PeptidesEvidence ReviewAug 2026

Best Peptides for Brain Function in 2026

For each peptide tied to cognition and mood, this page reports the studies behind it: who was enrolled, what was measured, what the paper found. Every citation was retrieved through NCBI E-utilities on 9 August 2026. Some records are clinical trials in people with a diagnosed condition, and many are in rats, mice or zebrafish. Cognitive decline, stroke, brain injury, anxiety and depression are diagnosed and managed by a doctor, and the population column is where each result is pinned to the people or animals it came from rather than read as advice.

597

Participants pooled in the Cerebrolysin vascular dementia review (PMID 23440834)

185

Patients pooled in the Cerebrolysin traumatic brain injury meta-analysis (PMID 33620612)

Patients in the Selank anxiety comparison (PMID 25176261)

The Studies

One row per study, not one per compound. A compound studied several times gets several rows, because those papers asked different questions in different populations. Read the population and design columns before the result, because a pooled trial in people and a single toxin model in rats do not carry the same weight.

Compound	Population (n)	What was measured	Result	Design	PMID
Semax	187 patients with cerebrovascular insufficiency	Neurological and neuropsychological scales, tolerability, and the incidence of stroke or transient ischaemic attack during the disease course	Reported clinical improvement and fewer strokes and transient ischaemic attacks than before treatment, with few side effects; the abstract gives no control arm or effect size	Open clinical study, intranasal, published in Russian	15792140
Semax	27 adults with motor neuron disease	Needle EMG denervation, the Norris and ALS functional rating scales, and the ALSAQ-40 quality-of-life scale	Quality-of-life total score improved through better emotional state and motivation; the denervation course and the clinical rating scales did not change	Open-label clinical trial, intranasal 1 percent solution, published in Russian	18379501
Semax	Rats given a single intranasal dose, n not stated in the abstract	Hippocampal BDNF protein, TrkB phosphorylation, and conditioned avoidance reactions	BDNF protein rose about 1.4-fold and exon III BDNF mRNA about 3-fold; treated rats showed more conditioned avoidance reactions	Controlled rat study	16996037
Semax and a derivative	APPswe/PS1dE9 transgenic mice modelling Alzheimer disease, n not stated in the abstract	Open field, novel object recognition and Barnes maze behaviour, and cortical and hippocampal amyloid inclusions	Both peptides improved the behavioural tests and reduced the number of amyloid inclusions versus untreated transgenic mice	Controlled transgenic mouse study	41479572
N-acetyl Semax (Ac-Semax)	Cell-free copper(II) and zinc(II) solutions with SH-SY5Y and RBE4 cell lines, no participants	Metal coordination geometry and redox stability of the acetylated peptide	Acetylation shifted the main copper complex from a CuN4 to a CuN3O chromophore and changed its redox behaviour compared with unmodified Semax	In vitro coordination-chemistry study	27586814
Selank	60 patients with phobic-anxiety and somatoform disorders (ICD-10 F40.2 to F45.1)	Anxiolytic effect, nootropic effect and tolerability versus phenazepam	Reported an anxiolytic effect with a mild nootropic effect that persisted about a week after the last dose, on a par with the phenazepam comparator	Comparative clinical study, published in Russian	25176261
Selank	BALB/c and C57BL/6 mice, n not stated in the abstract	Open-field anxiety behaviour with and without the opioid blocker naloxone	Selank 0.25 mg/kg raised locomotor activity in high-anxiety BALB/c mice; naloxone pretreatment attenuated that effect	Controlled mouse study, published in Russian	22550852
Dihexa (PNB-0408)	Larval zebrafish lateral-line hair cells exposed to aminoglycosides, no participants	Hair-cell survival after neomycin or gentamicin across a dose range	About 1 micromolar Dihexa protected hair cells; protection fell when the HGF antagonist 6-AH or Akt, TOR and MEK inhibitors were added	In vivo larval zebrafish model	25674052
Dihexa (PNB-0408)	40 male Wistar rats given 3-nitropropionic acid to model Huntington disease	Body weight, motor function and spatial learning over 5 weeks	Dihexa did not protect the rats from the weight, motor or memory deficits caused by the toxin	Randomised controlled rat study	38489193
Cerebrolysin	597 participants with mild to moderate vascular dementia, pooled from 6 randomised controlled trials	MMSE, ADAS-cog+ and global clinical response rate	MMSE weighted mean difference 1.10 (95 percent CI 0.37 to 1.82) and ADAS-cog+ -4.01 (-5.36 to -2.66) versus control; the review judged the evidence insufficient to recommend routine use	Cochrane meta-analysis of randomised trials	23440834
Cerebrolysin	185 patients with moderate to severe traumatic brain injury (mean Glasgow Coma Score 10.3), pooled from 2 randomised double-blind placebo-controlled trials	A multidimensional ensemble of functional and neuropsychological outcome scales at days 10, 30 and 90, added to usual care	Favoured Cerebrolysin at day 30 and day 90 (standardised mean difference 0.31 and 0.34; p = 0.0156 and p = 0.0146) with comparable safety	Prospective meta-analysis of randomised trials (CAPTAIN series)	33620612
Cerebrolysin	60 patients within 12 hours of acute ischaemic stroke	NIHSS and Barthel Index at days 11 and 21, versus DL-3-n-butylphthalide and placebo	NIHSS and Barthel Index improved more than placebo at days 11 and 21 (P below .05); the butylphthalide arm improved the 21-day NIHSS more than Cerebrolysin	Randomised double-blind placebo-controlled trial	27168844

Semax And NA-Semax

Semax is a heptapeptide built from the ACTH(4 to 7) fragment plus a Pro-Gly-Pro tail, developed and registered in Russia. The human Semax records are Russian-language reports: an open study of 187 patients with cerebrovascular insufficiency that recorded clinical improvement and fewer strokes and transient ischaemic attacks, without a control arm in the abstract (PMID 15792140), and an open-label trial of 27 patients with motor neuron disease where the quality-of-life score improved but the denervation course and clinical scales did not (PMID 18379501). The mechanism rows are in rodents: a single intranasal dose raised hippocampal BDNF protein about 1.4-fold in rats (PMID 16996037), and in APPswe/PS1dE9 mice Semax and a derivative improved maze and recognition behaviour while reducing amyloid inclusions (PMID 41479572). More on the molecule sits on the Semax page.

NA-Semax, the N-acetylated form, appears in a different kind of record. The entry read here is a coordination-chemistry study in cell-free solutions and cell lines, showing that acetylation changes how the peptide binds copper and shifts its redox behaviour versus unmodified Semax (PMID 27586814). That is a chemistry result in a test tube, not an outcome in a person, and the provenance section records the indexed search counts for the acetylated form.

Selank

Selank is a synthetic analog of the immune peptide tuftsin, also developed in Russia. The human record cited here is a Russian-language comparative study of 60 patients with phobic-anxiety and somatoform disorders, in which Selank produced an anxiolytic effect with a mild nootropic effect that persisted about a week after the last dose, on a par with the phenazepam comparator (PMID 25176261). The animal row is a mouse study where Selank raised locomotor activity in high-anxiety BALB/c mice and where blocking the opioid system with naloxone attenuated that effect (PMID 22550852). Anxiety is a clinical condition managed by a doctor, so the anxiety angle beyond peptides sits on the anxiety supplements guide, and the compound background on the Selank page.

Cerebrolysin Trials

Cerebrolysin is a mixture of neuropeptides and free amino acids given by injection, and it has been tested in randomised trials in people with a diagnosed condition. A Cochrane meta-analysis of 6 randomised trials in 597 people with mild to moderate vascular dementia found an MMSE weighted mean difference of 1.10 points (95 percent CI 0.37 to 1.82) and an ADAS-cog+ difference of -4.01, while the review itself concluded the evidence was insufficient to recommend routine use (PMID 23440834). The CAPTAIN meta-analysis pooled 2 randomised double-blind trials in 185 people with moderate to severe traumatic brain injury and favoured Cerebrolysin on a combined outcome at days 30 and 90, with standardised mean differences of 0.31 and 0.34 (PMID 33620612).

A separate randomised double-blind trial gave Cerebrolysin, DL-3-n-butylphthalide or placebo to 60 patients within 12 hours of acute ischaemic stroke and reported NIHSS and Barthel Index gains over placebo at days 11 and 21, with the butylphthalide arm improving the 21-day NIHSS more than Cerebrolysin (PMID 27168844). These are treatment-intent studies in people with a diagnosed condition, and stroke and brain injury are emergencies managed in hospital. How verification of any injectable product works before it reaches a clinic is covered on the COA verification guide.

Dihexa

Dihexa, also labelled PNB-0408, is an angiotensin IV analog studied as a hepatocyte growth factor mimetic. The Dihexa records here are preclinical and point in opposite directions. In larval zebrafish, about 1 micromolar Dihexa protected lateral-line hair cells from aminoglycoside toxicity, and that protection fell when an HGF antagonist or Akt, TOR and MEK inhibitors were added, which the authors read as evidence for the HGF pathway (PMID 25674052). In a randomised rat study, Dihexa given alongside a Huntington-model toxin did not protect the animals from the weight, motor or memory deficits the toxin caused (PMID 38489193). The provenance section records what a randomised-controlled-trial search returned for this compound. Where Dihexa sits among cognition compounds generally is covered on the nootropics guide, and the fatigue side of brain fog on the energy hub.

The Trial Regimens

The regimens those trials administered, each named with its paper:

Semax as a 1 percent intranasal solution, 12 mg daily in two 10-day courses with a 2-week break, in the motor-neuron-disease trial (PMID 18379501). Cerebrolysin 50 mL per day intravenously for 10 days, followed by two further cycles of 10 mL per day for 10 days, added to usual care in the CAPTAIN traumatic brain injury trials (PMID 33620612). Cerebrolysin by 10-day intravenous course in the acute ischaemic stroke trial (PMID 27168844).

Disclaimer: these are trial arms reported for comparison, not recommendations and not a titration schedule. Each was administered under medical supervision inside its study, in patients with a diagnosed condition, and injectable use in particular is a clinical decision made with a doctor.

How These Records Were Found

Each line states a query, an index and a date. A search result describes what a string matched in one database on one day, nothing beyond that, and a compound-name search cannot establish that a study does not exist.

semax in PubMed on 9 August 2026 returned 231 records; semax AND randomized controlled trial[pt] returned 1. Much of the clinical record sits in Russian-language journals such as Zh Nevrol Psikhiatr Im S S Korsakova, so the retrieved human entries PMID 15792140 and PMID 18379501 are Russian-language reports.
The acetylated derivative was searched as "acetyl semax" OR "Ac-Semax" in PubMed on 9 August 2026, which returned 2 records; the one read here, PMID 27586814, is a coordination-chemistry study, and Ac-Semax was also tried against the parent-name results.
selank in PubMed on 9 August 2026 returned 135 records and selank AND anxiety returned 29; the retrieved human entry PMID 25176261 is a Russian-language clinical comparison against phenazepam.
dihexa in PubMed on 9 August 2026 returned 18 records and dihexa AND randomized controlled trial[pt] returned 0; the compound was also tried as its label name PNB-0408, and the entries read here, PMID 25674052 and PMID 38489193, were a zebrafish model and a rat model.
cerebrolysin AND vascular dementia in PubMed on 9 August 2026 returned 34 records and cerebrolysin AND traumatic brain injury returned 76; the entries cited, PMID 23440834, PMID 33620612 and PMID 27168844, were pooled or single randomised trials in people.
A compound name bounds a search, so synonyms and MeSH entry terms were tried where known: Semax as ACTH(4-7)PGP, Selank as an analog of tuftsin, and Dihexa as PNB-0408.

Frequently Asked Questions

What are the best peptides for brain function?+

This page does not rank them. It reports what each cited study enrolled, what it measured and what it found, so a 597-participant vascular-dementia review and a 40-rat toxin model can be told apart. Reading the population and design columns first shows which results came from people and which came from mice, rats or zebrafish, and cognition and mood problems are diagnosed and managed with a doctor rather than chosen from a table.

Why are several rows in this table rats, mice or zebrafish?+

Because a row is a study and its population is whoever the study enrolled. The Semax BDNF work (PMID 16996037) and the Alzheimer-model work (PMID 41479572) were in rodents, and the Dihexa hair-cell work (PMID 25674052) was in zebrafish. Those results describe those animals, and the design column says so. A result in a mouse reads across to a person only through further study.

Why is so much of the Semax and Selank research in Russian?+

Semax and Selank were developed in Russia and are registered there, so a large part of their clinical literature is published in Russian-language journals. The human entries cited here, PMID 15792140 and PMID 18379501 for Semax and PMID 25176261 for Selank, are Russian-language reports, and the provenance section records the search counts behind them.

Does Cerebrolysin help after a stroke or brain injury?+

The cited trials measured specific outcomes in specific patients. A Cochrane review of 6 trials in 597 people with vascular dementia reported an MMSE difference of 1.10 points (PMID 23440834). The CAPTAIN meta-analysis of 185 people with moderate to severe traumatic brain injury favoured Cerebrolysin at days 30 and 90 (PMID 33620612). A trial of 60 people within 12 hours of acute ischaemic stroke found NIHSS and Barthel gains over placebo (PMID 27168844). Each number applies to the condition its trial enrolled, and the vascular-dementia review itself judged the evidence insufficient to recommend routine use.

Is Dihexa shown to improve memory in people?+

The Dihexa studies cited here are in zebrafish hair cells (PMID 25674052) and in rats given a Huntington-model toxin (PMID 38489193), and the rat study reported no protective effect. The provenance section records what a randomised-controlled-trial search returned for the compound and its label name PNB-0408. Take that record, not a compound name, to a clinician.

Can these peptides treat anxiety or depression?+

Anxiety and depression are clinical conditions diagnosed and managed by a doctor, and nothing here is a treatment plan. The Selank clinical entry (PMID 25176261) enrolled people already diagnosed with phobic-anxiety and somatoform disorders and compared the peptide against a prescription anxiolytic under medical supervision. If anxiety or low mood is the question, that is a conversation with a clinician. The energy side of fatigue is covered separately on the energy hub, and non-peptide options sit on the anxiety supplements guide.

What doses did these trials use?+

A few are named in the regimens section with their trial and a disclaimer, for example the intranasal Semax course in the motor-neuron-disease study (PMID 18379501) and the intravenous Cerebrolysin schedule in the CAPTAIN traumatic brain injury trials (PMID 33620612). Those are trial arms reported for comparison, administered under medical supervision, not recommendations and not a titration schedule.

Research And Sources

Every figure above comes from the record its PMID links to, retrieved through NCBI E-utilities on 9 August 2026. The vascular-dementia MMSE and ADAS-cog+ differences come from PMID 23440834, the traumatic brain injury standardised mean differences from PMID 33620612, and the acute ischaemic stroke NIHSS and Barthel results from PMID 27168844. The provenance section records what each search returned, including the randomised-controlled-trial-tag counts, rather than the body claiming anything about what does or does not exist.