Semax

Overview

Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. The first four amino acids match positions 4 to 7 of adrenocorticotropic hormone (ACTH), and the added Pro-Gly-Pro tail slows breakdown by enzymes. Russian papers therefore often call it ACTH(4-7)PGP. It was designed to keep the brain-related activity reported for short ACTH fragments without the hormone's effects on the adrenal glands.

Research has focused on two areas: learning and memory in rodents, and neuroprotection in models of stroke. A well-cited line of work links Semax to increased levels of brain-derived neurotrophic factor (BDNF), a protein involved in nerve cell survival and synaptic plasticity.

Semax is a registered medicine in Russia, but it has no approval in the United States or the European Union. Nearly all published studies come from a small set of Russian institutes, and much of the clinical literature is in Russian. Independent Western replication is limited, and there are no large international randomized trials.

Research history

Semax grew out of Soviet research into short fragments of ACTH, which had been reported to influence attention and learning in animals without acting as a full hormone. Groups at the Institute of Molecular Genetics of the Russian Academy of Sciences, led by Nikolai Myasoedov, and at Moscow State University developed the stabilized fragment that became Semax.

It entered Russian clinical practice, where it has been used in stroke care and other neurological settings. English-language mechanistic papers appeared mainly from the 2000s onward. A 2006 collaboration between Moscow researchers and a German lab (Dolotov and colleagues, with Engele) reported specific Semax binding sites in rat brain tissue and rises in BDNF.

Over the following decade, the Institute of Molecular Genetics group shifted toward genome-wide studies of how Semax changes gene expression in rat brain after experimental stroke, publishing in journals such as BMC Genomics.

What published studies have examined

Animal and cell studies

• BDNF in rat hippocampus (2006). Dolotov and colleagues reported that a single dose of Semax given to rats raised hippocampal BDNF protein about 1.4-fold and increased activation of its receptor, trkB. Treated animals showed more conditioned avoidance responses in a learning task.
• Binding sites (2006). A companion paper found specific, reversible binding of labeled Semax in membranes from the rat basal forebrain, and rapid increases in BDNF there but not in the cerebellum.
• Stroke models (2014). Medvedeva and colleagues ran a genome-wide expression study in rats after permanent occlusion of a brain artery. Semax mainly altered genes tied to the immune response and blood vessel formation.
• Normal brain (2024). Filippenkov and colleagues used RNA sequencing to compare Semax with a related peptide in healthy rats. Both peptides changed hundreds of genes, mostly lowering immune-related expression. The authors note that effects under normal conditions, including possible risks, need study in their own right.

Human studies

• Stroke rehabilitation (2018). Gusev and colleagues studied 110 patients recovering from ischemic stroke, split into early and late rehabilitation groups with and without Semax. Those given Semax had higher plasma BDNF, and the authors reported faster functional recovery. The abstract does not describe randomization or blinding, and the study was not placebo-controlled in the Western sense.

Most other clinical reports are small Russian-language studies that are hard to assess from outside.

Open questions

• Independent replication. The mechanistic and clinical literature comes largely from a few Moscow institutes, often with overlapping authors. Replication by unrelated groups, particularly outside Russia, is thin.
• Trial quality. No large, preregistered, double-blind, placebo-controlled trial with published results has been found in the indexed literature. Claims of cognitive effects in healthy people rest on older, small reports that are hard to evaluate from the indexed record.
• Mechanism. BDNF changes and immune gene shifts are consistent findings in rats, but which effect matters, if any, for people remains unclear.
• Safety. Long-term safety data in the international literature are sparse. Because Semax is derived from ACTH, any hormonal effects deserve careful measurement.
• Regulation. Outside Russia it has no approved medical status that we could verify. Products sold elsewhere are unregulated research chemicals; see how to read a certificate of analysis.