Comparing Semax and Selank: A Detailed Look at Two Synthetic Peptides

In this blog, we will take a close look at Semax and Selank, two synthetic peptides with nootropic properties. We will compare structures, mechanisms of action, and therapeutic uses, highlighting their unique roles in neurology and psychiatry.
Frederika Malichová

Frederika Malichová

Neuroscientist at the University Of Cambridge.



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Semax vs Selank

Both Semax and Selank are synthetic peptides. Semax is a synthetic analog for ACTH and Selank is a synthetic derivative of tuftin. In addition to the effect on cognition, Semax is known mostly for its neurotropic properties and Selank is involved in the modulation of the immune system and anxiety.

Comparing Semax and Selank

Both Semac and Selank are synthetic peptides with nootropic properties (increasing cognitive functions). However, they differ in their effects and uses. Semax is primarily used for its cognitive-enhancing effects, while Selank is known for its anti-anxiety effects. Despite their differences, both peptides are used in neurology and psychiatry for their neuroprotective properties.

What is Semax?

Semax is a synthetic peptide. It consists of seven amino acids and is a synthetic analogue of a fragment of the adrenocorticotropic hormone (ACTH). This means that structurally it is similar to the ACTH fragment, however, it has some modifications [1, 2].

Semax is believed to have neuroprotective properties, protecting the nerve cells from damage or degeneration [1, 2]. In addition, it also affects learning and memory formation. This has been determined in studies using both rodents and humans [1, 2].

Moreover, Semax has a variety of other potential benefits. For instance, it can increase resistance to hypoxia (a condition in which the body or a specific region of the body does not have a sufficient amount of oxygen supply), it can improve brain circulation and can help stimulate the synthesis of brain-derived neurotrophic factor (which is a protein that supports the survival of existing neurons and formation of new neurons and synapses) [1, 2]. Supporting this, Semax has been found to affect the expression of the VEGF gene family and their receptors, suggesting its role in neuroprotection after ischemic stroke [3].

Usually, Semax is administered intranasally, which means that it is taken through the nose. Intranasal administration allows Semax to bypass the digestive system and enter the bloodstream directly [2].

What is Selank?

Selank is a synthetic derivative of a peptide called tuftsin.

Selank has anxiolytic (helps with anxiety) and psychostimulant effects and has completed the third phase of clinical testing as a selective anxiolytic [3]. According to these results, it shows a potential in treating anxiety disorders [3].

Selank is believed to have a role in modulating neurotransmission [4] as it increased the density of G-(3)HMK-801 binding sites by 23% with no effect on GABA receptors (a set of receptors in the nervous system which respond to neurotransmitters). In addition to this, Selank also significantly changes the expression of genes involved in neurotransmission, including the major subunit of the GABA receptor, transporters, ion channels, dopamine, and serotonin receptors [5].

Additionally, Selank is known for immunomodulatory effects. The mechanism behind having these effects is that it alters the expression of genes for chemokines, cytokines and their receptors in the spleen which are important players in the immune system. It has the ability to alter the expression of these genes after a single dose [6]. This also suggests its possible role in influencing inflammation and regulation of inflammatory processes in the body [5].

In addition to its involvement in the immune system, Selank has been found to have antiviral properties, particularly against the influenza virus strain A/Aichi 2/68 (H3N2) [7].

In terms of influencing cognitive function, Selank improves sensory attention levels and helps facilitate learning processes and normalises investigative activity in rats [7].

What are the differences between Selank and Semax?

Both Semax and Selank are synthetic peptides. However, they have different structures, mechanisms of action and different therapeutic uses.

Semax is a synthetic analog for ACTH and Selank is a synthetic derivative of tuftin.

While both Semax and Selank can have effects on cognition such as learning and operational memory, each has its own set of structures as well. In addition to the effect on cognition, Semax is known mostly for its neurotropic properties and Selank is involved in the modulation of the immune system and anxiety.

In terms of use, Selank has been primarily used for its anxiolytic and nootropic effects, while Semax has been used in the treatment of acute ischemic stroke, and optic nerve disease, and to improve memory and attention under extreme conditions of activities [2, 8, 9].

Frederika Malichová

Frederika Malichová

Frederika is a postgraduate researcher at the University of Cambridge, where she investigates new biomarkers for Frontotemporal Dementia and other tauopathies. Her research has been published at prestigious conferences such as the Alzheimer’s Association International Conference 2023. She obtained her BSc in Biomedical Sciences from UCL, where she worked closely with the UK Dementia Research Institute.