PE-22-28

Beginner Protocol

Intermediate Protocol

Advanced Protocol

Reconstitution and handling notes

Stacking Notes

Additional Dosage Notes

There are no human clinical trials of PE-22-28. As of 2026 there are no published Phase 1 (or later) studies, no ClinicalTrials.gov registrations, and no human pharmacokinetic, safety or efficacy data. The evidence base is entirely preclinical - cell-based electrophysiology and rodent behavioral pharmacology, largely from the academic group (Mazella, Borsotto, Heurteaux and colleagues at IPMC, CNRS / Universite Cote d'Azur) that discovered spadin.

In the key report, PE 22-28 was identified from spadin's serum-degradation fragments as the shortest peptide that still blocks TREK-1, and it inhibited TREK-1 in hTREK-1/HEK cells with an IC50 of about 0.12 nM - more potent and more selective than spadin (~40-60 nM) [PMID:28955242]. In mice, a single low-dose intraperitoneal injection (about 3 micrograms per kilogram) reduced immobility in the forced-swim test, and a 4-day sub-chronic course reduced immobility in the forced-swim and learned-helplessness tests and shortened latency to feed in the novelty-suppressed-feeding test, including in a corticosterone-induced model of depression. Over the same 4-day window PE 22-28 increased hippocampal neurogenesis (BrdU-positive cells) and cortical synaptogenesis (PSD-95), consistent with a rapid, neurogenesis-linked antidepressant mechanism rather than the multi-week onset of SSRIs [PMID:28955242]. These are the same directional findings first shown for the parent peptide spadin, which produced antidepressant-like effects across five rodent models, raised dorsal-raphe 5-HT firing, and increased hippocampal CREB phosphorylation and neurogenesis after a 4-day treatment [PMID:20405001]. Related work from the same group extended the concept to retro-inverso spadin analogs [PMID:25080852] and to a short "mini-spadin" that acted biphasically on TREK-1 (activating it at very low doses to give neuroprotection, inhibiting it at higher doses to give antidepressant effects) and protected against stroke and post-stroke depression in mice [PMID:31325429]; the broader TREK-1/TASK-3 antidepressant strategy is reviewed in [PMID:25263033].

Every one of these results is in mice or cell lines. Rodent behavioral antidepressant assays (forced swim, learned helplessness, novelty-suppressed feeding) have limited predictive validity for human depression, effect sizes vary, and many compounds that looked promising preclinically have failed to translate to human efficacy. A handful of positive animal studies from a single originating laboratory is preliminary signal, not proof of human efficacy. Human use of PE-22-28 today is self-experimentation with research-chemical vendor material; community self-reports (mood lift, calmer affect, or no effect) are uncontrolled, unblinded and subject to expectancy effects, and do not constitute clinical evidence.

No human side-effect data exist for PE-22-28 because it has never been tested in people. What can be said comes from rodent studies of PE-22-28, spadin and their analogs, plus general considerations for injected research peptides.

In the preclinical work, the appeal of the TREK-1 approach is a clean off-target profile: PE-22-28 was selective for TREK-1 and did not block the related potassium channels TREK-2, TRAAK, TRESK or TASK-1, and - importantly for safety - it did not affect the cardiac hERG channel, so the authors argue it should not carry the QT-prolongation/arrhythmia risk seen with some antidepressants [PMID:28955242]. The originating group also reported that spadin and its retro-inverso analogs had no obvious deleterious effects on pain processing, seizure thresholds, or cardiac function in their models [PMID:25080852]. These are short-term rodent observations, not formal toxicology, and they do not establish human safety.

Mechanism-based theoretical concerns center on TREK-1 itself, which is widely expressed and involved in neuroprotection, pain and vascular tone. A short analog studied for stroke ("mini-spadin") was biphasic - activating TREK-1 at very low doses but inhibiting it at higher doses [PMID:31325429] - so dose matters and the net effect of chronic TREK-1 blockade in humans is unknown. Because the proposed use is mood-related, paradoxical psychiatric effects (worsening mood, anxiety, irritability, or mood instability, particularly in people with bipolar or psychotic vulnerability) cannot be excluded for any centrally acting compound used without supervision.

The most concrete real-world risks are those of the research-chemical supply chain rather than the peptide's known pharmacology: injection-site reactions (redness, swelling, bruising) and flu-like symptoms from bacterial endotoxin/pyrogen contamination or from impure or mislabeled/under-purity material. Short peptides like this are easy to substitute or synthesize impurely, so batch-to-batch quality varies. Allergic and hypersensitivity reactions are possible with any injected peptide. Anyone using vendor material should insist on third-party analytical testing (HPLC/LC-MS) and stop if injection-site or systemic reactions occur.