Dihexa

The Dihexa evidence base cited here is 5 sources — 3 preclinical, 2 review. Critically, that evidence is almost entirely preclinical (animal and in-vitro) — no human clinical trials are cited, so efficacy and safety in people remain unproven. Regulatory status: Not FDA-approved.

• Dihexa is a small, orally active oligopeptide derived from angiotensin IV, developed at Washington State University and studied for cognition and Alzheimer's disease.
• Its proposed mechanism is potentiating hepatocyte growth factor (HGF) at the c-Met receptor to drive synaptogenesis — the formation of new synaptic connections.
• The headline claim — that it is roughly 10 million times (7 orders of magnitude) more potent than BDNF at promoting synapse formation — comes from a 2014 in-vitro assay (Harding et al.) and should be read as a cell-based potency figure, not a clinical outcome.

Dihexa (N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide) is a synthetic oligopeptide engineered from angiotensin IV to enhance cognition by building new synaptic connections. It was developed at Washington State University as a candidate for Alzheimer's disease and other conditions involving cognitive decline, and is notable for crossing the blood-brain barrier and being active orally.

All of its evidence is preclinical — animal and cell studies. There are no human clinical trials, it is not FDA-approved, and it is sold for laboratory research only. Everything below is research context, not medical guidance.

Dihexa is a small molecule by peptide standards — a ~505 Da modified tripeptide (sequence Hexanoyl-Tyr-Ile-Ahx-NH2). The N-terminal hexanoic-acid group makes it lipophilic, which is what lets it penetrate the blood-brain barrier and survive metabolism better than a typical peptide.

That lipophilicity also makes it chemically unusual among research peptides: it is not water-soluble, so it cannot be reconstituted with bacteriostatic water like the others — it requires a DMSO-based solvent system (see Reconstitution).

Dihexa binds hepatocyte growth factor (HGF) with high affinity and potentiates its activity at the c-Met receptor, activating downstream PI3K/AKT signaling that drives synaptogenesis — the formation of new synaptic connections. In cell-based assays (Harding et al., 2014) it promoted synapse formation at picomolar concentrations, which the authors reported as roughly seven orders of magnitude (about 10 million times) more potent than BDNF. That figure is an in-vitro potency comparison, not a measure of clinical benefit.

There is no validated human dose. Figures below come from animal studies and anecdotal use, included for research context only.

• Animal injectable studies used ~0.5 mg/kg/day (IP or subcutaneous)
• Reported anecdotal oral research-use range: ~5–15 mg once daily, usually in the morning
• Taken earlier in the day — late dosing is associated with sleep disruption in reports
• Cycling is commonly discussed to limit tolerance; there is no evidence base establishing an optimal schedule

Unlike water-soluble research peptides, dihexa requires a co-solvent system. A commonly cited research protocol for a 10 mg vial, adding each solvent in order and clearing before the next:

• Add ~100 µL pharmaceutical-grade DMSO — dissolve fully (10%)
• Add ~400 µL PEG300 — swirl until clear (40%)
• Add ~50 µL Tween 80 — swirl until clear (5%)
• Add ~450 µL sterile saline — swirl until clear (45%) → 1 mL total at 10 mg/mL
• Store at 2–8°C, protect from moisture, use within ~30 days, avoid freeze-thaw. Oral capsules need no reconstitution.

The DMSO solvent system is the single biggest handling difference from every water-soluble peptide on this site — standard bacteriostatic-water reconstitution will NOT dissolve dihexa.

Reported effects are mostly mild — headaches (most common), anxiety or overstimulation, and sleep disruption if taken late. The serious open question is a theoretical cancer risk: because dihexa works by activating c-Met (a pathway implicated in tumor growth), it is generally avoided by anyone with a cancer history, and there is no long-term human safety data of any kind. Not for use in pregnancy or breastfeeding.

• APP/PS1 Alzheimer's mouse model (2021): oral dihexa (~1.4–2.9 mg/kg, 3 months) restored spatial learning/memory, increased neurons and synaptophysin, and reduced neuroinflammation.
• Synaptogenic potency comparison (Harding et al., 2014): in vitro, reported ~10 million× more effective than BDNF at synapse formation via HGF/c-Met.
• Injectable-route efficacy (2013): in rats, 0.5 mg/kg fully reversed scopolamine-induced memory deficits; lower doses partial.

These are animal and cell-culture results. They motivate human research but do not establish that dihexa is effective — or safe — in people.

Dihexa is not approved by the FDA or any regulatory agency for any indication. It is sold as a research chemical for laboratory use only and is not intended for human consumption.

All citations link to the original source (PubMed, journal site, or regulatory filing). Independent research database — no vendor influence on what's cited.