What it is
Dihexa is a small lab-made compound built from angiotensin IV, a piece of a hormone that controls blood pressure. Scientists at Washington State University developed it. It has only two amino acids, tyrosine and isoleucine, with chemical groups added to each end. That design makes it act like a peptide while resisting the enzymes that break peptides down. Researchers say it boosts hepatocyte growth factor, or HGF, at its receptor, c-Met. HGF and c-Met help brain cells form new connections, called synapses. The c-Met receptor is also overactive in several types of cancer, so long-term safety is an open question. Other names: N-hexanoic-Tyr-Ile-(6) aminohexanoic amide.
What researchers study it for
- Memory and learning in rats and mice
- New synapse formation
- Alzheimer's disease models in mice
- The HGF and c-Met signaling pathway
What the studies found
1. Rats with memory problems did better on maze tests. The journal later flagged the paper.
This 2013 study tested dihexa in rats given a drug that impairs memory and in old rats with natural memory loss. Both groups performed better on water maze and radial arm maze tests. It also worked when given by mouth. In 2021, the journal published an Expression of Concern on this paper. That is a formal notice that questions have been raised about the data.
2. A key follow-up paper was retracted in 2025.
A 2014 paper from the same group described how dihexa builds synapses through HGF and c-Met. That paper was retracted, meaning it was officially withdrawn. This link is the retraction notice. Two of the core papers behind dihexa now have integrity problems.
3. An outside lab found better memory in Alzheimer's model mice.
A 2021 study from a separate research group in China used mice bred to develop Alzheimer's-like brain changes. Treated mice did better on spatial learning and memory tests than untreated mice. The researchers measured higher activity in a cell survival pathway called PI3K/AKT in the hippocampus, the brain area that handles memory. This is the first repeat of the memory result from outside the original lab. Mouse data only.
4. The developers proposed HGF and c-Met as a target for Alzheimer's disease.
This 2015 review was written by the Washington State University scientists who built dihexa. It describes how HGF and c-Met help form synapses and keep brain cells alive. It argues that boosting this system could help in Alzheimer's disease. This is a review, not new test data.
5. An independent review found memory gains across many animal studies of this system.
A 2018 review by outside researchers looked at all animal studies of angiotensin IV and a related peptide. Turning on this system improved memory test scores in many animal models. The review also pointed out weak spots in the evidence. Animal data only.
How much research exists
All research is in animals or lab cells. Most of it comes from one lab, and two of its key papers have a concern notice or a retraction. No human trial has been published.
Facts
- Formula: C27H44N4O5
- Weight: 504.7 g/mol
- CAS number: 1401708-83-5
- Structure: hexanoic acid-Tyr-Ile-aminohexanoic acid amide
- Time in the blood: never measured
- Storage: freeze the dry powder. It does not dissolve well in water.
Legal status
Not approved by the FDA or any other agency for human use. Banned in sports by WADA under section S0, which covers drugs not approved for human use.
For research use only. Not for human use. Nothing here is medical advice.