# ARA-290 (Cibinetide): Helix-B Mimetic Design, Receptor Logic and Research Use > An 11-residue peptide copied from one face of erythropoietin — built to activate the tissue-protective receptor complex while leaving red cell production untouched. Web page: https://peptidemedixeu.com/en/learn/what-is-ara-290/ · Peptide Medix EU · 6 min read · Updated: 2026-05-19 Also listed as [cibinetide](https://peptidemedixeu.com/en/products/ara-290/), ARA-290 is an 11-residue peptide patterned on the external surface of erythropoietin's helix B and intended to activate the tissue-protective erythropoietin receptor complex without setting off red blood cell production. That one design choice accounts for why a molecule descended from a haematopoietic hormone shows up almost entirely in work on neuroprotection, neuropathic pain and inflammation instead of haematology. The sections below set out what ARA-290 is, how its sequence was selected, the receptor reasoning behind it, what has been published about it, and how the material is specified and handled at the bench. ARA-290 is provided as a lyophilized powder for laboratory research only. ## Reading a peptide off a protein surface: origin and structure Erythropoietin is a glycoprotein of roughly 165 amino acids folded into a four-helix bundle. Its haematopoietic effect is transmitted through a homodimer of the erythropoietin receptor, and the residues that make that contact lie on particular faces of helices A and D. Beginning in the mid-2000s, a line of research proposed that erythropoietin carries a second and structurally distinct activity — protection of tissue — conveyed by a heterocomplex in which the erythropoietin receptor pairs with the beta-common receptor, the signalling subunit shared by the GM-CSF, IL-3 and IL-5 receptors. The literature commonly calls this assembly the innate repair receptor. To obtain ARA-290, the solvent-exposed face of helix B — a stretch not involved in classical receptor binding — was copied as a short linear peptide: pyroglutamate-Glu-Gln-Leu-Glu-Arg-Ala-Leu-Asn-Ser-Ser. Its N-terminal pyroglutamate is a [cyclised glutamine](https://peptidemedixeu.com/en/glossary/cyclic-peptide/) that shields the free N-terminus from aminopeptidase attack, a stabilising trick used widely in short synthetic peptides. The intent behind the design is worth spelling out, because it is what the molecule is. Anyone studying erythropoietin-driven tissue protection with the intact glycoprotein cannot disentangle protective signalling from erythropoiesis, rising haematocrit and the [vascular](https://peptidemedixeu.com/en/learn/research-catalog-cardiovascular/) confounders that accompany it. ARA-290 exists to eliminate that confound. It is essentially a purpose-built experimental instrument, which is why it functions as a reference agonist for the innate repair receptor. ## The proposed mechanism What the literature describes is selective binding to the EPOR/beta-common heterocomplex. Downstream of that, published work reports activation of pathways linked to cell survival and to the resolution of inflammation — JAK2/STAT signalling and PI3K/Akt among them — along with lower output of pro-inflammatory mediators from immune cells. Since the beta-common subunit is present on macrophages, neurons, endothelium and other non-erythroid tissues, the proposed receptor's distribution matches the tissues in which the peptide has been investigated. A second mechanistic thread involves the transient receptor potential vanilloid channel TRPV1 and the biology of small nerve fibres, with reports that ARA-290 alters nociceptor behaviour and epidermal nerve fibre density in model systems. These accounts complement rather than contradict one another, and none should be treated as settled: they are the mechanisms that published investigators have put forward and tested in cell systems and animal models. One thing is comparatively well documented and unusual for a research peptide — the negative finding. Studies consistently report no meaningful stimulation of erythropoiesis, and for an experimental tool an activity that is reliably absent tells you as much as one that is present. ## Fields of published research ### Small nerve fibre and neuropathic pain models The largest and most characteristic portion of the ARA-290 literature sits here. The peptide has been tested in rodent neuropathic pain models and in human phase 2 studies run under the cibinetide name, including work on small fibre neuropathy associated with sarcoidosis and on neuropathy in type 2 [diabetes mellitus](https://peptidemedixeu.com/en/learn/research-catalog-diabetes/), with reported endpoints spanning corneal nerve fibre measures and patient-reported symptom scores. Those trials relate to the investigational drug candidate rather than to research-grade material sold for laboratory purposes, and the compound has never received marketing authorisation. ### Inflammation and immune modulation Studies in cells and rodents have looked at macrophage phenotype, cytokine release and markers of inflammatory resolution. This puts ARA-290 in roughly the same research territory as sequences such as KPV, although the point of entry is completely different: one acts through a receptor heterocomplex, the other through intracellular NF-kappa B signalling. ### Ischaemia, organ protection and metabolic models Preclinical studies have explored the peptide in ischaemia-reperfusion injury across several organ systems and in islet and transplantation models, following the tissue-protection hypothesis that inspired its design. All of these findings come from rodents and in vitro systems. ### Immune and repair comparisons Laboratories surveying immunomodulatory peptides often set ARA-290 beside [thymosin alpha-1](https://peptidemedixeu.com/en/products/thymosin-alpha-1/), which works via toll-like receptor signalling and T-cell maturation, or beside BPC-157 in repair models. The comparison is useful exactly because the mechanisms have nothing in common. ## Available presentations We stock ARA-290 as a lyophilized powder in sealed, crimp-stoppered vials of 10 mg (€100) and 20 mg (€180). With a mass of 1259.34 g/mol, a 10 mg vial holds about 7.9 micromoles — a middling molar amount, above what full-length proteins provide and below the yields of tripeptides. Comparable material is grouped under anti-inflammatory peptides, and for immune-focused work under immune peptides. ## Reconstitution and storage at the bench Reconstituting the vial is a matter of concentration arithmetic. Adding 2 [mL of bacteriostatic water to](https://peptidemedixeu.com/en/products/bacteriostatic-water/) a 10 mg vial produces 5 mg/mL, that is 5,000 mcg/mL, so 0.1 mL — 10 units on a U-100 syringe — contains 500 mcg. Expressed molar, 5 mg/mL of a 1259.34 g/mol peptide is about 3.97 mM, and that is the figure you need when making up nanomolar or micromolar working solutions for cell assays. The peptide goes into aqueous buffer without difficulty. Run the diluent slowly down the vial wall instead of squirting it onto the cake, and swirl rather than shake, because mechanical agitation encourages aggregation at air-liquid interfaces. Keep lyophilized vials at −20 °C out of the light; refrigerate reconstituted solution and split it into aliquots so that nothing is warmed repeatedly. The reconstitution guide gives the method step by step, and the storage guide covers temperature and stability in detail. ## Purity, the COA and how to read it Every lot is purified by reversed-phase HPLC to at least 99% with the mass confirmed, and the certificate corresponds to the lot number on the vial. With an 11-residue peptide carrying an N-terminal pyroglutamate, two checks warrant special attention. The first is that the observed mass should agree with 1259.34 g/mol; an unmodified N-terminal glutamine would read 17 Da higher, making the mass the direct proof that cyclisation took place. The second is that this sequence contains asparagine and serine residues liable to deamidate or degrade under [unsuitable storage conditions](https://peptidemedixeu.com/en/learn/how-to-store-peptides/), and the HPLC trace is where the resulting shoulder peaks show up. Read the chromatogram itself, not just the headline number. Our COA reading guide works through genuine traces and explains what net peptide content means relative to gross vial weight. ## Regulatory position Cibinetide has gone through clinical investigation yet holds no marketing authorisation in the United States or the European Union, and ARA-290 is neither an approved medicine nor a food supplement nor a generally available [compounded product](https://peptidemedixeu.com/en/glossary/compounding-pharmacy/). Published human trial data describe the investigational candidate under controlled conditions; they do not carry over to research-grade material, for which no therapeutic claim is made. ## Related peptides and further reading For a broader view of repair-focused research peptides and how investigators decide between mechanisms, see the healing and recovery research overview. Within this catalogue KPV, VIP and thymosin alpha-1 offer three further, mechanistically unrelated routes into inflammation research; ARA-290 is still the only one designed expressly to separate a receptor heterocomplex from the dominant activity of its parent hormone. ## Frequently asked questions ### What is ARA-290? ARA-290, known in clinical work as cibinetide, is a synthetic peptide of 11 residues copying the solvent-exposed face of erythropoietin's helix B. Its mass is 1259.34 g/mol and it begins with a pyroglutamate residue. The molecule was created as a research and investigational tool for activating the tissue-protective erythropoietin receptor complex in place of the classical haematopoietic receptor. ### Does ARA-290 increase red blood cell numbers? Published work reports no appreciable stimulation of erythropoiesis, and that absence was intended. The sequence was lifted from a part of erythropoietin that plays no role in classical receptor binding, specifically so that tissue-protective signalling could be examined without changes in haematocrit clouding the result. ### What does "innate repair receptor" refer to? The term used in the literature for a heterocomplex formed between the erythropoietin receptor and the beta-common receptor subunit, the same subunit shared by the GM-CSF, IL-3 and IL-5 receptors. This complex is proposed to carry the tissue-protective and anti-inflammatory activity of erythropoietin, and it appears on macrophages, neurons and endothelium rather than on erythroid precursors. ### Do human data on ARA-290 exist? They do, under the name cibinetide. Reported phase 2 studies cover small fibre neuropathy associated with sarcoidosis and neuropathy in type 2 diabetes, using endpoints such as corneal nerve fibre measurements and symptom scores. Those studies examined an investigational drug candidate under controlled conditions, and their findings do not extend to research-grade material supplied for laboratory work. ### What purpose does the N-terminal pyroglutamate serve? Pyroglutamate is glutamine in cyclised form. By eliminating the free primary amine at the N-terminus it prevents aminopeptidase cleavage and so stabilises the peptide. There is a practical consequence for certificates of analysis: a glutamine that had not cyclised would give a mass about 17 Da greater, so the observed mass shows directly whether the modification is present. ### In what form and sizes is ARA-290 supplied? As a lyophilized white powder in sealed glass vials with crimped stoppers, offered in 10 mg and 20 mg sizes. Every lot is purified by reversed-phase HPLC to 99% or better with the mass confirmed, and a certificate of analysis corresponding to the vial's lot number can be requested. ### How does ARA-290 compare with KPV or thymosin alpha-1? The three turn up in inflammation research but work by entirely separate routes. ARA-290 binds a receptor heterocomplex at the cell surface; KPV is reported to act inside the cell on NF-kappa B signalling once taken up by a transporter; thymosin alpha-1 operates through toll-like receptor signalling and the maturation of T cells. They complement each other as comparators rather than replacing one another. ### Does ARA-290 hold any approval? It does not. Even though it has been investigated clinically as cibinetide, it has no marketing authorisation in either the United States or the European Union, is not a food supplement, and is not a widely available compounded preparation. --- For laboratory research use only. This page is provided for scientific and educational information. Materials referenced here are sold strictly for in-vitro laboratory research by qualified professionals — not for human or veterinary use, and nothing on this page is medical advice.