Antidepressant Peptide · TREK-1

PE-22-28: Spadin Analogue & TREK-1 Antagonist

A UK-focused, evidence-based comparison of PE-22-28 and Dihexa — mechanism, benefits, dosing, side effects, legal status, and stacking.

PE-22-28 is a short-chain synthetic peptide derived from spadin, the endogenous TREK-1 potassium channel antagonist generated from sortilin precursor protein. Developed in the laboratory of Catherine Heurteaux and Marc Borsotto in Sophia Antipolis (France) as a rapid-onset, mechanistically novel antidepressant lead. PE-22-28 is the most-studied stable analogue of spadin and was the basis of the original startup TREK-1 Pharmaceuticals (later Theranexus). The compound is not approved as a medicine anywhere and exists in the nootropic space as an investigational antidepressant peptide with a distinct mechanism — blocking the TREK-1 two-pore potassium channel, which is upregulated in depression and downregulated by SSRIs.

What is PE-22-28?

PE-22-28 is a 7-amino-acid synthetic peptide engineered from the parent peptide spadin (residues 22-28 of the propeptide), with the smallest TREK-1 antagonist activity retained. It is sold as a lyophilised powder for reconstitution and intranasal delivery in the research-chemical market. The peptide is the subject of approximately 15-20 published peer-reviewed papers, almost entirely from the originating Heurteaux/Borsotto group, with limited independent replication. There is no clinical Phase 1+ data in humans for PE-22-28 itself, though related TREK-1 antagonist programmes (some now at Theranexus and elsewhere) have moved towards clinical development.

Chemistry: Synthetic 7-amino-acid spadin analogue · proprietary sequence
Origin: Borsotto / Heurteaux laboratory (Sophia Antipolis, France), 2010s
Primary route: Intranasal spray (primary); subcutaneous occasionally reported
Pharmacokinetics: Brief plasma half-life (minutes) but functional antidepressant effects emerge within hours and persist with daily dosing.
Class: TREK-1 channel antagonist peptide

Mechanism of Action

PE-22-28 is a selective antagonist of the TREK-1 two-pore-domain potassium channel, also known as KCNK2. TREK-1 is a leak channel responsible for stabilising neuronal resting membrane potential — it is increased in expression in depression and reduced by chronic SSRI treatment. Blocking TREK-1 with PE-22-28 destabilises neurons towards firing, producing a rapid antidepressant-like effect in rodent models (Mazella et al., 2010; Devader et al., 2015). Downstream this is associated with: rapid restoration of hippocampal BDNF expression, dendritic spine density improvements in the dentate gyrus, normalisation of HPA-axis activity under chronic stress, and behavioural effects equivalent to fluoxetine but emerging in days rather than weeks. The mechanism is mechanistically novel and does not involve serotonin reuptake, monoamine oxidase, NMDA receptors, or any of the established antidepressant targets.

Proposed Benefits

The proposed benefits are entirely investigational and based primarily on preclinical evidence: rapid antidepressant effect (days rather than the 4-6 weeks typical of SSRIs), absence of the sexual / weight / sleep disturbance side effects of SSRIs, possible neuroprotection during chronic stress, and possible cognitive benefit secondary to restored hippocampal plasticity. Community reports in the nootropic space describe mood lift within 3-7 days of daily intranasal dosing, reduced anhedonia, improved emotional resilience, and a "ceiling raised" feeling without stimulation. These reports are anecdotal and uncontrolled. There are no published human clinical trials of PE-22-28; all reported effects in humans are unblinded self-experimentation.

Evidence Base

The evidence base is preclinical and concentrated. Key references: Mazella et al. 2010 (PLoS Biology) introducing spadin as a TREK-1 antagonist with rapid antidepressant effects in rodents; Borsotto et al. 2015 reviewing the spadin/PE-22-28 series; Devader et al. 2015 demonstrating dendritic spine density restoration; Moha ou Maati et al. 2012 examining cardiac safety. No human clinical trial data exists for PE-22-28 itself. Related TREK-1 modulator programmes have progressed towards clinical work at small biotech, but as of 2026 there is no published clinical efficacy or safety data in humans. This is a far thinner evidence base than Semax, Selank, or Cerebrolysin.

Dosage & Administration

No medically approved dose exists. Community-reported protocols use lyophilised research-grade vials reconstituted to deliver 200-400 µg intranasally 1-2 times per day, typically cycled 14-21 days on then 14+ days off. Reported time-to-effect is 3-7 days for the antidepressant signal. Subcutaneous administration is occasionally reported but offers no documented advantage over the intranasal route for a CNS target. Reconstitute with bacteriostatic water and refrigerate; use within 14-21 days of reconstitution. This is a poorly-characterised compound in humans and dosing assumptions are extrapolated from preclinical doses in rodents.

This is a community-reported protocol summary, not a medical recommendation. There is no established human dose. Consult a qualified healthcare professional before using any research compound.

Side Effects & Risks

The safety profile in humans is essentially uncharacterised. Preclinical data does not show major acute toxicity or significant cardiac effects (TREK-1 is also expressed in cardiac tissue, so this was checked early). Anecdotal reports from the nootropic community include occasional headache, mild irritability, vivid dreams, and rare transient mood instability — the same pattern reported with many investigational antidepressants. Theoretical concerns from the TREK-1 mechanism include: cardiac arrhythmia (TREK-1 is cardioactive), seizure threshold reduction (less leak current = more excitable neurons), and unknown long-term effects of chronic TREK-1 blockade. Strong contraindications in any user with: epilepsy, cardiac arrhythmia, active mood disorder under treatment, pregnancy/breastfeeding, or anyone taking SSRIs/SNRIs/MAOIs without medical supervision.

UK Legal Status

In the United Kingdom PE-22-28 is not a controlled substance under the Misuse of Drugs Act 1971, not licensed as a medicine by the MHRA, and arguably not scheduled under the Psychoactive Substances Act 2016 (the PSA exemption for "investigational medicinal products" is interpretable, and peptide antidepressants have not been formally tested in court). It is sold as a research chemical for laboratory use. Commercial human-use sale would not be lawful. The compound has not been added to WADA, MHRA, or FDA scheduling. The lack of any clinical data makes the legal status more clearly "research only" than for compounds with registered foreign medical use.

PE-22-28 vs Dihexa

PE-22-28 and Dihexa share an antidepressant / pro-plasticity / pro-BDNF profile in rodent studies but via different mechanisms. PE-22-28 blocks TREK-1 to destabilise neuronal resting potential, indirectly restoring BDNF and synaptic plasticity over days. Dihexa activates HGF/c-Met to drive direct synaptogenic structural change over weeks. Both are positioned in roughly the same "rapid synaptic plasticity restoration" space but with very different time courses, evidence bases, and risk profiles. Dihexa has more independent preclinical data and a longer history; PE-22-28 has a more mechanistically novel target but virtually no human evidence. For users seeking a depression-focused intervention, PE-22-28 is interesting but should be approached with significant caution given the absent human safety data. For broad cognitive plasticity Dihexa is the better-characterised choice.

Stacking with Dihexa

PE-22-28 is sometimes stacked in the nootropic community with Semax (for combined trophic upregulation), Selank (for anxiety overlay on depression), or Lion's Mane mushroom (for NGF support). With Dihexa the rationale would be complementary mechanisms acting on the same broad goal of restored synaptic plasticity. No published interaction data exists for any PE-22-28 combination. The most important caution is the SSRI/SNRI/MAOI question: PE-22-28 acts on TREK-1 which is downregulated by chronic SSRI treatment, so co-administration could be either redundant or unpredictable. Combining novel investigational antidepressants with established psychiatric medications without medical oversight is high-risk; do not do this without appropriate professional guidance.

Frequently Asked Questions

There are no published human clinical trials of PE-22-28 itself. Related TREK-1 modulator programmes have progressed towards clinical work, but PE-22-28 specifically is at preclinical stage with anecdotal human self-experimentation in the nootropic community.

In preclinical rodent models PE-22-28 produces antidepressant-like effects in 3-7 days vs the 4-6 weeks for SSRIs. Whether this translates to humans is unknown — no head-to-head trial exists.

Not without medical supervision. TREK-1 is downregulated by chronic SSRI treatment, so co-administration is mechanistically complex and has no human safety data.

PE-22-28 is the smallest peptide fragment of spadin that retains TREK-1 antagonist activity. It is a synthetic analogue, not the endogenous spadin itself.

TREK-1 is expressed in cardiac tissue. Preclinical cardiac safety data (Moha ou Maati 2012) does not show major adverse effects but human safety is uncharacterised. Anyone with arrhythmia or cardiac disease should avoid this compound.

Lyophilised powder is stable at -20°C for years and at 2-8°C for months. Reconstituted solution should be refrigerated and used within 14-21 days.

The Bottom Line

PE-22-28 is a mechanistically novel investigational peptide with intriguing preclinical antidepressant activity through TREK-1 channel antagonism. The complete absence of human clinical data and the theoretical cardiac and seizure-threshold concerns mean it sits firmly in the experimental category. Dihexa, by contrast, has independent preclinical data, a defined mechanism, and oral bioavailability. PE-22-28 may be of academic interest for users tracking the TREK-1 antidepressant lineage, but it is not a substitute for established treatments or for better-characterised peptides like Cerebrolysin, Semax, or Dihexa itself.