Human-derived material does not make an experiment a human treatment trial. This distinction is essential when biochemical findings are used to explain neuropeptide activity. Primary study
What was reported
The study reported concentration-dependent inhibition of enkephalin-degrading enzymes in human serum by Semax and Selank. Some pentapeptide fragments also showed activity, while the tested tri-, tetra-, and hexapeptide fragments did not. The authors proposed enzyme inhibition as one possible contribution to biological activity. The work measured a biochemical effect, not patient improvement. Primary report
Our appraisal: potency has a specific experimental meaning
An inhibitory concentration describes performance in a defined assay. It depends on the substrate, enzyme mixture, incubation conditions, and method of detection. It is not a recommended exposure for a person and does not establish whether a comparable concentration occurs in the relevant tissue.
Serum and brain tissue are different biological environments. Moving from a serum assay to a claim about central nervous system function requires evidence about distribution, intact-compound persistence, and target engagement. The assay does not supply those steps automatically.
Fragment results are also informative because they show why sequence matters. Activity cannot be attributed to every fragment simply because the molecules share some residues. Nor should the result for a tested parent peptide be transferred to a chemically modified product without appropriate evidence.
Finally, similar enzyme effects do not establish that Semax and Selank have the same overall action, equal clinical efficacy, or a synergistic combination effect. Each stronger statement asks a different experimental question.
This study provides a biochemical hypothesis to investigate. It is not a head-to-head clinical ranking, evidence of a beneficial blend, or proof that protecting an endogenous peptide necessarily improves health outcomes.
Frequently asked questions
Was human serum used?
Yes.
Were patients treated in this experiment?
It was an enzyme-assay study, not a treatment trial.
Did both parent peptides inhibit the measured degradation?
Yes.
Were all tested fragments active?
No.
Is assay potency a human dose recommendation?
No.
Does a serum result establish brain target engagement?
No.
Does this demonstrate blend synergy?
No.