Reviewed & approved by Dr. Nova Reyes · Last checked 2026-10-25. ← Back to Evidence Library
Dihexa: what the evidence says
At a glance
Dihexa has never been tested in people in any published trial. R1
What it is: a small lab-made molecule built from angiotensin IV, designed to cross into the brain. Lab studies say it boosts HGF/c-Met signaling. R1, R2
What the evidence says: only rat and mouse studies. Warning: the key paper describing how it works was retracted in 2025, and the original dihexa paper carries an expression of concern from the journal. R1, R2, R5
Biggest risks: unknown in humans. HGF/c-Met is a growth pathway also involved in cancer, so long-term effects are a theoretical concern that has not been studied. Unknown
Rating
| Human Human evidence | No human data: no published human studies found |
| Animal Animal evidence | Rodent memory studies; one key paper retracted, one under expression of concern R1, R2, R3, R5 |
| Regulatory | Not FDA-approved (no Drugs@FDA record) · Not approved anywhere in the world · WADA 2026: not named; S0 (non-approved substances) or S2.3 (HGF/growth factor modulators) applies R4 |
| Established human dose | None. Never studied in people |
Evidence verdict: Human: No human data · Animal: rodent studies with serious integrity flags Card verdict: No human data (rat/mouse cognitive studies only; key mechanism paper retracted in 2025)
This page reports what studies used. It is not dosing advice.
Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source
What is it?
Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide) was made at Washington State University as an oral, brain-penetrating version of angiotensin IV fragments. R1 It is sold online as a "nootropic" (memory enhancer).
Does it work?
- Animal Rats: reversed drug-induced memory problems and age-related deficits in water-maze tests. R1 The journal published an expression of concern about this paper in 2021. R5
- Animal Mechanism paper retracted: the 2014 paper reporting that dihexa works through HGF/c-Met was retracted in 2025. R2
- Animal Mice: in an Alzheimer's mouse model, an independent group reported better memory and less brain inflammation. R3
- Unknown People: no trials. Claims of memory gains in humans are anecdotal.
Is it safe?
- Unknown No human safety data of any kind.
- Unknown Theoretical: c-Met is a growth signal also active in some cancers; long-term effects are unstudied.
Gray-market "research use only" Dihexa: extra risks
Unknown contents. Products sold online as "research use only" or "not for human use" are not made under drug-quality rules, so identity, strength and sterility are unknown. This is a general caution; we have not found testing data for this product specifically. Unknown
What we don't know
- Unknown Whether it does anything in people
- Unknown Whether the animal findings hold up, given the retraction and expression of concern
- Unknown Any human safety data
Is it legal?
Not FDA-approved (no Drugs@FDA record, openFDA query Oct 24, 2026) and not approved as a medicine by any regulator we know of. WADA: not named on the 2026 Prohibited List. S2.3 bans hepatocyte growth factor (HGF) and "growth factor modulators", and S0 bans unapproved substances not covered elsewhere; either could apply to dihexa, but WADA has not ruled on it by name R4.
Study details
These are doses researchers used, not recommendations.
R1–R3 Animal Animal / lab studies
| Study | People / model | Route | Dose used | Follow-up | Reported | Side effects / dropouts | Citation |
|---|---|---|---|---|---|---|---|
| McCoy 2013 (expression of concern 2021, PMID 34551989) | Rats (scopolamine and aged models) | Oral and other routes | See paper | Not in abstract | Improved water-maze performance; more synapse formation | Not in abstract | PMID 23055539 |
| Benoist 2014 (2021 Notice of Concern PMID 34551987; RETRACTED April 2025 PMID 40312093) | Rats, cells | Oral | See paper | Not in abstract | Claimed HGF/c-Met mechanism | Retracted for data-integrity issues | PMID 25187433 |
| Sun 2021 | APP/PS1 mice | Oral | Several amounts, not in abstract | Not in abstract | Better water-maze scores; less glial activation | Not in abstract | PMID 34827486 |
Full reference list (PubMed entries verified Oct 24, 2026)
- R1 McCoy AT, et al. J Pharmacol Exp Ther. 2013;344(1):141-54. PMID 23055539 (expression of concern: reference 5)
- R2 Benoist CC, et al. J Pharmacol Exp Ther. 2014;351(2):390-402. RETRACTED 2025. PMID 25187433
- R3 Sun X, et al. Brain Sci. 2021;11(11):1487. PMID 34827486
- R4 WADA. World Anti-Doping Code International Standard: Prohibited List 2026 (in force Jan 1, 2026). https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf (text read Oct 24, 2026)
- R5 Notice of Concern: McCoy AT, et al. (2013). J Pharmacol Exp Ther. 2021;378(3):313. doi:10.1124/jpet.112.199497concern. PMID 34551989
- R6 Notice of Concern (
PMID 34551987) and Retraction Notice (PMID 40312093) for Benoist CC, et al. (2014). J Pharmacol Exp Ther. 2021;378(3):310 and 2025;392(4):103546. PMID 34551987 · PMID 40312093
Disclaimer
This page summarizes published research for education and harm reduction; it is not medical advice or a recommendation to use Dihexa. Talk to a clinician you trust before using any drug, and report side effects to FDA MedWatch.
Approved for Adam Greene by Dr. Nova Reyes, 2026-10-25.