Dihexa is frequently discussed in cognitive enhancement and anti ageing communities as a potent compound for memory and brain health. However, a wide gap exists between how it is promoted online and what the scientific literature actually supports. While laboratory research suggests it can influence the physical connections between neurons, the compound has never been tested in human clinical trials.
What is Dihexa?
Dihexa, also known chemically as N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, is a synthetic molecule developed by researchers at Washington State University. It was designed as an analogue of angiotensin IV, a naturally occurring peptide fragment that is part of the renin angiotensin system. Mechanistic 1
Research in the late 1990s and early 2000s revealed that angiotensin IV had effects in the brain that were entirely separate from blood pressure regulation. When administered to rodents, it appeared to improve memory retention and learning. Animal 2
Native angiotensin IV is a poor candidate for a medicine. It is a small peptide that is rapidly degraded by peptidases in the blood, giving it a very short half life. It also does not easily cross the blood brain barrier, meaning it cannot reach its target receptors in the central nervous system when administered systemically. Mechanistic 1
To solve this, researchers synthesised a series of analogues. By modifying the peptide structure, they aimed to create a molecule that resisted enzymatic breakdown and could penetrate brain tissue. Dihexa was the result of adding a hexanoic acid group to one end and an aminohexanoic amide to the other. These changes created a peptidomimetic that was highly stable and, according to early animal studies, orally active. Animal 1
The proposed HGF and c-Met mechanism
The primary mechanism attributed to Dihexa involves the hepatocyte growth factor (HGF) and its receptor, c-Met. Mechanistic 3
When HGF binds to c-Met, it triggers a cascade of intracellular signals. In the brain, this signalling pathway is heavily involved in the development of the nervous system and the ongoing maintenance of neural networks. It regulates dendritic arborisation, which is the branching of neurons to form new connections, and synaptogenesis, the creation of the synapses themselves. Mechanistic 3
Dihexa was reported to act as an HGF mimetic or enhancer. The originating laboratory claimed that it bound directly to HGF, increasing its affinity for the c-Met receptor and amplifying the resulting cellular signals. The papers reporting that work have since been retracted (see below). The hypothesis was that this amplified signal would force the brain to build new synaptic connections, bypassing the physical degradation caused by conditions like Alzheimer's disease. In vitro 4
Preclinical evidence and data integrity
The claims surrounding Dihexa's cognitive benefits originate entirely from animal and cell culture studies. In early rodent research, rats treated with oral Dihexa showed improved performance in the Morris water maze, a standard test of spatial learning and memory. The researchers reported that the compound was effective even when memory deficits were chemically induced using scopolamine. This 2013 paper, which introduced and named Dihexa, now carries an Expression of Concern from the journal. Animal 1
The same laboratory also reported that Dihexa increased the density of dendritic spines in the hippocampus, a brain region essential for memory formation, and presented this as proof that the compound was a structural modifier of neural networks. That work appeared in a 2014 paper that has since been retracted. Animal 5
A few groups outside the originating laboratory have reported procognitive effects in other animal models, including a mouse model of Alzheimer's pathology. These are animal results only. Animal 6
The scientific foundation of these claims has recently been compromised. In April 2025, the Journal of Pharmacology and Experimental Therapeutics retracted three papers from the originating group, published in 2011, 2012 and 2014, including the 2014 paper that set out the HGF and c-Met mechanism. Mechanistic 5 4 7
While the chemical identity of Dihexa is not in dispute, the retraction of key mechanistic data means that the HGF and c-Met mechanism is a hypothesis rather than an established finding. Mechanistic 5
The absence of human clinical trials
Despite the preclinical promises, Dihexa has never advanced to human testing. A search of major trial registries shows zero completed, ongoing or planned human clinical trials for Dihexa in any indication. Human 8
This absence of clinical data creates a total void regarding human pharmacokinetics. There is no established human half life, no known therapeutic dose and no documented side effect profile. The doses discussed in online communities are entirely speculative, extrapolated from rodent studies without the rigorous safety testing required for human pharmacology. Human 8
Fosgonimeton is not Dihexa
The commercial development of the HGF and c-Met concept was eventually taken up by Athira Pharma, a biotechnology company spun out of the original university research. The company did not advance Dihexa itself. Instead, they developed a related prodrug called fosgonimeton, also known by the development code ATH-1017. Mechanistic 9
Fosgonimeton was designed to be administered subcutaneously and convert into an active metabolite in the body. It progressed through Phase 1 safety trials and entered Phase 2 and Phase 3 efficacy trials, including a 26 week randomised, placebo controlled trial for mild to moderate Alzheimer's disease. Human 9
In September 2024, the company announced that the LIFT-AD trial did not meet its primary endpoint or its key secondary endpoints over 26 weeks compared with placebo. Human 10
The two molecules must be distinguished. Fosgonimeton is a different molecule with a different delivery method and pharmacokinetic profile. Its progression into human trials does not validate Dihexa, and its subsequent clinical failure highlights the difficulty of translating HGF and c-Met targeted therapies from animal models to human patients. Human 9
UK regulatory status
Dihexa has no UK marketing authorisation from the MHRA. 11
Under the Human Medicines Regulations 2012, a person may not sell or supply, or offer to sell or supply, an unauthorised medicinal product. 12
WADA status
For athletes subject to anti doping regulations, the World Anti-Doping Agency (WADA) Prohibited List issues a blanket ban under the S0 Unapproved Substances category on any pharmacological substance that is not currently approved by a governmental regulatory health authority for human therapeutic use. 13
The BioRx conclusion
Dihexa is a synthetic angiotensin IV analogue that demonstrated an ability to influence synapse formation in early animal models. However, its development has not progressed beyond the preclinical stage.
The compound lacks any published human clinical trials and has seen some of its foundational mechanistic research retracted. Until controlled human data exists, Dihexa remains an experimental laboratory chemical, not a validated therapeutic or cognitive enhancer, and lacks regulatory approval for human use.
Frequently asked questions
What is Dihexa?
Dihexa is a synthetic peptidomimetic derived from angiotensin IV. It was developed in a university laboratory to cross the blood brain barrier and activate pathways associated with synapse formation.
How does Dihexa work?
Its developers proposed that Dihexa boosts hepatocyte growth factor (HGF) signalling through the c-Met receptor, a pathway involved in forming new synaptic connections. The key papers supporting that mechanism were retracted in 2025, so how it works is not established.
Has Dihexa been tested in humans?
No. There are no published or registered human clinical trials evaluating Dihexa for safety, pharmacokinetics or efficacy. All claims regarding its cognitive benefits are based on preclinical animal and cell studies.
Is Dihexa safe?
The human safety profile of Dihexa is entirely unknown.
Is Dihexa the same as fosgonimeton?
No. Fosgonimeton (ATH-1017) is a related prodrug developed by a biotechnology company that targets the same pathway. Fosgonimeton entered human clinical trials for Alzheimer's disease but did not meet its primary endpoint in 2024. Dihexa itself was not the compound tested in those trials.
Is Dihexa an approved medicine in the UK?
No. Dihexa has no marketing authorisation from the MHRA, and the Human Medicines Regulations 2012 prohibit selling or supplying an unauthorised medicinal product.
References
Studies marked "View study in BioRx" sit in the clinical studies index with their design and evidence grade.
- McCoy AT, Benoist CC, Wright JW et al. (2013). Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents. Journal of Pharmacology and Experimental Therapeutics.PubMed · DOI · View study in BioRx
- Ho JK, Nation DA (2018). Cognitive benefits of angiotensin IV and angiotensin-(1-7): A systematic review of experimental studies. Neuroscience and Biobehavioral Reviews.PubMed · DOI · View study in BioRx
- PubMed, PMID 25649658
- Kawas LH, McCoy AT, Yamamoto BJ, Wright JW, Harding JW (2025). Retraction notice to 'Development of Angiotensin IV Analogs as Hepatocyte Growth Factor/Met Modifiers'. Journal of Pharmacology and Experimental Therapeutics.PubMed · DOI · View study in BioRx
- Benoist CC, Kawas LH, Zhu M et al. (2025). Retraction notice to 'The Procognitive and Synaptogenic Effects of Angiotensin IV-Derived Peptides Are Dependent on Activation of the Hepatocyte Growth Factor/c-Met System'. Journal of Pharmacology and Experimental Therapeutics.PubMed · DOI · View study in BioRx
- Sun X, Deng Y, Fu 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.PubMed · DOI · View study in BioRx
- Kawas LH, Yamamoto BJ, Wright JW, Harding JW (2025). Retraction notice to 'Mimics of the Dimerization Domain of Hepatocyte Growth Factor Exhibit Anti-Met and Anticancer Activity'. Journal of Pharmacology and Experimental Therapeutics.PubMed · DOI · View study in BioRx
- ClinicalTrials.gov, Search results for Dihexa
- ClinicalTrials.gov, LIFT-AD Trial Record
- Athira Pharma, LIFT-AD topline results (SEC filing)
- MHRA, Find product information about medicines
- Human Medicines Regulations 2012, regulation 46
- WADA, Prohibited List 2026
