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 Dihexa and Selank — mechanism, dosing, side effects, legal status, and pricing.
Dihexa (PNB-0408) is a small-molecule hexapeptide-like analog of angiotensin IV developed at Washington State University by the Harding/Wright group as a preclinical candidate for Alzheimer's disease and cognitive decline. It is NOT FDA-approved and has never been tested in human clinical trials. The often-quoted claim that it is 'roughly ten million times more potent than BDNF' refers to EC50 comparisons in an in vitro dendritic spine assay, not clinical efficacy.
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.
Dihexa
Selank
Category
Legal Status
Mechanism
Dose Range
Route
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
Dihexa
Selank
COA corpus from Disclosed Labs — independently tested batches only.
Dihexa
4
COAs
99.1%
Avg purity
4
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. Dihexa 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.
McCoy et al. (J Pharmacol Exp Ther 2013, PMID 23055539) is the original dihexa characterization: oral dihexa reversed scopolamine-induced memory deficits and improved Morris water maze performance in aged rats at low doses. Sun et al. (Brain Sci 2021, PMID 34827486) reported that dihexa rescued cognitive impairment in the APP/PS1 Alzheimer's mouse via PI3K/AKT signaling, with increased synaptophysin and reduced neuroinflammation. Wright & Harding (J Alzheimers Dis 2015, PMID 25649658) reviewed the brain HGF/c-Met system as an Alzheimer's target. Note: Benoist et al. (JPET 2014, PMID 25187433), which reported the HGF/c-Met-dependent synaptogenesis mechanism, was retracted in 2025 and should not be relied on as primary evidence. The 'roughly seven orders of magnitude more potent than BDNF' descriptor refers to in vitro dendritic spine EC50 values, not clinical efficacy. Dihexa has never entered human clinical trials; Athira Pharma's related analog fosgonimeton failed its Phase 2/3 LIFT-AD Alzheimer's endpoint in 2024 and was discontinued, after which Athira shifted focus to ATH-1105 for ALS.
Key references
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.
Dihexa 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
Key references
Disclosed Labs