ARA-290 (Cibinetide): The Erythropoietin-Derived Peptide in the Research Literature

Research-use-only context. This article summarizes published third-party scientific literature and laboratory practice. It is not medical advice, not a therapeutic or performance claim, and not a usage guide. US Prime Peptides products are supplied strictly for in vitro laboratory research and are not for human or veterinary use.

This article explains what ARA-290 is at the sequence level, how it was derived from the three-dimensional structure of erythropoietin, what the "innate repair receptor" hypothesis claims and what evidence supports it, what rodent studies measured, what the clinical program under the name cibinetide reported, its regulatory status, and what a certificate should show for an 11-residue peptide with a pyroglutamate N-terminus and no aromatic residue.

ARA-290 is an 11-residue peptide copied from the water-facing side of erythropoietin's helix B

ARA-290 is pyroGlu-Glu-Gln-Leu-Glu-Arg-Ala-Leu-Asn-Ser-Ser, an 11-residue linear peptide whose N-terminal glutamine has cyclized to pyroglutamate. It does not reproduce a contiguous stretch of erythropoietin (EPO). Instead, it strings together the residues that form the aqueous face of EPO's helix B, the part of the hormone that points away from the classical EPO receptor when EPO is bound to it. The older literature calls it pHBSP, "pyroglutamate helix B surface peptide." Its INN is cibinetide. Formula C₅₁H₈₄N₁₆O₂₁, average mass about 1,257 daltons, CAS 1208243-50-8, PubChem CID 91810664.

The sequence has no cysteine, methionine, tryptophan, tyrosine or phenylalanine. Three glutamates and one arginine give it a net negative charge at neutral pH, so it is readily water-soluble and, unlike many cationic research peptides, not strongly adsorptive. The pyroglutamate cap removes the free N-terminal amine, which blocks aminopeptidase attack and Edman sequencing alike. For how such caps are written and read, see How to Read a Peptide Sequence: One-Letter Codes, Modifications, and Salt Forms.

It came out of a program to separate EPO's two activities

ARA-290 exists because a group of researchers set out to make EPO derivatives that kept its tissue-level signaling but lost its effect on red-cell production. Leist, Brines, Cerami and colleagues reported in Science in 2004 that carbamylated EPO and certain EPO mutants did not bind the classical EPO receptor, showed no hematopoietic activity in human cell signaling assays or in animals, yet remained cytoprotective in vitro and active in rodent models of stroke, spinal-cord compression, diabetic neuropathy and experimental autoimmune encephalomyelitis.

The same year, Brines and colleagues proposed in the Proceedings of the National Academy of Sciences what the alternative receptor might be. Membrane proteins from rat brain, heart, liver and kidney, enriched on EPO or CEPO affinity columns, contained the EPO receptor covalently complexed with the common beta receptor (beta_cR, CD131), the signaling subunit shared by the GM-CSF, IL-3 and IL-5 receptors. Antibodies to the EPO receptor co-immunoprecipitated beta_cR from P-19 neuronal-like cells, the two proteins co-localized in spinal-cord neurons and cardiomyocytes, and neither EPO nor CEPO was active in cardiomyocyte or spinal-cord injury models in beta_cR knock-out mice.

In 2008, Brines and colleagues reported in the same journal that the tissue-level activity could be delimited to short peptides. Helix B itself (residues 58 to 82) was active in vitro and in rodent models, and so was an 11-residue peptide assembled from the residues forming its aqueous face. Neither was erythropoietic in vitro or in animals. That 11-mer is ARA-290. The authors disclosed that several of them were employees of Warren Pharmaceuticals, the company developing the compounds.

The "innate repair receptor" is a hypothesis with specific supporting evidence and open questions

The claim behind ARA-290 is that an EPO receptor / beta_cR heterocomplex, which the developers named the innate repair receptor, is expressed by injured tissue and is what the peptide engages. The supporting evidence is of three kinds: biochemical co-purification and co-immunoprecipitation of the two receptor subunits (the 2004 PNAS paper), loss of response in beta_cR knock-out mice (2004), and loss of response after knocking down beta_cR. For the last, Wang and colleagues reported in CNS Neurosci Ther in 2024 that in male C57BL/6J mice subjected to middle cerebral artery occlusion, ARA290 reduced infarct measures, neuronal apoptosis and inflammatory cytokines in brain tissue without changing blood parameters, and that siRNA against beta_cR suppressed the effect.

What remains open is the structural biology. No crystal or cryo-EM structure of ARA-290 bound to any receptor has been published, and the peptide's binding affinity to the proposed heterocomplex has not been reported in the way a conventional ligand's would be. The heteroreceptor concept is widely cited, but readers should hold it as a working model supported by genetic and biochemical evidence rather than as a settled receptor assignment. Dennhardt and colleagues' 2022 study in Frontiers in Immunology illustrates the current approach: they found endogenous EPO elevated in plasma from humans, piglets and mice with hemolytic-uremic syndrome, then tested pHBSP in a mouse model, reporting improved 7-day survival and reduced renal oxidative and nitrosative stress markers without change in several other renal injury measures.

What the rodent studies measured

The most-cited preclinical ARA-290 paper measured allodynia scores and glial markers in a rat nerve-injury model. Swartjes, Dahan and colleagues reported in Molecular Pain in 2014 that after spared nerve injury in rats, ARA 290 at four exposure levels reduced mechanical and cold allodynia measurements relative to vehicle for up to 20 weeks, and that animals at the two higher levels did not show the increase in spinal-cord microglial iba-1 immunoreactivity seen with vehicle at 2 weeks. Astrocyte GFAP immunoreactivity did not differ between groups. The authors read this as a link between suppression of the spinal microglial response and the behavioral readout.

Across the rodent literature, the model systems are nerve injury, cerebral ischemia, renal ischemia-reperfusion and toxin challenge, and the endpoints are behavioral scores, histology, immunostaining, cytokine panels and survival. These are rodent measurements. They do not describe or predict any effect in a person, and the clinical program described next was a separate, regulated undertaking with pharmaceutical-grade material.

The clinical program ran under the name cibinetide

ARA-290 is unusual among research peptides in having a published, placebo-controlled clinical program, which is a matter of record, not a property of a research vial. Araim Pharmaceuticals, successor to Warren, sponsored the trials with Leiden University Medical Center as the main academic partner. Heij and colleagues reported in Molecular Medicine in 2012 a randomized, double-blind pilot in 22 adults with sarcoidosis and small-fiber neuropathy symptoms over 4 weeks; no safety concerns were raised by clinical or laboratory assessment, and the small-fiber neuropathy screening list score changed more in the ARA 290 group than with placebo.

Dahan and colleagues reported a 28-day blinded, placebo-controlled study in the same journal in 2013, adding corneal confocal microscopy: corneal small-nerve-fiber density increased in the ARA 290 group, along with changes in cutaneous temperature sensitivity and 6-minute-walk distance. Brines and colleagues reported a 28-day phase 2 study in adults with type 2 diabetes and neuropathic symptoms in Molecular Medicine in 2015, with hemoglobin A1c, lipid profile, PainDetect scores and corneal nerve-fiber density as outcomes. Culver and colleagues reported the largest study, a 28-day phase 2b trial in 64 adults with sarcoidosis-associated small-fiber loss, in Investigative Ophthalmology & Visual Science in 2017; the primary endpoint was change in corneal nerve-fiber area, which rose significantly in the middle of three exposure groups, correlating with regenerating intraepidermal fibers and walk distance.

No phase 3 result has been published and cibinetide has not been approved in any jurisdiction. The program sought orphan-designation status for sarcoidosis-associated small-fiber neuropathy. For where this compound sits relative to approved peptides, see FDA Status of Common Research Peptides: A Reference Table.

Regulatory status and what a certificate should show

ARA-290 is not an approved drug in the United States or elsewhere, and a research vial is not the investigational product used in the trials above. Research use is in vitro: receptor-biology, cell-signaling and biochemical assays of the kind the primary literature describes. US Prime Peptides supplies it strictly on that basis.

For the certificate, three sequence features matter. First, the pyroglutamate N-terminus: cyclization of Gln to pGlu releases ammonia, so the correct peptide is 17 daltons lighter than the open-chain Gln form, and the identity line should show the pGlu mass (monoisotopic [M+H]⁺ near 1,257.6). A certificate reporting a mass 17 daltons higher is describing an uncyclized product. Second, the sequence contains Asn-Ser and Gln, two deamidation-prone motifs; deamidation adds one dalton and produces isoaspartate variants that may partially resolve on HPLC as a shoulder. Third, with no aromatic residue, absorbance at 280 nm cannot be used for content, so the certificate should state a far-UV, amino acid analysis or nitrogen method. See LC-MS Identity Confirmation and Net Peptide Content vs Purity.

US Prime Peptides posts a lot-matched certificate before purchase for ARA-290 10 mg, covering identity by mass spectrometry, HPLC purity, net peptide content, endotoxin, sterility and heavy metals, with an independent third-party report. The 10 mg label mass is the lyophilized fill and should be read against the content and counter-ion lines.

Frequently Asked Questions

What is ARA-290 derived from?

From erythropoietin. It is an 11-residue peptide assembled from the residues on the water-facing side of EPO's helix B, the surface that points away from the classical EPO receptor. It was reported in 2008 by the group that had earlier made carbamylated EPO, and it does not stimulate red-cell production in the assays and animals tested.

Is ARA-290 the same as cibinetide?

Yes. Cibinetide is the International Nonproprietary Name assigned to ARA-290 when it entered clinical development with Araim Pharmaceuticals. The older code pHBSP, "pyroglutamate helix B surface peptide," refers to the same sequence.

What is the innate repair receptor?

It is the developers' name for a proposed heterocomplex of the EPO receptor and the common beta receptor (CD131). Evidence includes co-purification of the two subunits from rat tissue, loss of response in CD131 knock-out mice, and loss of response after CD131 knockdown in a 2024 mouse stroke study. No structure of the complex with ARA-290 has been published.

Is ARA-290 FDA approved?

No. Cibinetide completed phase 2 and 2b trials between 2012 and 2017 but has not been approved in the United States or any other country, and no phase 3 result has been published. Research vials are supplied for in vitro work only.

Citations

1. Leist M, Ghezzi P, Grasso G, et al. Derivatives of erythropoietin that are tissue protective but not erythropoietic. Science. 2004;305:239-242. PMID 15247477
2. Brines M, Grasso G, Fiordaliso F, et al. Erythropoietin mediates tissue protection through an erythropoietin and common beta-subunit heteroreceptor. Proc Natl Acad Sci USA. 2004;101:14907-14912. PMID 15456912
3. Brines M, Patel NS, Villa P, et al. Nonerythropoietic, tissue-protective peptides derived from the tertiary structure of erythropoietin. Proc Natl Acad Sci USA. 2008;105:10925-10930. PMID 18676614
4. 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. Mol Med. 2012;18:1430-1436. PMID 23168581
5. 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. Mol Med. 2013;19:334-345. PMID 24136731
6. Swartjes M, van Velzen M, Niesters M, et al. ARA 290, a peptide derived from the tertiary structure of erythropoietin, produces long-term relief of neuropathic pain coupled with suppression of the spinal microglia response. Mol Pain. 2014;10:13. PMID 24529189
7. 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. Mol Med. 2015;20:658-666. PMID 25387363
8. 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. Invest Ophthalmol Vis Sci. 2017;58:BIO52-BIO60. PMID 28475703
9. Dennhardt S, Pirschel W, Wissuwa B, et al. Targeting the innate repair receptor axis via erythropoietin or pyroglutamate helix B surface peptide attenuates hemolytic-uremic syndrome in mice. Front Immunol. 2022;13:1010882. PMID 36211426
10. Wang RL, Yang ZH, Huang YY, et al. Erythropoietin-derived peptide ARA290 mediates brain tissue protection through the β-common receptor in mice with cerebral ischemic stroke. CNS Neurosci Ther. 2024;30:e14676. PMID 38488446

This article is for laboratory research reference only. US Prime Peptides products are supplied strictly for in vitro research. Not for human consumption.

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