNF mRNA and protein in rats, Volkova et al. (2016, Front Pharmacol; PMID 26924987) demonstrating modulation of GABAergic gene expression, and Vyunova et al. (2018, Protein Pept Lett; PMID 30255741) proposing a positive allosteric GABA-A mechanism. No US or EU regulatory clinical trials have been conducted; safety data outside Russia is limited.
Key references
P21 and Selank are both in the Cognitive category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Frequency
Dosing Notes
Half-life
Side Effects
Contraindications
Lab Testing
Disclosed Labs