ARA-290, also known as cibinetide, is an eleven-amino-acid peptide carved in the laboratory out of erythropoietin — the hormone that tells the bone marrow to make red blood cells. The trick is that the piece chosen can no longer drive red cell production, while keeping erythropoietin's second, less familiar job: protecting injured tissue and damping inflammation. It is one of the few “research” peptides that genuinely reached human testing — five randomised, controlled trials, mainly in people with sarcoidosis and type 2 diabetes. The results are mixed, though: all the trials were small, none reached phase 3, and clinical development has been stalled for years. Below we set out what was actually shown and what was not.
What ARA-290 is
Erythropoietin (EPO) is a hormone made mainly by the kidneys. Everyone associates it with blood and with doping, but the body also produces it locally, inside injured tissue, where it plays a completely different role — it keeps cells from dying and holds inflammation back. For years people tried to exploit that second property by giving EPO itself, but then tissue protection arrives together with thickened blood, higher pressure and a risk of clots.
ARA-290 is an attempt to separate the two actions: a short fragment reproducing the shape of one patch of the erythropoietin surface, and nothing more. The name given to it by Araim Pharmaceuticals is cibinetide; it is the same substance.
Where it comes from — helix B of erythropoietin
The erythropoietin molecule has four helical stretches labelled A to D. In a 2008 paper, the team of Brines and Cerami noticed that once EPO is docked on its “red cell” receptor, one side of helix B faces outwards, into the water — meaning it takes no part in that binding and might be responsible for something else.
The authors cut out that region (residues 58-82) and tested it in animal models of stroke, retinal oedema and nerve trauma. The fragment was protective. They then shortened it further, down to eleven amino acids reproducing the aqueous face of helix B alone. That small peptide still protected tissue, accelerated wound healing and improved cognitive testing in rodents. And — the whole point of the exercise — neither helix B nor the eleven-amino-acid peptide stimulated red cell production, either in culture or in animals. That small peptide is ARA-290.
How it works — two different receptors
The key is that erythropoietin meets two different “sockets” on cells. The first is an EPO receptor made of two identical parts, and that one drives red cell production. The second is a mixed socket: one part of the EPO receptor joined to a protein called CD131, the beta-common receptor. This second combination, named the innate repair receptor, switches on a programme of tissue protection and repair: it holds back cell death, quietens inflammatory cells and favours rebuilding.
ARA-290 fits only the second socket. The evidence is not theoretical: in a 2011 animal study the peptide relieved neuropathic pain in rats and in ordinary mice, whereas in mice lacking the beta-common receptor it did nothing at all. Remove the lock and the key stops working — the cleanest kind of mechanistic proof an animal experiment can deliver.
What was studied — animals
The most telling preclinical result concerns neuropathic pain, the pain that arises from damage to the nerve itself. In rats with a peripheral nerve injury, ARA-290 abolished hypersensitivity to touch and cold, and the effect persisted as long as fifteen weeks — even when dosing was confined to the first two weeks after surgery. The authors attribute this to the quenching of inflammation inside the nervous system rather than to anaesthesia: the peptide does not so much silence pain as interrupt the process that sustains it. Earlier work in the same family showed tissue protection in models of stroke, kidney ischaemia, retinal oedema and nerve trauma. The picture is coherent, but animal models of pain and stroke have a long history of promises that failed to carry over to people.
Human data — sarcoidosis
Sarcoidosis is an inflammatory disease in which some patients lose the thinnest nerve fibres of the skin and cornea. This causes burning pain and disturbed sensation, and treatment is unsatisfactory. All three sarcoidosis trials of ARA-290 were run in exactly this group — not in healthy volunteers, but in patients with measurable nerve damage.
The first trial (2012) enrolled 22 people: twelve received the peptide intravenously over four weeks, ten received placebo. No safety concerns emerged. On the small-fibre neuropathy symptom scale the treated group improved significantly more than placebo, and the pain and physical-functioning domains of the quality-of-life questionnaire improved as well. But overall pain intensity and fatigue improved equally in both groups, and depressive symptoms did not shift at all. Even this first trial therefore showed a partial effect.
The second trial (2013) ran for 28 days with subcutaneous dosing, and alongside the question of symptoms it measured something hard: the density of small nerve fibres in the cornea, assessed by confocal microscopy. Symptoms improved significantly, fibre density rose, skin sensitivity to temperature changed, and the distance covered in the six-minute walk test increased.
The third and largest trial (2017) was a phase 2b study in 64 patients with three different amounts of peptide against placebo. The primary endpoint was corneal nerve fibre area at 28 days. In the middle-dose group the increase was significant (697 units above placebo, confidence interval 159 to 1236, p = 0.012), and regenerating fibres in the skin increased too. But pain improved in every group, placebo included, and once the placebo effect was subtracted the difference was not statistically significant (p = 0.157). This detail matters a great deal: the best-documented human effect of ARA-290 is the regrowth of nerve fibres visible under a microscope, and not the relief the patient feels.
Human data — type 2 diabetes
In a phase 2 trial, participants with type 2 diabetes and painful neuropathy took the peptide subcutaneously for 28 days and were then followed for a further month without treatment. No safety issues were reported. Across the whole 56-day observation period the treated group improved on glycated haemoglobin (HbA1c, the marker of diabetic control) and on the lipid profile, and neuropathy symptoms on the PainDetect questionnaire fell significantly. Corneal fibre density rose, but only in the subgroup whose density was clearly below normal at baseline. The authors themselves described this as a result encouraging further study, not as proof of efficacy.
Where it did not work
Erythropoietin is sometimes described as a mood-lifting compound, so ARA-290 was checked for the same property. In a randomised, placebo-controlled study of 36 healthy volunteers, emotional processing and mood were assessed a week after dosing. The peptide shifted a few minor measures of how emotional stimuli are handled, but it had no effect on mood or on affective symptoms. This is an honestly published negative result.
The second trail leads to ophthalmology. The ClinicalTrials.gov registry lists a study of ARA-290 in diabetic macular oedema (NCT06626971) that was terminated after nine participants had been enrolled. The reason the centre gave is not a medical one: the study drug expired and no replacement was available.
Safety and the limits of the evidence
None of the human trials described above reported meaningful safety problems, and the chief worry attached to erythropoietin — thickened blood — does not apply to this peptide, because in preclinical work it did not stimulate red cell production. That is still not enough to call the compound safe. The combined enrolment of every trial described here is under two hundred people, the longest course of treatment lasted 28 days, and almost all the studies were run by the same team of anaesthetists from Leiden, together with the company developing the peptide. So there are no data on treatment longer than a month, and no replication by a centre independent of the developer.
Two things deserve a separate mention, because data on them simply do not exist. First: the innate repair receptor switches on cell-survival programmes, which is in itself a theoretical reason for caution in cancer — no study has ever assessed or excluded that risk. Second: ARA-290 remains an investigational compound, is not registered as a medicine in any country, and the furthest stage it reached is phase 2. We deliberately give no methods of use and no doses.
Sport is a separate matter. Because the compound descends from erythropoietin, anti-doping laboratories treat it as a substance that has to be detectable, and they have developed methods of measuring it in samples taken from athletes. It makes no difference that the peptide itself does not raise haematocrit; what counts is its origin and its membership of the group of peptidic drug candidates.
The wider context — “repair” peptides
ARA-290 belongs to the family of compounds sold under the banner of tissue regeneration, which also includes TB-500 (thymosin beta-4) and BPC-157. The difference is worth noticing: those two rest almost entirely on rodents, whereas ARA-290 has five randomised human trials with objective endpoints — nerve fibres counted under a microscope, not merely what participants report. That is the strongest evidence base in this group, which does not make it strong in absolute terms.
Summary
ARA-290 (cibinetide) is an eleven-amino-acid slice of erythropoietin, designed to keep its tissue-protective action and lose its blood-forming one. The mechanism is well documented: the peptide acts through a receptor assembled from part of the EPO receptor and the CD131 protein, and in mice lacking that second component it stops working altogether. In humans, small controlled trials repeatedly showed increased density of small nerve fibres in the cornea and improved neuropathy symptoms in sarcoidosis and type 2 diabetes. What was not shown matters just as much: no advantage over placebo in pain intensity itself in the largest trial, no effect on mood in healthy volunteers, and no phase 3 result of any kind. The evidence can be described as moderate, resting on a handful of small but methodologically sound human trials, unconfirmed in a large study and without regulatory approval.
Sources
- Culver DA, Dahan A, Bajorunas D, et al. Cibinetide Improves Corneal Nerve Fiber Abundance in Patients With Sarcoidosis-Associated Small Nerve Fiber Loss and Neuropathic Pain. Investigative Ophthalmology & Visual Science. 2017;58(6):BIO52-BIO60. PMID: 28475703. DOI: 10.1167/iovs.16-21291. pubmed.ncbi.nlm.nih.gov/28475703
- Dahan A, Dunne A, Swartjes M, et al. ARA 290 improves symptoms in patients with sarcoidosis-associated small nerve fiber loss and increases corneal nerve fiber density. Molecular Medicine. 2013;19(1):334–345. PMID: 24136731. DOI: 10.2119/molmed.2013.00122. pubmed.ncbi.nlm.nih.gov/24136731
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- Heij L, Niesters M, Swartjes M, et al. Safety and efficacy of ARA 290 in sarcoidosis patients with symptoms of small fiber neuropathy: a randomized, double-blind pilot study. Molecular Medicine. 2012;18(1):1430–1436. PMID: 23168581. DOI: 10.2119/molmed.2012.00332. pubmed.ncbi.nlm.nih.gov/23168581
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- Swartjes M, Morariu A, Niesters M, et al. ARA290, a peptide derived from the tertiary structure of erythropoietin, produces long-term relief of neuropathic pain: an experimental study in rats and β-common receptor knockout mice. Anesthesiology. 2011;115(5):1084–1092. PMID: 21873879. DOI: 10.1097/ALN.0b013e31822fcefd. pubmed.ncbi.nlm.nih.gov/21873879
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- Collino M, Thiemermann C, Cerami A, Brines M Flipping the molecular switch for innate protection and repair of tissues: Long-lasting effects of a non-erythropoietic small peptide engineered from erythropoietin. Pharmacology & Therapeutics. 2015;151:32–40. PMID: 25728128. DOI: 10.1016/j.pharmthera.2015.02.005. pubmed.ncbi.nlm.nih.gov/25728128
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For in-vitro laboratory research only. It is not a human medicine and is not for treatment.