What Is Dihexa? Read the Retraction Notice First

Cover illustration: AI-generated editorial artwork. Conceptual only; not an exact molecular structure, actual laboratory result or evidence of clinical effects.

Dihexa is a small synthetic molecule derived from angiotensin IV, studied in connection with the hepatocyte growth factor (HGF) / c-Met system. Anyone reading about it needs one fact first: two of the foundational papers from the originating laboratory are now retracted or carry an expression of concern. That does not settle whether the compound is active, but it changes which sources can carry weight.

For laboratory research use only. The research materials supplied by HealthyWelness are not approved medicines, foods or cosmetics and are not for human or veterinary use. This article summarises published research and is not medical advice.

Key points

Derived from the N-terminal tripeptide of angiotensin IV, then chemically modified.
Associated mechanism: HGF / c-Met signalling.
A 2014 JPET paper was retracted in 2025; a 2013 JPET paper carries a 2021 expression of concern.
Independent work exists, including a 2021 APP/PS1 mouse study from a separate group.
Usually classed as a peptidomimetic rather than a peptide.

The publication record

Paper	Year	Status	Group
Metabolically stabilized AngIV analogs as procognitive agents (JPET)	2013	Expression of concern (2021)	Originating lab
Procognitive and synaptogenic effects dependent on HGF/c-Met (JPET)	2014	Retracted (2025), concern from 2021	Originating lab
Small molecule AngIV analogs for Alzheimer’s and Parkinson’s (Prog Neurobiol)	2015	No notice found	Originating lab (review)
HGF mimetic protects lateral line hair cells (Front Cell Neurosci)	2015	No notice found	Independent
AngIV cognitive benefits: systematic review (Neurosci Biobehav Rev)	2018	No notice found	Independent review
Dihexa in APP/PS1 mice via PI3K/AKT (Brain Sci)	2021	No notice found	Independent (Nanjing)

The two flagged papers are heavily cited in secondary material about Dihexa, including the frequently repeated claim that it is “several orders of magnitude more potent” than other nootropic agents. Anyone repeating such figures should check which paper they trace back to.

What a retraction means, and does not

A retraction withdraws specific published results from the scientific record. It does not establish that the compound has no activity, and it does not invalidate separate work by other groups. What it does mean in practice:

Claims resting only on the retracted paper have no support until replicated.
Secondary sources (reviews, blog posts, product pages) written before the retraction may carry those claims forward unknowingly.
The mechanistic story needs independent confirmation rather than citation count.

The angiotensin IV background

Angiotensin IV (AngIV, sequence VYIHPF) has long been discussed as having procognitive properties in animal models. The practical obstacles were metabolic instability and poor barrier penetration. The design route taken was to identify the minimal active fragment, reported as the three N-terminal residues, and then to modify the termini chemically to improve stability and permeability (McCoy et al., 2013 — note the expression of concern on this paper). Dihexa emerged from that programme.

A 2018 systematic review examined the cognitive effects of angiotensin IV and angiotensin-(1-7) across experimental studies (Ho et al., 2018). Reading that review alongside the retraction notices is the most efficient way to see which parts of the AngIV literature stand independently of the flagged work.

The independent studies

Study	Model	Reported findings
Sun et al., 2021	APP/PS1 mice, several doses, oral	Restored performance in the Morris water maze; increased neuronal cells and SYP protein on Nissl staining; reduced astrocyte and microglial activation and lowered IL-1β and TNF-α
Uribe et al., 2015	Zebrafish lateral line hair cells, aminoglycoside exposure	HGF mimetic protected hair cells, supporting the HGF-linked mechanism in a non-mammalian system

These are animal and non-mammalian models. No human clinical trial of Dihexa was identified in our search.

Why the HGF/c-Met link matters

HGF and its receptor c-Met are involved in tissue growth and repair in several organs, and the brain HGF/c-Met system has been proposed as a target in Alzheimer’s research. A compound acting on this pathway is not narrowly “a nootropic”; c-Met signalling is also implicated in cell proliferation generally, which is why reviews of this target discuss both therapeutic interest and the need for careful characterisation.

Handling in the lab

Supplied as a lyophilized powder; store sealed at −20 °C, protected from light.
As a modified peptidomimetic it is more hydrophobic than a typical short peptide, so check the data sheet before assuming it dissolves in plain water.
Confirm identity by MS; the modified termini give a mass distinct from the parent tripeptide.
Store solutions at 2–8 °C and avoid repeated freeze–thaw. See storing reconstituted peptides.
Concentrations: peptide reconstitution calculator.

Our Dihexa research material is supplied in 10 mg vials. Certificates are available for listed products — contact us for the latest report.

Open questions

Which of the originally reported effects replicate in independent laboratories?
What is the pharmacokinetic profile in a species other than rodents?
Given c-Met’s role in cell proliferation, what does long-term exposure do in normal tissue?

What is PE-22-28?
Semax compared with other cognitive research compounds
What “research use only” means

Frequently asked questions

What is Dihexa?

Dihexa is a small synthetic molecule derived from angiotensin IV, developed at Washington State University. It is described as an orally active, blood-brain-barrier-permeable analogue studied in relation to the hepatocyte growth factor (HGF) and its receptor c-Met.

Has any Dihexa research been retracted?

Yes. A 2014 paper in the Journal of Pharmacology and Experimental Therapeutics on the procognitive and synaptogenic effects of angiotensin IV-derived peptides was retracted in 2025, and had carried an expression of concern since 2021. A separate 2013 paper from the same laboratory also carries an expression of concern.

Does that mean Dihexa does not work?

No. A retraction means specific published results can no longer be relied upon; it is not a finding that the compound is inactive. It does mean the mechanistic claims resting on those papers need independent support.

Is there independent research on Dihexa?

Yes. A 2021 study from a group in Nanjing reported effects in APP/PS1 mice, and a 2015 study used an HGF mimetic in a zebrafish lateral line hair cell model. These are separate from the originating laboratory.

Is Dihexa a peptide?

It is derived from a tripeptide fragment of angiotensin IV but is heavily modified with N- and C-terminal groups to improve stability and permeability, so it is usually described as a peptidomimetic small molecule rather than a peptide.

References

Sun X, et al. AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling Pathway. Brain Sci. 2021. PMID: 34827486 https://pubmed.ncbi.nlm.nih.gov/34827486/
Uribe PM, et al. Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposure. Front Cell Neurosci. 2015. PMID: 25674052 https://pubmed.ncbi.nlm.nih.gov/25674052/
Ho JK, et al. Cognitive benefits of angiotensin IV and angiotensin-(1-7): A systematic review of experimental studies. Neurosci Biobehav Rev. 2018. PMID: 29733881 https://pubmed.ncbi.nlm.nih.gov/29733881/
Wright JW, et al. The development of small molecule angiotensin IV analogs to treat Alzheimer's and Parkinson's diseases. Prog Neurobiol. 2015. PMID: 25455861 https://pubmed.ncbi.nlm.nih.gov/25455861/
Benoist CC, et al. The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-met system. J Pharmacol Exp Ther. 2014. RETRACTED 2025. PMID: 25187433 https://pubmed.ncbi.nlm.nih.gov/25187433/
McCoy AT, et al. Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents. J Pharmacol Exp Ther. 2013. Expression of concern 2021. PMID: 23055539 https://pubmed.ncbi.nlm.nih.gov/23055539/