PEPITEM: natural peptide that calms inflammatory diseases
A naturally occurring peptide that blocks immune cells from flooding joints, nerves, and skin; studied in animals for arthritis, multiple sclerosis, lupus, and psoriasis; experimental, not yet an approved drug.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
Snapshot
Class: Endogenous immunoregulatory peptide
Evidence tier: Animal-only evidence
Status: No approved therapeutic status. Preclinical research compound; not commercially available.
Best-supported effect: Reduced T-cell tissue infiltration and joint/CNS inflammation in rodent models of inflammatory arthritis, multiple sclerosis, lupus, psoriasis, bone loss, and age-related immune decline
Main caveat: No human clinical trials of any phase have been conducted; all efficacy data is preclinical
What this is
PEPITEM (Peptide Inhibitor of Trans-Endothelial Migration) is a 14-amino-acid endogenous peptide derived proteolytically from the 14-3-3 zeta delta protein and released by B cells in response to adiponectin signaling. It was identified by researchers at the University of Birmingham and described in a 2015 Nature Medicine publication as a selective regulator of T-cell trans-endothelial migration — blocking T cells from crossing blood vessel walls into tissues without affecting other immune cell types such as neutrophils or monocytes.
The therapeutic concept being explored is "PEPITEM replacement therapy": circulating PEPITEM is measurably reduced in patients with rheumatoid arthritis, type 1 diabetes, and in aging, and ex vivo studies using patient-derived blood samples indicate that the pathway dysfunction can be partially corrected by exogenous PEPITEM. This positions it as a potential restorative intervention rather than a broad immunosuppressant, and distinguishes it mechanistically from cytokine-targeting biologics like TNF inhibitors. No human clinical trial has been conducted.
Evidence map
| Evidence layer | Grade | What it supports |
|---|---|---|
| Human | None identified | No human clinical trials have been conducted. Ex vivo studies of patient-derived blood samples confirm the PEPITEM pathway is impaired in rheumatoid arthritis, type 1 diabetes, and aging; these are mechanistic/biomarker observations, not exogenous therapy trials. |
| Animal | Strong | Reduced joint swelling, cartilage damage, and bone erosion in inflammatory arthritis models (effects described as comparable to infliximab); delayed EAE onset and reduced CNS inflammation and demyelination; inhibited T-cell infiltration and glomerulonephritis in lupus models; halted bone loss and stimulated bone formation; restored immune cell trafficking in aged mice; reduced psoriasis severity with topical application; reduced leukocyte infiltration in peritonitis models. Multiple independent publications across multiple disease models from the University of Birmingham research program. |
| In vitro | None identified | No dedicated in vitro assay evidence individually extracted from the available literature. |
| Computational | None identified | No docking, structure prediction, or model scoring data present in the available literature. |
| Mechanism | Strong | Adiponectin → B-cell PEPITEM release → CDH15 binding on endothelium → sphingosine kinase 1 activation → S1P synthesis → Spns2 export → S1PR1 engagement on T cells → LFA-1 and ICAM-1 reduction → selective T-cell trans-endothelial migration block. Separate NCAM-1-dependent bone pathway: direct osteoblast maturation stimulation and osteoprotegerin-mediated RANKL sequestration. Pathway characterized in the 2015 Nature Medicine paper. |
The majority of published evidence originates from the University of Birmingham research program and its commercial partner Revolo Biotherapeutics. Independent replication by unaffiliated research groups is a key limitation of the current evidence base.
Claim check
| Claim | Verdict | Evidence layer | Confidence |
|---|---|---|---|
| Reduces T-cell infiltration into inflamed tissues | Supported (animal) | Animal | High — multiple independent animal models across disease areas |
| Inflammatory arthritis treatment effect in animal models (described as comparable to infliximab) | Supported (animal) | Animal | Medium — rodent arthritis model data only; no human translation established; "comparable to infliximab" refers to preclinical endpoints, not clinical equivalence |
| Anti-resorptive and anabolic bone effect | Supported (animal) | Animal | Medium — bone-loss model data showing halted resorption and new bone formation |
| Reduces neuroinflammation in MS models | Supported (animal) | Animal | Medium — EAE model data; human MS translation not established |
| Effective replacement therapy for age-related immune decline | Weak (animal) | Animal | Low — aged-mouse trafficking data; large gap to human efficacy |
| Human therapeutic efficacy for any indication | Not established | Human | High confidence in this verdict — no human clinical trial of any phase has been conducted |
| Lifespan or healthspan extension | Not established | Human | High confidence in this verdict — no human data; animal observation of restored trafficking in aged mice is not a longevity endpoint |
| Safe for human administration | Not established | Human | High confidence in this verdict — no human safety study exists; preclinical data shows no adverse effects in animal studies, but human safety has not been characterized |
Experimental exposure
This section reports exposure used in animal experiments. It does not establish human dosing.
| Context | System | Experimental exposure | Duration | Endpoint | Limitation |
|---|---|---|---|---|---|
| Rodent inflammatory arthritis model | Mouse | Intraperitoneal or subcutaneous injection; micromolar or low mg/kg concentrations per source | 2–6 weeks per source | Joint swelling, cartilage damage, bone erosion, inflammatory markers | No human pharmacokinetic or dose-response data; rodent dose not translatable without human PK study |
| EAE model (MS) | Mouse | Injection; exact regimen not individually extracted in source | Multi-week; disease onset and progression endpoints | CNS inflammation, demyelination, disease onset delay | Mouse EAE is an induced model; human MS translation not established |
| Lupus glomerulonephritis model | Mouse | Injection; exact regimen not individually extracted in source | Not individually extracted | T-cell infiltration, glomerulonephritis markers | Murine lupus model; no human data |
| Osteoporosis / bone loss model | Mouse | Injection; exact regimen not individually extracted in source | 8–12 weeks per source context | Bone density, osteoblast activity, RANKL markers | Bone endpoints assessed over months; human translation uncharacterized |
| Aged mouse model (inflammaging) | Aged mouse | Injection; exact regimen not individually extracted in source | Not individually extracted | Immune cell trafficking restoration | Aged-mouse model; human aging translation not established |
| Psoriasis model | Mouse or topical application | Topical formulation; exact regimen not individually extracted in source | Not individually extracted | Disease severity markers | Preclinical only; topical route studied in animal model, not validated in humans |
| Peritonitis model | Mouse | Injection; exact regimen not individually extracted in source | Acute (hours to days) | Leukocyte infiltration | Acute model; does not characterize chronic dosing or systemic safety |
Preclinical safety signals
| Signal | System | Notes |
|---|---|---|
| No adverse effects reported | Rodent models across multiple disease indications | Per available sources, no adverse effects in preclinical studies. Study duration, surveillance quality, and dosing intensity vary across models; these findings do not characterize human safety. |
| Long-term immunosuppression consequences | Not established | The selectivity argument (T-cell trafficking only, other immune cells unaffected) has not been rigorously tested over long durations or in the context of infection challenge. |
| Bolus exogenous administration vs endogenous physiology | Not characterized | Endogenous PEPITEM is released by B cells in regulated, pulsatile patterns. The pharmacological and safety consequences of exogenous non-physiologic administration have not been systematically studied. |
| Human safety | No human data | No adverse event data from any human study exists. All safety observations are preclinical and subject to the full uncertainties of animal-to-human translation. |
Contraindications described in the available literature represent mechanistic inference and precautionary language for research use, not clinically characterized contraindications. Contexts of concern mentioned include: pregnancy and breastfeeding (no data on placental or fetal immune effects); active severe infection (T-cell trafficking blockade not evaluated in infection contexts); concurrent use of other immunomodulatory agents (additive effects uncharacterized in humans); active hematologic malignancy or post-transplant immunosuppression (T-cell trafficking interference not evaluated in these settings). These are source-identified caution areas, not clinically established contraindications.
Regulatory status
| Region / body | Status | Notes |
|---|---|---|
| US (FDA) | Not approved | Not FDA-approved for any indication. Not a controlled substance. No compounded or research-chemical supply exists in current US markets per source. |
| EU (EMA / MHRA) | Not approved | Not approved by EMA or MHRA. Primary development activity is UK-based (University of Birmingham, Revolo Biotherapeutics). |
| Canada / International | Not approved | Not approved by Health Canada, TGA, or any other major regulatory authority per source. |
| WADA | Not specifically named; S0 clause may apply | Per available sources, PEPITEM is not currently named on the WADA Prohibited List. As an unapproved investigational substance, WADA's general S0 category (non-approved substances) is noted in available literature as potentially applicable. WADA list status not independently refreshed in this card. |
| Clinical availability | No therapeutic product exists | No FDA-approved product, no compounded preparation, and no research-chemical supply for PEPITEM is described in the available literature. |
Mechanism
PEPITEM is proteolytically derived from the 14-3-3 zeta delta protein and released by B cells when adiponectin activates adiponectin receptors on B-cell surfaces. The released peptide binds cadherin-15 (CDH15) on vascular endothelial cells, activating sphingosine kinase 1, which synthesizes sphingosine-1-phosphate (S1P). S1P is exported via the Spns2 transporter to the extracellular space, where it engages S1P receptor 1 (S1PR1) on adherent T cells. This signaling cascade reduces T-cell LFA-1 integrin expression and decreases endothelial ICAM-1 display, selectively blocking T-cell trans-endothelial migration. Neutrophil and monocyte recruitment are reported to be unaffected by this mechanism.
In bone tissue, PEPITEM operates through a separate NCAM-1-dependent pathway: it directly stimulates osteoblast maturation and new bone formation while triggering osteoprotegerin release from osteoblasts, which sequesters RANKL and limits osteoclast-mediated bone resorption. This dual anabolic and anti-resorptive bone activity is proposed to be independent of the endothelial T-cell trafficking mechanism.
The pathway is impaired in rheumatoid arthritis, type 1 diabetes, and aging, with measurably lower circulating PEPITEM concentrations in patient serum compared to healthy controls. This impairment, combined with the ex vivo restoration of trafficking control by exogenous PEPITEM in patient-derived samples, forms the mechanistic basis for the replacement-therapy concept.
Primary target: CDH15 (cadherin-15) on endothelial cells — inferred as primary from the published pathway description. The bone NCAM-1 target is separately characterized. Target confidence: verified for the endothelial mechanism in the original Nature Medicine paper and subsequent preclinical work.
Chemistry
| Field | Value |
|---|---|
| Length | 14 amino acids |
| Origin | Proteolytically derived from the 14-3-3 zeta delta protein |
| Topology | Linear |
| Modifications | None described for the native 14-mer; active tripeptide pharmacophores and peptidomimetic analogues are under development by the Birmingham group and Revolo Biotherapeutics |
| Natural source | Secreted by B cells in response to adiponectin receptor activation |
| Sequence | Not individually extracted from the available literature |
| Sequence confidence | Not provided in available literature |
| Administration in preclinical studies | Intraperitoneal, subcutaneous (injection); topical (psoriasis models) |
the available literature does not provide a specific amino-acid sequence for the native 14-mer. Exact sequence data should be verified against primary chemistry sources (e.g., the Nature Medicine 2015 paper) before populating.
Open questions
- Human pharmacokinetics: Absorption, distribution, metabolism, and excretion of neither the full 14-mer nor the active tripeptide pharmacophores have been characterized in humans. This is a prerequisite for any human trial.
- First-in-human safety: No Phase I study has been conducted. Whether selective exogenous T-cell trafficking blockade is tolerated in humans, and what the infection-risk profile looks like over longer durations, remains entirely open.
- Optimal route and formulation: Subcutaneous, intravenous, topical (psoriasis), and intra-articular routes are all conceivable based on preclinical work; no head-to-head data exists, and formulation for clinical use has not been established.
- Indication prioritization: Preclinical work spans inflammatory arthritis, MS, lupus, psoriasis, bone loss, and inflammaging. Which indication offers the most favorable risk-benefit ratio for a first-in-human program has not been determined.
- Long-term immune surveillance: The selectivity for T-cell migration (sparing other immune cells) is the central safety argument. However, long-term consequences for infection defense, tumor surveillance, and immune homeostasis with continuous or repeated T-cell trafficking blockade have not been studied.
- Patient stratification by PEPITEM levels: Circulating PEPITEM is reduced in RA, T1D, and aging. Whether baseline PEPITEM level predicts response to replacement therapy — a natural personalized-medicine question — has not been addressed in any trial.
- Comparative efficacy versus established biologics: Preclinical arthritis data shows effects described as comparable to infliximab, but head-to-head human trials versus current standard-of-care biologics will be the meaningful translational test.
- Independent replication: The bulk of the published evidence originates from the University of Birmingham research program. Replication by independent research groups would strengthen confidence in the preclinical findings.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Could replacing a peptide that naturally declines with age slow down the smoldering inflammation that drives heart disease, diabetes, and cognitive decline?
Chronic low-grade inflammation in aging quietly damages the heart, brain, and joints for decades. A peptide that restores the body's natural brake on immune-cell infiltration could potentially reduce the risk of many age-related diseases at once, offering a more targeted approach than broad anti-inflammatory drugs.
Does PEPITEM selectively turn on just one of the several switches inside its receptor, rather than all of them?
Drugs that activate a receptor without triggering all its downstream effects can be far safer. If PEPITEM works this way on its target, it could explain how it calms inflammation without causing the cardiovascular or immune side effects seen with other drugs targeting the same receptor family.
Could scientists find the essential active core of PEPITEM by trimming away the parts the body quickly destroys?
PEPITEM is currently only tested by injection. A shorter, more stable version might be manufacturable more cheaply, last longer in the body, and potentially even be developed into a pill, dramatically widening access for patients with inflammatory diseases.
Does PEPITEM only affect T cells because those cells happen to display the receptor PEPITEM targets at exactly the right moment during inflammation?
Understanding why PEPITEM spares infection-fighting cells (neutrophils) while blocking tissue-damaging T cells could help doctors use it safely during infections and flares, and could guide development of other selective anti-inflammatory drugs that do not leave patients vulnerable to bacteria.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.7730000615119934 | openfold3-mlx |
| ranking score | 0.8526287078857422 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.479 | global PDE — lower = better |
| disorder | 0.127 | fraction disordered |
| chain pair ipTM (A, B) | 0.773 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | — |
| hardware | — |
| mlx version | — |
| python | — |
| random seed | — |
| msa strategy | — |
| diffusion samples | 1 |
| runtime | 84s |
| predicted by | mlx@peptide |
| predicted at | 2026-05-03 |
▸citationbibtex
@peptide{pep10918,
sequence = {KGHFQALSVATVSD},
target = {s1pr2},
author = {peptidemodel},
year = {2026},
status = {computed}
}