Dihexa is a lab-made compound built from angiotensin IV. In rats and cell cultures it has driven new synapse growth and helped memory. No published human trial has tested dihexa itself, and the key paper behind its mechanism has been retracted. It is sold online as a “research chemical” and is not approved for any use.
What Is Dihexa?
Dihexa (also called PNB-0408) is a small molecule derived from angiotensin IV, a brain peptide. Researchers at Washington State University built it to survive the gut and cross the blood-brain barrier. A 2013 paper describes it as orally active and able to cross the blood-brain barrier (McCoy et al., 2013).
How Is Dihexa Supposed To Work?
The developer lab proposed that dihexa binds hepatocyte growth factor (HGF) and boosts its signal through the c-Met receptor, which drives new synapse formation. The main paper for this idea (Benoist et al., 2014) was retracted in 2025. Treat the mechanism as unconfirmed. The 2013 paper above also carries a 2021 expression of concern.
In cultured neurons, the developer lab reported that dihexa was about 10 million times more potent than BDNF at driving new connections. That number comes from the lab that makes the compound, and it is a cell-culture result.
What Do The Animal Studies Show?
All the evidence is in rodents and cells. Dihexa was tested in scopolamine and aged-rat models of memory loss and showed procognitive effects (McCoy et al., 2013). In APP/PS1 Alzheimer’s model mice it improved water-maze performance, raised a synapse marker and reduced neuron loss (Sun et al., 2021). That study used 6 to 12 mice per group and did not measure amyloid plaques.
A 2015 review calls the HGF/c-Met system an overlooked Alzheimer’s target and dihexa a first-in-class compound that “may be efficacious.” That is a hypothesis, not a result.
Has Dihexa Been Tested In People?
No published human trial has tested dihexa itself. A related drug, fosgonimeton, was built to boost the same HGF/c-Met system, and it was tested in people. A Phase 1 study in healthy volunteers found it well tolerated. But in September 2024 the Phase 2/3 LIFT-AD trial in mild to moderate Alzheimer’s missed its primary endpoint and its key secondary endpoints.
That result does not test dihexa. It does show that this approach has not yet produced a clear benefit in people.
Is Dihexa Safe?
Nobody knows. There are no human safety data for dihexa, and no toxicology study is published.
Cancer risk: the main theoretical concern
The HGF/c-Met pathway drives cell growth, cell survival, new blood vessels and cell movement. Some cancer drugs are designed to block it, and c-Met is abnormal in several tumors, including lung, brain, breast, stomach and liver cancers. A compound that boosts this pathway could, in theory, speed the growth of a tumor that is already there. Nobody has tested this for dihexa.
Feeling fine after a short course tells you nothing about cancer risk, which can take years to show. If you have a cancer history, a family history of cancer, or a cancer risk factor, do not take it.
What users report
Online users report headaches, vivid dreams, anxiety and sleep problems. These are unverified reports, not trial data.
What Is The Correct Dose?
There is no approved or tested human dose. This page does not list doses, schedules or stacks, because there are no human data to base them on.
Is Dihexa Legal Or FDA-Approved?
Dihexa is not FDA-approved for any use. FDA listed “dihexa acetate” among the bulk drug substances that may pose significant safety risks when compounded. It left that list in April 2026 when the nominators withdrew their request, which did not approve it. FDA plans to take it to its advisory committee before the end of February 2027 (see FDA’s compounding page).
Dihexa is not a controlled substance under federal law. Sellers label it “research use only,” but FDA has said that label does not make a product legal to sell for human use. If you compare sellers of any peptide, check the lab report for your lot first. See our peptide vendors ranked by lab-report evidence.
Athletes: WADA bans non-approved substances at all times under class S0, which covers dihexa for tested athletes.
Dihexa vs Semax vs Cerebrolysin
These three are often grouped as brain peptides. They are very different in evidence.
| Dihexa | Semax | Cerebrolysin | |
|---|---|---|---|
| What it is | Small angiotensin IV analog | Synthetic peptide | Mixture of peptides from pig brain |
| Proposed action | HGF/c-Met boost | BDNF and NGF effects | Broad neurotrophic effects |
| Human evidence | None for dihexa itself | Small studies, mostly Russian stroke trials | Several human trials |
| Approval | Not approved anywhere | Approved in Russia, not by FDA | Prescription drug in some countries, not FDA-approved |
Does Dihexa Help Alzheimer’s, Parkinson’s Or TBI?
Not in people. The animal results above are the whole case, and the one human trial of a related drug in Alzheimer’s failed. If you or someone you know has a diagnosed condition, talk to a neurologist about treatments that have trial support.
What Works Instead?
For brain health, the options with the best evidence are boring: exercise, good sleep, a Mediterranean-style diet and stress control. For a diagnosed condition, ask your neurologist about approved treatments.
Bottom Line
Dihexa is interesting science. It has rodent data, no human data, a retracted mechanism paper, and a related drug that failed in Alzheimer’s. Calling it a “miracle molecule” is not accurate. For more background, read the Alzheimer’s Drug Discovery Foundation review (PDF).