ACTH(4-7)PGP · Heptapeptide · Met-Glu-His-Phe-Pro-Gly-Pro
A synthetic heptapeptide derived from ACTH developed in Russia in the 1980s and used clinically for stroke recovery, cognitive impairment and ADHD for decades. Works primarily through BDNF upregulation — increasing the brain's own neuronal growth factor — with additional dopamine and serotonin modulation. One of the most well-characterised cognitive enhancement peptides with genuine clinical history behind it.
Semax is a synthetic analogue of a fragment of ACTH (adrenocorticotropic hormone), specifically the 4-10 fragment modified with a proline-glycine-proline (PGP) sequence that dramatically extends its half-life and CNS activity. It was developed in the 1980s at the Institute of Molecular Genetics of the Russian Academy of Sciences specifically for neurological applications. Unlike many research peptides that remain exclusively preclinical, Semax has been approved and used clinically in Russia and several Eastern European countries for over 30 years — giving it a clinical track record that most nootropic compounds lack.
It is registered in Russia under the brand name Semax and has been used in hospitals for stroke recovery, cognitive rehabilitation and as a prescription treatment for attention deficit conditions. This clinical history provides a level of real-world human safety data that distinguishes it from most compounds in the research peptide space.
Semax's primary mechanism centres on its ability to rapidly and significantly upregulate BDNF (Brain-Derived Neurotrophic Factor) — often described as the brain's most important growth factor. BDNF promotes neuronal survival, growth of new neural connections (neurogenesis), synaptic plasticity and the maintenance of existing neural pathways. Low BDNF is associated with depression, cognitive decline, poor memory consolidation and reduced neurological resilience.
Beyond BDNF, Semax modulates several additional pathways:
Intranasal administration is strongly preferred for cognitive applications. The nasal route provides direct access to the olfactory nerve pathway which connects to the brain without passing through the systemic circulation — meaning the compound reaches CNS tissue more efficiently and at lower doses than SubQ. Onset via intranasal route is typically 15-30 minutes versus 30-60 minutes for SubQ. The blood-brain barrier is effectively bypassed.
SubQ administration works and is used for its systemic neuroprotective effects, but for the acute cognitive and focus enhancement that Semax is most valued for, intranasal is the correct route. Standard intranasal preparation involves reconstituting with bacteriostatic saline and using a nasal spray applicator.
The strongest human evidence for Semax comes from Russian clinical research in stroke recovery. Multiple published trials demonstrated that Semax administration in the acute and subacute phases after ischaemic stroke significantly improved neurological outcomes, reduced brain damage markers and accelerated functional recovery compared to standard care alone. The mechanism — BDNF upregulation and neuroprotection against oxidative stress — is directly relevant to the pathophysiology of stroke-induced neuronal death.
Research in cognitive impairment and memory disorders has shown consistent improvements in attention, memory consolidation and processing speed in both healthy subjects and those with neurological conditions. ADHD studies demonstrated improvements in sustained attention and working memory comparable to standard pharmacological interventions.
In healthy individuals Semax is consistently reported to produce enhanced focus and mental clarity — typically described as cleaner, more directed thinking rather than stimulant-like effects. Unlike traditional stimulants (caffeine, modafinil) that work primarily through catecholamine release or reuptake inhibition, Semax's BDNF-driven mechanism produces a more sustainable cognitive enhancement that builds over time with repeated use rather than producing acute peaks and troughs.
Memory consolidation improvements are particularly well documented — Semax appears to enhance the transfer of information from working memory to long-term memory, making it relevant for learning-intensive periods. Mood stabilisation at lower doses is commonly reported — not euphoric elevation but a more consistent, even baseline.
BDNF declines with age — this decline is associated with cognitive decline, increased depression risk and reduced neuroplasticity. Semax's ability to upregulate BDNF addresses this age-related deficit directly. In the context of a broader longevity stack, Semax complements compounds like SS-31 and MOTS-c (which address mitochondrial energy in all tissues including neurons) with specific neurological growth factor support.
The oxidative stress protection in neuronal tissue is an additional neuroprotective mechanism — neurons are particularly vulnerable to oxidative damage and Semax's antioxidant activity in CNS tissue provides ongoing protection that becomes increasingly relevant with age.
Semax runs cleanly alongside virtually all peptide stacks. It has no known interactions with GH secretagogues (CJC/Ipam), metabolic peptides (Reta, MOTS-c, SS-31) or immune modulators (TA-1). It synergises particularly well with NAD+ — both support neuronal energy metabolism through different pathways, with NAD+ addressing mitochondrial substrate availability and Semax addressing BDNF-driven neuroplasticity and dopaminergic function.
Semax has one of the cleanest safety profiles in the research peptide space, supported by decades of clinical use in Russia. No significant adverse effects have been documented in published literature or clinical use at standard doses. It is non-addictive, does not produce tolerance at standard doses, and has no significant withdrawal effects. As with all BDNF-upregulating compounds, individuals with active cancer should exercise caution as BDNF has growth-promoting properties in some tumour types.