Semax (ACTH 4-10 Analog): Neurotrophic Factor Modulation and Preclinical Research

Development History

Semax was developed in the late 1980s at the Institute of Molecular Genetics of the Russian Academy of Sciences under the direction of Nikolai Myasoedov (the same laboratory that produced Selank). It is a synthetic heptapeptide derived from the adrenocorticotropic hormone (ACTH) fragment 4-10, corresponding to the sequence Met-Glu-His-Phe-Pro-Gly-Pro (MW ~813 Da).

The parent fragment, ACTH(4-10), was identified in the 1960s-70s as the minimal active sequence responsible for the neurotropic (non-endocrine) effects of ACTH. While full-length ACTH (39 amino acids) primarily drives adrenal cortisol synthesis, the 4-10 fragment retains neurotrophic activity without significant effects on the hypothalamic-pituitary-adrenal (HPA) axis.

Chemical Structure

Semax extends native ACTH(4-7) with a C-terminal Pro-Gly-Pro tripeptide sequence—the same stabilizing motif used in Selank. The Met-Glu-His-Phe core is derived from ACTH residues 4-7 and contains the essential pharmacophore for melanocortin receptor interaction. Key structural features:

• N-terminal methionine: susceptible to oxidation (Met→Met(O)), which can be monitored as a +16 Da mass shift by ESI-MS
• His-Phe dipeptide: part of the conserved melanocortin receptor-binding His-Phe-Arg-Trp motif found in α-MSH and ACTH
• C-terminal Pro-Gly-Pro: confers resistance to carboxypeptidases and extends biological half-life

Published Research

Neurotrophic Factor Expression

The most extensively documented activity of semax in the published literature is upregulation of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) gene expression. Studies using rat brain tissue and primary neuronal cultures have demonstrated dose-dependent increases in BDNF mRNA levels following semax administration.

Reference: Dolotov OV et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117(1):54-60.

Gene Expression Studies

Transcriptomic analysis of semax-treated neuronal cell cultures identified differentially expressed genes involved in neurotransmitter signaling, immune response modulation, and vascular function. Notably, semax affected expression of genes in the MAPK/ERK signaling cascade downstream of neurotrophin receptor activation.

Reference: Agapova TY et al. Effect of semax on the temporary dynamics of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) gene expression. Mol Genet Microbiol Virol. 2008;23(3):130-3.

Melanocortin Receptor Pharmacology

Semax retains partial affinity for melanocortin receptors (MC3R, MC4R) but with substantially lower potency than α-MSH or full-length ACTH. Research has examined whether semax's neurotropic effects are melanocortin receptor-dependent or operate through an independent mechanism.

Key Published Studies

• Levitskaya NG et al. (2008) — Structure-activity relationship studies of ACTH(4-10) analogs and melanocortin receptor binding.
• Filippenkov IB et al. (2014) — Transcriptomic profiling of semax effects on gene expression in rat brain tissue.

Future Research Directions

Ongoing research areas include definitive identification of semax's primary molecular target (melanocortin-dependent vs. independent pathways), investigation of its effects on adult neurogenesis in hippocampal cell models, and comparative pharmacology with other ACTH-derived nootropic fragments.

Available at Crush Research: Semax 10mg. View Certificates of Analysis.

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