TL;DR: ARA-290 (cibinetide) is an 11-amino-acid peptide copied from a small loop of erythropoietin (EPO) — but it deliberately leaves out the part of EPO that raises red blood cells. Instead it acts on the innate repair receptor, an EPOR/CD131 heteromer, to dampen inflammation and support nerve and tissue repair. Unusually for a repair peptide, it reached Phase 2 human trials for small-fiber neuropathy in sarcoidosis and in diabetes, and it holds FDA orphan status. Its original sponsor wound down, but the compound itself is well characterized.
Most peptides in the tissue-repair conversation live almost entirely in animal and cell-culture data. ARA-290 is the interesting exception: it carries the best human evidence in its niche, having been taken into controlled Phase 2 trials in people with small-fiber neuropathy. It reaches that niche from an unusual starting point — it is a fragment of the hormone erythropoietin, redesigned so that it keeps EPO’s tissue-protective signaling while dropping the red-cell-raising activity that EPO is famous for. This guide covers what ARA-290 is, the innate repair receptor it targets, what the trials showed, and why researchers working on neuropathy and metabolic-nerve questions keep coming back to it.
What Is ARA-290?
ARA-290, also known by its International Nonproprietary Name cibinetide, is a linear peptide of 11 amino acids. Its sequence is modeled on the aqueous-exposed face of helix B of erythropoietin — the region of the EPO molecule that faces outward when EPO is folded, and the part now thought to carry EPO’s tissue-protective signaling.
That design choice is the whole point. Full-length EPO does two very different jobs: it stimulates the bone marrow to make red blood cells (erythropoiesis), and, separately, it protects and repairs stressed tissue. Those two activities turn out to run through different receptor arrangements. By copying only the helix-B face and not the receptor-binding surface responsible for erythropoiesis, ARA-290 was built to keep the repair signaling while shedding the red-cell effect — which is why it is described as non-erythropoietic. In practical terms, it is not expected to raise hematocrit or hemoglobin the way EPO does, and that separation is the feature researchers care about most.
Mechanism: The Innate Repair Receptor
The receptor ARA-290 is built around is usually called the innate repair receptor (IRR). It is not a brand-new protein but a specific pairing of two known ones.
EPOR paired with CD131
The classic EPO receptor, EPOR, can assemble in more than one way. When two EPOR chains come together as a homodimer, that high-affinity form drives erythropoiesis. But EPOR can also pair with CD131 — the beta common receptor shared by several cytokine systems — to form a heteromeric receptor with lower affinity for EPO. This EPOR/CD131 heteromer is the innate repair receptor, and it is expressed on cells involved in injury and inflammation rather than on red-cell precursors. ARA-290 is designed to engage this heteromer selectively while largely ignoring the erythropoietic homodimer.
Downstream anti-inflammatory and repair signaling
Engaging the innate repair receptor is reported to shift injured tissue away from an inflammatory state and toward a repair state. In preclinical models this has been associated with reduced pro-inflammatory cytokine signaling, decreased immune-cell recruitment to damaged tissue, and support for cell survival — the kind of tissue-protective profile EPO shows without the hematologic effect. Because the receptor sits at the interface of innate immunity and repair, the compound is framed less as a growth stimulant and more as a signal that tells stressed tissue to stop amplifying inflammation and start healing.
Why this is mechanistically distinct
This is a different lane from the better-known repair peptides. BPC-157 is studied around angiogenesis and growth-factor signaling, and TB-500 around actin regulation and cell migration. ARA-290 instead works through a defined cytokine-family receptor with an explicit anti-inflammatory, neuroprotective emphasis — which is exactly why its most-studied application is nerve-related rather than tendon- or muscle-related.
What the Research Shows
The reason ARA-290 stands out is that it did not stay in rodents. It was carried into controlled human trials, mainly for small-fiber neuropathy — damage to the thin nerve fibers that carry pain and autonomic signals, which is difficult to treat and appears in both sarcoidosis and diabetes.
| Research area | Strongest evidence | Overall state of evidence |
|---|---|---|
| Sarcoidosis small-fiber neuropathy | Phase 2 randomized, placebo-controlled trials | Reported improvements in neuropathic symptoms and corneal nerve-fiber measures |
| Diabetic / metabolic neuropathy | Phase 2 trial in type 2 diabetes | Signals on nerve-fiber and metabolic readouts; not definitive |
| Neuropathic pain more broadly | Early clinical and preclinical work | Exploratory; mechanism-driven interest |
| General tissue protection | Preclinical injury models | Consistent with EPO tissue-protective literature, not yet human-confirmed |
Editorial rating of the current evidence base, not an efficacy claim.
Sarcoidosis small-fiber neuropathy
This is where ARA-290 has its most-cited human data. Sarcoidosis frequently comes with small-fiber neuropathy that conventional treatment handles poorly, which made it a logical proving ground. Phase 2 randomized, placebo-controlled work reported reductions in patient-rated neuropathic symptoms and pain, alongside changes in objective measures such as corneal nerve-fiber density measured by confocal microscopy — a way to look at small-fiber regeneration without a skin biopsy. The trials were modest in size, but they are genuine controlled human data, which is rare in this corner of peptide research.
Diabetic and metabolic neuropathy
ARA-290 was also studied in type 2 diabetes, where small-fiber damage is common and where the anti-inflammatory, nerve-supportive mechanism has an obvious rationale. Reported readouts touched both nerve-fiber measures and metabolic parameters. The metabolic-nerve angle is part of why the compound draws continued interest: it sits at an intersection of inflammation, nerve repair, and metabolic disease that few other research peptides address directly.
The honest limits
The trials were relatively small, single-program, and mostly tied to one developer’s work; independent large-scale replication is limited. Positive Phase 2 results are a meaningful step above preclinical-only compounds, but they are not the same as confirmed efficacy from large multicenter trials. The right reading is “promising and unusually well-characterized for its class,” not “proven.”
Sponsor History and Orphan Status
ARA-290 was developed by Araim Pharmaceuticals, which built the small-peptide-mimetic approach to EPO’s tissue-protective activity and ran the neuropathy trials. The compound received FDA orphan-drug designation for sarcoidosis-associated conditions, reflecting its focus on a rare, hard-to-treat indication. The sponsor later wound down its active development program, which is why ARA-290 has not advanced to approval despite its comparatively strong early data. Importantly, the science did not disappear with the company: cibinetide is a well-defined molecule with published trial results and a clear mechanism, so it remains a reference point for researchers working on innate-repair-receptor biology and small-fiber neuropathy.
Why the Research Community Stays Interested
Three things keep ARA-290 in the conversation. First, the clean mechanism — a designed, receptor-selective peptide that separates tissue protection from erythropoiesis is a tidy proof of concept for the innate repair receptor idea. Second, the human data — Phase 2 neuropathy trials give it an evidence footing that mechanism-only peptides lack. Third, the unmet-need angle — small-fiber neuropathy in sarcoidosis and diabetes has few good options, so a non-erythropoietic, anti-inflammatory nerve-repair candidate is conceptually attractive even where the clinical case is unfinished. For researchers mapping the anti-inflammatory and repair peptide landscape, ARA-290 occupies a distinct neuro-inflammation corner that BPC-157, TB-500, and KPV do not.
Forms and Handling
In research settings, ARA-290 (cibinetide) is typically supplied as a lyophilized (freeze-dried) powder in sealed vials. Like other lyophilized peptides, it is reconstituted with an appropriate diluent — commonly bacteriostatic water — before use in laboratory work. General handling that applies broadly to peptides of this size includes allowing the vial to reach room temperature before reconstitution, adding diluent slowly down the vial wall rather than onto the powder, swirling gently rather than shaking, and labeling each vial with the reconstitution date, diluent volume, and resulting concentration. For a full walkthrough of the arithmetic, see our peptide reconstitution guide; lyophilized material is generally stored frozen and protected from light, while reconstituted solution is refrigerated and used within a limited window.
Frequently Asked Questions
Does ARA-290 raise red blood cells like EPO?
No — that is the entire design goal. ARA-290 copies only the helix-B face of erythropoietin that carries tissue-protective signaling, and it leaves out the surface responsible for erythropoiesis. It acts on the innate repair receptor (an EPOR/CD131 heteromer) rather than the erythropoietic EPOR homodimer, so it is described as non-erythropoietic and is not expected to raise hematocrit the way EPO does.
What is the innate repair receptor?
It is a heteromeric receptor formed when EPOR pairs with CD131, the beta common receptor, instead of pairing with a second EPOR chain. This EPOR/CD131 combination has lower affinity for EPO and is found on cells involved in injury and inflammation rather than red-cell precursors. ARA-290 was designed to engage this receptor selectively, which is how it channels EPO’s repair signaling without the hematologic effect.
How far did ARA-290 get in human trials?
It reached Phase 2 — randomized, placebo-controlled trials — mainly for small-fiber neuropathy in sarcoidosis, plus a trial in type 2 diabetes. Reported readouts included patient-rated neuropathic symptoms and objective small-fiber measures such as corneal nerve-fiber density. That is unusually advanced human evidence for a peptide in this class, though the trials were small and the program did not continue to approval.
How is ARA-290 different from BPC-157 or TB-500?
Mechanism and focus. BPC-157 is studied around angiogenesis and growth-factor signaling, and TB-500 around actin regulation and cell migration. ARA-290 works through the innate repair receptor with an explicit anti-inflammatory, neuroprotective emphasis, which is why its research centers on nerve repair and small-fiber neuropathy rather than tendon or muscle models.
Is cibinetide the same thing as ARA-290?
Yes. Cibinetide is the International Nonproprietary Name for the same 11-amino-acid EPO helix-B mimetic peptide; ARA-290 is the development code from its original sponsor. The two names refer to one molecule.
Why did ARA-290 not become an approved drug?
Its developer, Araim Pharmaceuticals, wound down active development, so the program did not advance past Phase 2 despite comparatively strong early data. The compound remains well characterized in the literature, which is why it is still referenced in innate-repair-receptor and neuropathy research even though it is not an approved medicine.
Related reading
References
- Brines M, Cerami A. “The receptor that tames the innate immune response.” Molecular Medicine. 2012;18(1):486-496.
- Brines M, Dunne AN, van Velzen M, et al. “ARA 290, a nonerythropoietic peptide engineered from erythropoietin, improves metabolic control and neuropathic symptoms in patients with type 2 diabetes.” Molecular Medicine. 2015;20(1):658-666.
- 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.
- 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.
Disclaimer: This information is for educational and research purposes only. Peptides are research chemicals not intended for human consumption.