What is dihexa?

• What dihexa is and how it descends from angiotensin IV
• The proposed HGF/c-Met mechanism, framed as a hypothesis not a fact
• Why two of dihexa's foundational papers were retracted or flagged
• How the fosgonimeton trials and the c-Met oncology signal reframe the hype

1. 01 What is dihexa? Big animal claims, and human trials of its prodrug that failed free
2. 02 Chemistry & structure How dihexa is built from angiotensin IV paid
3. 03 The HGF/c-Met hypothesis The proposed mechanism, and why it is a hypothesis paid
4. 04 The preclinical evidence What the animal and cell studies actually show paid
5. 05 The research-integrity problem The retraction and the expression of concern paid
6. 06 The fosgonimeton translation The prodrug that took dihexa into humans, and failed paid
7. 07 Dosing & Administration What the community reports, and why no dose is established paid
8. 08 Safety & Side Effects The c-Met oncology signal and the missing safety data paid
9. 09 Regulatory context Not approved, and in regulatory limbo paid
10. 10 Final Exam & Certification Pass the final exam to earn your certificate of completion. Exam

Dihexa was not discovered by accident. It is the end point of a decades-long program in the Harding and Wright lab at Washington State University, which studied how a fragment of the blood-pressure hormone system could sharpen memory in rats. Each generation of molecule was trimmed and stabilized to survive longer in the body.

Notice how the marketing-friendly story arrived late and then partly collapsed. The clean, early work is about angiotensin IV analogs and spines; the bold HGF/c-Met headline came in 2014 and was retracted in 2025.

Dihexa is often called a "hexapeptide". Chemically it is not: it is a core of just two building blocks (two residues, tyrosine and isoleucine) wearing two fatty caps. The 2013 paper that named it, which is under a notice of concern, describes those chemical modifications as designed to increase hydrophobicity, meaning how strongly the molecule avoids water and favors fat, and to decrease hydrogen bonding, yielding an orally active, blood-barrier permeant, metabolically stabilized analog.

The chemical name does the describing that the short name does not: N-hexanoic-Tyr-Ile-(6)aminohexanoic amide is a hexanoyl group, a two-residue core, and a 6-aminohexanoyl amide. No source in this course's research explains where the short name "dihexa" comes from, so treat it as a nickname and read the chemical name instead. That is where most misunderstandings of dihexa begin, so it is worth fixing early.

Search dihexa and you will meet confident superlatives: "reverses Alzheimer's", "regrows neurons", "ten million times stronger than BDNF". Each is either an overreach, a result borrowed from a different molecule, or a number this course could not trace to any source at all. The useful skill is holding each claim against its actual evidence.

Most of these claims are not simply false. They are real laboratory observations that have been rounded up into human promises they cannot support, or numbers whose origin nobody checks. Learning to see that gap is what this course trains.

Before any mechanism detail, here is the honest ceiling: what is genuinely supported for dihexa, and what is merely hoped for. The distance between the top and bottom rows of this table is the entire point of the course. Read down the tiers and notice how quickly the evidence thins, from a real but narrow animal signal at the top to human trials, run on an injected prodrug, that found no benefit at the bottom.

A gauge this low is unusual for a compound with so much online enthusiasm, and that mismatch is the story. The score is not a verdict that dihexa does nothing; it is a measure of how little we can actually claim to know about it in people.

The "ten million times stronger than BDNF" line is the most-repeated dihexa claim, so it deserves a careful look. Taken at face value it is a potency statement, about how low a concentration produces an effect in a dish, not about how well either molecule treats a human brain. It is worth separating those two questions before worrying about the number, because no source in this course's research reports a BDNF comparison at all.

A drug can be extraordinarily potent and still completely fail, because potency is a laboratory concentration and efficacy is a clinical result. Conflating the two is the single most common error in how dihexa is promoted.

The rest of the course walks the evidence in order: the chemistry, the proposed mechanism, the preclinical data, the integrity actions, the failed prodrug trials, the dosing and safety picture, and the regulatory limbo. Each unit keeps the same honest posture.

By the end you should be able to state cleanly what is established, what is hypothesized, and what is simply unknown about dihexa, and to spot the claims that blur those lines.