Cerebrolysin vs Semax

Cerebrolysin

Cerebrolysin is a mixture of short peptides and free amino acids made by controlled enzymatic digestion of pig brain protein. Because it is a mixture, it has no single sequence, formula or molecular weight; its composition is defined by the manufacturing process and by batch standardisation. Laboratory and animal studies have examined it for activity resembling that of neurotrophic factors. It has also been studied in human clinical trials, mainly in acute stroke, traumatic brain injury and dementia, and systematic reviews of those trials have reached differing conclusions. The biologically relevant components of the mixture have not been identified, which limits how far any single mechanism can be attributed to it.

Semax

Semax is a synthetic seven-residue peptide, Met-Glu-His-Phe-Pro-Gly-Pro, built from a short fragment of adrenocorticotropic hormone (ACTH). Its first four residues match positions 4 to 7 of ACTH; the Pro-Gly-Pro tail does not occur there in the hormone and is reported to slow breakdown by peptidases. Short ACTH fragments of this kind are described as lacking the steroid-releasing activity of the full hormone. Semax was developed by Russian researchers, and most of its literature comes from Russian groups working in rats and cell cultures. Controlled human studies are few, many are published only in Russian, and independent replication elsewhere is limited.

How Cerebrolysin acts

No single molecular target has been assigned to Cerebrolysin, since it contains many peptides and amino acids. Cell and animal studies have described activity resembling that of neurotrophic factors, the proteins that regulate neuronal survival and differentiation, and have examined markers of apoptosis, synaptic density and neurogenesis in rodent models of stroke, brain injury and neurodegeneration. Some papers have proposed involvement of specific signalling routes downstream of neurotrophic receptors. How much of the peptide content crosses the blood–brain barrier, and which components account for which reported observation, have not been established.

How Semax acts

No specific receptor for Semax has been identified. Studies in rats have reported higher expression of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the hippocampus, and other work has examined dopamine and serotonin turnover in the striatum. Transcriptome studies in rat models of cerebral ischaemia describe shifts in the expression of genes tied to immune and vascular processes. Because its core derives from ACTH, an interaction with melanocortin receptors has been proposed, though direct binding evidence is limited. How these separate observations connect has not been worked out.

The records side by side

• Type: Cerebrolysin, Proprietary mixture; Semax, Synthetic ACTH analog (heptapeptide)
• Length: Cerebrolysin, not recorded; Semax, 7 amino acids
• Molecular weight: Cerebrolysin, not recorded; Semax, 813.9 g/mol
• Molecular formula: Cerebrolysin, not recorded; Semax, C37H51N9O10S

Reading a comparison

A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.