Heptapeptide Nootropic — ACTH(4-10) Analog
Semax is a synthetic heptapeptide analog of adrenocorticotropic hormone (ACTH) fragment 4-10, developed at the Institute of Molecular Genetics of the Russian Academy of Sciences by Nikolai Myasoedov and Isaak Ashmarin in the 1980s. It was approved for medical use in Russia in 2001 as a nootropic and neuroprotectant, where it has been used clinically for over two decades for cognitive enhancement, stroke recovery, and optic nerve disorders — an unusual regulatory status that provides a clinical evidence base unavailable for most research peptides. The peptide consists of the ACTH(4-10) sequence (Met-Glu-His-Phe-Pro-Gly-Pro) with an additional Pro-Gly-Pro tripeptide extension at the C-terminus that confers resistance to enzymatic degradation. Notably, Semax lacks the steroidogenic activity of full-length ACTH — it does not stimulate cortisol production despite being derived from the ACTH sequence. This dissociation of nootropic from hormonal activity was a deliberate design objective. Semax's primary mechanisms involve upregulation of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) expression, enhancement of dopaminergic and serotonergic neurotransmission, and modulation of gene expression in over 24 functional gene groups related to the immune system, vascular system, and neurotransmitter signaling. Its intranasal administration route provides rapid CNS delivery, bypassing the blood-brain barrier via the olfactory epithelium.
Directly increases brain-derived neurotrophic factor and nerve growth factor expression — key mediators of neuroplasticity and neuronal survival.
Activates dopaminergic and serotonergic neurotransmission, improving motivation, focus, and cognitive processing speed.
Demonstrated neuroprotection in stroke, traumatic brain injury, and neurotoxicity models through anti-oxidant and anti-apoptotic mechanisms.
Approved in Russia since 2001 with over two decades of clinical use data — unusual for a research peptide.
Delivered intranasally for rapid CNS access via olfactory epithelium — no injection required.
Despite ACTH origin, Semax lacks steroidogenic activity — no cortisol elevation or adrenal effects at any dose studied.
Modulates expression of 24+ functional gene groups including immune, vascular, and neurotransmitter pathways.
Semax's nootropic and neuroprotective effects arise from multiple convergent mechanisms. The primary pathway involves melanocortin receptor (MC3R, MC4R, MC5R) activation in the central nervous system, though Semax interacts with these receptors differently from classical melanocortin agonists like α-MSH or PT-141. This atypical binding profile may explain why Semax produces cognitive rather than appetitive or sexual effects. The most well-characterized mechanism is upregulation of BDNF expression. Semax increases BDNF mRNA and protein levels in the hippocampus, cortex, and basal forebrain — regions critical for memory consolidation, learning, and executive function. BDNF activates TrkB receptors, triggering PI3K/Akt and MAPK/ERK signaling cascades that promote long-term potentiation (LTP), dendritic branching, and synaptic strengthening. Simultaneously, Semax upregulates NGF expression, supporting cholinergic neuron survival and function. Semax also modulates monoaminergic neurotransmission. It enhances dopaminergic signaling through increased dopamine turnover in the striatum and prefrontal cortex, and serotonergic signaling through 5-HT system activation. These monoaminergic effects contribute to improvements in attention, motivation, and emotional regulation. In neuroprotection, Semax activates anti-apoptotic Bcl-2 family proteins while inhibiting pro-apoptotic caspase cascades. It also reduces oxidative stress through upregulation of antioxidant enzymes and suppresses neuroinflammation through modulation of microglial activation. Gene expression profiling has revealed that Semax modulates over 24 functional gene groups, including those controlling immune response, angiogenesis, and blood-brain barrier integrity — suggesting mechanisms of action that extend well beyond classical nootropic pathways.
BDNF-mediated improvements in memory consolidation, learning capacity, and executive function in healthy and impaired models.
Approved (Russia)Neuroprotection and recovery acceleration in ischemic stroke models — approved indication in Russia since 2001.
Approved (Russia)Treatment of optic nerve atrophy and glaucoma-related optic neuropathy — approved indication in Russia.
Approved (Russia)BDNF/NGF upregulation and anti-apoptotic signaling for neuroprotection following TBI in rodent models.
PreclinicalDopaminergic enhancement studies on attention, processing speed, and working memory capacity.
ActiveGene expression profiling shows modulation of 24+ immune-related gene groups — studying peptidergic immune-nervous system crosstalk.
Preclinical| Period | Dose | Frequency | Notes |
|---|---|---|---|
| 1–2 | 300 mcg | 1–2× daily (intranasal) | Standard starting dose — 1–2 drops per nostril (100–200 mcg/drop) |
| 3–4 | 600 mcg | 1–2× daily (intranasal) | Standard therapeutic dose range in Russian clinical use |
| 5+ | 300–600 mcg | 1–2× daily (intranasal) | Maintenance — typical protocols run 10–20 days with 10-day breaks |
Semax is administered intranasally, typically as a nasal spray or drops. The intranasal route provides rapid CNS delivery via the olfactory epithelium, bypassing the blood-brain barrier and first-pass hepatic metabolism. Standard dosing is 1–2 drops per nostril (100–200 mcg per drop) 1–2 times daily. The nasal mucosa provides efficient peptide absorption directly into the CNS compartment.
No. Despite being derived from the ACTH(4-10) fragment, Semax completely lacks steroidogenic activity. Full-length ACTH activates MC2R on adrenal cortex cells to stimulate cortisol production; the ACTH(4-10) fragment used in Semax does not bind MC2R. No cortisol elevation has been observed at any dose studied. This dissociation of nootropic from hormonal effects was a deliberate design goal.
NA-Semax (N-Acetyl Semax) is an acetylated derivative with a modified amino acid (acetyl group on the N-terminal methionine and an amide on the C-terminal proline). NA-Semax is reported to have increased potency and longer duration of action compared to standard Semax, though fewer published studies exist for the modified form. NA-Semax Amidate adds further modifications claimed to enhance BDNF upregulation.
Russian clinical protocols typically recommend 10–20 day treatment courses followed by a 10-day break before repeating. This cycling approach is believed to maintain receptor sensitivity and prevent downregulation of melanocortin and neurotrophic signaling pathways. Some research protocols use continuous administration for 30 days, though the cyclical approach is more traditional.
Reconstitute lyophilized Semax with normal saline (0.9% NaCl) for intranasal delivery — NOT bacteriostatic water, as benzyl alcohol can cause nasal irritation. A typical concentration is 1–3 mg/mL. Store reconstituted solution at 2–8°C and use within 14 days. The saline vehicle provides comfortable nasal administration without mucosal irritation.
While subcutaneous injection is possible and has been used in some research contexts, intranasal administration is the standard and preferred route for Semax. The intranasal route provides direct CNS access via the olfactory epithelium, achieving higher brain concentrations per dose than systemic injection, which must cross the blood-brain barrier. The ~813 Da molecular weight of Semax is well within the range for efficient nasal absorption.
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