Dihexa

Dihexa (developmental code PNB-0408) is a synthetic oligopeptide drug derived from angiotensin IV, acting as a potent brain-repair compound. Engineered to cross the blood-brain barrier, it is designed for potential cognitive improvement and neuroprotection, often described as a “neuroregenerative” compound that binds with high affinity to hepatocyte growth factor (HGF).

Key Benefits

• May support cognitive function, memory formation, and learning capacity
• Commonly researched for neuroprotection and brain cell connectivity support
• May help promote mental clarity, focus, and cognitive performance
• Research suggests potential benefits for healthy brain aging and neurological recovery support

FDA-Approved Uses

Conditions studied in preclinical/animal research (NO human RCTs):

1. Alzheimer’s disease / cognitive decline — primary research focus
2. Parkinson’s disease
3. Traumatic brain injury (TBI) — neuroprotection
4. Cognitive enhancement in healthy subjects
5. Depression (neuroplasticity-mediated)

Related compound in human trials:

• Fosgonimeton (ATH-1017) — a prodrug/analogue of Dihexa developed by Athira Pharma
• Phase 2 completed for Alzheimer’s disease
• Associated with Athira’s $4M settlement; data integrity under scrutiny

WADA status: Not explicitly on WADA Prohibited List (no performance-enhancing application defined)

Trade Names in the USA and Manufacturers

• Developed at Washington State University (WSU), Pullman, WA, USA
• Primary researchers: Joseph Harding, Charles Chavkin, and colleagues at WSU
• Derived from angiotensin IV (a metabolic fragment of angiotensin II) through medicinal chemistry optimization for BBB penetration and HGF/c-Met receptor activity
• Athira Pharma (Seattle, WA) developed the prodrug fosgonimeton (ATH-1017) based on the same HGF/c-Met platform — paid $4M False Claims Act settlement for research misconduct

US availability (as of May 2026):

• Removed from Category 2 April 22, 2026 — formal Category 1 status pending PCAC (February 2027)
• Research peptide vendors: Available as lyophilized powder (‘research use only’)
• 503A compounding: Not yet formally authorized; await PCAC February 2027 review outcome

Molecular identity:

• Synthetic hexapeptide (6 amino acids); angiotensin IV analogue
• Chemical name: N-hexanoic-Tyr-Ile-(6) Aminohexanoic Amide
• MW: ~504.67 Daltons — notably small for a peptide; enables oral and sublingual bioavailability and blood-brain barrier penetration
• Dissolves poorly in aqueous solution — DMSO required for research reconstitution
• Critical stability note: Dihexa aggregates in pure aqueous/saline solution within hours. Research protocols dissolve at 10 mg/mL in 100% DMSO, aliquot, then dilute 1:100 in PBS immediately before use. This hidden variable explains failed replication attempts.

Dosage

Oral / sublingual (most accessible route due to BBB penetration):

• Community-reported range: 5–20 mg once daily
• Most cited dose: 8–45 mg oral/sublingual daily
• Reported duration: Effects described as lasting up to 10 days per dose

Subcutaneous injection (research-grade use):

• Community reported: 2–5 mg SC per injection
• Frequency: Once daily or less frequently given long effect duration

Animal data reference doses (NOT for human translation):

• Peak synaptogenesis in rodents: 100–300 mcg/kg
• Doses >1 mg/kg showed DIMINISHING RETURNS and increased glial activation — INVERTED-U dose-response
• The inverted-U curve means MORE is NOT BETTER. Supramaximal dosing may reduce effects and increase off-target risks.

Reconstitution for research (not for human use):

• Dissolve in 100% DMSO at 10 mg/mL
• Aliquot into single-use volumes (DMSO stock stable at -20°C)
• Dilute each aliquot 1:100 in PBS or cell culture media immediately before use
• Do NOT store in aqueous solution — aggregation occurs within hours

Pricing

No FDA-approved commercial pricing.

Research chemical vendors (unregulated):
Per mg cost: Dihexa is relatively expensive due to complex synthesis
Typical: ~$50–$150 per 10 mg
Monthly cost at common community doses: ~$150–$400/month

Note: Dihexa’s solubility requirements (DMSO) add preparation complexity and cost vs. simple water-reconstituted peptides.

If Category 1 status is granted after February 2027 PCAC review:
Compounded versions from licensed 503A pharmacies would become available
Estimated ~$150–$350/month based on comparable compounded nootropic peptides

Tips

• The PCAC review for Dihexa is the FEBRUARY 2027 cohort — NOT July 2026. This reflects the thinner and more contested evidence base vs. other peptides reviewed in July 2026.
• The most serious risk with Dihexa is oncogenic potential via c-Met pathway activation. FDA-approved anti-cancer drugs (capmatinib, tepotinib) work specifically by BLOCKING this same pathway. Anyone with active malignancy, family history of cancer, or cancer risk factors should not use Dihexa until human safety data is available.
• The foundational research integrity concern (Athira Pharma $4M False Claims Act settlement) means the primary published evidence base has documented credibility issues. Before evaluating efficacy claims, verify whether the specific papers cited have been retracted, corrected, or are under scrutiny.
• The inverted-U dose-response in animal models means higher doses do NOT produce more synaptogenesis — they produce diminishing returns and increased glial activation. Community dosing at the high end may actually be less effective and more risky.
• Dissolution in DMSO is required for research-grade Dihexa — products that dissolve cleanly in water/saline without DMSO may be impure, mislabeled, or degraded.
• Fosgonimeton (ATH-1017) is a related Athira Pharma pro-drug — it is NOT the same compound as Dihexa. Do not conflate clinical trial data from fosgonimeton with Dihexa’s evidence base.

Side Effects

From animal studies and community reports:

Nervous system (stimulant-like profile):
– Nervousness / anxiety: Most commonly reported in community use
– Insomnia / sleep disruption: Reported; possibly related to synaptogenic/pro-plasticity stimulation
– Headache
– Nausea (mild)
– Overstimulation or mood agitation at higher doses

Theoretical / mechanism-derived risks (SERIOUS):
– ONCOGENIC RISK — c-Met pathway activation:
HGF/c-Met is a well-established driver of tumor growth, invasion, and metastasis across multiple cancer types (lung, gastric, hepatocellular, colorectal)
FDA-approved cancer drugs capmatinib (Tabrecta) and tepotinib (Tepmetko) work by INHIBITING the same pathway Dihexa ACTIVATES
No carcinogenicity studies for Dihexa have been conducted
This is the most serious unresolved safety concern

– Maladaptive neuroplasticity:
Building new synaptic connections indiscriminately may strengthen not just productive neural circuits but also pathological ones (anxiety circuits, compulsive patterns, trauma-related pathways)
This theoretical risk is unique to synaptogenic compounds

– Unknown long-term effects:
No chronic toxicology data in any species exists for Dihexa at community-used doses

⚠️ Inverted-U dose-response: Doses exceeding ~300 mcg/kg in rodents increased glial (inflammatory) activation. Translating this ceiling to human dosing is undefined.

Contraindications

Based on mechanism — STRONG CAUTION / AVOID:
– Active malignancy or significant cancer history/risk: c-Met activation is a tumor-promoting pathway — most significant contraindication
– Pregnancy and breastfeeding: No safety data; synaptogenic effects in developing fetal brain are unpredictable and potentially harmful
– Children and adolescents: Developing brain with ongoing synaptic pruning — uncontrolled synaptogenesis raises unpredictable neurodevelopmental risk

Use with caution:
– Patients with anxiety disorders: Pro-synaptogenic effects may strengthen anxiety-related neural circuits
– Patients with PTSD: Consolidating trauma-related synaptic connections is a theoretical concern
– Patients with active psychiatric conditions: Neuroplasticity enhancement without therapeutic direction may worsen symptoms
– DMSO carrier solvent: Tissue penetration properties of DMSO may enhance systemic absorption of other compounds — use with caution in multi-drug protocols
– Hypersensitivity to Dihexa or components

Pharmacology

Dihexa (N-hexanoic-Tyr-Ile-(6) Aminohexanoic Amide) is a synthetic hexapeptide and medicinal chemistry-optimized analogue of angiotensin IV (a metabolic fragment of angiotensin II, the vasoactive peptide). Developed at Washington State University. MW ~504.67 Daltons — unusually small for a peptide, enabling:
1. Oral bioavailability (crosses gastrointestinal mucosa)
2. Blood-brain barrier penetration (passive diffusion enabled by small size and lipophilicity)
3. Sublingual absorption

This combination (oral/sublingual + BBB penetration) distinguishes Dihexa from most peptide nootropics which require injection and have poor CNS penetration.

Functions as an HGF (hepatocyte growth factor) mimetic — it activates the c-Met receptor (HGF receptor) without requiring the full HGF protein itself.

Solubility challenge: Dihexa does NOT dissolve in aqueous solutions. It aggregates in water/saline within hours, rendering it inactive for research purposes. DMSO (dimethyl sulfoxide) is required as a carrier solvent for research reconstitution. This is a critical quality control consideration that explains why many research replication attempts have failed.

Reported potency: Benoist et al. (2014, Journal of Pharmacology and Experimental Therapeutics): 10 million times (7 orders of magnitude) more potent than BDNF at promoting synaptogenesis in hippocampal neuron assays. This extraordinary potency claim requires independent replication — which is limited due to the Athira/data integrity concerns.

Mechanism of action

Dihexa’s mechanism centers on HGF/c-Met receptor pathway activation:

1. c-Met Receptor (HGF Receptor) Activation (primary mechanism):
Dihexa binds to and activates the c-Met receptor tyrosine kinase — the receptor for hepatocyte growth factor (HGF).
In the brain, the HGF/c-Met pathway promotes:
– Dendritic spine formation and growth (structural synaptogenesis)
– Synaptic connection strengthening
– Neuronal survival and protection
– Axon guidance and circuit repair
This is the basis for claimed cognitive enhancement and neuroprotective effects.

2. Structural Synaptogenesis:
Unlike most nootropics that modulate existing neurotransmitter signaling, Dihexa is proposed to physically build new synaptic connections — new dendritic spines and synapses. This structural change is theoretically more persistent and powerful than functional modulation alone.

3. c-Met vs. AT4R (Angiotensin IV Receptor) debate:
Earlier papers attributed Dihexa’s effects to AT4R (insulin-regulated aminopeptidase / IRAP) binding — a mechanism proposed for angiotensin IV peptides. Subsequent work by Benoist et al. (2014) provided evidence for HGF/c-Met as the primary mechanism. The debate is not fully resolved; both pathways may contribute.

4. BBB Penetration:
Unlike native HGF (a large ~90 kDa protein that cannot cross the BBB), Dihexa’s small size (~504 Da) enables CNS penetration — allowing it to act directly on brain c-Met receptors.

⚠️ THE DUAL-EDGE PROBLEM: The HGF/c-Met pathway that Dihexa activates is also a key driver of cancer cell proliferation, invasion, and metastasis. FDA-approved anti-cancer drugs specifically INHIBIT this pathway for tumor control. Dihexa ACTIVATES it.

Result Claims from Different Companies

Washington State University / Benoist et al. (primary researchers):

– Benoist et al. (2011/2014, Journal of Pharmacology and Experimental Therapeutics):
Dihexa described as 7 orders of magnitude more potent than BDNF at promoting synaptogenesis in hippocampal neuron assays.
Spatial learning improvements demonstrated in aged animal models.
c-Met receptor identified as primary mechanism.
⚠️ These papers form the primary evidence base — limited independent replication exists.

– 2025 Journal of Neurochemistry (University of Arizona replication):
43% increased dendritic spine density in rodent hippocampal neurons at 100 nM Dihexa within 72 hours vs. vehicle controls — partial independent replication of synaptogenesis effect.
Inverted-U dose-response confirmed: Peak effect at 100–300 mcg/kg; diminishing returns and increased glial activation above 1 mg/kg.

Athira Pharma (fosgonimeton / ATH-1017 — related pro-drug compound):
– Phase 2 clinical trial for Alzheimer’s disease: Completed
– Showed improvements in EEG gamma oscillations (biomarker of cognitive function)
– ⚠️ Athira Pharma paid a $4 million False Claims Act settlement for image manipulation and data misconduct in research publications
This settlement directly implicates the credibility of the foundational HGF/c-Met platform science

The Peptide Catalog (2026 independent review):
– ‘The foundational science behind Dihexa comes with a $4 million False Claims Act settlement.’
– ‘The primary evidence linking Dihexa’s cognitive effects to HGF/c-Met synaptogenesis has documented data integrity concerns.’

⚠️ Summary: Promising mechanism and early animal data. Significant data integrity concerns from primary research group. No human trials. Serious oncogenic theoretical risk from c-Met activation. February 2027 PCAC review reflects the thinner and contested evidence base.

Disclaimer

This content about “Dihexa (N-hexanoic-Tyr-Ile-(6) Aminohexanoic Amide) HGF Mimetic / Angiotensin IV Analogue” is for informational and educational purposes only, is not medical advice, does not replace consultation with a licensed healthcare professional, and affiliate links may result in compensation at no additional cost to you.