PE-22-28: A Spadin-Derived TREK-1 Channel Inhibitor for Antidepressant Research

This content is provided by Superpower Health for educational and informational purposes only. Superpower Health does not prescribe, sell, or facilitate access to PE-22-28. PE-22-28 is not FDA-approved for human use. This page is not a substitute for medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

The nootropics community has latched onto a category of peptides that target potassium channels in the brain rather than the serotonin transporters that conventional antidepressants address. The most discussed of these is PE-22-28, a synthetic seven-amino-acid fragment engineered from a naturally occurring peptide called spadin. The premise is genuinely interesting: blocking a specific potassium channel appears to activate serotonin neurons and promote hippocampal neurogenesis in rodent models. What is harder to find in the forums is an honest account of what the published research actually includes — and what it does not.

This article covers what PE-22-28 is, how TREK-1 channel biology relates to mood regulation, what the preclinical data shows, and where the evidence ends. No human efficacy or safety data for PE-22-28 exists as of April 2026.

Key Takeaways

• Regulatory Status: Not FDA-approved for human use; no regulatory classification as a bulk drug substance eligible for compounding. Sold only through gray-market research chemical vendors as of April 2026.
• Research Stage: Preclinical only; all evidence is from rodent models. No completed or registered human clinical trials for PE-22-28 or spadin as of April 2026.
• Availability: Not legally marketed for human use; Superpower does not offer this substance.
• What it is: A synthetic 7-residue peptide derived from residues 22–28 of spadin, studied for antidepressant-like effects via selective TREK-1 potassium channel inhibition.
• What the evidence actually shows: Rodent behavioral studies show antidepressant-like effects and enhanced hippocampal neurogenesis; no completed, published human efficacy trials exist as of April 2026.
• Prescribing information: View compound reference data (PubChem CID 165437303)

Where PE-22-28 Comes From and How It Works

Origin and discovery: from sortilin to spadin to PE-22-28

PE-22-28 traces its lineage to a 2010 paper in PLoS Biology by Mazella, Pétrault, Lucas, and colleagues that identified a peptide they named spadin. Spadin is a 17-residue fragment cleaved from the propeptide of sortilin, a sorting receptor encoded by the SORT1 gene, during its processing in the Golgi apparatus. The key finding was that this naturally occurring fragment selectively blocks the TREK-1 potassium channel and produced fast-onset antidepressant-like effects in mouse behavioral paradigms, including the forced swim test, novelty-suppressed feeding assay, and learned helplessness model. Spadin's discovery established a new research target: TREK-1, a two-pore domain (K2P) background potassium channel first functionally characterized in the brain by Heurteaux and colleagues in 2004 in EMBO Journal, as a plausible pharmacological lever for mood regulation. A 2012 paper in Neuropharmacology by Moha ou Maati, Veyssière, Labbal, and colleagues demonstrated that spadin lacks the epileptogenic and cardiac side effects observed with broader TREK-1 modulators, reinforcing the rationale for selectivity.

The limitation of spadin itself was practical: it has a short plasma half-life of approximately seven hours, which motivated the search for more stable analogs. A 2014 paper in Psychopharmacology by Veyssiere, Moha ou Maati, Mazella, and colleagues showed that retro-inverso analogs of spadin produced stronger antidepressant effects and enhanced hippocampal neurogenesis — the first step of the optimization campaign that led to PE-22-28. Djillani, Pietri, Moreno, Heurteaux, Mazella, and Borsotto described the final pathway in a 2017 paper in Frontiers in Pharmacology. The authors synthesized a library of shortened spadin fragments and tested them for TREK-1 binding affinity, in vivo plasma stability, and behavioral effects. PE-22-28, spanning residues 22 through 28 of the original spadin sequence, emerged as the lead candidate, with an IC50 of approximately 0.12 nM against TREK-1 (a roughly 300-fold improvement in potency over spadin) and substantially extended plasma stability compared to the parent peptide. A subsequent 2015 review in the British Journal of Pharmacology by Borsotto, Veyssiere, Moha ou Maati, and colleagues situated TREK-1 (and the related TASK-3 channel) within the broader landscape of two-pore domain K+ channel drug targets for depression. The parent protein sortilin itself continues to be explored as a regulator of TREK-1 membrane trafficking, as covered in a 2019 review in Frontiers in Pharmacology by Mazella, Borsotto, and Heurteaux.

Proposed mechanisms: TREK-1, serotonin, and hippocampal neurogenesis

TREK-1 (KCNK2) is a background potassium channel that maintains a resting hyperpolarizing current in neurons. When TREK-1 is open, it makes neurons less excitable by allowing potassium to flow out of the cell. Blocking it has the opposite effect: neurons become more responsive to depolarizing inputs. In the context of depression research, the relevant population appears to be serotonergic neurons in the dorsal raphe nucleus. A 2016 study in Brain Structure and Function (online 2014) by Moha ou Maati, Bourcier-Lucas, Veyssiere, and colleagues demonstrated that spadin increases the firing rate of 5-HT neurons in the dorsal raphe through a mechanism involving prefrontal cortex 5-HT4 receptors and mGluR2 metabotropic glutamate receptors. PE-22-28 is assumed to share this mechanism, though direct neurophysiology data for the shorter analog specifically is limited. A more recent 2020 paper in Frontiers in Pharmacology by Ma and Lewis refined the mechanism further, showing that spadin selectively antagonizes arachidonic acid activation of TREK-1 — a clue to why the channel block is pharmacologically selective.

A second proposed mechanism involves BDNF (brain-derived neurotrophic factor) and synaptogenesis. A 2015 study in the British Journal of Pharmacology by Devader, Khayachi, Veyssière, and colleagues showed that spadin stimulates synaptogenesis and BDNF expression in hippocampal neurons. The earlier retro-inverso spadin study by Veyssière and colleagues also found enhanced hippocampal neurogenesis in the dentate gyrus. Neurogenesis in this region is consistently associated with antidepressant response across multiple drug classes, though causal relationships remain a subject of active debate. A 2024 paper in Experimental Neurology by Francis-Oliveira, Higa, Viana, and colleagues extended this body of work, showing that TREK-1 inhibition promotes synaptic plasticity in the prelimbic cortex. Separately, a 2018 paper in Frontiers in Pharmacology by Moreno, Devader, Pietri, and colleagues showed that sortilin-deficient mice display altered TREK-1 function and decreased depressive-like behavior, tying the upstream biology together.

The genetic foundation for TREK-1 as a valid target was established even earlier: a 2006 paper in Nature Neuroscience by Heurteaux, Lucas, Guy, and colleagues demonstrated that TREK-1 knockout mice display a depression-resistant behavioral phenotype across multiple paradigms, including the forced swim test, tail suspension test, and learned helplessness. Independent research has replicated and extended this finding. A 2021 paper in CNS Neuroscience & Therapeutics by Wu, Sun, Gong, and colleagues confirmed that both genetic and pharmacological TREK-1 inhibition altered depression-related behaviors and hippocampal plasticity in mice. A 2019 paper in the International Journal of Molecular Sciences by Kim, Jung, Kim, and colleagues found that TREK-1 knockdown in hippocampal neurons attenuated lipopolysaccharide-induced depressive-like behavior. A 2022 paper in ACS Chemical Neuroscience by Xu, Ding, Qi, and colleagues demonstrated that TREK-1 blockade improved neurogenesis deficits in the dentate gyrus of rats with depressive-like behavior. A 2015 paper in CNS Neuroscience & Therapeutics by Lin, Zhang, Ye, and colleagues further linked TREK-1 activity to the antidepressant effects of escitalopram in a rat model of post-stroke depression, connecting the channel's biology to an established therapeutic mechanism. Independent replication outside the Borsotto laboratory includes a 2015 paper in European Neuropsychopharmacology by Ye, Li, Zhang, and colleagues, which showed that TREK-1 channel blockade synergizes with 5-HT1A receptor signaling through CREB-BDNF. Developmental and sex-dependent contributions have also been examined: a 2021 paper in Behavioural Brain Research by Francis-Oliveira, Shieh, Vilar Higa, and colleagues reported that maternal separation induces sex-dependent changes in TREK-1 and 5-HT1A expression.

What the animal research shows, and what it cannot confirm

The primary PE-22-28 behavioral data comes from the 2017 Frontiers in Pharmacology paper by Djillani, Pietri, Moreno, and colleagues. In C57BL/6J mice, PE-22-28 was administered by intraperitoneal injection at 3.2–4.0 µg/kg (roughly 25-fold lower than the 100 µg/kg dose required for spadin) or by oral gavage at 1.0 mg/kg. Across both acute (single-dose) and subchronic (four-day, once-daily) protocols, PE-22-28 significantly reduced immobility time in the forced swim test (reported at p < 0.05 to p < 0.001 depending on the analog and route) and shortened latency to feed in the novelty-suppressed feeding assay — standard rodent behavioral proxies for antidepressant-like activity. Duration of pharmacodynamic action was reported as up to ~23 hours, compared with ~7 hours for spadin. Specific per-group n values and absolute effect sizes for the behavioral endpoints are not stated in the abstract, a limitation for cross-study comparison. The comparison compound in several of these experiments was fluoxetine (an approved SSRI), included for assay calibration rather than as a clinical equivalence claim. Neuroprotection beyond depression models has also been explored: a 2019 paper in Neuropharmacology by Pietri, Djillani, Mazella, and colleagues described protective effects of sortilin-derived peptides on stroke recovery and post-stroke depression. Non-peptide TREK-1 inhibitors such as Lig4-4 have shown comparable neuroprotective effects in rodent middle cerebral artery occlusion models, as described in a 2018 paper in Neuroscience Letters by Wang, Liu, Xiao, and colleagues, offering a useful comparator to the peptide approach.

An important counterpoint in the literature comes from studies examining TREK-1 in vascular and neuroinflammatory contexts. A 2019 paper in the Journal of Neuroinflammation by Fang, Tian, Huang, and colleagues found that TREK-1 deficiency worsened blood-brain barrier damage and neuroinflammation after intracerebral hemorrhage in mice, and a 2022 paper in Molecular Neurobiology by Zheng, Yang, Zhu, and colleagues showed that TREK-1 promotes blood-brain barrier breakdown and neuronal death after focal cerebral ischemia. These findings are a caution against oversimplified narratives: TREK-1's role in the brain is region-specific and context-dependent, and chronic blockade could plausibly carry risks in certain neurovascular settings that rodent depression models would not detect. No rodent toxicology data specific to PE-22-28 is publicly available in peer-reviewed form. The standard limitations of preclinical depression research apply: forced swim and tail suspension tests measure behavioral despair in rodents as proxies for antidepressant activity, but these assays have a high false-positive rate and a poor historical record of predicting human clinical outcomes. Rodent neurophysiology, plasma pharmacokinetics, and blood-brain barrier properties differ substantially from those in humans.

What the Human Evidence Looks Like

How many human studies exist

As of April 2026, a PubMed search for "PE-22-28 human" returns zero results. A search for "spadin human" returns no completed, peer-reviewed efficacy trials. A 2019 comprehensive review in Pharmacology & Therapeutics by Djillani, Mazella, Heurteaux, and Borsotto, covering the full TREK-1 blocker program including PE-22-28, explicitly acknowledges that no human pharmacokinetic, safety, or efficacy data existed at time of publication, and identifies blood-brain barrier penetration in humans as an unresolved question. That gap has not been closed in the five years since. No registered clinical trials for PE-22-28, spadin, or any direct spadin analog appear on ClinicalTrials.gov as of April 2026.

What that absence means for online claims

PE-22-28 is described on vendor websites and in nootropics forums with language suggesting antidepressant activity in humans. That characterization is not supported by the published evidence. Behavioral effects in rodents in standardized despair-based paradigms are mechanistically plausible starting points for drug development — they are not evidence of human efficacy. The translation gap between rodent behavioral pharmacology and human antidepressant response is well documented: the majority of compounds that show robust preclinical antidepressant-like activity do not demonstrate superiority over placebo in human trials. PE-22-28 has not undergone any testing that would establish its pharmacokinetic profile in humans, its ability to cross the blood-brain barrier at relevant concentrations after systemic administration, its safety, or its tolerability. The 2019 Pharmacology & Therapeutics review by Djillani and colleagues notes that bioavailability and translational feasibility remain unresolved for all spadin-derived analogs.

Regulatory and Legal Status

FDA classification

As of April 2026, PE-22-28 is not approved by the FDA for any human indication. It does not appear on any FDA bulk drug substance list, Category 1 or Category 2, that would make it eligible for use in compounded medications under Section 503A or 503B. It is not on the USP monograph list. There is no active Investigational New Drug (IND) application or NDA for PE-22-28 or any spadin analog on the public FDA record. The compound exists entirely outside the regulated pharmaceutical supply chain for human use.

What this means practically

Products labeled as PE-22-28 sold through online research chemical vendors are not regulated by the FDA. There is no manufacturing oversight, no requirement for identity testing, no specification for purity, and no validated dose-response relationship established for humans. Independent testing of gray-market peptide products has documented contamination, incorrect concentrations, and misidentified compounds in a significant fraction of commercially available samples. There is no legal pathway to obtain pharmaceutical-grade PE-22-28 for human use in the United States. Any human use of substances sourced from unregulated vendors occurs entirely outside the safety infrastructure that clinical trials and pharmaceutical manufacturing are designed to provide.

Safety: What Is and Is Not Known

Absence of clinical safety data

No Phase 1 safety study for PE-22-28 has been conducted or published. This means the human side effect profile is completely unknown. Standard unknowns for any compound at this stage include immunogenicity, off-target receptor binding at higher concentrations, metabolite safety, effects in medically complex populations, and interactions with existing medications. The rodent studies do not report toxicology findings in detail, and even if they did, rodent safety data has limited predictive value for human tolerability.

Mechanistic risk signals from TREK-1 biology

The neurovascular counterweight evidence is worth stating plainly. TREK-1 activity in the brain is not uniform: it has different functional roles in neurons, astrocytes, and vascular endothelial cells, and its effects depend on the regional and cellular context. The 2019 paper by Fang and colleagues in Journal of Neuroinflammation and the 2022 paper by Zheng and colleagues in Molecular Neurobiology both demonstrate that TREK-1 deficiency in mouse models of stroke and intracerebral hemorrhage worsens outcomes — suggesting that chronic, broad TREK-1 blockade could plausibly be harmful in individuals with compromised cerebrovascular status, even if it produces behavioral benefit in healthy rodents. This is a theoretical risk, not a documented clinical adverse event, but it illustrates why preclinical data in controlled rodent depression models is not sufficient to characterize the full safety profile of a TREK-1 inhibitor.

Risks from unregulated sources

Research chemical vendors are not subject to current Good Manufacturing Practice (cGMP) requirements. Peptide purity and identity vary substantially across suppliers, and dosing consistency is not guaranteed. Injection of unverified compounds sourced outside the pharmaceutical supply chain carries risks independent of the compound's specific pharmacology, including sterility failures, endotoxin contamination, and incorrect peptide sequences. These are not theoretical risks in the gray-market peptide market.

Who Should Not Use PE-22-28

Because no human safety data exists, any use of PE-22-28 by humans carries unknown risk. Based on the compound's proposed mechanisms, the following groups face elevated theoretical risk:

• Individuals with a history of stroke, intracerebral hemorrhage, or cerebrovascular disease — TREK-1's role in maintaining blood-brain barrier integrity in ischemic contexts suggests that chronic blockade could worsen neurovascular outcomes in vulnerable individuals.
• Individuals currently taking antidepressant medications, including SSRIs, SNRIs, MAOIs, or other serotonergic compounds — the proposed mechanism of PE-22-28 involves increasing serotonergic neuron firing; pharmacodynamic interactions with drugs targeting the same system have not been characterized.
• Pregnant or breastfeeding individuals — no safety data exists for these populations.
• Competitive athletes — PE-22-28 is a non-approved substance and falls under the S0 category of the 2026 WADA Prohibited List, which prohibits all pharmacological substances not approved by any regulatory authority and not covered by a more specific category.
• Individuals with active psychiatric diagnoses who are under the care of a provider — self-administration of an uncharacterized research compound represents a significant risk in this population and could interfere with established clinical management.

Which Biomarkers Are Relevant if You Are Exploring Peptide Science?

Depression and mood dysregulation are rarely attributable to a single mechanism. Several biomarkers that are measurable through standard bloodwork can reveal biological contributors to low mood, poor energy, and cognitive symptoms, providing an objective baseline before exploring any intervention:

• Thyroid-stimulating hormone (TSH): Thyroid dysfunction is a common and reversible cause of depressive symptoms. Hypothyroidism produces low mood, fatigue, cognitive slowing, and cold intolerance that are frequently mistaken for primary depression. Measuring TSH is a standard first step in any workup of mood symptoms.
• Vitamin D (25-hydroxyvitamin D): Low vitamin D is consistently associated with increased risk of depression and mood dysregulation. The guide on vitamin D and depression covers the evidence base in detail. Deficiency is extremely common and easily identified through bloodwork.
• High-sensitivity CRP (hs-CRP): Chronic low-grade inflammation is increasingly recognized as a driver of depression, particularly in individuals who do not respond to standard antidepressants. TREK-1 biology intersects with neuroinflammatory pathways: the 2019 study by Kim and colleagues found that TREK-1 knockdown attenuated LPS-induced (inflammatory) depressive-like behavior, suggesting that the channel may be particularly relevant in inflammation-associated mood states. Measuring hs-CRP provides an objective measure of this contributor.
• Cortisol: Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, reflected in abnormal cortisol patterns, is one of the most replicated biological findings in depression. The stress resilience and nervous system balance biomarker guide provides context for interpreting cortisol alongside related markers.
• Complete blood count (CBC) and iron panel: Iron deficiency anemia and B12/folate deficiencies produce depressive and fatigue symptoms through mechanisms entirely distinct from potassium channel biology. Identifying these through standard bloodwork eliminates treatable contributors before considering investigational compounds.
• Comprehensive metabolic panel: Establishes liver and kidney function as a safety baseline relevant to any investigational compound, including peptides whose metabolic clearance in humans is unknown.

The useful biomarkers to test for mood and mental wellbeing guide covers the full landscape of measurable contributors to mood, including neurotransmitter precursor nutrients, hormonal factors, and inflammatory markers.

When to Take This Seriously

If you are experiencing persistent low mood, anhedonia, fatigue, poor sleep, or cognitive symptoms, those experiences are real and worth investigating through established clinical pathways. A primary care physician, psychiatrist, or integrated medicine provider can conduct a thorough evaluation, rule out reversible biological contributors through standard bloodwork, and discuss evidence-based options, which include FDA-approved medications with decades of safety data, structured psychotherapy with strong efficacy evidence, and lifestyle interventions with robust research support. The gap between what PE-22-28 shows in rodent models and what any patient would actually need to know before using it, including human pharmacokinetics, effective dose range, tolerability, and interaction profile, is wide and currently unbridged by published data. Understanding your own biology through objective measurement is the most productive starting point for any decision about mood support.

That commitment to data before decisions is what drives Superpower's approach to preventive health: the belief that understanding your biology is the foundation for every health decision, whether you are exploring established therapies or following emerging research.

IMPORTANT SAFETY INFORMATION

PE-22-28 is NOT FDA-approved for any human indication. It is not eligible for use in compounded medications under 503A or 503B of the Federal Food, Drug, and Cosmetic Act. No Investigational New Drug application or New Drug Application exists for PE-22-28. Superpower Health does not prescribe, sell, compound, or facilitate access to PE-22-28. This educational content is provided for informational purposes only and does not constitute medical advice.

There are no human clinical safety data for PE-22-28. The compound's side effect profile, tolerability, drug interactions, and pharmacokinetics in humans are entirely unknown. All published evidence is from rodent preclinical models and cannot be used to characterize human risk.

Theoretical risk signals based on proposed mechanism: individuals with cerebrovascular disease or history of stroke may face elevated risk from chronic TREK-1 blockade based on neurovascular evidence from rodent ischemia models; individuals taking serotonergic medications may experience uncharacterized pharmacodynamic interactions; pregnant and breastfeeding individuals should not use this compound.

Products sold as PE-22-28 by research chemical vendors are not subject to FDA oversight, cGMP manufacturing standards, or identity and purity verification requirements. Contamination, dosing inconsistency, and misidentified compounds are documented risks in the gray-market peptide supply chain.

As of the 2026 WADA Prohibited List, PE-22-28 is prohibited in competitive sport under category S0 (non-approved substances).

If you are experiencing depression, persistent low mood, or related symptoms, consult a qualified healthcare provider. FDA-approved treatments with established safety and efficacy data are available.

Additional Questions

What is TREK-1 and why does it matter for depression?

TREK-1 (KCNK2) is a two-pore domain background potassium channel expressed widely in the brain, including in serotonergic neurons of the dorsal raphe nucleus. When open, TREK-1 hyperpolarizes neurons and reduces their firing rate. A foundational 2006 paper in Nature Neuroscience by Heurteaux, Lucas, Guy, and colleagues — available at PubMed — showed that mice with TREK-1 deleted are resistant to behavioral depression across multiple paradigms. This provided genetic validation that TREK-1 inhibition is a plausible antidepressant strategy, which is the mechanistic foundation all subsequent spadin and PE-22-28 research builds on.

How does PE-22-28 relate to ketamine's antidepressant mechanism?

A 2026 paper in Neuropharmacology by Song, Song, Du, and colleagues found that TREK-1 channel blockade mediates the antidepressant-like effects of hydroxynorketamine, a metabolite of ketamine that contributes to ketamine's rapid antidepressant action in rodent models. This finding connects TREK-1 biology to the most actively studied rapid-acting antidepressant mechanism currently in clinical use. It suggests the channel may be a convergence point for multiple antidepressant pathways rather than a niche target. Whether this mechanistic overlap translates into comparable or additive clinical effects in humans is unknown.

Are peptides legal again after the 2026 FDA reclassification?

The February 2026 reclassification affected specific peptides that were previously on the FDA's Category 2 bulk drug substance list; it did not create a general legalization of research peptides for human use. PE-22-28 was not affected by this reclassification because it was never classified as a Category 2 substance in the first place — it simply falls outside the regulated pharmaceutical framework entirely. As of April 2026, no change in PE-22-28's regulatory status has occurred.