Underground Biohacking
Cognition

Dihexa

Chris Hallewell, founder of Underground Biohacking

By , Founder, Underground Biohacking

Last reviewed

Research use only. Not FDA-approved.

Dihexa is a small synthetic molecule built from a fragment of angiotensin IV, a natural brain peptide. It is studied for memory. The honest answer is that there is no human evidence. Every result below comes from rats, mice, zebrafish or cells in a dish. FDA states it has found no human exposure data for dihexa by any route. Nobody knows how it behaves in a person, including whether it is safe.

What is Dihexa?

Dihexa is a lab made molecule, not something your body produces. Chemists call it N-hexanoic-Tyr-Ile-(6) aminohexanoic amide. It was built at Washington State University from angiotensin IV. That is a six amino acid peptide the brain makes as part of the renin-angiotensin system, the hormone network best known for controlling blood pressure. The starting peptide had a problem. Angiotensin IV breaks down fast in the body. It also struggles to cross the blood brain barrier, the filter that keeps most molecules out of the brain. Researchers cut it back to its three active amino acids, then added fatty chains at both ends. Those changes made the molecule greasier and harder for enzymes to break apart. The result survives the gut and reaches the brain. So it is no longer a classic peptide, and it is not a stimulant. It acts on the hepatocyte growth factor system through its receptor, c-Met, a pathway that tells cells to grow, move and connect. In animal brains that shows up as more connections between nerve cells. It is not an approved medicine anywhere.

What is Dihexa used for?

  • In mice bred to develop Alzheimer's-like disease, dihexa restored spatial learning and memory in a water maze test.[1]Animal or lab study only
  • In those same mice, dihexa increased nerve cell numbers and levels of a protein found at synapses.[1]Animal or lab study only
  • In rats, dihexa taken by mouth reversed drug-induced memory loss and improved memory in aged animals.[2]Animal or lab study only
  • A systematic review of animal studies found eight of nine reported that angiotensin IV analogues, dihexa included, improved memory task scores.[3]Animal or lab study only
  • Reviews of the animal data report that dihexa drives branching of nerve cell dendrites and the growth of new synapses.[6]Animal or lab study only
  • In zebrafish larvae, dihexa protected the sensory hair cells used for hearing against chemicals that damage them.[4]Animal or lab study only
  • In rats whose sciatic nerve was cut and repaired, dihexa given alongside stem cells helped limb function recover.[5]Animal or lab study only
Dihexa dosage chart
Typical dose8-15mg per day oral (limited human protocols).
Cycle length4-6 weeks experimental cycles
FormOral capsules, transdermal cream

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How does Dihexa work?

Dihexa is a lab built copy of angiotensin IV, a small peptide the brain makes. Angiotensin IV acts at a docking site called the AT4 receptor. Dihexa was designed to survive the gut and reach the brain, and in mice it does raise brain angiotensin IV. For years its action was described as switching on hepatocyte growth factor and its partner c-Met, a pair that helps neurons build connections. Treat that account with caution. Both papers behind it have now been retracted by the journal. What survives is thinner. In mice, dihexa activates PI3K/AKT, a survival signal inside cells. All of this is animal and cell work.

How much Dihexa should you take?

8-15mg per day oral (limited human protocols).

How long should you run Dihexa?

4-6 weeks experimental cycles

How is Dihexa supplied?

Oral capsules, transdermal cream

What are the side effects of Dihexa?

EffectHow seriousWhat to watch
There is no human safety record at all. FDA states it has found no human exposure data for dihexa acetate by any route. No one can say what it does in a person.UnknownNone can be given. There is no human data to base monitoring on.
Dihexa acts on c-Met, a receptor that pushes cells to divide, move and change shape, and not only in the brain.[6]UnknownLong term effects on cell growth have never been studied in people. Raise any personal or family cancer history with a doctor.
Its activity is not limited to nerve tissue. Labs use dihexa as a growth factor substitute to turn human stem cells into liver cells.[7]UnknownNo established marker. Any effect on the liver in people is untested.
Tiny changes to the molecule change what it does. Adding a single amino group weakened its protective effect in zebrafish.[4]UnknownPurity cannot be judged by eye. Unverified material may not behave like the compound that was studied.

Is Dihexa legal in 2026?

Dihexa is not an approved medicine. No regulator has cleared it for any use. FDA keeps a list of bulk drug substances that may present significant safety risks. Dihexa acetate is on that list. We checked the page on 6 August 2026, and its content is marked current as of 22 April 2026. Dihexa acetate sits in the section for substances that were nominated for compounding, placed in category 2, then withdrawn by the nominator. FDA writes that it has found no human exposure data for dihexa acetate by any route. FDA also states it lacks important information about safety, including whether the substance would cause harm in humans.

Status checked against the primary source.

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Dihexa protocols

Frequently Asked Questions

Does dihexa work in humans?
Nobody knows. There is no published human trial of dihexa. Search the medical literature and you find animal studies, cell studies, and reviews of those studies. FDA states it has found no human exposure data for the substance by any route. That is not the same as saying it failed. It means the question has never been asked properly in people, so any claim about human results is guesswork.
What did the animal studies actually show?
Mostly memory results. In mice bred to develop Alzheimer's-like changes, dihexa restored water maze performance and raised markers of healthy nerve tissue. In rats, it reversed drug-induced memory loss and helped aged animals. A systematic review of angiotensin IV analogues found benefit in eight of nine models of memory impairment. There is also work in zebrafish hearing cells and in rat nerve repair, both positive.
How does dihexa work?
It switches on the hepatocyte growth factor system through its receptor, c-Met. That growth factor tells cells to grow, move and form connections. In brain tissue it shows up as more branching of nerve cells and more synapses. One caution is worth knowing: a 2014 paper that set out this mechanism has since been retracted. Later work still points at the same pathway, but the foundation is thinner than confident write-ups suggest.
Is dihexa safe?
There is no evidence-based answer. No human safety study exists. FDA says plainly that it lacks important information about any safety issues raised by dihexa acetate, including whether it would cause harm in people. The mechanism itself invites care. c-Met drives cell division and movement, which is useful for repair and unhelpful if something is already growing that should not be.
Do the animal results all point the same way?
No. A 2024 rat study tested dihexa, under the name PNB-0408, against a chemical model of Huntington's disease. It did not protect the animals from the damage caused. The authors concluded it may not be a useful treatment strategy in that model. That matters, because most write-ups quote only the positive memory studies. The overall picture is mixed, and the total number of studies is small.
What should I ask a doctor about it?
Start with why you want it. If the goal is memory or focus, ask what is actually causing the problem. Sleep, thyroid, mood and medication side effects are far more common causes and all are treatable. Then ask the harder question: would any doctor prescribe a substance with no human data at all? Most will say no, and the reason is not paperwork. It is that nobody has measured what it does.

References

  1. 1.Sun X, et al. (2021). AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling Pathway. Brain Sciences. PMID: 34827486. DOI: 10.3390/brainsci11111487.
  2. 2.McCoy AT, et al. (2012). Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents. The Journal of Pharmacology and Experimental Therapeutics. PMID: 23055539. DOI: 10.1124/jpet.112.199497.
  3. 3.Ho JK, Nation DA. (2018). Cognitive benefits of angiotensin IV and angiotensin-(1-7): A systematic review of experimental studies. Neuroscience and Biobehavioral Reviews. PMID: 29733881. DOI: 10.1016/j.neubiorev.2018.05.005.
  4. 4.Uribe PM, et al. (2015). Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposure. Frontiers in Cellular Neuroscience. PMID: 25674052. DOI: 10.3389/fncel.2015.00003.
  5. 5.Weiss JB, et al. (2021). Stem cell, Granulocyte-Colony Stimulating Factor and/or Dihexa to promote limb function recovery in a rat sciatic nerve damage-repair model: Experimental animal studies. Annals of Medicine and Surgery. PMID: 34703584. DOI: 10.1016/j.amsu.2021.102917.
  6. 6.Wright JW, Harding JW. (2015). The Brain Hepatocyte Growth Factor/c-Met Receptor System: A New Target for the Treatment of Alzheimer's Disease. Journal of Alzheimer's Disease. PMID: 25649658. DOI: 10.3233/JAD-142814.
  7. 7.Mathapati S, et al. (2016). Small-Molecule-Directed Hepatocyte-Like Cell Differentiation of Human Pluripotent Stem Cells. Current Protocols in Stem Cell Biology. PMID: 27532814. DOI: 10.1002/cpsc.13.
  8. 8.Wells RG, et al. (2024). Effects of an Angiotensin IV Analog on 3-Nitropropionic Acid-Induced Huntington's Disease-Like Symptoms in Rats. Journal of Huntington's Disease. PMID: 38489193. DOI: 10.3233/JHD-231507.

This content is for educational purposes only. These compounds are intended for research use. Nothing here is medical advice.