Semax versus selank: two Russian research peptides that are constantly confused

Every row cites its source. Where a cell reflects our own reading of the evidence rather than an external source, the row says so.

Compounded, not FDA-approved

Semax is not FDA approved for any use in the U.S. It is sold as a research chemical; FDA has proposed not to allow it in compounded drugs, and efficacy has not been established to FDA standards.

RESEARCH-ONLY in the United States. No FDA-approved product contains semax; a Drugs@FDA query for it as an active ingredient returns no matches. FDA lists Semax (heptapeptide) on its page of bulk drug substances that may present significant safety risks in compounding, and at the July 23 to 24, 2026 Pharmacy Compounding Advisory Committee meeting FDA proposed that both Semax (free base) and Semax acetate NOT be included on the 503A Bulks List. Peer-reviewed literature describes semax as a Russian clinical drug; this site could not verify a Russian marketing authorisation against the state register and therefore does not assert one.

Semax versus selank: two Russian research peptides that are constantly confused
Aspect	Semax	Selank	Source
Parent molecule	ACTH(4-7), a fragment of adrenocorticotropic hormone, extended with Pro-Gly-Pro. Sequence Met-Glu-His-Phe-Pro-Gly-Pro, 813.9 Da	Tuftsin (Thr-Lys-Pro-Arg), an immune tetrapeptide, extended with the same Pro-Gly-Pro tail. Sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, 751.9 Da	source
Classification in the 2022 Russian peptide review	Nootropic drug (Table 1, row 3)	Anxiolytic (Table 1, row 13)	source
Published literature, identical Europe PMC query	206 records, of which 83 Russian-language (40.3 percent)	68 records, of which 29 Russian-language (42.6 percent)	source
Records tagged Randomized Controlled Trial	1 (27 patients, motor neuron disease, Russian)	2	source
Human pharmacokinetics published	None. Zero records pair semax with pharmacokinetic	None. Zero records pair selank with pharmacokinetic	source
FDA compounding safety-risks entry	Listed as Semax (heptapeptide): immunogenicity risk from aggregation and peptide-related impurities; FDA "has no, or limited, safety-related information for proposed routes of administration"	Listed as Selank acetate (TP-7): the same immunogenicity wording, followed by FDA lacking important information regarding safety issues in humans	source
July 2026 PCAC outcome	FDA proposed that Semax (free base) and Semax acetate NOT be included on the 503A Bulks List; both nominations had already been withdrawn and FDA proceeded anyway	Not among the seven substances reviewed at the July 2026 meeting; selank's own nomination was withdrawn earlier	source
Head-to-head in human serum (in vitro)	Inhibits enkephalin-degrading enzymes, IC50 10 micromolar	Inhibits the same enzymes, IC50 20 micromolar	source
Head-to-head in animals	In 6-OHDA parkinsonian rats, no effect on motor activity or passive defensive behaviour	Same null on motor activity, but selank reduced anxiety in that model	source
Head-to-head in healthy humans	Both appeared in the same 2020 placebo-controlled resting-state fMRI study of 52 participants; connectivity differences reported, no cognitive or clinical outcome measured	Same 2020 study, same 52 participants, same limitation: connectivity differences only, no cognitive or clinical outcome measured	source
Anti-doping status (2025 specialist review)	Unclear status, paired with tetracosactide (WADA class S2) as a similar substance	Unclear status, no similar prohibited substance listed	source
Found together in seized preparations	Yes. A Belgian government laboratory identified both in preparations seized in 2017 and 2018, and wrote that neither had completed any clinical trials	Yes, in the same samples	source

Both compounds are covered by this fleet: selank has its own site at selankco.com. Every census row here was produced by running one identical Europe PMC query for both compounds on the same day, because a comparison built from two different search methods is not a comparison.