Cibinetide (ARA-290)
ARA-290, ARA 290, cibinetide, pHBSP, PHBSP, pyroglutamate helix B surface peptide
Cibinetide is an eleven-amino-acid peptide engineered from the helix-B surface of erythropoietin. It activates the tissue-protective innate repair receptor without stimulating red cell production, avoiding the thrombotic risks that ended EPO's development as a neuroprotectant. It has the most credible human trial data of any compound in this class, and it still has not been approved for anything.
Mechanism
Erythropoietin has two separable functions. Erythropoiesis is driven by the homodimeric EPO receptor, (EPOR)2, expressed on erythroid progenitors. Tissue protection is mediated by a distinct receptor complex: a heterodimer of EPOR with the beta-common receptor (CD131, CSF2RB), which the developers named the innate repair receptor. This second receptor has much lower affinity for EPO and is expressed at sites of injury and inflammation. Recognising this split explains why high-dose EPO trials for stroke and neuroprotection produced thrombotic and hypertensive harm: the doses needed to engage the tissue-protective receptor also drove erythropoiesis.
ARA-290 is a rational solution to that problem. It reproduces the aqueous face of EPO's helix B, the region that contacts the innate repair receptor, as a linear eleven-residue peptide with an N-terminal pyroglutamate for stability. It has essentially no affinity for the homodimeric EPOR and does not raise haematocrit. Engagement of the innate repair receptor triggers JAK2/STAT3 and PI3K/Akt signalling with downstream anti-apoptotic effects, dampens pro-inflammatory macrophage and mast cell activation, and shifts the local tissue response from injury propagation towards repair. A separate line of work implicates modulation of the TRPV1 nociceptor channel in its analgesic effect, which may be partly distinct from the repair mechanism.
What the research shows
Dahan's 2013 randomised placebo-controlled trial in sarcoidosis-associated small nerve fibre loss found that 28 days of daily subcutaneous ARA-290 improved neuropathic symptoms, increased corneal nerve fibre density, altered cutaneous temperature sensitivity and improved six-minute walk distance. Culver's 2017 Phase 2b (NCT02039687, registered enrolment 64) tested 1, 4 and 8 mg daily against placebo with corneal nerve fibre area as the primary endpoint. The placebo-corrected mean change from baseline at day 28 was 109 square micrometres (95% CI -429 to 647) at 1 mg, 697 (159 to 1236; P=0.012) at 4 mg and 431 (-130 to 992) at 8 mg, with a significant increase in regenerating intraepidermal GAP-43-positive fibres in the 4 mg group (P=0.035); changes in corneal nerve fibre area correlated with GAP-43-positive fibres and with the six-minute walk test. Brines's 2015 Phase 2 in type 2 diabetes reported improvements in HbA1c, lipid profile and PainDetect scores over 28 days with a further month of follow-up.
These results should be read carefully rather than enthusiastically. The dose response in the Phase 2b was non-monotonic: 8 mg performed worse than 4 mg, which is a pattern that can reflect true inverted-U pharmacology or can reflect noise in a small trial. The pain endpoint, arguably what a patient cares most about, did not reach significance even in the best-performing group (P=0.157). The primary endpoints were surrogate morphometric measures of nerve fibre abundance, not clinical outcomes. All trials ran 28 days. A Phase 2 in diabetic macular oedema was terminated after nine participants (NCT06626971), and a separate Phase 2 in the same indication reported by Lois in 2020 did not lead to further development. The registry also lists a Phase 2 in prediabetes and type 2 diabetes (NCT01933529, n=24, status unknown) and a Phase 1/2 in depression (NCT02070783, n=36). Fifteen years after the concept was published, the compound has no Phase 3 programme and no approval. That is the honest summary: the best-supported compound in this class, and still unproven.
Evidence assessment
Mixed evidence
Multiple randomised, placebo-controlled Phase 2 trials in humans with positive results on prespecified surrogate endpoints, but all short (28 days), small (largest registered enrolment n=64), concentrated among a small network of related investigators, with a non-monotonic dose response and no confirmatory Phase 3 or approval.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
ARA 290 improves symptoms in patients with sarcoidosis-associated small nerve fiber loss and increases corneal nerve fiber density Mixed evidence
Improved neuropathic symptoms, increased corneal small nerve fibre density, altered cutaneous temperature sensitivity and increased six-minute walk distance.
Cibinetide Improves Corneal Nerve Fiber Abundance in Patients With Sarcoidosis-Associated Small Nerve Fiber Loss and Neuropathic Pain Mixed evidence
Placebo-corrected corneal nerve fibre area increased significantly in the 4 mg group (697 square micrometres, 95% CI 159-1236, P=0.012) with increased GAP-43-positive intraepidermal fibres (P=0.035); pain intensity in moderate-severe subjects did not reach significance (P=0.157) and the dose response was non-monotonic, with 8 mg below 4 mg.
ARA 290, a nonerythropoietic peptide engineered from erythropoietin, improves metabolic control and neuropathic symptoms in patients with type 2 diabetes Mixed evidence
Improvements in HbA1c and lipid profile sustained over 56 days, significant improvement in PainDetect neuropathic symptom scores, and increased corneal nerve fibre density in the subgroup with the greatest baseline deficit; no safety issues identified.
A Phase 2 Clinical Trial on the Use of Cibinetide for the Treatment of Diabetic Macular Edema Mixed evidence
Evaluated cibinetide in diabetic macular oedema; the programme did not progress to later-phase development in this indication.
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 Preclinical only
Produced durable relief of neuropathic pain with suppression of the spinal microglial response, supporting a neuroimmune mechanism.
ARA 290 relieves pathophysiological pain by targeting TRPV1 channel: Integration between immune system and nociception Preclinical only
Implicates modulation of the TRPV1 channel in ARA-290's antinociceptive action, linking immune and nociceptive mechanisms.
Safety
Well tolerated across the published 28-day trials, with no identified safety signal and, critically, no increase in haematocrit, which was the central design objective and appears to have been achieved. Injection site reactions were the main reported adverse effect. Nothing is known beyond roughly one month of continuous exposure in any published study. Because the innate repair receptor pathway is a broad anti-apoptotic and tissue-protective programme, the theoretical question of long-term effects on tumour surveillance has not been addressed by any study of adequate duration. Material obtained outside a clinical trial carries the usual unregulated-manufacture risks.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | No MHRA marketing authorisation. Investigational status only; not an authorised medicine and not available on prescription. |
| United States | Not FDA-approved for any indication. Developed as an investigational agent by Araim Pharmaceuticals and taken through Phase 2 trials, but no marketing application has resulted. Any material available to consumers is outside the investigational supply chain and is not the trial product. |
| WADA (sport) | Not individually named on the Prohibited List. Athletes should be aware that erythropoietin and erythropoietin-receptor agonists are prohibited under S2.1, and while ARA-290 is specifically engineered to be non-erythropoietic, anti-doping authorities may treat an EPO-derived peptide as captured by S2 or by S0 as a non-approved substance. Seek guidance from your anti-doping organisation before use. |
Questions
No, and that is the entire point of the molecule. ARA-290 was designed to engage only the innate repair receptor, the EPOR/CD131 heterodimer that mediates tissue protection, and it has essentially no affinity for the homodimeric EPO receptor that drives red cell production. The published trials found no increase in haematocrit, confirming the design worked.
No. It completed several Phase 2 trials, including a Phase 2b in sarcoidosis-associated small fibre neuropathy, but never advanced to Phase 3 and has no marketing authorisation from the FDA, EMA or MHRA. Material sold online is not the investigational product used in those trials.
It is the best in this class and still limited. The trials were randomised and placebo-controlled, which most peptides never manage, but they were short at 28 days, small at up to 64 patients, and their primary endpoints were surrogate measures of corneal nerve fibre abundance rather than clinical outcomes. The pain endpoint did not reach statistical significance even in the best-performing dose group, and 8 mg performed worse than 4 mg.
It is a heterodimeric receptor formed from the erythropoietin receptor paired with the beta-common receptor (CD131), rather than the two EPO receptors that pair up to drive red cell production. It appears at sites of tissue injury and inflammation, has lower affinity for EPO, and mediates the anti-apoptotic and anti-inflammatory arm of erythropoietin's biology.