Dihexa

Typical use cases

Dosing guidelines

Titration

Community reports often describe starting at the low end and adjusting over days to weeks while monitoring tolerance; no clinically validated titration schedule exists. Educational information only — not a dosing recommendation.

Reconstitution

Typically handled as an oral preparation (capsule or oral/sublingual solution), so no reconstitution is required for that route. For lyophilized powder intended for solution, community protocols describe dissolving with a suitable solvent (e.g., bacteriostatic water, or a co-solvent such as DMSO for poorly water-soluble lots) under aseptic technique. Educational description only.

Injection sites

Primarily studied/used as an oral (or sublingual) compound — not an injectable peptide; N/A for injection sites.

Storage & handling

Lyophilized powder is commonly stored frozen (around -20°C), protected from light and moisture; once in solution, refrigerated (2-8°C) and used within roughly 2-4 weeks while avoiding repeated freeze-thaw cycles.

Side effects

• Headache Mild · Uncommon
• Overstimulation, anxiety, or irritability Mild · Uncommon
• Insomnia or disrupted sleep Mild · Uncommon
• Fatigue or brain fog Mild · Uncommon
• Theoretical pro-proliferative risk from c-Met/growth-factor activation (unconfirmed in humans) Severe · Rare
• Unknown long-term safety (no human safety data) Moderate · Common

Research summary

Dihexa was developed by Joseph Harding and John Wright at Washington State University as a metabolically stabilized analog of angiotensin IV, designed to retain procognitive activity while resisting enzymatic degradation and crossing the blood-brain barrier. Its proposed mechanism is that it binds hepatocyte growth factor (HGF) and allosterically potentiates the c-Met (HGFR) receptor, driving downstream PI3K/AKT signaling, dendritic spinogenesis, and synaptogenesis; reported in vitro potency figures (e.g., being far more potent than BDNF at stimulating spine formation) and in vivo rescue of memory in scopolamine, APP/PS1 Alzheimer's-model, and Parkinson's-model rodents come from this body of work. Importantly, several foundational Washington State University / Journal of Pharmacology and Experimental Therapeutics papers underpinning the HGF/c-Met mechanism (the 2012 and 2014 reports) were formally retracted in 2025 following a misconduct investigation that found image manipulation by co-author Leen Kawas (later Athira's CEO), and a related 2013 paper carries an expression of concern; this substantially weakens the original mechanistic and efficacy evidence base. The entire efficacy and safety record for dihexa itself remains preclinical, with no completed human clinical trials, no established human pharmacokinetics, and half-life/dosing figures originating from vendor and community sources rather than peer-reviewed human data. A phosphate prodrug, fosgonimeton (ATH-1017), advanced into human trials by Athira Pharma, but the Phase 2/3 LIFT-AD trial of 40 mg once-daily subcutaneous fosgonimeton failed to meet its primary and key secondary cognitive endpoints, tempering enthusiasm for the mechanism's clinical benefit. Key limitations include the retracted source literature, unknown long-term safety, a theoretical concern that strong c-Met/growth-factor activation could influence aberrant cell proliferation, and reliance on uncontrolled potency extrapolations.

Key references

• https://en.wikipedia.org/wiki/Dihexa
• https://drugs.ncats.io/drug/9WYX65A5C2
• https://pmc.ncbi.nlm.nih.gov/articles/PMC8615599/
• https://pubmed.ncbi.nlm.nih.gov/40312093/
• https://www.globenewswire.com/news-release/2024/09/03/2940069/0/en/Athira-Pharma-Announces-Topline-Results-from-Phase-2-3-LIFT-AD-Clinical-Trial-of-Fosgonimeton-for-Mild-to-Moderate-Alzheimer-s-Disease.html
• https://retractionwatch.com/2021/09/24/four-papers-by-athira-ceo-earn-expressions-of-concern/

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