Peptides and Brain Health

Educational Overview

Peptides and Brain Health: What the Research Shows

Published 10/6/2026

Traumatic brain injury (TBI), repeated head impacts such as those linked to chronic traumatic encephalopathy (CTE), and age-related memory and thinking changes are among the hardest problems in medicine. Researchers have been exploring a number of peptides in this area, including Semax, Selank, Cerebrolysin, and Dihexa. This article explains what each one is, what has been studied, and, just as importantly, what has not been shown.

Important

None of the peptides discussed here is FDA-approved to treat, prevent, or diagnose any brain injury, CTE, Alzheimer’s disease, dementia, or other cognitive condition.
Most of the research is laboratory or animal work. Human studies are limited and small.
If you have had a head injury or are noticing changes in memory or thinking, please see a licensed clinician. Seek emergency care for severe symptoms.
Nothing here is medical advice, a recommendation, or a promise of results.

At a Glance

Peptide	What it is	Research so far	U.S. status
Semax	A synthetic peptide related to a fragment of ACTH, developed in Russia	Mostly laboratory and animal work^[2]	Not FDA-approved. Slated for FDA advisory review in 2027
Selank	A synthetic peptide related to the immune peptide tuftsin, developed in Russia	Mostly laboratory and animal work^[1]	Not FDA-approved. Slated for FDA advisory review in 2027
Cerebrolysin	A mixture of peptides derived from pig brain tissue, given by infusion	Small randomized trials in traumatic brain injury and vascular dementia^[4]^[5]	Not FDA-approved
Dihexa	A synthetic peptide derived from angiotensin IV	Preclinical (rodent) studies only^[3]	Not FDA-approved. Slated for FDA advisory review in 2027

Explore the Topic

Open any section below to learn more.

Why brain injury and neurodegeneration are hard research problems
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Traumatic brain injury (TBI), repeated head impacts, and age-related cognitive conditions each involve complex, overlapping biology, including inflammation, disrupted nerve-cell signaling, and loss of connections between neurons. Chronic traumatic encephalopathy (CTE) is currently diagnosed definitively only by examining brain tissue after death.

Because of this complexity, researchers are exploring many different approaches, including peptides. Most of that work is early, and none of the peptides discussed here is FDA-approved to treat, prevent, or diagnose any brain injury or neurodegenerative condition.

Semax
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Semax is a synthetic peptide related to a fragment of adrenocorticotropic hormone (ACTH), developed in Russia. In rat studies, it changed the expression of brain-derived neurotrophic factor (BDNF) and its receptor trkB in the hippocampus, a brain region involved in learning and memory^[2].

That is a laboratory finding about gene and protein expression in rats. It does not show that Semax improves memory, protects the brain, or helps any condition in people. In the sources we reviewed, we did not find large, independently replicated randomized trials in Western populations.

Selank
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Selank is a synthetic peptide related to tuftsin, a fragment of an immune protein, also developed in Russia. In a rat study, Selank and the neurotransmitter GABA changed the expression of many of the same genes in the frontal cortex, with a strong correlation between the two at one hour (r=0.86). The authors suggested this may reflect an allosteric effect on GABA receptors, and noted that the full mechanism needs further study^[1].

As with Semax, this is early mechanistic work in animals. It does not establish an effect on mood, anxiety, cognition, or any condition in people.

Cerebrolysin
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Cerebrolysin is a mixture of low-molecular-weight peptides and amino acids derived from pig brain tissue, given by intravenous infusion. It is the most clinically studied item on this page, and it is not FDA-approved.

Traumatic brain injury: a prospective meta-analysis of two phase IIIb/IV randomized, double-blind, placebo-controlled trials (185 patients with moderate to severe TBI) reported a small-to-medium effect on a combined set of functional and neuropsychological scales at day 30 (p=0.0156) and day 90 (p=0.0146), with comparable safety to placebo^[5]. One of those trials, the 46-patient CAPTAIN I study, narrowly missed significance on its primary analysis, and its authors recommended larger trials.

Vascular dementia: a Cochrane review of six randomized trials (597 participants) found improved cognition and general function with Cerebrolysin, but rated all of the evidence as very low quality and called the supporting evidence base weak. The authors noted the effects may lack clinical meaningfulness. This review covers vascular dementia, not Alzheimer’s disease^[4].

Dihexa
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Dihexa is a synthetic peptide derived from angiotensin IV and chemically modified for stability. In a 2013 study, it showed activity in rat models of induced memory impairment and increased synapse formation in laboratory preparations. The authors proposed it as a candidate for further development^[3].

We are not aware of controlled human trials. Findings in rodents frequently do not translate to people, and Dihexa remains an investigational research compound.

Other peptides in early research
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Other peptides, including BPC-157 and thymosin beta-4, have appeared in early animal research involving nervous-system injury. We did not review that literature for this article, the evidence is preclinical, and neither is approved for any brain-related use. See our BPC-157 vs. TB-500 article for what is and is not known about them.

What the evidence can — and can’t — tell us
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What has been found	What is still unknown
Semax, Selank, and Dihexa have been studied in rodents or cell models^[1]^[2]^[3].	Whether any of those effects occur in people, or lead to a meaningful outcome.
Cerebrolysin has been tested in small randomized trials in TBI and vascular dementia^[4]^[5].	Whether results hold in larger, independent trials. The Cochrane review rated the evidence very low quality^[4].
Brain injury and dementia involve many biological pathways.	Whether any peptide can affect the course of CTE, TBI recovery, or Alzheimer’s disease. No peptide discussed here is approved for those uses.

Regulatory status
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None of the peptides discussed here is FDA-approved. Semax, Selank, and Dihexa are listed in our FDA Peptide Review as slated for FDA advisory committee review in 2027, with no committee recommendation yet. Compounded drugs are made by licensed pharmacies for individual patients and have not been evaluated by the FDA for safety, effectiveness, or quality.

Regulatory decisions can change as the FDA completes its review process. We track developments in the FDA Peptide Review.

Safety Considerations
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Head injury is a medical emergency when severe. Seek immediate care for loss of consciousness, repeated vomiting, worsening headache, confusion, seizures, weakness, or unusual drowsiness after a blow to the head. Do not substitute any peptide for evaluation.
Memory or thinking changes have many possible causes, some treatable. A licensed clinician should evaluate them.
Not FDA-approved: safety and effectiveness for brain-related uses have not been established through FDA review.
Limited human data: for Semax, Selank, and Dihexa, the sources we reviewed are laboratory and animal studies. Long-term safety in people is unknown.
Cerebrolysin is an infused animal-derived product given under medical supervision. The trials cited here reported safety comparable to placebo, but they were small^[4]^[5].
“Research Use Only” and unlicensed sources carry risks of wrong contents, wrong dose, contamination, or no sterility testing.
Pregnancy, breastfeeding, and other medicines: there is no established safety data. Tell your clinician about all medications and supplements you take, especially those affecting the brain or mood.

Our Perspective

This section is editorial. Brain health is a topic where hope runs ahead of evidence, and we think patients deserve a clear picture of both. If you come across any of these peptides from any source, we suggest asking three questions:

What is the evidence, in people? Ask which study supports the claim, how large it was, and whether it was in humans or animals.
What is its regulatory status, and who prepared it?
Has the underlying problem been properly evaluated? Memory changes and post-injury symptoms need a clinical workup first.

Have questions about peptide research?

Talk with our clinical team about your questions, in person or via telemedicine.

Call (561) 214-3323

Referenced Research

In male Wistar rats (n=30), Selank and GABA each changed the mRNA levels of 45 genes in the frontal cortex at one hour, with a strong correlation between the two (r=0.86). At three hours, 22 genes were altered. The authors suggested Selank acts through allosteric modulation of GABA receptors and noted that its full mechanism needs further investigation. This is an animal study.

Volkova A, Shadrina M, Kolomin T, et al. “Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission.” Frontiers in Pharmacology, 2016;7:31. doi:10.3389/fphar.2016.00031.

A rat study reported that Semax, a synthetic analogue of an ACTH fragment, regulated the expression of brain-derived neurotrophic factor (BDNF) and its receptor trkB in the hippocampus. This is an animal study of gene and protein expression.

Dolotov OV, Karpenko EA, Inozemtseva LS, et al. “Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus.” Brain Research, 2006;1117(1):54–60.

Researchers chemically modified an angiotensin IV fragment to improve its stability and ability to cross the gut and blood-brain barriers, producing dihexa. Dihexa showed activity in scopolamine-induced and aged rat models and marked synaptogenic activity in the laboratory. The authors proposed it for further development. This is preclinical work.

McCoy AT, Benoist CC, Wright JW, et al. “Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents.” Journal of Pharmacology and Experimental Therapeutics, 2013;344(1):141–154. doi:10.1124/jpet.112.199497.

A Cochrane review of six randomized trials (597 participants) of intravenous Cerebrolysin in vascular dementia found improved cognition (SMD 0.36; 3 studies, 420 participants) and general function (RR 2.69; 2 studies, 379 participants) with no difference in adverse effects. All findings were rated very low-quality evidence. The authors concluded the supporting evidence is weak and the effects may lack clinical meaningfulness, and called for adequately powered trials.

Cui S, Chen N, Yang M, et al. “Cerebrolysin for vascular dementia.” Cochrane Database of Systematic Reviews, 2019;(11):CD008900.

A prospective meta-analysis combined two phase IIIb/IV randomized, double-blind, placebo-controlled trials of Cerebrolysin as an add-on to standard care in 185 patients with moderate to severe traumatic brain injury. A combined set of functional and neuropsychological outcome scales indicated a small-to-medium effect favoring Cerebrolysin at day 30 (p=0.0156) and day 90 (p=0.0146), with comparable safety profiles between groups.

Vester JC, Buzoianu AD, Florian SI, et al. “Cerebrolysin after moderate to severe traumatic brain injury: prospective meta-analysis of the CAPTAIN trial series.” Neurological Sciences, 2021;42(11):4531–4541. doi:10.1007/s10072-020-04974-6.

Important Disclosures

This article is for educational purposes only and is not medical advice. These statements have not been evaluated by the U.S. Food and Drug Administration. Nothing on this site is intended to diagnose, treat, cure, or prevent any disease.
The peptides discussed are not FDA-approved. Compounded medications are not FDA-approved and have not been evaluated by the FDA for safety, effectiveness, or quality.
The regulatory situation is evolving. The “Our Perspective” section is editorial and does not represent FDA policy.
Treatment decisions are made solely by an independent, licensed clinician after an individualized evaluation, and a doctor-patient relationship is established only after a qualifying consultation. Individual results vary.

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