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What it is
Semax with an acetyl group added at the N-terminus, sold as a research chemical. Some vendors additionally offer an amidated form. Neither is the registered Russian medicine.
How it is proposed to work
The acetylation is marketed as extending duration by resisting aminopeptidase cleavage. Removing the free alpha-amino group would be expected to alter the molecule's handling — but 'altered' is not the same as 'improved for longer', and that distinction is where the marketing outruns what is known.
Approved medical uses
None. N-Acetyl Semax has no approved human medical indication in the jurisdictions we track. Any use is outside an approved label.
Human research
Each entry states what the study found and, separately, what it cannot show.
No adequate published human research. This absence is the reason for the evidence grade above — it is not a gap we can fill with animal data.
Preclinical research
Animal and laboratory work. Useful for generating hypotheses; it cannot establish that something works in people.
- In vitro2016
N-terminal acetylation of Semax alters copper handling and does not protect cells from copper toxicity
Finding. Laboratory characterisation of Semax against its N-terminally acetylated form (Ac-Semax) found that acetylation changes the molecule's metal-binding chemistry and its behaviour in cells. At physiological pH the acetylated peptide formed a different copper complex from the parent peptide, with a more positive formal redox potential; in the amino-free form the complex was redox-stable and unreactive towards ascorbic acid, unlike the acetylated form. In a SH-SY5Y neuroblastoma cell line, acetylation did not protect against copper-induced toxicity, which the authors read as showing that the free N-terminal amino group is what does the protecting. Zinc binding was comparable for both peptides, and confocal imaging indicated acetylation does not affect zinc influx into the cells. The authors' own forward-looking proposal for Ac-Semax is as a metal ionophore in antibody-drug conjugates, to disrupt metal homeostasis in tumour cells.
Limitation. Cell-free metal-coordination chemistry plus one neuroblastoma cell line - no animal or human data. The peptide studied is N-terminally acetylated Semax; the abstract says nothing about the additionally amidated form some vendors sell. The abstract reports copper and zinc handling and cell toxicity; it does not report proteolytic stability, absorption or duration of action, so it cannot support the marketing claim that acetylation extends how long the peptide lasts. On the cell-based endpoint the authors treat as protective, acetylation showed no protection, which they attribute to loss of the free N-terminal amino group.
Potential safety concerns
- CautionInsufficient
Semax's clinical use history does not transfer to a chemically modified variant. A change that alters pharmacokinetics also alters the safety profile, and nobody has characterised that here.
Known interactions and contraindication considerations
- Uncharacterised.
This list is not exhaustive and is not a substitute for a clinician reviewing your full medication history.
Regulatory status
Status is shown per jurisdiction and is accurate only as of the date stated. Where a compound is approved, the approval is bound to a specific formulation, manufacturer and indication — shown in the detail column.
| Jurisdiction | Standing | Detail |
|---|---|---|
United States FDA | Unapproved / investigational as of 11 Aug 2026 | No marketing authorisation. The FDA has not evaluated this compound — that is an absence of any opinion, not a negative finding. |
European Union EMA | Unapproved / investigational as of 11 Aug 2026 | No marketing authorisation. |
India CDSCO | Unapproved / investigational as of 11 Aug 2026 | Not approved for human use. A first-time synthetically manufactured peptide falls under the new-drug pathway. |
Russian Federation Ministry of Health / Roszdravnadzor | Unapproved / investigational as of 11 Aug 2026 | The registered Russian medicine is Semax. This acetylated variant is not the registered product and should not inherit its status. |
How it is being used
What the grey community actually runs, the reasoning they give, and our read on whether it follows from known biology. This is observation, not evidence, and not a recommendation.
No community use documented for this compound yet. Absence here means our editorial team has not reviewed and verified a pattern — not that none exists.
Active clinical trials
No registered trials currently tracked for N-Acetyl Semax.
What remains unknown
The questions that would change our assessment if they were answered.
- Does the acetylated form do anything the parent does not, in a human?
- Is the claimed duration advantage real or assumed from chemistry?
References
- 1.Magri A, Tabbi G, Giuffrida A, Pappalardo G, Satriano C, Naletova I, Nicoletti VG, Attanasio F. Influence of the N-terminus acetylation of Semax, a synthetic analog of ACTH(4-10), on copper(II) and zinc(II) coordination and biological properties. J Inorg Biochem. 2016 Nov;164:59-69.PMID 27586814doi
Editorial change history
When we change a grade or a regulatory note, we log it here rather than editing quietly.
Dossier created. Vendor-sourced CAS number excluded as unverifiable.
Spotted something wrong? Tell us — we publish corrections.