PE-22-28

Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide) is a small synthetic peptide built from angiotensin IV, engineered at Washington State University to be orally active and to cross into the brain. The pitch is bold: it is studied as a procognitive compound that may rebuild synaptic connections, and lab claims of extreme potency made it a darling of the nootropic underground. The reality check: every supporting study is in cells or rodents, there are zero human clinical trials, and a foundational 2012 biochemistry paper describing its target was later retracted.

P21 (also written P021) is a small synthetic peptide reverse-engineered from the most active region of ciliary neurotrophic factor (CNTF), with an adamantane group bolted on to help it survive in the body and reach the brain. It is studied as a neurogenic and neurotrophic compound for Alzheimer's disease and other memory disorders, with the appeal of getting CNTF-like benefits in a small, orally available molecule. The honest status: it looks genuinely promising in mouse models, but the entire evidence base comes from a single research group and there are no human trials.

Selank is a synthetic seven-amino-acid peptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) built from the natural immune peptide tuftsin, with a small chemical tweak to make it last longer in the body. It was developed in Russia as an anti-anxiety and nootropic agent and is approved there for generalized anxiety disorder, but it has no FDA or EMA approval and almost no Western clinical data. The pitch is calm and focus without the sedation, dependence, or withdrawal that come with benzodiazepines.

Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) developed in Russia in the 1980s as an analog of the ACTH(4-10) fragment, with a Pro-Gly-Pro tail added to resist breakdown. It is researched and used as a neuroprotective and nootropic agent, typically intranasally, and keeps the cognitive and neurotrophic effects of the ACTH fragment without the parent hormone's cortisol-raising activity. It is used clinically and registered in Russia (including for ischemic stroke and cognitive disorders) but is not approved by the FDA or EMA, and Western evidence is limited.

Cerebrolysin is not a single peptide but a mixture: a preparation of small peptides and free amino acids made by enzymatically breaking down purified porcine (pig) brain protein, manufactured by EVER Neuro Pharma in Austria. It is given by injection and is approved as a prescription drug in dozens of countries for stroke, traumatic brain injury, and dementia, but it is not FDA-approved in the United States. Despite decades of use abroad, the human evidence remains genuinely contested.

GB-115 is a synthetic dipeptide anxiolytic developed in Russia, chemically the amide of N-phenylhexanoyl-glycyl-L-tryptophan and described as a retro-analogue of cholecystokinin-4. Rather than acting like a benzodiazepine, it blocks cholecystokinin receptors, a different anti-anxiety route. It has been studied in animals and in a small pilot human study, but it is not an approved or widely available medication.