dihexa vs semax
updated
dihexa (tier D) vs semax (tier B): what each is, why each got its grade, half-life and source counts side by side.
dihexa · tier D
rodent nootropic with zero human trials and a proposed mechanism that's a named oncology concern.
tier rationale
D-tier because the human benefit is unproven (zero trials) and the proposed mechanism carries a specific, named oncology concern that hasn't been characterized in humans. The paper reporting that mechanism was retracted in 2025, so the concern stays theoretical. This isn't only a 'we don't know' evidence gap. It's a 'we have mechanistic reason to worry about a specific pathway' situation. Not F-tier because the underlying research is legitimate. The science is real. Dihexa specifically has no human program, and the related fosgonimeton program no longer rescues the gray-market narrative.
semax · tier B
russian nootropic. approved there, not here. for focus, stroke recovery, and cognitive decline. real mechanism, thin US trials.
tier rationale
B-tier because the evidence base is real but geographically and linguistically constrained. Russian regulatory approval for three indications, two decades of clinical use, confirmed BDNF mechanism. Held back from A-tier because Western clinical replication is limited and most primary literature requires Russian-language fluency to read. FDA's 503A process could change the U.S. compounding lane, but that would not be drug approval.
at a glance
| dihexa | semax | |
|---|---|---|
| tier | D | B |
| category | nootropic / longevity | nootropic / longevity |
| sources | 18 | 26 |
| claims evaluated | 5 | 6 |
| half-life | about 1.5 hours in human plasma as ATH-1001, measured after the fosgonimeton prodrug, not after direct dosing; oral bioavailability shown in rodent models | minutes in plasma; effects persist for hours due to CNS penetration and BDNF induction cascade |
| dosing data | yes | yes |
reptides grades the research record and cites the literature behind every call. research reference only; not medical advice.