What Is Dihexa? A Research Compound Overview

Dihexa is a synthetic peptide-derived research chemical, catalogued as PNB-0408, built from the structure of angiotensin IV. It exists as a laboratory material and nothing else. No regulator has approved it for human use anywhere, and the US Food and Drug Administration has stated it found no human exposure data for it by any route of administration. Nordic Chems supplies research chemicals for research and development use only. They are not for human consumption of any kind.

This page covers what Dihexa is chemically, where it came from, and what the published record supports in 2026. That last part matters more than usual here. The work this material is known for includes 2 papers retracted in April 2025 after an investigation found fabricated data.

Disclaimer. Dihexa (PNB-0408) is a research chemical supplied for laboratory research and development only. It is not approved by the FDA or any other regulator for human use, and it is not for human consumption of any kind. Nordic Chems products are not intended to diagnose, treat, cure, or prevent any disease.

What Is Dihexa?

Dihexa is a synthetic angiotensin IV analog, chemically N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, also designated PNB-0408. It was developed at Washington State University as a metabolically stabilized, orally active laboratory material. Its proposed mechanism involves the hepatocyte growth factor and c-Met receptor system. It holds no regulatory approval for human use in any jurisdiction.

That is the short version. The long version has a complication in it, and we will get to it.

Dihexa Chemical Identification

A receiving lab needs the identity data before anything else, and the chemistry is the most settled part of the Dihexa record. It is worth separating from the biology for exactly that reason.

• Common name: Dihexa

• Research designation: PNB-0408

• Chemical name: N-hexanoic-Tyr-Ile-(6) aminohexanoic amide

• Peptide shorthand: Hexanoyl-Tyr-Ile-Ahx-NH2

• Systematic name: N-(1-Oxohexyl)-L-tyrosyl-N-(6-amino-6-oxohexyl)-L-isoleucinamide

• CAS number: 1401708-83-5

• Molecular formula: C27H44N4O5

• Molecular weight: 504.66 g/mol

• PubChem CID: 129010512

• Parent structure: Angiotensin IV

The systematic name, formula, and CID come from the US National Library of Medicine's PubChem record, CID 129010512. Anyone sourcing this material should cross-check the CAS against the certificate rather than the container label, since a label is printed by whoever filled the container and a certificate is produced by whoever ran the analysis. Those are the identifiers to verify against any research-grade Dihexa before it enters a study.

Where Dihexa Came From

Dihexa came out of a research program at Washington State University led by Joseph Harding and John Wright. The group worked on angiotensin IV, a short peptide in the brain renin-angiotensin system, and built a family of chemically modified analogs from it.

The problem they were solving was stability. Angiotensin IV breaks down fast. The group modified the structure to reduce hydrogen bonding and raise hydrophobicity, and the material that came out of that work was Dihexa. It was reported as orally active and able to cross the blood-brain barrier, which is unusual for a peptide-derived molecule and is the reason the research community paid attention.

The program produced 2 patents, US 8598118 and US 9051351, covering the chemistry and the analog family. The patent record is a reasonable place to start if you want the synthesis background, and it has not been affected by anything described in the next section.

What Is the HGF/c-Met System?

The hepatocyte growth factor and c-Met system is a signaling pathway that controls cell growth, movement, and tissue organization across a wide range of cell types. HGF is the growth factor. c-Met is the receptor it activates.

This pathway carries 2 points worth stating plainly.

First, it is one of the most studied systems in cancer biology. c-Met is a proto-oncogene. Several approved oncology medicines work by inhibiting this exact pathway, because overactive HGF/c-Met signaling drives tumor growth, invasion, and metastasis. Any material described as potentiating this pathway sits in a research category that calls for caution rather than enthusiasm, and no carcinogenicity work has been published on Dihexa in any species.

Second, the specific claim that Dihexa acts through this pathway is the claim that got retracted.

Why 2 Foundational Dihexa Papers Were Retracted

In April 2025, the Journal of Pharmacology and Experimental Therapeutics retracted 2 papers behind the Dihexa mechanism, both following a Washington State University investigation.

The 2014 paper by Benoist and colleagues, which proposed that the angiotensin IV-derived peptides work by activating HGF/c-Met, was retracted on the finding that Figures 1B and 2A/C and data in a later erratum submission contained falsified or fabricated data. The notice names Leen H. Kawas and Joseph W. Harding as solely responsible. You can read the retraction notice on PubMed, PMID 40312093.

The 2012 paper by Kawas and colleagues, which framed the analog family as HGF dimerization modifiers, was retracted on the finding that Figures 3A and 4 contained falsified or fabricated data. That notice is PubMed PMID 40312092.

A third paper, McCoy and colleagues 2013, is the one that first characterized Dihexa itself, including the oral activity and the picomolar potency figures that marketing copy across this category still quotes. It has not been retracted. It does carry an Expression of Concern issued in September 2021 over possible image manipulation, PubMed PMID 23055539.

Here is why this belongs on a supplier page rather than buried. If you are designing an experiment and citing Dihexa's mechanism, 2 of the 3 citations you would reach for first are withdrawn from the literature. The most-repeated Dihexa claim in circulation, that it is 7 orders of magnitude more potent than BDNF at building synapses, comes from the concern-flagged paper and describes an in-vitro dendritic spine assay. It is an assay-specific number from a flagged source. It is not a statement about a living brain.

The chemistry is intact. The mechanism is not independently established.

Is Dihexa FDA Approved in 2026?

No. Dihexa is not approved by FDA for any use in humans. There is no New Drug Application and no Biologics License Application for it.

The regulatory record is more specific than that, and it is being reported incorrectly across this category.

FDA added dihexa acetate to 503A Category 2 on September 29, 2023. Category 2 covers substances where the agency identified safety risks and declined to extend its interim enforcement policy. The stated reason for dihexa acetate was blunt: FDA had not identified any human exposure data on products containing it administered by any route, and lacked the information needed to know whether it would cause harm if given to humans.

On FDA's current page, updated April 22, 2026, dihexa acetate no longer appears in the Category 2 table. It appears in a separate table of substances previously in Category 2 whose nominations were withdrawn by the nominators.

Several pages have reported that move as FDA removing Dihexa from its safety-risk list. That reading is wrong, and it matters. A nomination withdrawal is a filing action by whoever nominated the substance. It is not a safety finding, not a review, and not a clearance. The risk statement for dihexa acetate is still published, word for word, on FDA's bulk substances safety risk page. Nothing in the April 2026 update changes the underlying position, which is that no human exposure data exists.

For a research supplier, the honest version is simpler than the misreading. FDA says there is no human data. That is the whole reason this material ships under research-use-only terms.

Is Dihexa the Same as Fosgonimeton?

No, and this is the most common factual error in Dihexa coverage.

Fosgonimeton, also called ATH-1017, is a separate molecule developed by Athira Pharma. The confusion comes from shared lineage. Athira grew out of the same Washington State program, and Leen Kawas, named in one of the retraction notices above, was the company's CEO.

The distinction is worth holding onto because of what happened to the clinical program. Athira ran fosgonimeton through LIFT-AD, a phase 2/3 randomized placebo-controlled trial of 312 participants with mild-to-moderate Alzheimer's disease over 26 weeks, registered on ClinicalTrials.gov as NCT04488419. On September 3, 2024, the company announced the trial missed its primary endpoint and its key secondary endpoints. An earlier phase 2 trial in Parkinson's disease dementia and dementia with Lewy bodies also missed its primary endpoint.

So the HGF/c-Met approach to cognition has been taken into human trials, by a different molecule, and it did not produce a statistically significant result on the endpoints it was measured against. Dihexa itself has never entered a completed human trial at all.

Research Disciplines That Reference Dihexa

Dihexa appears in preclinical neuropharmacology work concerned with synaptic structure, receptor signaling, and growth factor pathways. Research framing centers on the angiotensin IV and AT4 receptor system, HGF and c-Met receptor signaling, hippocampal spinogenesis and synaptogenesis in cell culture, and peptidomimetic chemistry and blood-brain barrier permeability as a design problem.

Every one of those is a mechanism-level or cell-level question. None of it describes a human outcome, and nothing on this page should be read as describing one.

Researchers in these areas also reference adjacent materials in the research chemical catalog, including the racetam family, which is studied around glutamatergic and cholinergic signaling rather than growth factor pathways.

What a Dihexa Certificate of Analysis Should Show

A certificate that cannot be tied to the container in front of you is close to useless. Before accepting any Dihexa material into a study, check that the paperwork does 4 things:

• Carries a batch or lot number that matches the container label, not just the product name

• Carries the date the analysis was run, so you can tell the certificate was not recycled from an earlier lot

• Reports identity and purity by a named method, with the chromatogram or spectrum included rather than summarized

• Comes as readable output rather than a photograph of a screen, so the retention times and peak areas can be inspected

The CAS number on the certificate should match 1401708-83-5. If it does not, the material is not Dihexa regardless of what the label says. Nordic Chems publishes its analytical documentation position on the quality control page, and documentation requests go through support.

Handling and Storage in a Laboratory

Dihexa is handled with standard laboratory practice: appropriate PPE, and handling, storage, transport, and disposal in line with applicable regulations. That is the same baseline that applies across every powder format material in the catalog, and it is not optional for a material with no established toxicity profile and no published carcinogenicity work.

Storage conditions should come from the certificate and the safety data sheet supplied with the specific lot rather than from a general reference. Peptide-derived materials vary, and a figure copied from another vendor's page is not a specification for the container on your bench. Check the paperwork that arrives with the specific lot of Dihexa 5mg rather than relying on a general figure.

Research Use Only: The Terms

Nordic Chems states the position plainly on every page of the site: "All products on this site are for Research, Development use only. Products are Not for Human consumption of any kind."

Two further statements run alongside it: "The statements made within this website have not been evaluated by the US Food and Drug Administration," and "The statements and the products of this company are not intended to diagnose, treat, cure or prevent any disease."

Nothing on this page is guidance on how to run a study. That judgment belongs to the qualified researcher, which is who this material is sold to. Products are offered for research use only, and accounts may be placed on a no-sell list where misuse is suspected.

On fulfillment, orders ship within 24 hours excluding weekends and holidays, with US delivery estimated at 2 to 5 business days. Shipping is limited to the United States and Canada. Returns are subject to prior approval and must be arranged by email before anything is sent back. Shipping and returns questions are answered on the FAQ page, and researchers who order Dihexa online accept those terms at checkout.

Dihexa remains a preclinical research material with a partly withdrawn evidence base, no human exposure data, and a mechanism target that oncology medicine is built to inhibit rather than activate. Anyone planning work with Dihexa should read the retraction notices before the review articles. That is the most useful thing a supplier can tell you about Dihexa in 2026.

FAQs

What is Dihexa? 

Dihexa is a synthetic angiotensin IV analog, chemically N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, also designated PNB-0408. It was developed at Washington State University as an orally active, metabolically stabilized laboratory material. It is supplied for research use only and is not approved for human use anywhere.

Is Dihexa FDA approved? 

No. There is no New Drug Application or Biologics License Application for Dihexa. FDA added dihexa acetate to its 503A Category 2 list on September 29, 2023, stating it had not identified any human exposure data for products containing it by any route of administration.

Were any Dihexa research papers retracted? 

Yes, two. The Journal of Pharmacology and Experimental Therapeutics retracted the Benoist 2014 paper and the Kawas 2012 paper in April 2025, both after a Washington State University investigation found falsified or fabricated figure data. A third paper, McCoy 2013, carries an Expression of Concern from September 2021 and has not been retracted.

Is Dihexa the same as fosgonimeton? 

No. Fosgonimeton, also called ATH-1017, is a separate molecule developed by Athira Pharma, a company that emerged from the same Washington State research program. Fosgonimeton missed its primary endpoint in the 312-participant LIFT-AD phase 2/3 trial, announced September 3, 2024. Dihexa itself has never completed a human trial.

What is Dihexa's CAS number and molecular weight? 

Dihexa's CAS number is 1401708-83-5. Its molecular formula is C27H44N4O5 and its molecular weight is 504.66 g/mol. Its PubChem CID is 129010512. Verify the CAS against the certificate of analysis rather than the container label alone.

Has Dihexa been tested in humans? 

No completed human trial of Dihexa exists. FDA stated in its 503A Category 2 listing of September 29, 2023 that it had not identified any human exposure data for dihexa acetate by any route of administration. A related but separate molecule, fosgonimeton, reached human trials and missed its primary endpoint.

Is Dihexa sold for human use? 

No. Nordic Chems states that all products on the site are for research and development use only and are not for human consumption of any kind. The site also states that its statements have not been evaluated by the US Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease.