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 Semax — 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.
Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) derived from ACTH(4-10) with a Pro-Gly-Pro C-terminal extension for metabolic stability. It was developed at the Institute of Molecular Genetics (Russian Academy of Sciences) and registered as a drug in Russia in 1994. It is not FDA-approved.
Dihexa
Semax
Category
Legal Status
Mechanism
Dose Range
Route
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
Dihexa
Semax
COA corpus from Disclosed Labs — independently tested batches only.
Dihexa
4
COAs
99.1%
Avg purity
4
Labs
Semax
82
COAs
99.5%
Avg purity
16
Labs
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 (JPET 2014, PMID 25187433), which reported the HGF/c-Met-dependent synaptogenesis mechanism, was retracted in 2025 and should not be relied on as primary evidence.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
Semax's evidence base is primarily Russian-language clinical literature. Gusev, Skvortsova and colleagues reported improved neurological recovery in acute hemispheric ischemic stroke when Semax was added to conventional therapy (Zh Nevrol Psikhiatr, 1997; PMID 11517472), and subsequent Russian studies extended use to cerebrovascular insufficiency (PMID 15792140). Preclinical work by Dolotov, Myasoedov and colleagues demonstrated that intranasal Semax rapidly elevates BDNF protein and TrkB activation in rat hippocampus and basal forebrain (Brain Res 2006, PMID 16996037; J Neurochem 2006, PMID 16635254). Genome-wide transcriptional analysis by Medvedeva et al. in rat focal ischemia showed Semax modulates a broad panel of immune-response and vascular-system genes (BMC Genomics 2014, PMID 24661604). Western evidence is limited; Semax has not been evaluated by the FDA and has no pivotal trials in the US or EU.
Dihexa and Semax 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