N-Acetyl Semax: The Complete Guide

This guide covers two related but distinct vendor derivatives of Semax:

Name	Sequence	Modifications vs parent
Semax (parent)	Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP)	Russian Academy ACTH(4–7) analog with Pro-Gly-Pro stability cap. Russian-registered nasal solution drug since 1996.
N-Acetyl Semax	Ac-MEHFPGP	N-terminal acetylation only.
N-Acetyl Semax Amidate (NASA)	Ac-MEHFPGP-NH2	N-terminal acetylation plus C-terminal amidation.

Don’t confuse with Adamax. Adamax is Ac-MEHFPGP-AG-NH₂ — N-Acetyl Semax with an additional adamantyl-AG cap copied from the P21 peptidomimetic. Adamax is a fourth distinct molecule. See the Adamax guide for that lineage.

The audit-critical asymmetry:

Parent Semax has substantial Russian and some Western primary literature. N-Acetyl Semax and N-Acetyl Semax Amidate have ZERO published pharmacology on the named molecules.

Direct PubMed searches for "N-acetyl Semax," "Ac-Semax," "Ac-MEHFPGP," and "Semax amidate" return nothing. Every potency claim, BDNF-fold-increase claim, and half-life claim in vendor copy and in the existing StackTrax encyclopedia entry is design-rationale extrapolation from parent Semax.

The one direct chemistry paper:

PMID 27586814 — Magrì A et al. J Inorg Biochem 2016. Title: "N-terminus acetylation of Semax: effect on copper and zinc binding." Demonstrates N-acetylation provably alters Cu(II)/Zn(II) coordination chemistry. Translation: the modified molecule is NOT pharmacodynamically identical to parent Semax — but in which direction (stronger or weaker BDNF/cognitive effect) has never been measured in published research. Tomasello 2025 (PMID 40496623) is a follow-on copper-chelation study.

Regulatory status:

• FDA (US): never approved (parent or derivatives). Sold as research chemical.
• EMA (EU): not approved.
• Russia: parent Semax IS registered as a nasal solution drug (1996/1997). N-Acetyl forms are NOT registered separately. The regulatory authorization is for the unmodified parent.
• WADA 2026: not on the prohibited list by name. As an unapproved investigational substance, S0 (non-approved substances) catch-all may apply. Note: Semax is an ACTH(4–7) fragment; while the (4–7) fragment was specifically designed without HPA-axis activation, an anti-doping panel ruling on an ACTH-analog could plausibly invoke S2.4 (Corticotrophins). Athletes should consult their governing body.

Every mechanism claim below is anchored to the parent Semax literature. None has been measured for N-Acetyl Semax or Semax Amidate as discrete molecules.

Parent Semax pharmacology (verified):

• Indirect BDNF / NGF / TrkB upregulation in rat hippocampus — Dolotov 2006 (PMID 16996037); Dolotov 2006 binding-site characterization (PMID 16635254, J Neurochem).
• Mesolimbic dopamine modulation only with stimuli — Eremin 2005 (PMID 16362768): Semax modulates dopamine and serotonin in the presence of amphetamine but not at baseline. Glazova 2021 (PMID 33418449) extended this in a behavioral model.
• PK in rats — Shevchenko 2006 (PMID 16523722).
• Anti-inflammatory / immune gene expression in rat focal-ischemia and immune contexts — Dmitrieva 2010 (PMID 19633950); Samotrueva 2019 (PMID 31028579).
• ACTH(4–7) framework, designed without HPA-axis activation — ACTH(4–10) is the "behavioral / nootropic" portion of ACTH. Semax was specifically designed to keep cognitive effects while losing adrenocortical activation. Vyunova 2017 (PMID 27921334) characterizes the ACTH/Semax structure-activity relationship.
• Russian-Academy N-terminal SAR — Glazova 2005 (PMID 16212268): N-terminal modifications of Semax and effects on neurotropic activity. This is the closest published literature to direct N-acetyl-Semax pharmacology, but still on broader N-terminal modifications, not specifically Ac-MEHFPGP.
• Russian clinical use — Gusev 2001 (PMID 11517472), Gusev 2018 (PMID 29798983, n=110): acute ischemic stroke and cognitive disorders. Russian-registered indications.

What the modifications are hypothesized to do:

• N-acetylation — reduces aminopeptidase cleavage at the N-terminus (extends plasma residence). Confirmed chemically in Magrì 2016 to alter metal-binding chemistry — mechanism altered, but direction unmeasured.
• C-terminal amidation (Semax Amidate only) — reduces carboxypeptidase cleavage at the C-terminus.
• Vendor framing: "stronger and longer-acting Semax" / "more potent BDNF upregulation."

None of these has been measured for N-Acetyl Semax or Semax Amidate specifically.

The Magrì 2016 finding matters:

Semax binds copper and zinc at its N-terminus (the histidine and methionine residues are involved). N-acetylation occupies the N-terminus, which alters the metal-binding profile. Some Semax mechanism work proposes the metal-binding plays a role in CNS effects. So the N-acetyl modification isn’t pharmacodynamically silent — it changes something measurable about the molecule. What that means for clinical effect: nobody has published.

Claim	Source	What it actually measured
Hippocampal BDNF / TrkB upregulation	Dolotov 2006 PMID 16996037, PMID 16635254	Parent Semax only. Rat hippocampus.
Cognitive enhancement / nootropic effects	Russian clinical lit: Gusev 2001 (PMID 11517472), Gusev 2018 (PMID 29798983)	Parent Semax only. Russian-registered indications.
N-terminal SAR (closest direct work)	Glazova 2005 PMID 16212268	N-terminal modifications of Semax broadly — not specifically Ac-MEHFPGP.
N-acetylation alters metal coordination	Magrì 2016 PMID 27586814; Tomasello 2025 PMID 40496623	Direct evidence on N-Acetyl Semax chemistry. Establishes the modification isn’t pharmacodynamically silent. Direction of clinical effect: not measured.
"More potent than parent Semax"	None — vendor / community framing	Not measured. Pure design-rationale extrapolation.
"Longer half-life"	None	Not measured for N-Acetyl Semax. Inferred from N-terminal acetylation chemistry generally.
"BDNF fold-increase X" (specific number)	None for the derivative	Not measured. Some sources cite parent-Semax BDNF data and present it as derivative data.
Human PK / safety of N-Acetyl Semax	None	No published study.

Honest framing for any claim: if the source is a parent-Semax paper, label it "(parent Semax — extrapolated)" rather than silently importing it as if it measured the derivative.

No published trial of N-Acetyl Semax or Semax Amidate exists. Dosing reflects vendor / community convention extrapolated from parent Semax.

Parameter	Common Range
Dose (intranasal)	200–600 µg/spray, 1–3 sprays/day; total ~600–1800 µg/day
Dose (SC, less common)	200–500 µg/day
Frequency	Daily, morning preferred (avoid late-day to reduce insomnia per parent-Semax community convention)
Cycle length	2–6 weeks (community)
Route	Intranasal most common (mirrors Russian-registered Semax formulation); SC less common

The "longer half-life" framing is sometimes used to justify less-frequent dosing, but no published PK study supports specific intervals for the N-acetyl forms.

For a typical 5 mg lyophilized vial:

• Add 2 mL bacteriostatic water → 2.5 mg/mL (2500 µg/mL).
• On a U-100 insulin syringe, 1 unit = 25 µg.
• For a 500 µg intranasal dose — 0.2 mL (20 units).

Storage:

• Lyophilized: stable at room temperature short-term; refrigerate longer-term.
• Reconstituted: refrigerate. Use within 28 days.
• Nasal solution: protect from light; refrigerated.

For the full reconstitution protocol, see the Bacteriostatic Water guide.

No published human safety data on N-Acetyl Semax or Semax Amidate.

Parent Semax safety profile (extrapolated):

• Generally well-tolerated in Russian clinical trials at registered doses (parent Semax).
• Insomnia with afternoon/evening dosing — consistent with the modest stimulating effect.
• Mild stimulation; some users report increased focus / drive that can cross into irritability at higher doses.
• Nasal irritation with intranasal route.
• Mild headache, transient.
• No abuse potential or withdrawal pattern reported for parent Semax.

What N-acetylation might change:

The Magrì 2016 finding (altered Cu/Zn coordination) is a chemical change that could propagate to a different effect profile in vivo. None of this is characterized.

• Pregnancy / breastfeeding — no safety data; default contraindication.
• History of seizure disorder — theoretical concern (BDNF/TrkB pathway upregulation in parent Semax extrapolated to derivatives).
• Concurrent stimulant use (amphetamines, modafinil, high-dose caffeine) — insomnia / sympathomimetic stack risk.
• Active hypertension — ACTH(4–7) lineage warrants caution; no data either way.
• Active mood disorder requiring evidence-based treatment — not a substitute for SSRIs / approved antidepressants.
• Athletes subject to anti-doping testing — consult your governing body. WADA S2.4 (Corticotrophins, ACTH analogs explicitly named) is plausibly applicable; S0 catch-all also applies.

This area has the highest-confusion risk in the gray-market peptide world. Four similar names sit on top of four different molecules:

Name	Sequence	What it is
Semax (parent)	Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP)	Russian-registered drug. Substantial primary literature. The actual measured-pharmacology molecule.
N-Acetyl Semax (this guide)	Ac-MEHFPGP	N-terminal acetylation. Zero published pharmacology on the molecule. One direct chemistry paper (Magrì 2016) shows altered metal binding.
N-Acetyl Semax Amidate (NASA) (this guide)	Ac-MEHFPGP-NH2	N-terminal acetylation plus C-terminal amidation. Zero published pharmacology.
Adamax	Ac-MEHFPGP-AG-NH2	N-Acetyl Semax + adamantyl-AG cap from P21. Different molecule. Zero PubMed papers on Adamax. See the Adamax guide for the full lineage.

Other adjacencies:

• N-Acetyl Selank — same N-acetyl modification on a different parent (Selank = TKPRPGP, tuftsin analog). Same modification logic, different parent peptide, different mechanism.
• Selank (parent) — sister Russian Academy peptide; GABAergic anxiolytic; not a parent of N-Acetyl Semax.
• Cerebrolysin — porcine brain extract, multi-component; different family entirely.
• P21 / P021 — the source of the adamantyl C-cap that was added to make Adamax. Iqbal-lab Alzheimer’s preclinical candidate; no human trial.

Vendor identity confidence:

Research-chem vendors selling "N-Acetyl Semax" may be supplying Ac-MEHFPGP, Ac-MEHFPGP-NH₂ (the amidate), parent Semax mislabeled, or other vendor-specific variants. There is no industry-standard verification — no monograph, no reference standard. Buyer-beware framing applies.