| |
|---|
| Compound type | Synthetic heptapeptide |
| Length | 7 amino acids |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro |
| Abbreviated sequence | MEHFPGP |
| Derived from | ACTH fragment 4–7 |
| Primary research areas | Neuroprotection, cognition and cerebral ischaemia |
| Confirmed primary receptor | None |
| Human evidence | Limited clinical studies |
| Approved UK medicine | No |
| Typical research route | Intranasal |
Semax contains the first four amino acids of the ACTH 4–7 sequence followed by a Pro-Gly-Pro tripeptide intended to increase stability.
What is Semax?
Semax is a synthetic peptide containing seven amino acids.
Its sequence is:
Met-Glu-His-Phe-Pro-Gly-Pro
This is commonly abbreviated to:
MEHFPGP
The first four amino acids are derived from positions 4–7 of ACTH:
Met-Glu-His-Phe
A three-amino-acid sequence was then added:
Pro-Gly-Pro
This modification was designed to increase resistance to enzymatic degradation and prolong biological activity.
Semax is therefore commonly described chemically as:
ACTH(4–7)-Pro-Gly-Pro
or:
ACTH(4–7)PGP
It is not full-length ACTH and should not be assumed to produce the same endocrine effects.
What is ACTH?
Adrenocorticotropic hormone is a peptide hormone produced by the anterior pituitary gland.
Its principal endocrine role is stimulating the adrenal cortex to produce hormones including cortisol.
Full-length ACTH contains 39 amino acids.
Different sections of the ACTH molecule may have different biological properties.
Semax was developed from a short N-terminal ACTH fragment rather than the complete hormone.
Researchers were interested in evidence suggesting that some ACTH fragments could influence:
without necessarily producing the full adrenal effects of ACTH.
Does Semax increase cortisol?
Semax is not equivalent to full-length ACTH.
The short ACTH-derived sequence used in Semax was selected partly because it was believed to retain neuroactive properties without strongly stimulating the adrenal cortex.
However, this does not mean that all endocrine interactions have been conclusively excluded in every population or at every exposure level.
There is insufficient large-scale human evidence to describe Semax as having no possible influence on the hypothalamic-pituitary-adrenal system.
It should not be used as a substitute for investigating abnormal cortisol or adrenal function.
How was Semax developed?
Semax was developed by researchers associated with the Institute of Molecular Genetics of the Russian Academy of Sciences.
Its development formed part of broader research into short regulatory peptides derived from naturally occurring hormones.
The aim was to create a compound with potential:
The resulting heptapeptide was investigated in laboratory models of:
Cerebral ischaemia
Hypoxia
Memory impairment
Stress
Neuroinflammation
Optic-nerve injury
Human studies later examined its possible use in neurological and cognitive disorders.
What does neuroprotective mean?
A neuroprotective compound is one that may reduce damage to nerve cells or help preserve neurological function during harmful conditions.
Examples of harmful conditions include:
Oxygen deprivation
Reduced blood flow
Inflammation
Oxidative stress
Excitotoxicity
Traumatic injury
The term does not automatically mean that a substance prevents neurological disease in humans.
Many compounds appear neuroprotective in cell cultures or animal models but fail to produce meaningful benefits in clinical trials.
For Semax, much of the neuroprotective evidence remains preclinical.
Is Semax a nootropic?
Semax is often described as a nootropic because research has investigated possible effects on:
Some animal and human studies have reported cognitive effects following intranasal administration. A scientific review described findings involving memory and attention, while also discussing proposed effects on dopamine and BDNF pathways.
However, the term nootropic is broad and is often used commercially without a consistent scientific definition.
Evidence that a compound influences memory after stroke or experimental brain injury does not establish that it improves intelligence or mental performance in healthy people.
How does Semax work?
Semax does not have one conclusively identified primary receptor.
Its proposed effects appear to involve several overlapping biological systems.
These include:
Researchers have also proposed that metabolites produced when Semax is broken down may contribute to its biological effects.
Because multiple pathways change after administration, it remains difficult to determine which mechanism is primarily responsible for any observed clinical effect.
Semax and BDNF
One of the best-known proposed mechanisms involves brain-derived neurotrophic factor, or BDNF.
BDNF is a protein involved in:
Animal research has reported increased BDNF expression after intranasal Semax administration.
One study found that Semax influenced BDNF levels and signalling in the rat basal forebrain.
Other experimental work has reported changes in BDNF, its receptor TrkB and nerve growth factor pathways.
These results are biologically interesting, but they do not prove that Semax prevents dementia, permanently increases brain function or produces meaningful cognitive enhancement in healthy humans.
What is BDNF?
Brain-derived neurotrophic factor is part of the neurotrophin family.
It contributes to:
Growth of developing neurons
Survival of existing neurons
Synaptic communication
Learning-related plasticity
Memory formation
BDNF concentrations and activity are influenced by many factors, including:
Exercise
Sleep
Stress
Age
Metabolic health
Neurological disease
Increasing one BDNF measurement does not necessarily produce a clinically beneficial outcome.
The location, timing and duration of the change are all important.
Semax and nerve growth factor
Nerve growth factor, or NGF, is another neurotrophin involved in the development and maintenance of nerve cells.
Experimental studies have reported altered NGF-related gene expression after Semax exposure.
Research in rat brain tissue and glial cells suggests Semax may stimulate both BDNF- and NGF-associated pathways.
The significance of these findings for human neurological disease remains uncertain.
Semax and dopamine
Dopamine is a neurotransmitter involved in:
Motivation
Reward
Movement
Attention
Learning
Reinforcement
Preclinical work suggests Semax may modify dopamine release or dopamine-related signalling.
A review of Semax research reported that it could augment psychostimulant-associated dopamine release in experimental models.
This does not establish Semax as a treatment for:
ADHD
Parkinson’s disease
Depression
Low motivation
Substance-use disorders
Dopamine systems are complex, and increasing dopamine activity is not automatically beneficial.
Semax and serotonin
Serotonin contributes to:
Animal research has suggested that Semax may influence serotonergic signalling within the striatum.
One study reported a modulatory effect on serotonin release and metabolism in rat brain tissue.
These findings have not established Semax as an antidepressant or anxiety treatment in humans.
Semax and gene expression
Semax has been studied using transcriptomic and gene-expression methods.
Researchers have reported changes involving genes associated with:
Inflammation
Neurotransmission
Neurotrophic signalling
Vascular function
Immune responses
Cell survival
Oxidative stress
In rodent models of cerebral ischaemia, Semax was associated with changes in gene-expression patterns disturbed by reduced brain blood flow.
These studies help identify possible mechanisms.
However, a change in gene expression does not automatically demonstrate:
Gene-expression findings must be interpreted alongside functional and clinical outcomes.
Semax and cerebral ischaemia
Cerebral ischaemia occurs when blood flow to part of the brain is reduced or blocked.
This deprives neurons of:
Within minutes, a cascade of injury can begin involving:
Semax has been extensively investigated in animal models of cerebral ischaemia.
Reported findings include:
Reduced neurological damage
Improved behavioural recovery
Changes in inflammatory gene expression
Increased neurotrophic signalling
Improved performance in learning tasks
Modern reviews describe substantial preclinical evidence, but also make clear that the mechanisms remain under investigation.
Semax and stroke
Stroke has been one of the main clinical research areas for Semax.
Several older Russian studies examined its addition to conventional treatment following acute ischaemic stroke.
One study involved 30 patients treated during the acute phase of hemispheric ischaemic stroke and compared outcomes with a larger conventionally treated control group.
Another publication described clinical and immunobiochemical research into Semax during acute ischaemic stroke.
These studies reported favourable findings, but they have significant limitations when judged against modern evidence standards.
Potential limitations include:
Small treatment groups
Non-randomised comparisons
Limited blinding
Older standards of stroke treatment
Incomplete reporting
Limited independent international replication
Semax has not become part of standard UK stroke treatment.
Suspected stroke is a medical emergency requiring immediate evidence-based care.
Can Semax reverse a stroke?
No evidence establishes that Semax can reverse an established stroke.
The most effective stroke treatments depend on:
Experimental neuroprotection should never delay emergency treatment.
Semax should not be presented as a substitute for thrombolysis, thrombectomy, antiplatelet therapy, rehabilitation or other established stroke care.
Semax and stroke recovery
Some research suggests Semax may influence neurological recovery after ischaemic injury.
Possible mechanisms include:
Neurotrophin activation
Reduced inflammatory signalling
Support of neuronal survival
Changes in synaptic plasticity
However, neurological recovery depends on many factors:
The available evidence is not strong enough to establish Semax as a routine stroke-rehabilitation medicine internationally.
Semax and hypoxia
Hypoxia means reduced oxygen availability.
Neurons are particularly vulnerable to oxygen deprivation because the brain has high energy demands and limited energy storage.
Laboratory and animal studies suggest Semax may influence cellular responses to hypoxia.
Reported mechanisms include:
Mitochondrial stabilisation
Neurotrophic signalling
Oxidative-stress regulation
Reduced inflammatory activity
These findings remain predominantly preclinical.
Semax and oxidative stress
Oxidative stress occurs when the production of reactive oxygen species exceeds the ability of antioxidant systems to control them.
Excess oxidative stress can damage:
DNA
Proteins
Cell membranes
Mitochondria
It plays a role in many neurological disorders but is not the sole cause of any one disease.
Semax has demonstrated antioxidant- and stress-related effects in some experimental models.
This does not establish it as a proven antioxidant therapy in humans.
Semax and inflammation
Inflammation is an important part of the brain’s response to injury.
After ischaemic stroke, immune signalling can contribute both to:
Animal studies suggest Semax may modify inflammatory gene-expression patterns following cerebral ischaemia.
The aim of neuroprotective treatment is not necessarily to eliminate inflammation completely, because some inflammatory processes support repair.
The clinical significance of Semax’s reported anti-inflammatory effects remains uncertain.
Semax and mitochondria
Mitochondria generate most cellular ATP.
Brain cells rely heavily on mitochondrial energy because neuronal signalling requires substantial and continuous ATP production.
Experimental literature suggests Semax may help stabilise mitochondrial function during certain forms of cellular stress.
It has not been proven to repair all forms of mitochondrial dysfunction or treat inherited mitochondrial disease.
Semax and nitric oxide
Nitric oxide is a signalling molecule involved in:
Blood-vessel relaxation
Cerebral circulation
Immune signalling
Neurotransmission
Oxidative stress
Semax has been reported to influence nitric-oxide-related pathways in experimental research.
Nitric oxide can have both protective and harmful effects depending on:
Concentration
Cellular source
Timing
Disease state
It is therefore inaccurate to describe nitric oxide as universally beneficial or harmful.
Semax and memory
Memory is one of the most widely promoted applications of Semax.
Animal studies have investigated:
Passive-avoidance learning
Food-motivated learning
Spatial memory
Stress-induced memory impairment
Memory after cerebral ischaemia
Several studies have reported improved performance under specific experimental conditions.
A review of ACTH-derived peptides described Semax as facilitating certain learning tasks and reducing memory impairment in animal models.
These findings do not establish that Semax reliably improves everyday memory in healthy humans.
Semax and learning
Learning in animal experiments is often measured through tasks such as:
Maze navigation
Avoidance behaviour
Conditioned responses
Reward-based tasks
These are useful scientific tools but do not directly reproduce:
A positive result in a rodent learning test is a starting point for research, not proof of human cognitive enhancement.
Semax and attention
Some publications report that Semax may influence selective attention.
The available research includes experimental and small human studies, but it does not establish Semax as an approved treatment for attention disorders.
Attention is influenced by:
Sleep
Anxiety
Depression
Medication
Motivation
ADHD
Stress
Physical health
Improved performance on one attention test does not necessarily translate into broad everyday cognitive improvement.
Semax and ADHD
Semax is sometimes promoted online for attention-deficit hyperactivity disorder.
There is insufficient high-quality evidence to establish it as a treatment for ADHD.
Established ADHD treatments have undergone extensive controlled research examining:
Symptom reduction
Functional improvement
Long-term outcomes
Adverse effects
Dosing
Interactions
Semax has not accumulated an equivalent evidence base.
Semax and healthy cognition
A small functional MRI study examined changes in the brain’s default mode network after intranasal Semax in healthy volunteers.
The study included 24 participants, with scans performed before and shortly after Semax or placebo administration.
Another study examined whole-brain functional connectivity after Semax and Selank in 52 healthy participants.
Brain-imaging changes are not equivalent to proven improvements in:
Memory
Intelligence
Productivity
Mental health
Long-term brain health
Imaging findings are exploratory and require replication alongside meaningful cognitive outcomes.
What is the default mode network?
The default mode network is a group of brain regions that show coordinated activity during internally focused mental states.
It is associated with processes such as:
Self-referential thought
Autobiographical memory
Mind wandering
Future planning
Changes in default mode network connectivity occur in many circumstances.
A measurable connectivity change is not automatically beneficial or harmful.
Semax and executive function
Executive function includes:
Planning
Working memory
Inhibition
Flexible thinking
Decision-making
Some functional-connectivity research has examined brain regions associated with executive control after Semax administration.
Evidence remains insufficient to conclude that Semax reliably improves executive function in healthy adults.
Semax and dementia
Semax has been discussed as a potential neuroprotective compound in relation to age-related neurological disease.
However, it has not been proven to prevent or treat:
Alzheimer’s disease
Vascular dementia
Lewy body dementia
Frontotemporal dementia
Laboratory findings involving BDNF, inflammation or oxidative stress are not equivalent to demonstrating slower cognitive decline in patients.
Recent experimental work continues to explore Semax and modified derivatives for Alzheimer’s-related mechanisms, but this remains investigational.
Semax and Parkinson’s disease
Dopamine-related findings have led to interest in possible applications involving Parkinson’s disease.
Parkinson’s disease involves progressive loss of dopamine-producing neurons and multiple non-dopaminergic systems.
There is insufficient clinical evidence to establish Semax as a treatment for Parkinson’s disease.
It should not replace established neurological care.
Semax and traumatic brain injury
Traumatic brain injury may involve:
Semax is sometimes promoted for concussion or traumatic brain injury because of its preclinical neuroprotective profile.
Robust human trials demonstrating improved recovery after traumatic brain injury are lacking.
Concussion symptoms require proper assessment, particularly when accompanied by:
Loss of consciousness
Repeated vomiting
Worsening headache
Confusion
Weakness
Seizure
Unequal pupils
Semax and spinal-cord injury
Recent animal research has examined ACTH-derived peptides in models of spinal-cord injury.
A 2025 experimental study investigated possible anti-inflammatory and neuroprotective effects of Semax in this context.
This remains preclinical research and does not demonstrate that Semax restores spinal-cord function in humans.
Semax and optic-nerve research
Semax has also been investigated in relation to optic-nerve and retinal disorders.
The proposed rationale includes:
Neurotrophic signalling
Vascular effects
Reduced oxidative damage
Neuronal survival
The evidence base is not sufficient to establish Semax as an internationally accepted treatment for optic neuropathy, glaucoma or retinal disease.
Sudden visual loss is a medical emergency and should not be self-treated.
Semax and stress
Semax is derived from an ACTH fragment, and ACTH is closely related to the physiological stress response.
Animal studies suggest Semax and related melanocortin fragments may alter behavioural responses to acute and chronic stress.
Reported findings include reduced stress-associated cognitive impairment in rodents.
These results do not establish Semax as a treatment for chronic stress, anxiety disorders or post-traumatic stress disorder.
Semax and anxiety
Semax is less directly associated with anxiety research than Selank.
Some preclinical findings suggest it may influence stress-related behaviour, but the human evidence is insufficient to classify it as an established anxiolytic.
Selank was developed more specifically around anxiety-related applications, while Semax has been researched more heavily in cognition and neuroprotection.
Neither is an authorised UK anxiety medicine.
Semax and depression
Neurotrophins, dopamine and serotonin are all relevant to depression research.
This has led to speculation that Semax might have antidepressant effects.
However, there is insufficient robust clinical evidence demonstrating that Semax treats major depressive disorder.
Depression is a complex medical condition involving biological, psychological and social factors.
Experimental peptide use should not replace appropriate mental-health treatment.
Semax and motivation
Because dopamine contributes to motivation and reward, Semax is sometimes described as a motivation enhancer.
This claim remains unproven.
Motivation can be reduced by:
Depression
Sleep deprivation
Anxiety
Burnout
Chronic illness
Medication effects
Nutritional deficiencies
ADHD
A compound influencing dopamine in animal experiments does not automatically improve healthy human motivation.
Semax and physical performance
There is no strong evidence establishing Semax as a physical-performance enhancer.
Any proposed effects would likely be indirect and could involve:
Attention
Stress tolerance
Perceived fatigue
Motor learning
These possibilities have not been adequately demonstrated through controlled athletic-performance trials.
How is Semax administered in research?
Semax has commonly been investigated through intranasal administration.
The nasal route may offer several theoretical advantages:
Rapid absorption
Avoidance of gastrointestinal digestion
Access to highly vascular nasal tissue
Possible nose-to-brain transport pathways
However, intranasal delivery does not guarantee that intact Semax reaches the brain in large or predictable amounts.
Absorption may vary according to:
Formulation
Nasal inflammation
Spray technique
Mucus clearance
Enzymatic degradation
Product concentration
Can Semax cross the blood-brain barrier?
The precise human brain exposure following intranasal administration has not been fully characterised.
Possible routes of action include:
Central nervous-system effects do not prove that a large proportion of intact Semax crosses the blood-brain barrier.
Semax metabolites
Semax is broken down by peptidase enzymes into shorter fragments.
The Pro-Gly-Pro sequence and related fragments may have biological activity of their own.
This has led researchers to propose that Semax may act as a parent peptide that produces multiple active metabolites.
The importance of each metabolite in humans remains uncertain.
Semax and Pro-Gly-Pro
Pro-Gly-Pro is the three-amino-acid sequence added to the ACTH-derived portion of Semax.
It was intended partly to improve stability.
Experimental research suggests Pro-Gly-Pro may also influence some of the same gene-expression pathways as Semax.
The complete contribution of the PGP sequence to Semax’s effects remains under investigation.
What is the half-life of Semax?
Comprehensive human pharmacokinetic data remain limited.
A precise universal half-life should therefore be treated cautiously.
Peptides may disappear from blood relatively quickly while producing signalling changes that persist longer.
The duration of a biological response is not necessarily the same as the time the intact peptide remains measurable.
How quickly does Semax work?
There is no universally established onset time.
Small imaging studies have detected brain-connectivity changes within minutes of intranasal administration.
This does not prove that clinically meaningful cognitive effects occur within the same period.
Onset may differ according to:
Outcome measured
Route
Formulation
Individual biology
Health condition
Human clinical evidence
The human Semax literature includes studies involving:
The evidence is more substantial than for some research peptides but far weaker than the evidence supporting internationally approved neurological medicines.
Major limitations include:
Small participant groups
Older studies
Limited randomisation
Limited placebo control
Research concentrated in one region
Incomplete long-term follow-up
Limited independent replication
Differences from modern treatment standards
Positive findings should therefore be viewed as preliminary rather than definitive.
Is Semax approved?
Semax has been described in scientific literature as a peptide medicine developed and used in Russia.
However, it is not an authorised medicine in the United Kingdom.
It has not received approval from the MHRA for treating:
Regulatory recognition in one jurisdiction does not automatically establish approval, legal status or accepted medical use elsewhere.
Semax vs Selank
Semax and Selank are frequently discussed together, but they are different compounds.
| Semax | Selank |
|---|
| Length | 7 amino acids | 7 amino acids |
| Derived from | ACTH fragment | Tuftsin-related fragment |
| Main research focus | Cognition and neuroprotection | Anxiety and stress |
| Sequence | MEHFPGP | TKPRPGP |
| Known receptor | No confirmed single receptor | No confirmed single receptor |
| UK approval | No | No |
Semax has been studied more heavily in:
Cerebral ischaemia
Memory
Attention
Neurotrophic signalling
Selank has been studied more heavily in:
Anxiety
Stress
GABA-related signalling
Enkephalin metabolism
They should not be treated as interchangeable.
Semax vs ACTH
Semax contains only a small ACTH-derived sequence.
Full ACTH:
Semax:
Contains seven amino acids.
Was designed around a short ACTH neuroactive fragment.
Is investigated mainly for central nervous-system effects.
Does not have the established endocrine profile of full ACTH.
Evidence involving ACTH cannot automatically be applied to Semax.
Semax vs cerebrolysin
Cerebrolysin is a mixture of peptides and amino acids derived from porcine brain proteins.
Semax is a single defined synthetic heptapeptide.
Although both are discussed in neuroprotection research, they differ substantially in:
Composition
Manufacturing
Mechanism
Clinical evidence
Regulatory status
Studies involving one cannot be used as proof for the other.
Safety and adverse effects
Published Semax studies generally describe short-term tolerability as acceptable.
However, the total safety database remains limited.
Potential concerns include:
Small trials are unlikely to detect rare adverse effects.
Long-term safety in healthy users has not been established.
Nasal adverse effects
Intranasal products may cause:
Burning
Dryness
Irritation
Sneezing
Congestion
Nosebleeds
Repeated exposure may be affected by preservatives, pH and formulation quality.
A product intended for laboratory research may not have been assessed for repeated use on human nasal tissue.
Psychiatric considerations
Substances that influence dopamine, serotonin or neurotrophic signalling may produce different effects in different individuals.
Particular caution is warranted in people with:
Unexpected changes in mood, sleep, behaviour or perception require medical assessment.
Semax and antidepressants
There is insufficient controlled evidence to establish the safety of combining Semax with:
Potential interactions remain uncertain because Semax may influence serotonergic and dopaminergic systems.
Absence of a documented interaction is not proof of safety.
Semax and stimulant medication
Preclinical evidence suggests Semax may alter psychostimulant-related dopamine release.
This raises theoretical questions about combining it with stimulant medicines.
Controlled human interaction studies are lacking.
Possible concerns could include:
Anxiety
Insomnia
Elevated heart rate
Mood changes
Excessive stimulation
Semax and alcohol
There is insufficient evidence to define the interaction between Semax and alcohol.
Combining experimental neuroactive compounds with alcohol may produce unpredictable effects on:
Judgement
Coordination
Mood
Alertness
Sleep
Pregnancy and breastfeeding
Adequate reproductive and developmental safety data are lacking.
Semax cannot be considered established as safe during:
Pregnancy
Breastfeeding
Fertility treatment
Peptides affecting neurological or hormonal signalling could theoretically influence fetal or infant development.
Children and adolescents
Semax has been discussed in relation to paediatric neurological and attention disorders in some regional literature.
However, large modern safety trials in children and adolescents are lacking.
Developing nervous systems may respond differently from adult brains.
Cancer considerations
Semax has not been established as a carcinogen.
However, its proposed influence on:
creates theoretical questions that require long-term study.
BDNF and other growth-related pathways can have different effects depending on tissue and disease context.
There is insufficient evidence to determine the safety of Semax in people with active cancer.
Product-quality concerns
Commercially available Semax may not be identical to the compound used in published studies.
Important quality factors include:
A stated purity percentage does not establish that a product is sterile, accurately concentrated or suitable for human use.
Analytical testing
