PE-22-28 vs Pinealon.

PE-22-28 is a synthetic seven-residue peptide corresponding to residues 22 to 28 of spadin, itself a fragment derived from the sortilin propeptide (also called neurotensin receptor-3). It was developed as a shortened, more stable analog of spadin intended to block the TREK-1 potassium channel. It has been studied as a fast-acting antidepressant candidate in rodent models. It is a preclinical research compound with no human data.

Pinealon is a synthetic ultrashort tripeptide with the sequence glutamic acid–aspartic acid–arginine (Glu-Asp-Arg, abbreviated EDR). It belongs to the class of "peptide bioregulators" developed in Russia by Vladimir Khavinson and colleagues at the St. Petersburg Institute of Bioregulation and Gerontology, who designed short peptides intended to mirror regulatory sequences associated with the pineal gland. It is a research chemical, not an approved drug.

PE-22-28 acts by inhibiting the TREK-1 two-pore-domain potassium channel, which is implicated in mood regulation and in resistance to conventional antidepressants. By blocking TREK-1, it is proposed to increase serotonergic neurotransmission and promote hippocampal neurogenesis. Reported potency is high, with a sub-nanomolar IC50 and improved metabolic stability compared with spadin. These effects are characterized in cell and animal systems.

The proposed mechanism, advanced primarily by the Khavinson group, is that short peptides like EDR penetrate cell and nuclear membranes and interact directly with DNA and chromatin to act as epigenetic modulators of gene expression and protein synthesis. In cell and biophysical studies the EDR peptide has been reported to bind deoxyribooligonucleotides/DNA and to enter the nucleus of HeLa cells, and proposed downstream effects include reduced reactive oxygen species, modulation of MAPK/ERK signaling, lowered pro-apoptotic markers (caspase-3, p53), increased antioxidant enzymes (SOD2, GPX1), and stimulation of serotonin-related (tryptophan hydroxylase) expression in cortical neurons. These are mechanistic hypotheses derived largely from in vitro and computational/biophysical work rather than from established receptor pharmacology.

Evidence for PE-22-28 is preclinical only. In the foundational study, shortened spadin analogs including PE-22-28 showed stronger TREK-1 inhibition, longer in-vivo stability and antidepressant-like activity in behavioral tests such as forced swim and novelty-suppressed feeding, along with induction of neurogenesis after a short treatment course (Djillani et al., Frontiers in Pharmacology 2017). A review of TREK-1 blockers situates spadin and its analogs within antidepressant drug discovery (Djillani et al., Pharmacology and Therapeutics 2019). Related work describes the sortilin/NTSR3 origin of spadin and its role in the membrane expression of TREK-1, which supplies the mechanistic rationale for the shortened analogs (Frontiers in Pharmacology, 2018). Separate mouse work using genetic and pharmacological inhibition of TREK-1 reported changes in depression-related behavior and hippocampal neuronal plasticity (CNS Neuroscience and Therapeutics, 2021); that work supports the target as biologically interesting but does not test this peptide. The design of the supporting studies limits the conclusions available. They are rodent experiments run in academic laboratories, largely the group that originated spadin, over short treatment courses. The behavioral readouts are screening assays rather than models of depression: forced swim, tail suspension and novelty-suppressed feeding are sensitive to known antidepressants, which makes them useful filters, but a long list of compounds that performed well in them has failed in human trials. The reports are not blinded multi-centre studies, are not pre-registered, and have not been replicated head to head by an independent group. No completed or registered human clinical trial exists for PE-22-28. There is consequently no Phase 1 safety or tolerability dataset, no human pharmacokinetic profile, no measured central nervous system exposure in people, and no published toxicology package. This is a weaker position than that of compounds it is informally compared with: approved rapid-acting antidepressants such as esketamine were established through randomized, placebo-controlled trials with standard depression rating scales before approval, and even TREK-1 or novel-mechanism candidates that ultimately failed generally reached Phase 1 and produced human exposure and tolerability data. Antidepressant-like signals in rodents do not establish human efficacy or safety.

There are no completed human efficacy trials of pinealon; the evidence base is preclinical (in vitro cell culture, biophysical, and rodent) and clusters heavily around a single research lineage. Reported findings include increased neuronal cell viability and suppression of free radicals in culture (Khavinson, Rejuvenation Research 2011), nuclear penetration and DNA binding of fluorescently labeled short peptides (Fedoreyeva, Biochemistry Moscow 2011), stimulation of serotonin expression in brain cortex cells (Khavinson, Bull Exp Biol Med 2014), and antioxidant/neuroprotective effects in aged-rat hypoxia and carotid-occlusion models (Mendzheritsky, Adv Gerontol 2011, 2014). A 2020 Molecules review by the developers frames EDR as a candidate neuroprotective agent for early Alzheimer's disease, but it is a hypothesis-generating review of the group's own animal and in vitro data, not clinical proof. Independent, non-affiliated replication is essentially absent, so reported effects should be treated as preliminary.

No human safety data exist for PE-22-28; all information comes from short-term rodent studies. There is no published Phase 1 tolerability study, no human pharmacokinetic or elimination data, no immunogenicity assessment, and no repeat-dose or reproductive toxicology package in the public literature. Because TREK-1 is expressed in tissues outside the brain, including cardiovascular, smooth muscle and immune-related tissues, systemic and off-target effects are theoretically possible; the channel also contributes to cellular responses to mechanical and thermal stimuli, so blocking it chronically could have consequences that short rodent behavioral experiments were never designed to detect. Effects on mood-related circuitry are themselves a caution: psychoactive compounds acting on serotonergic signaling and neurogenesis can produce agitation, sleep disruption or worsening mood, and no monitored human exposure exists to characterize any of this. Purity, identity and long-term toxicology of material sold as a research chemical are not controlled. Such products are made outside pharmaceutical good manufacturing practice, carry no verified certificate of analysis for peptide content, impurity profile or endotoxin, and are labeled for laboratory use only. Buyers cannot confirm what the vial holds or whether a reconstituted solution is sterile. The lack of reported adverse events reflects the lack of supervised human use rather than a safety record. With no clinical trials, no pharmacovigilance reporting and no registry, harms occurring in unsupervised use would not be captured. It is not a medicine and is not intended for human use.

Documented safety data in humans are effectively nonexistent; there are no published controlled human safety or pharmacokinetic trials, and no established toxicology dossier in the peer-reviewed literature. Materials sold as "pinealon" are research chemicals not manufactured to pharmaceutical GMP standards, so identity, purity, sterility, and endotoxin content are unverified and vary by vendor. Long-term effects, immunogenicity, and any consequences of the proposed DNA-interacting mechanism are unstudied in humans. Because the compound is unapproved and unregulated for human use, its risk profile is genuinely unknown rather than established as safe.

PE-22-28 is not approved by the FDA or any other regulator and has no approved medical use. It exists only as a preclinical research compound. This summary is educational and includes no dosing guidance.

Pinealon is not approved by the FDA or, to public knowledge, any major regulatory authority; it has no ATC code and no standard pharmaceutical identifiers (DrugBank/KEGG/UNII), and is sold only as a research-use-only chemical. It is not a recognized therapeutic and is not WADA-listed as a named substance, though related growth/peptide categories may fall under broader anti-doping provisions.