ARA-290 Peptide UK Guide: Cibinetide Research and Trial Data

Erythropoietin has a problem. The hormone that tells bone marrow to produce red blood cells also turns out to protect and repair injured tissue — and for decades researchers could not use the second property without triggering the first.

Give someone EPO for nerve repair and you also thicken their blood. That is not an acceptable trade.

ARA-290 exists because two researchers worked out that these were not one effect but two, running through two different receptors — and that the parts of the molecule responsible could be separated. The result is an eleven-amino-acid peptide that reproduces one surface of erythropoietin, activates the repair pathway, and leaves the blood-production pathway entirely alone.

It also has something most research peptides do not: completed human trials with published results, including endpoints that were met and some that were not. Both are covered below.

ARA-290 is supplied as a research compound for laboratory use only — it is not approved for any therapeutic indication in the UK or the United States, and is not sold for human consumption or clinical purpose.

What ARA-290 Actually Is

ARA-290, also known as cibinetide, is a synthetic linear peptide of eleven amino acids, with the sequence pyroglutamate-EELERALNSS and a molecular weight of approximately 1,257 Da.

That pyroglutamate at the N-terminus is worth noting. It is a cyclised form of glutamate that caps the terminus, protecting the peptide from aminopeptidases that would otherwise degrade it from that end. Several naturally occurring peptides carry the same modification, and here it serves the same protective purpose.

The sequence is not arbitrary. It reproduces the helix-B surface of erythropoietin — a specific face of the folded hormone, chosen from its three-dimensional structure rather than its linear sequence. That distinction matters: this is a structural mimic, not a fragment taken from the chain.

The Discovery That Made It Possible

The compound emerged from work by Michael Brines and Anthony Cerami on erythropoietin’s non-haematopoietic effects — everything EPO does that has nothing to do with red blood cells.

Their central finding was that EPO signals through two distinct receptor systems.

The first is the classical EPO receptor homodimer, written EPOR₂ — two identical receptor subunits paired together. It sits on erythrocyte precursor cells in bone marrow, binds EPO with high affinity, and drives red blood cell production by inhibiting apoptosis in those precursors. This is the pathway everyone knew about.

The second is the innate repair receptor, or IRR. It is a heteromeric receptor — built from two different subunits rather than two identical ones: the EPO receptor combined with the beta-common receptor, designated CD131 or CSF2RB. It belongs to the Type 1 cytokine receptor family, and it mediates EPO’s tissue-protective effects through paracrine and autocrine signalling rather than endocrine action.

Two receptors, both containing an EPO receptor subunit, doing entirely different jobs.

The elegant part

If a molecule could bind the heteromeric IRR without engaging the EPOR homodimer, it would deliver tissue protection with no effect on red blood cell production.

That is precisely what ARA-290 does. By reproducing only the helix-B surface — the region involved in IRR binding — rather than the whole hormone, it selectively activates repair signalling while leaving erythropoiesis untouched.

The endogenous equivalent is interesting too. The natural ligand for the IRR appears to be hyposialated erythropoietin — a form of EPO carrying fewer sialic acid residues, produced locally in tissue rather than systemically. The biology is characterised by temporal and spatial separation of the receptor subunits, which associate to form the IRR under specific conditions rather than sitting permanently assembled.

In other words, the body already runs this two-channel system. ARA-290 targets one channel.

What the Human Trials Found

Here ARA-290 separates itself from most compounds in research use. It has been through randomised, placebo-controlled human trials, and the results are published.

The first randomised trial

A randomised, double-blind pilot study enrolled 22 sarcoidosis patients with symptoms of small fiber neuropathy — indexed on PubMed under PMID 23168581.

Small fiber neuropathy is a frequent complication of sarcoidosis, producing burning neuropathic pain, autonomic dysfunction and substantially reduced quality of life. Standard management consists largely of immune suppression and symptomatic treatment, and is typically unsatisfactory.

The ARA-290 group showed significant improvement in the Small Fiber Neuropathy Screening List score compared with placebo at week four, at p less than 0.05. Haemoglobin was unchanged — the selectivity working as designed.

The 28-day trial

A subsequent blinded, placebo-controlled trial, PMID 24136731, evaluated 28 days of daily subcutaneous ARA-290 in patients with documented small nerve fiber loss.

Neuropathic symptoms improved significantly. And the trial measured something more objective than symptom scores: corneal nerve fiber density, assessed by confocal microscopy. That increased too.

Corneal nerve fiber density is a genuinely useful endpoint because it is a direct structural measurement of small nerve fibres rather than a questionnaire. A compound that improves how patients feel is interesting. One that also increases measurable nerve fibre density is making a stronger claim.

The dose-ranging trial

A larger dose-ranging study, registered as NCT02039687 and run at the Cleveland Clinic and Leiden University Medical Center, compared 1mg, 4mg and 8mg daily against placebo over 28 consecutive days.

At the 4mg dose, corneal nerve fibre area increased, as did GAP-43-positive regenerating skin fibres — GAP-43 being a marker specifically associated with axonal growth, which makes it evidence of regeneration rather than merely preservation.

Pain scores did not separate from placebo in this trial. That is worth stating plainly rather than omitting. Structural markers improved; the pain endpoint did not reach significance.

The trial that missed

A Phase 2 open-label study examined cibinetide in diabetic macular oedema with nine participants. The primary visual acuity endpoint was not met. The study used fixed dosing rather than body-weight adjusted dosing, which the authors noted as a caveat.

A parallel clinical programme also investigated ARA-290 in type 2 diabetes, and the reproducibility of corneal nerve fibre density improvement across both sarcoidosis and diabetic populations is one of the stronger features of the evidence base — the same structural signal appearing in two different patient groups.

Where Development Stopped

ARA-290’s regulatory story is unusual and worth understanding, because it explains why a compound with positive Phase 2 data is not a medicine.

Araim Pharmaceuticals received orphan drug designation for sarcoidosis-associated small fiber neuropathy — a status granted to encourage development for rare conditions. But no New Drug Application or Biologics License Application was ever submitted, no Phase 3 trials were initiated, and development stalled following the company’s closure.

So the compound was not rejected by a regulator. It was never submitted to one. That is a commercial and organisational outcome rather than a scientific verdict, and it is a meaningfully different thing from a drug that failed.

The practical consequence is that ARA-290 sits in an unusual position: better human evidence than most research compounds, and no approval anywhere.

ARA-290 Research Peptide

HPLC and MS verified · batch certificate published · dispatched from the UK before 2pm

from£39.99View ARA-290 Research Peptide

Why the Selectivity Is the Whole Point

It is worth being explicit about why avoiding the erythropoietic pathway matters so much.

EPO’s effect on red cell production is not merely an unwanted side effect in this context — it carries real risk. Raising haematocrit thickens the blood, which increases thrombotic risk. That is why EPO use is carefully controlled in clinical settings and why it cannot simply be repurposed for tissue protection.

A compound delivering the repair signalling without touching haematocrit removes that constraint entirely. The unchanged haemoglobin observed in the sarcoidosis pilot study is therefore not a minor safety observation — it is confirmation that the central design premise works.

One caveat the literature raises honestly: while short-term immunomodulation appears beneficial, the consequences of sustained innate repair receptor activation on immune surveillance are not established. That is an open question rather than a known problem, and it is the kind of thing longer studies exist to answer.

Why Eleven Residues Can Replace a Glycoprotein

Erythropoietin is a 165-amino-acid glycoprotein carrying substantial carbohydrate modification. ARA-290 is eleven residues with no sugars at all. The obvious question is how something that much smaller can do any of the same work.

The answer lies in how proteins actually engage receptors.

A folded protein presents its surface to the world, not its sequence. Residues that sit far apart along the chain can end up adjacent once the molecule folds, and the binding interface is built from whichever residues happen to face outward at that point. Large stretches of the chain exist to hold that surface in shape rather than to contact anything.

The helix-B region of erythropoietin is one such surface. It faces away from the interface used by the classical EPO receptor homodimer, and it is the region implicated in innate repair receptor engagement. Reproduce that face and you reproduce the interaction — provided the peptide adopts a comparable conformation.

This is why ARA-290 is described as a structural mimic rather than a fragment. A fragment is a piece cut from the chain. A structural mimic is a molecule designed to present the same surface, which may or may not correspond to a contiguous stretch of sequence.

Two practical consequences follow. The peptide is far cheaper and simpler to manufacture than a recombinant glycoprotein, with no cell culture, no glycosylation to control and no batch-to-batch carbohydrate variation. And because it engages only one of the two receptor systems, it avoids the effect that makes the parent hormone unusable for this purpose.

The trade-off is potency and duration. A small unmodified peptide is cleared quickly and lacks the albumin-binding or glycan-mediated half-life extension that larger molecules carry, which is reflected in the daily dosing used across the clinical trials.

Designing Research With ARA-290

Several practical considerations follow from the mechanism, and most concern distinguishing the two receptor systems cleanly.

Measure haematocrit as a control, not just a safety endpoint. The entire premise is that the IRR is engaged and the EPOR homodimer is not. An unchanged red cell parameter is therefore positive evidence that the selectivity held, and it belongs in the results rather than in a safety appendix.

Confirm CD131 expression in your system. The innate repair receptor requires the beta-common receptor subunit. Cells lacking CD131 cannot assemble the IRR regardless of how much EPO receptor they express, so a negative result in such a system says nothing about the compound. RT-PCR or protein-level confirmation before testing avoids that trap.

Choose structural endpoints over symptom proxies where possible. The strongest findings in the human literature are corneal nerve fibre density and GAP-43-positive regenerating fibres, both direct measurements. The weakest are pain scores, which did not separate from placebo. That pattern is worth replicating in design: structural readouts have been more informative for this compound than subjective ones.

Account for the dosing frequency. The trials used daily subcutaneous administration over 28 days. A small unmodified peptide clears quickly, so intermittent designs are not reduced versions of the same experiment.

Consider body-weight dosing. The macular oedema study that missed its endpoint used fixed rather than weight-adjusted dosing, and the authors flagged it. Where a study is being designed from scratch, weight-adjusted dosing avoids inheriting that limitation.

Watch the duration question. Short-term immunomodulation via the IRR appears beneficial in the published work. The effect of sustained activation on immune surveillance is not established, which makes long-duration protocols a genuine open question rather than a routine extension.

What Small Fiber Neuropathy Actually Is

The condition ARA-290 was tested against deserves explanation, because it shapes why the endpoints were chosen as they were.

Peripheral nerves come in different calibres. Large myelinated fibres carry touch, vibration and position sense, and they are what standard nerve conduction studies measure. Small fibres — thinly myelinated A-delta and unmyelinated C fibres — carry pain, temperature and autonomic signals.

Small fiber neuropathy affects the second group while leaving the first intact. That creates a diagnostic problem: conventional nerve conduction studies come back normal, because they are not measuring the fibres that are damaged.

The symptoms are nonetheless substantial. Burning pain, abnormal temperature sensation, and autonomic disturbance affecting sweating, heart rate and gastrointestinal function. In sarcoidosis it is a recognised complication, and the available management — immune suppression and symptomatic treatment — is generally regarded as unsatisfactory.

Because conduction studies are uninformative, the field relies on different measurements. Skin biopsy quantifies intraepidermal nerve fibre density directly. Corneal confocal microscopy images the corneal sub-basal nerve plexus, which is among the most densely innervated tissue in the body and accessible without a biopsy.

That explains why corneal nerve fibre density appears throughout the ARA-290 literature. It is not an incidental endpoint — it is one of the few direct structural measures available for this fibre population, and it can be repeated over time in the same individual.

It also explains why the GAP-43 finding carries weight. GAP-43 is expressed by growing axons rather than mature ones, so GAP-43-positive fibres in skin indicate active regeneration rather than preserved structure. Measuring more fibres tells you the population is larger; measuring more GAP-43-positive fibres tells you regeneration is underway.

Related Compounds Worth Studying Alongside

ARA-290 connects to several research areas through its repair and anti-inflammatory mechanisms.

Tissue repair compounds. BPC-157 and TB-500 are the obvious comparators, both studied extensively in tissue repair and angiogenesis through mechanisms unrelated to the IRR. The Wolverine Stack combines both, and the gut and digestive research bundle groups repair-focused compounds for comparative work.

Anti-inflammatory compounds. Since the IRR simultaneously activates anti-inflammatory and tissue repair pathways, compounds studied in inflammatory contexts are natural comparators. KPV is a tripeptide fragment of alpha-MSH studied in inflammatory signalling, Thymosin Alpha-1 in immune modulation, and LL-37 in innate immune research. The allergy and immune research bundle collects several of these.

Neuroprotective compounds. Given the nerve regeneration findings, Semax, Selank and the Semax and Selank blend are studied in neurological contexts through unrelated mechanisms. Pinealon is studied for direct interaction with neuronal nucleic acids.

Mitochondrial and cellular protection. SS-31 targets mitochondrial function, MOTS-c is a mitochondrially-encoded peptide, and Glutathione addresses oxidative stress — all relevant where cellular protection is the broader question.

Longevity research. Epitalon and NAD+ approach age-related decline through different routes again.

Why Verification Matters for This Sequence

ARA-290 presents a specific analytical question that many peptides do not.

The pyroglutamate terminus must have formed. The N-terminal residue is a cyclised glutamate, and that cyclisation eliminates a water molecule. A peptide where the cyclisation failed carries an uncyclised glutamate and a molecular weight approximately 18 Da higher than expected. Mass spectrometry detects this readily — provided the analysis is performed.

This matters functionally rather than cosmetically. The pyroglutamate cap is what protects the peptide from aminopeptidase degradation. Without it, stability drops considerably.

The serine residues at the C-terminus present a synthesis consideration, as adjacent identical residues are harder to couple cleanly than varied sequences — which can produce deletion sequences visible as peaks adjacent to the main one on a chromatogram.

Every batch Crown Peptides supplies carries its own certificate rather than a figure carried forward from an earlier run. Purity is measured by high-performance liquid chromatography, separating the target compound from related substances. Identity is confirmed independently by mass spectrometry.

The batch number on the vial matches the number on the certificate. Read any published certificate through the lab reports library, or scan the QR code on the vial. Guidance on interpreting the document is in the certificate of analysis guide.

Handling and Storage

ARA-290 contains no cysteine and no methionine, which makes it less oxidation-sensitive than many sequences. That is a genuine advantage, though it does not make it indifferent to conditions.

Store lyophilised at −20°C, protected from light, for long-term stability.

Bring to room temperature before opening — a cold vial opened into humid air condenses moisture onto the cake, and lyophilised peptide absorbs it readily.

Reconstitute down the vial wall and swirl gently rather than shaking, to avoid foaming and the air-liquid interface where peptides denature.

Keep reconstituted solution refrigerated and use within a defined window. Aliquot before freezing if freezing is necessary, since freeze-thaw cycling is among the most damaging things that can happen to a peptide in solution.

The peptide calculator handles reconstitution arithmetic, the dosage guide covers the underlying maths, and full guidance is in the storage information guide.

Reading an ARA-290 Certificate

A few figures carry specific meaning for this sequence.

Molecular weight. Expect approximately 1,257 Da. A result around 18 Da higher indicates the pyroglutamate did not form — the N-terminal glutamate remains uncyclised, retaining the water molecule that cyclisation eliminates. The sequence would be correct and the compound substantially less stable.

Purity by HPLC. ≥98% for analytical work. At eleven residues this is ten coupling steps, which is comfortably within what well-controlled synthesis achieves. The two adjacent serines at the C-terminal end and the two adjacent glutamates near the N-terminus are the positions where deletion sequences are most likely, and they appear as peaks adjacent to the main one.

Appearance. A white to off-white lyophilised cake. With no cysteine, methionine or tryptophan in the sequence, yellowing is less likely here than in many peptides — which makes it more notable if present.

Batch number. Matching the vial. Without that link the figures describe a production run rather than the material in front of you.

Frequently Asked Questions

What is ARA-290?

An eleven-amino-acid synthetic peptide, also called cibinetide, with the sequence pyroglutamate-EELERALNSS and a molecular weight of approximately 1,257 Da. It reproduces the helix-B surface of erythropoietin and selectively activates the innate repair receptor.

What is the innate repair receptor?

A heteromeric receptor formed from the erythropoietin receptor combined with the beta-common receptor, CD131. It belongs to the Type 1 cytokine receptor family and simultaneously activates anti-inflammatory and tissue repair pathways. It is distinct from the classical EPO receptor homodimer that drives red blood cell production.

Does ARA-290 affect red blood cell production?

No — that is the central design feature. By reproducing only the helix-B surface rather than the whole hormone, it activates the innate repair receptor without engaging the EPO receptor homodimer. Haemoglobin was unchanged in the sarcoidosis pilot study.

Is ARA-290 approved anywhere?

No. Araim Pharmaceuticals obtained orphan drug designation for sarcoidosis-associated small fiber neuropathy, but no application for approval was ever submitted and development stalled after the company closed. It is not approved for any indication.

What did the human trials show?

Two randomised placebo-controlled trials in sarcoidosis-associated small fiber neuropathy showed significant improvement in Small Fiber Neuropathy Screening List scores and increased corneal nerve fiber density. A dose-ranging trial found increased corneal nerve fibre area and GAP-43-positive regenerating skin fibres at 4mg, though pain scores did not separate from placebo.

Did any trials fail to meet their endpoints?

Yes. A Phase 2 open-label study in diabetic macular oedema with nine participants did not meet its primary visual acuity endpoint, with fixed rather than body-weight dosing noted as a caveat. Pain scores also failed to separate from placebo in the sarcoidosis dose-ranging trial.

What is cibinetide?

The generic name for ARA-290. The two terms refer to the same compound.

Why does the pyroglutamate matter?

It caps the N-terminus and protects against aminopeptidase degradation. If cyclisation failed during synthesis, the molecular weight sits around 18 Da higher than expected and the peptide is substantially less stable — which is why mass spectrometry verification matters for this sequence.

How should ARA-290 be stored?

Lyophilised at −20°C, protected from light. Reconstituted solution refrigerated and used within a defined window. It lacks cysteine and methionine, making it less oxidation-prone than many peptides, but standard handling still applies.

How does ARA-290 compare with BPC-157 or TB-500?

All three are studied in tissue repair, but through unrelated mechanisms. ARA-290 acts at a defined receptor — the innate repair receptor — with published randomised human trial data. BPC-157 and TB-500 have far larger preclinical literatures and no equivalent controlled human evidence. They are complementary comparators rather than alternatives.

What purity should ARA-290 be supplied at?

≥98% for analytical work, confirmed by HPLC with identity verified by mass spectrometry against a batch-specific certificate. The mass figure carries extra weight here because it is what confirms the pyroglutamate cyclisation completed.

A Compound Defined by What It Leaves Out

The interesting thing about ARA-290 is not what it adds but what it omits.

Erythropoietin is a large glycoprotein doing several jobs through two receptor systems. ARA-290 reproduces one face of it — enough to engage the repair receptor, not enough to touch the pathway that makes red blood cells. Everything else about the hormone is deliberately left behind.

That editorial decision is what turned an unusable observation into a testable compound, and the human trials suggest it worked. Corneal nerve fibre density increased. GAP-43-positive regenerating fibres increased. Haemoglobin did not move.

The story is incomplete. Pain endpoints did not separate in the dose-ranging trial, the macular oedema study missed its primary endpoint, no Phase 3 was ever run, and the company developing it closed. What remains is a well-characterised compound with genuine human data, an elegant and well-understood mechanism, and an unfinished development programme — which, for research purposes, is a considerably more interesting position than a closed case.

ARA-290 is available as research-grade material, HPLC and mass spectrometry verified, with the full certificate published against every batch number. Browse the wider research peptide range for related compounds.