Semax is a synthetic heptapeptide analogue of ACTH(4-10), modified with a C-terminal Pro-Gly-Pro to resist degradation. It was developed in the Soviet Union and later Russia and is registered there for cerebrovascular and cognitive indications.

It presents a specific appraisal problem worth naming: a substantial literature exists, most of it published in Russian-language journals that are not indexed in the databases Western reviewers use, with methods sections that are difficult to evaluate at a distance. That is not the same as the literature being bad. But it does mean confident claims in either direction are usually being made by people who have not read it.

Semax lacks the corticotropic activity of full ACTH, it does not stimulate cortisol release, while retaining reported neurotropic effects.

Proposed mechanisms include increased expression of BDNF and its receptor TrkB, modulation of dopaminergic and serotonergic systems, and effects on the melanocortin system. Intranasal administration is the usual route, with claims of direct nose-to-brain transport that are plausible in principle and not well quantified in humans.

Early clinical, and difficult to appraise.

Russian clinical trials report benefit in ischaemic stroke, cognitive impairment, and optic nerve conditions. These trials underpin its registration there. Independent replication outside Russia is essentially absent, and the trials that are accessible are generally small and inconsistently reported by international standards.

For healthy cognitive enhancement, the use that drives most community interest, there is no adequately powered controlled evidence in any language.

The honest position is uncertainty, not dismissal. "The evidence is in a literature I cannot appraise" is a different statement from "there is no evidence", and collapsing the two is its own error.

Reported tolerability in Russian clinical use is good, with the intranasal route producing local irritation as the main complaint. Decades of registered use provide some real-world observation.

The limits: little independent safety data, no long-term data in healthy users, and no characterised interaction profile. Effects on dopaminergic signalling raise the usual questions about interaction with psychiatric medication that have not been studied.

Registered in Russia and some neighbouring countries for specified neurological indications. Not approved in the United States, the European Union, or most other jurisdictions. Sold internationally as a research chemical.