Semax
Russian-developed ACTH(4-7)PGP heptapeptide studied for neuroprotection and cognition; modulates BDNF/NGF signaling. On the FDA PCAC July 2026 docket.
Reviewed by Mei Li, PhD, Chief Science Officer
What Semax is
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Structurally it consists of the ACTH(4-7) fragment of adrenocorticotropic hormone (Met-Glu-His-Phe) with an added C-terminal Pro-Gly-Pro tripeptide; in much of the literature it is described more loosely as an analog of the ACTH(4-10) fragment. The Pro-Gly-Pro extension increases metabolic stability, and the peptide lacks the hormonal (corticotropic) activity of full-length ACTH, so it does not stimulate steroid release. What remains is a peptide that published research has studied for effects on the central nervous system. It was developed in the 1980s at the Institute of Molecular Genetics of the Russian Academy of Sciences. Semax is distinctive because, unlike most research peptides in this space, it has been a registered pharmaceutical in Russia since the mid-1990s, used there in ischemic stroke and cognitive contexts, generally as an intranasal formulation. Because of that history, the overwhelming majority of the scientific literature is Russian in origin.
Mechanism of action
The mechanism most consistently reported is enhancement of neurotrophic signaling. In rodent models, Semax has been reported to elevate brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the hippocampus and basal forebrain and to increase nerve growth factor (NGF)-associated signaling. Dolotov et al. (Brain Research, 2006) reported that Semax administration raised hippocampal BDNF protein, TrkB activation, and the corresponding mRNA. As an ACTH-derived fragment, Semax also interacts with the melanocortin system. In cerebral ischemia, genome-wide transcriptional profiling by Medvedeva et al. (BMC Genomics, 2014) found that Semax predominantly modulated immune- and vascular-system genes, which the authors interpreted as immunomodulatory and anti-inflammatory mechanisms acting alongside neurotrophic support. Preclinical work has also described effects on serotonergic and dopaminergic systems.
What published research has examined
Research on Semax falls into three broad areas. The most developed is cerebral ischemia and stroke: animal middle-cerebral-artery-occlusion studies have examined infarct volume and neurological recovery, and Russian clinical studies have looked at outcomes across acute and rehabilitative stroke populations. A second area is cognition and attention, where studies have investigated learning, memory, and mild psychostimulant-like properties. A third, smaller line of work covers optic-nerve and other neurological conditions. Human clinical work includes studies such as Gusev, Martynov and colleagues (Zh Nevrol Psikhiatr, 2018), which examined 110 post-stroke patients across rehabilitation stages. PepSense frames all of these strictly as topics the literature has investigated, not as validated or approved uses.
Key findings and evidence quality
Across preclinical models, the recurring findings are BDNF/TrkB upregulation, reduced infarct size in ischemia models, and shifts in immune and vascular gene expression. In the human literature, the 2018 Gusev/Martynov study reported that intranasal Semax raised plasma BDNF and, combined with earlier rehabilitation, was associated with improved motor performance and functional recovery. The important caveat is evidence quality: most human studies are single-center, Russian, and modest in size or older in methodology, with limited independent Western replication and few large randomized controlled trials meeting contemporary standards. The result is a genuinely mixed evidence base, stronger in mechanistic and animal data than in rigorous, replicated human efficacy data.
Regulatory status
In the United States, Semax is not FDA-approved for any use. It is currently classified as Category 2 (a substance a 503A compounding pharmacy may not compound pending review) and is one of exactly seven peptides on the FDA Pharmacy Compounding Advisory Committee (PCAC) docket for July 23-24, 2026, alongside BPC-157, TB-500, KPV, MOTS-c, emideltide, and epitalon. The PCAC vote is non-binding and represents roughly the second of about six steps in FDA rulemaking; even a favorable, unanimous recommendation would not by itself make Semax legal to compound, and a realistic timeline to actual legal compounding availability is at least 12 to 18 months after any favorable vote. The FDA's preliminary review materials for these peptides raised concerns about characterization, human effectiveness evidence, and safety, and did not favor adding Semax to the 503A Bulks List, though the committee vote had not been finalized in the docket record. This is distinct from FDA-approved finished peptide drugs such as semaglutide, tirzepatide, and bremelanotide, which are not part of the compounding-bulks conversation. Semax's registration status in Russia carries no US regulatory weight.
Safety considerations and related compounds
In the Russian clinical literature, short-course intranasal Semax is generally described as well tolerated with few reported adverse effects, and it lacks the steroid-releasing activity of ACTH. From a regulatory standpoint, however, long-term controlled human safety data are limited, the evidence originates largely from one research tradition, and pharmacokinetic and immunogenicity characterization is incomplete, points the FDA emphasized in its 2026 review materials for the docketed peptides. Related compounds studied in overlapping contexts include Selank (an anxiolytic regulatory-peptide analog from the same Russian research lineage), the N-acetylated Semax variant, epitalon and MOTS-c (also on the July 2026 docket), and Cerebrolysin as a neurotrophic comparator. None of this is medical guidance; it summarizes what the published literature and regulators have reported.
Key published studies
| Study | Journal | Year | Finding |
|---|---|---|---|
| Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus | Brain Research (Dolotov et al.) | 2006 | Preclinical (rat): reported that Semax administration increased hippocampal BDNF protein, TrkB activation, and BDNF/trkB mRNA, establishing the neurotrophic mechanism most often cited for Semax. A companion 2006 Dolotov paper in the Journal of Neurochemistry examined specific binding and BDNF increases in rat basal forebrain. |
| The peptide semax affects the expression of genes related to the immune and vascular systems in rat brain focal ischemia: genome-wide transcriptional analysis | BMC Genomics (Medvedeva et al.) | 2014 | Preclinical (rat focal ischemia): genome-wide analysis found Semax predominantly altered immune- and vascular-system genes, which the authors interpreted as immunomodulatory and anti-inflammatory contributions to the reported neuroprotective effect. |
| The efficacy of semax in the treatment of patients at different stages of ischemic stroke | Zhurnal Nevrologii i Psikhiatrii im. S.S. Korsakova (Gusev, Martynov et al.) | 2018 | Clinical (110 post-stroke patients): reported that intranasal Semax raised plasma BDNF and, combined with earlier rehabilitation, was associated with improved motor performance and functional recovery; single-center Russian study, modest size. |
Regulatory status
Current status: Category 2 · PCAC July 2026 docket. Category 2 · PCAC July 2026 docket. PepSense tracks FDA filings and updates this record as the regulatory picture changes. See the FDA PCAC tracker for the July 2026 vote and what happens next.