Dihexa
A synthetic angiotensin IV-derived compound that potentiates HGF/c-Met signaling to drive synaptogenesis, with striking rodent potency but zero human trials.
Dihexa is a synthetic small-molecule angiotensin IV analog developed in Joseph Harding's lab at Washington State University, proposed to enhance cognition by potentiating hepatocyte growth factor (HGF) and its c-Met receptor to promote new synapse formation in the hippocampus and prefrontal cortex. In preclinical rodent models it has been reported to be orders of magnitude more potent than BDNF at improving cognitive performance, including in Alzheimer's disease models. However, no peer-reviewed human clinical trials of dihexa have been published, no human safety or pharmacokinetic data exists, and its mechanism activates a pathway (c-Met) that is centrally implicated in cancer proliferation.
Class
Synthetic small-molecule angiotensin IV analog (not a standard amino-acid peptide despite the naming)
Half-life
Unknown in humans; animal studies suggest rapid metabolism with sustained CNS effects
Routes
Oral, Intranasal, Subcutaneous, Transdermal (topical)
Category
Cognitive & Nootropic
Researched benefits
What it's studied for
Potent synaptogenesis
Dihexa binds and potentiates HGF signaling through the c-Met receptor, driving formation of new synaptic connections and increased dendritic spine density in rodent hippocampal and prefrontal neurons. The discoverer's published literature reports it as roughly seven orders of magnitude more potent than BDNF in synaptogenesis models, though this magnitude has not been independently replicated at that scale.
Memory enhancement in animal models
In rodent brain slices and aged-rodent behavioral tasks, dihexa increased spine density and improved memory performance at very low concentrations, including in Alzheimer's disease models. Evidence tier is preclinical only; human translation is unproven.
Hippocampal long-term potentiation (LTP)
The underlying AT4/IRAP receptor system on which dihexa is based has been shown in rodent hippocampal preparations to dose-dependently enhance LTP, a cellular correlate of learning and memory.
Neuroplasticity support
The parent angiotensin IV class facilitates synaptic remodeling and associative and spatial memory via interactions with the extracellular matrix and AT4/IRAP receptors, providing the mechanistic framework attributed to dihexa.
Proposed cognitive restoration and social behavior effects
Community and preclinical reports describe cognitive restoration and improvements in social behavior, and dihexa has been explored for potential Alzheimer's application. These remain anecdotal or animal-derived, with no controlled human data.
Mechanism
How it works
Dihexa is a small-molecule analog derived from angiotensin IV (and the angiotensin IV metabolite LVV-hemorphin-7), engineered for oral bioavailability and blood-brain barrier penetration. Its primary proposed mechanism is potentiation of hepatocyte growth factor (HGF) signaling through activation of the c-Met (MET) receptor. HGF/c-Met signaling promotes dendritic spine density, axonal sprouting, and the formation of new synaptic connections (synaptogenesis) in regions including the hippocampus and prefrontal cortex.
The compound is built on the pharmacology of the brain renin-angiotensin system. Angiotensin IV acts at the AT4/IRAP receptor system, which preclinical rodent work has linked to enhanced long-term potentiation and neuroplastic processes underlying memory formation. In this framework angiotensin IV facilitates synaptic remodeling and spatial/associative memory, whereas angiotensin II tends to impair these processes. Dihexa inherits this AT4/IRAP-associated activity from its precursor compounds while acting through the HGF/c-Met axis.
This mechanism is distinct from other nootropic peptides it is often compared to: unlike semax (an ACTH fragment thought to upregulate BDNF and provide neuroprotective signaling) or selank, dihexa's effects are HGF/c-Met dependent. The same c-Met pathway that drives its synaptogenic potency is one of the most thoroughly documented proliferation pathways in oncology, which is the source of the principal theoretical safety concern surrounding chronic use.
Notably, dihexa's proposed therapeutic value was pursued clinically not as dihexa itself but through the related compound fosgonimeton (ATH-1017), developed by Athira Pharma (formerly M3 Biotechnology). The pivotal LIFT-AD Alzheimer's readout failed in September 2024, and Athira subsequently paused the fosgonimeton program and rebranded. This clinical history does not validate the gray-market dihexa product.
Dosing protocols
Dosing & administration
Dosing reflects protocols reported in research and community literature for educational purposes. It is not medical advice or a recommendation. Most peptides here are not approved for human use.
Reconstitution
Available from some research vendors as a topical cream and as an oral powder. For oral powder, a precision milligram scale is essential because potency is extremely high and dosing accuracy is critical. No standardized reconstitution protocol exists.
Cautious start (titration)
- Dose
- 1 mg
- Frequency
- Once weekly
- Timing
- Assess response before escalating
- Duration
- Open-ended trial
- Route
- Oral or topical
Anecdotal only. Given the absence of human safety data and very high potency, some community sources advocate starting extremely low (1-5 mg every few days to weekly).
Beginner
- Dose
- 10 mg
- Frequency
- Once daily
- Timing
- Typically morning
- Duration
- 2 weeks
- Route
- Oral or intranasal
Highly experimental; start low.
Intermediate
- Dose
- 20 mg
- Frequency
- Once daily
- Timing
- Morning
- Duration
- 3 weeks
- Route
- Oral or intranasal
No clinical validation for these numbers.
Advanced
- Dose
- 20-40 mg
- Frequency
- Once daily
- Timing
- Morning
- Duration
- 4 weeks
- Route
- Oral or intranasal
Extreme caution advised due to limited human safety data.
- Community protocols cite a typical range of 10-40 mg oral or intranasal per day, once daily in the morning, cycled over 2-4 weeks; these figures are experimental and not backed by clinical trials.
- Some community sources instead treat dihexa as far more potent and dose only 1-5 mg every few days to weekly. The wide discrepancy reflects the absence of any established human dosing.
- Common vial sizes reported are 50 mg and 100 mg.
- No weight-based dosing protocol has been established.
- HIGHLY EXPERIMENTAL: the HGF/c-Met pathway is involved in cancer metastasis and long-term effects are unknown. Not recommended without thorough risk assessment.
Evidence
Research & clinical studies (2)
Neural plasticity and the brain renin-angiotensin system
Summarizes evidence that angiotensin IV facilitates synaptic remodeling, long-term potentiation, and associative and spatial memory through the extracellular matrix and AT4/IRAP receptors, providing the mechanistic framework for cognitive-enhancing angiotensin IV-class peptides including dihexa.
PMID 12367589Angiotensin IV enhances LTP in rat dentate gyrus in vivo
In rat hippocampal preparations, angiotensin IV (the peptide class dihexa is based on) dose-dependently enhanced long-term potentiation in dentate granule cell synapses, with the effect blocked by the Ang IV antagonist Divalinal, identifying AT4/IRAP receptor activation as the mechanism.
PMID 11514021Combinations
Stacking & blends
Dihexa + Semax: Memory & Cognitive Performance
Complementary routes to memory consolidation and cognitive resilience
Dihexa is researched as a potent HGF/c-Met modulator promoting synaptogenesis and spatial memory, while semax (an ACTH analog) is investigated for BDNF upregulation and neuroprotective signaling. The pairing combines two distinct pro-plasticity mechanisms. Preclinical tier only.
Dihexa cognitive stack
Broad neuroplasticity and cognitive support
Community interaction matrices list semax and Lion's Mane as synergistic with dihexa, and noopept and NSI-189 as compatible, reflecting anecdotal stacking practice rather than controlled evidence.
Safety
Side effects & considerations
Commonly reported effects
Contraindications & cautions
- Active cancer or history of cancer — HGF/c-Met is a documented oncogenic proliferation pathway; do not use without medical supervision
- Pregnancy or breastfeeding
- History of seizures
- Neurodegenerative disease with active degeneration (unknown interaction)
- Concurrent use of other potent nootropics without titration
- Unknown long-term safety
The central serious concern is theoretical but specific: dihexa activates the HGF/c-Met pathway, one of the most thoroughly documented proliferation and metastasis pathways in oncology, against which approved cancer drugs are designed. Chronic, unmonitored activation in healthy adults with no human PK data carries cancer-risk implications that have not been characterized in humans, and is a particular concern in anyone with undetected dysplasia or cancer-predisposing mutations. Short-term community reports are mild, but that does not establish safety.
FAQ
Dihexa — common questions
What is Dihexa?
Dihexa (PNB-0408) is a synthetic small molecule developed from angiotensin IV research at Washington State University. It potentiates hepatocyte growth factor (HGF) signaling via the c-Met receptor, driving synaptogenesis in preclinical rodent models. Despite the naming it is not a standard amino-acid peptide.
What does Dihexa do?
In rodent hippocampal neurons it produces measurable synaptogenesis (new synaptic connections) at very low concentrations and improves memory performance, including in Alzheimer's disease models. The discoverer's papers describe it as roughly seven orders of magnitude more potent than BDNF, a figure not independently replicated at that scale. No human clinical trials have been conducted, so translation to humans is unproven.
How is Dihexa administered?
It is reported to be orally bioavailable, unlike most peptides, and the research community discusses oral, sublingual, intranasal, transdermal, and subcutaneous routes. There is no FDA-approved dosing protocol; community ranges span from 1-5 mg every few days up to 10-40 mg daily.
What are the side effects of Dihexa?
Short-term community reports are mild — occasional headache, fatigue, sleep changes, and vivid dreams. The serious concern is theoretical: the c-Met/HGF pathway it activates is centrally involved in cancer proliferation and metastasis, and chronic activation without monitoring carries uncharacterized cancer-risk implications.
Is Dihexa FDA approved?
No. Dihexa has no FDA approval and no registered human clinical trials. The developer's pharmaceutical spinoff (M3 Biotechnology / Athira Pharma) advanced a related compound, fosgonimeton, into clinical trials rather than dihexa itself, and later moved away from that neurodegeneration program after failed late-stage Alzheimer's readouts.
Does the fosgonimeton / Athira story validate Dihexa?
No. Athira advanced fosgonimeton (ATH-1017), not dihexa itself. Its pivotal LIFT-AD trial failed in September 2024, after which Athira paused the program and rebranded. The gray-market dihexa product is not validated by Athira's clinical history.
How much does Dihexa cost?
There is no clinical retail price. On the research-chemical market it is among the more expensive nootropic research chemicals due to synthesis complexity, with per-mg prices reported roughly in the $4.60-$16 range depending on quantity, vendor, and formulation.
