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Neuro & cognitive

Dihexa

Also called dihexa acetate, PNB-0408, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide

Dihexa is a lab-made, modified mini-peptide based on angiotensin IV, a fragment of a blood-pressure hormone. In rodent studies it improved memory and boosted connections between brain cells. It has never been tested in published human trials, so its safety and effects in people are unknown.

Preclinical onlyStudied in cells or animals only. Effects in people are unknown.

All printable flashcards

Drawn from its published sequence: 3 residues, one bead each.

Overview

Dihexa is a lab-made, modified mini-peptide based on angiotensin IV, a fragment of a blood-pressure hormone. In rodent studies it improved memory and boosted connections between brain cells. It has never been tested in published human trials, so its safety and effects in people are unknown.

How it works

Proposed (animal and cell data only): dihexa is reported to enhance signaling by hepatocyte growth factor (HGF) through its receptor c-Met, which promotes growth of dendritic spines and new synapses. Because HGF/c-Met signaling also drives growth and spread of some cancers, researchers and FDA have raised theoretical concerns about cancer risk.

What research shows

  • Rats and cell assays (McCoy et al. 2013, J Pharmacol Exp Ther): dihexa, an angiotensin IV analog modified for metabolic stability and brain penetration, reversed memory deficits in a scopolamine model and in aged rats, and showed strong synaptogenic activity.
  • Rat hippocampal neurons and rats (Benoist et al. 2014, J Pharmacol Exp Ther): dihexa bound hepatocyte growth factor and promoted c-Met activation; its effects on synapse formation and on memory were blocked by an HGF antagonist, indicating dependence on the HGF/c-Met system.
  • No published human clinical trials.

Doses studied in people

No published human dosing data; doses circulating online are extrapolated from rodent studies.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Weekly protocol

How the schedule looks week by week. Each chart says where it comes from: a prescribing label, a clinical trial, or a protocol commonly reported online.

Community-reported oral protocol

Commonly reported, not studied

One week

D1D2D3D4D5D6D7

Once daily · Oral

Dose by week

5–10 mg (new users); 10–20 mg (experienced)wk 1–8
Course
4–8 weeks, followed by a break
Note
Anecdotal only; dihexa has never been tested in humans. Some report no added benefit above 20 mg.
Source
Peptide Protocol Wiki: Dihexa community protocols

Reference only, not a recommendation. Charts marked "commonly reported" describe what public sources say people use. They have not been tested in trials, and their safety and effect are unknown. Label and trial schedules were set for specific patients under medical supervision. Use the calculator only to understand the arithmetic.

Vial math

Many research vials hold 5 or 10 mg of powder. This table shows how much ends up in each mark on a U-100 insulin syringe for common amounts of added liquid. It is arithmetic only, not a dose.

VialLiquid addedConcentrationPer unit (0.01 mL)
5 mg1 mL5 mg/mL50 mcgOpen in calculator
5 mg2 mL2.5 mg/mL25 mcgOpen in calculator
5 mg3 mL1.67 mg/mL16.7 mcgOpen in calculator
10 mg1 mL10 mg/mL100 mcgOpen in calculator
10 mg2 mL5 mg/mL50 mcgOpen in calculator
10 mg3 mL3.33 mg/mL33.3 mcgOpen in calculator

More sizes: all vial sizes · How this works: Syringes and units · Reconstitution guide.

Safety

  • No human safety data from published trials.
  • Theoretical cancer concern because it boosts HGF/c-Met signaling, a pathway involved in tumor growth (mechanistic reasoning; FDA safety review).
  • FDA cited immunogenicity, impurity and lack-of-safety-data concerns when it placed dihexa in Category 2 (2023).
  • Unknown long-term safety.

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

History

Developed at Washington State University by Joseph Harding, John Wright and colleagues, with key rodent studies published in 2013-2014. A related company (M3 Biotechnology, later Athira Pharma) pursued a different HGF-enhancing compound, fosgonimeton, rather than dihexa. In the US, dihexa acetate was placed in FDA's 503A Category 2 in September 2023 and removed on April 15, 2026 after its nomination was withdrawn; FDA plans an advisory committee review before the end of February 2027.

Common questions

Has dihexa been tested in humans?

No published human clinical trials exist; the research is in rats and cells 12.

What does the research on dihexa show?

In rats, dihexa reversed memory problems caused by a drug and by aging, and boosted new connections between brain cells 1. These effects depended on the HGF/c-Met growth-signaling system 2.

Is dihexa safe?

There are no human safety data, and because it boosts HGF/c-Met signaling, a pathway that can drive some cancers, there is a theoretical cancer concern 25.

Can dihexa be legally compounded?

It was removed from FDA's Category 2 list in April 2026, but that does not make it legal to compound, and it is not on the 503A bulks list 345. An FDA advisory committee review is planned before the end of February 2027 4.

Is dihexa banned in sport?

It is not named on WADA's 2026 list, but as an unapproved substance it would likely fall under S0, prohibited at all times 6.

Related compounds

Neuro & cognitiveEarly human dataFlashcard

Semax

ACTH(4-7)-Pro-Gly-Pro · Met-Glu-His-Phe-Pro-Gly-Pro

Semax is a lab-made peptide built from a small piece of the stress hormone ACTH, with three amino acids added so it lasts longer.

Neuro & cognitiveEarly human dataFlashcard

Selank

TP-7 · selank acetate

Selank is a short lab-made peptide developed in Russia as an anti-anxiety medicine.

Sources

  1. Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents Journal
  2. The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-met system Journal
  3. Frier Levitt - FDA to Remove 12 Popular Peptides from the Category 2 List (Apr 2026) Regulatory
  4. Orrick - FDA Announces Removal of 12 Peptides from Category 2 and Schedules PCAC Meetings (Apr 2026) Regulatory
  5. FDA - Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (current as of April 22, 2026) Regulatory
  6. World Anti-Doping Agency - Prohibited List (2026) Regulatory

Last reviewed 2026-10-25 · How we research · Found an error? See our corrections policy.