The neuropeptide universe — from Semax and Cortexin to Dihexa, the cognitive enhancement field that doesn't show up in US pharma

That disconnect is not primarily about science. It is about pipelines, economics, and regulatory geography, and understanding it is necessary for making sense of where the cognitive peptide field actually stands today.

Semax is the most widely studied of the Soviet-era cognitive peptides. It is a synthetic heptapeptide — seven amino acids — derived from the ACTH(4-10) fragment, which had long been observed to influence learning and memory in rodents independent of its adrenal effects. Semax was developed at the Institute of Molecular Genetics in Moscow and approved in Russia for use in cognitive impairment, stroke recovery, and certain neurological conditions. Its mechanism involves upregulation of BDNF and other neurotrophins, as well as modulation of dopaminergic and serotonergic systems. It is typically administered intranasally. The intranasal route is important: it allows the peptide to bypass the blood-brain barrier via the olfactory pathway, delivering it directly to CNS tissue without the degradation that would occur with oral administration. Semax has a genuine evidence base in Russian clinical literature — it is not a purely preclinical compound. But that literature is largely inaccessible to US practitioners because it was published in Russian journals, conducted under Soviet and then Russian regulatory frameworks, and never submitted to the FDA as part of a drug approval application.

Selank is a related compound — a synthetic peptide based on tuftsin, an endogenous immunomodulatory tetrapeptide, with additional amino acids added for stability. It is prescribed in Russia primarily for anxiety and stress, but it has documented effects on memory consolidation and cognitive performance in animal models. The mechanism is distinct from Semax: Selank modulates GABA-A receptor activity and serotonergic tone, and it influences the expression of anxiety-relevant gene networks in ways that also appear to improve memory in stress contexts. It too is administered intranasally, and it too has clinical use in Russia without FDA approval or awareness in mainstream US pharmacology.

Cortexin and Cortagen represent a different tradition within the Soviet and post-Soviet pharmacology landscape — the polypeptide bioregulator tradition associated most prominently with Vladimir Khavinson, a Russian gerontologist who spent decades studying short peptide fragments derived from organ tissue. Cortexin is a polypeptide complex derived from the cerebral cortex of cattle, used in Russia and Eastern Europe for traumatic brain injury, cognitive impairment, epilepsy, and other neurological conditions. Cortagen is a tetrapeptide bioregulator thought to influence gene expression through nuclear receptor interactions — a mechanism that the Khavinson tradition has explored extensively. The theoretical basis of Khavinson's work is that short peptides derived from specific tissues act as epigenetic regulators, influencing gene expression in a tissue-specific way and potentially reversing or slowing age-related changes in cellular function. This framework is controversial outside of Russia — the evidence base is largely in Russian-language literature, and the mechanistic claims require independent replication — but the body of research is enormous by the standards of any single research tradition, and it cannot simply be dismissed as pseudoscience. It is, more accurately, science conducted outside the visibility of mainstream Western pharmacology.

Pinealon is a tripeptide bioregulator derived from the pineal gland — Glu-Asp-Arg, or EDP — associated in Khavinson's research with neuroprotective and potentially geroprotective effects. Adamax (sometimes called Adamax-Peptide or related compounds) is another short synthetic peptide from this tradition, with reported nootropic and neuroprotective properties studied primarily in Russian research contexts. These compounds are not FDA-approved, not available through US pharmacies, and essentially absent from the US medical literature. They are, however, legal to purchase as research compounds in most jurisdictions, which is how they have found their way into Western biohacker and longevity communities.

The Western academic research tradition, working largely independently, has produced its own set of cognitive peptide leads. Dihexa emerged from Joseph Harding's laboratory at Washington State University through a program investigating angiotensin IV analogues and their effects on memory. FGL came from Elisabeth Bock's laboratory at the University of Copenhagen, derived systematically from NCAM's FG loop region and its interaction with FGFR1. P21 emerged from work on cell-penetrating peptides and neurogenesis. PE-22-28 is a synthetic analogue of spadin, a peptide fragment of the TREK-1 potassium channel propeptide, which has been studied for antidepressant and cognitive effects. Each of these compounds has a well-documented discovery story in peer-reviewed Western journals. None of them has reached FDA approval. All of them are in a kind of suspended state — too interesting to ignore, too underdeveloped to prescribe.

The reasons for this suspension are structural, not scientific. Developing a compound through FDA approval requires safety pharmacology packages, Phase I dose-escalation studies in humans, Phase II proof-of-concept trials, and Phase III efficacy studies — a process that costs hundreds of millions of dollars and takes a decade or more. For cognitive peptides, which are typically unpatentable (because short amino acid sequences are often not protectable) or whose patents are held by academic institutions without the capital to fund clinical development, the commercial incentive to go through that process is weak. A major pharmaceutical company is unlikely to invest ten years and $500 million in a compound that any competitor could manufacture once the trials prove efficacy. This is the iron logic of pharmaceutical economics, and it explains more of the cognitive peptide landscape than any scientific consideration.

The non-academic commercial gray zone complicates the picture further. PE-22-28 and various other "research peptides" exist in a market where manufacturing quality varies enormously, where there is no FDA oversight of the product being sold, and where users are effectively running uncontrolled trials on themselves without the safety monitoring that even Phase I clinical research requires. This is not an endorsement of that activity. It is an acknowledgment that the gray zone exists, that it is populated by people with legitimate interest in cognitive enhancement who have outrun the formal research timeline, and that the compounds they are using are not simply snake oil. Some of them have real preclinical signals. The absence of human data is a genuine problem, not a technicality.

The conceptual diversity across these research traditions is striking when you map it. Semax and FGL both ultimately drive BDNF and neurotrophin expression, but they arrive there through completely different mechanisms — Semax via ACTH-fragment effects on neurotrophin gene expression, FGL via FGFR1 activation downstream of NCAM. Selank modulates GABA and serotonin in ways that intersect with both anxiety and memory. Dihexa potentiates HGF/c-Met signaling, which is upstream of synaptic structure rather than just neurotrophin expression. The Khavinson bioregulators appear to operate through epigenetic mechanisms — influencing which genes are expressed in aging neurons rather than directly modulating any single receptor or growth factor. P21 promotes hippocampal neurogenesis through BDNF upregulation and potentially anti-amyloid mechanisms. These are not variations on a theme. They are genuinely different approaches to the same underlying problem: the tendency of the aging brain to become less plastic, less connected, and less capable of forming and retaining new information.

What this fragmented landscape teaches about cognitive pharmacology is that the field is not one field. It is multiple traditions — Soviet neuropeptide biology, Western receptor pharmacology, academic CNS drug development, and gray-market biohacking — proceeding largely in parallel, with limited cross-pollination, different methodological standards, different regulatory horizons, and different audiences. The FDA's drug approval pathway was designed for the Western pharmaceutical model — large companies, patented molecules, multi-phase trials, post-market surveillance. It was not designed to evaluate a tradition of clinical practice built up in Russia over fifty years, or a preclinical discovery made in a university lab that no company has funded to move forward, or a community of users who are not waiting for clinical trials that may never happen.

None of this means all of these compounds work in humans. Most of them may not, or may work only in specific contexts, or may have safety profiles that only become apparent with large-scale human exposure. What it means is that the map of cognitive pharmacology is larger, more diverse, and more unevenly explored than the US prescribing landscape suggests. The compounds that show up on an American physician's radar represent one tradition, one regulatory pathway, one set of economic incentives. The compounds that don't show up represent something else — not necessarily better, not necessarily worse, but genuinely different in their origins, their evidence bases, and their accessibility. Understanding the difference is the beginning of thinking clearly about the whole field.