ARA-290

ARA-290 (cibinetide, helix B surface peptide, HBSP) is a synthetic 11 amino acid peptide, sequence Pyr-Glu-Glu-Leu-Glu-Arg-Ala-Leu-Asn-Ser-Ser, molecular weight 1257 Da, derived from the tissue-protective helix B surface domain of erythropoietin.

The design premise is receptor dissociation. EPO signals through two distinct assemblies: the homodimeric EPO receptor (EPOR) on bone marrow driving erythropoiesis, and the heteromeric innate repair receptor (IRR) — one EPOR subunit paired with the beta-common receptor (CD131) — mediating tissue protection. ARA-290 is selective for the IRR and does not activate the EPOR homodimer. That removes the haematocrit rise, viscosity change, hypertension, and thrombotic risk that constrain EPO itself.

The IRR is not expressed constitutively; it is upregulated on cells that are stressed, injured, or inflamed, so activity concentrates where damage already exists. Small-fibre neuropathy is therefore a natural fit and is the headline indication.

Regulatory position: FDA Orphan Drug and Fast Track designations for sarcoidosis-associated small-fibre neuropathy; EU Orphan Medicinal Product designation for prevention of graft loss in pancreatic islet transplantation; multiple completed Phase 2 trials in sarcoidosis and diabetic neuropathy; not FDA approved for any indication; available as a research chemical.

Subcutaneous administration, with phosphate buffered saline the trial-standard diluent. The compound carries a documented laboratory safety claim — no clinically significant changes in electrolytes, hepatic, renal, or pancreatic parameters, erythrocytes, platelets, or leukocytes — and haemoglobin unchanged versus placebo in every trial.

Receptor selectivity. EPO engages both the classical EPOR homodimer on erythroid precursors and the innate repair receptor (IRR), an EPOR/beta-common receptor (CD131) heterodimer expressed on stressed, injured, or inflamed cells rather than constitutively. ARA-290 binds the IRR selectively and does not activate the EPOR homodimer, which is why it separates tissue protection from erythropoiesis, viscosity, and blood pressure.

Anti-inflammatory cascade. IRR engagement activates JAK2 signalling, which inhibits NF-kB. Downstream, production of TNF-alpha, IL-1 beta, and IL-6 falls, reactive oxygen species generation is reduced, and NLRP3 inflammasome activation is inhibited. The net effect is attenuation of immune overreaction without broad immunosuppression.

Nerve regeneration. Corneal confocal microscopy in trials showed a 14.5% increase in corneal nerve fibre area at 28 days in sarcoidosis patients versus a 5.3% decrease on placebo, and in diabetic patients with reduced baseline density an increase of 2.6 fibres per square millimetre versus 0.7 on placebo. GAP-43 positive regenerating fibres increased significantly in the 4 mg group. Liu et al. 2025 adds that ARA-290 suppresses NLRP3 activation in Schwann cells after sciatic nerve crush by inhibiting NF-kB phosphorylation and reducing ROS.

TRPV1 modulation. ARA-290 directly inhibits TRPV1 channel activity on sensory neurons, giving a peripheral antinociceptive mechanism in addition to the anti-inflammatory arm.

Pharmacokinetics versus pharmacodynamics. Plasma half-life is approximately 2 minutes intravenously and about 20 minutes subcutaneously. Researchers describe a molecular switch: IRR activation initiates downstream signalling that persists after clearance. In animal models 2 weeks of treatment produced long-term analgesia; in humans a single week of intravenous dosing gave pain relief persisting 3 months.

Haematological neutrality. No change in red cell count, haematocrit, viscosity, or blood pressure in any trial; haemoglobin unchanged versus placebo; no polycythaemia, thrombotic, or cardiovascular signal from the blood side.

Neuropathic pain: the primary indication, small-fibre neuropathy in sarcoidosis and type 2 diabetes specifically. Sarcoidosis patients showed a 28% improvement in Small Fibre Neuropathy Screening List scores versus 9% on placebo; diabetic patients improved 18 to 23% on PainDetect, with significant gains in tingling, thermal pain, and allodynia.

Nerve regeneration: structural regrowth confirmed by corneal confocal microscopy at 28 days in multiple trials, with GAP-43 positive fibres increased in the 4 mg group and skin biopsies trending toward higher intraepidermal nerve fibre density.

Inflammation: reduction of TNF-alpha, IL-1 beta, and IL-6 via NF-kB inhibition, without broad immunosuppression; animal benefit in colitis, autoimmune neuritis, and systemic lupus erythematosus models.

Immune: restores immune balance in autoimmune disorders — rebalancing rather than suppression, consistent with preferential IRR expression on stressed tissue.

Tissue repair and organ protection: activity in injured, stressed, or ischaemic tissue; preclinical protection of kidney (ischaemia-reperfusion, cisplatin), heart (age-associated inflammatory decline), pancreatic islets (transplantation), and brain (ischaemic stroke). Winicki et al. 2023 showed preserved left ventricular ejection fraction, blunted age-associated blood pressure rise, and reduced frailty markers in aged rats.

Metabolic: HbA1c improved 0.21% at 56 days versus a 0.21% increase on placebo, with improved cholesterol to HDL ratio, higher HDL, and lower triglycerides, sustained through the 28 day follow-up.

Function: 6 minute walk improved 18.7 metres versus a 15.1 metre decline; pain interference fell 36% versus 16%.

Bone: cibinetide inhibited osteoclastogenesis and raised cortical BMD approximately 5.8% and trabecular BMD approximately 5.2% after one month in mice.

Safety as an active claim: no clinically significant changes in electrolytes, hepatic, renal, or pancreatic parameters, erythrocytes, platelets, or leukocytes; no haematocrit, viscosity, or blood pressure change.

Published timelines. Dahan et al. 2013: sarcoidosis patients on 4 mg subcutaneously daily showed significant neuropathic symptom improvement by week 4, persisting through the 16 week follow-up; the 28% SFNSL improvement and 14.5% corneal nerve fibre area increase were measured at 28 days, with 81% of treated patients showing clinically meaningful improvement versus 47% on placebo. Brines et al. 2015: diabetic patients improved at day 28 with continued improvement at day 56, 28 days post-dosing; HbA1c kept falling after cessation. Heij et al. 2012: significant symptom score improvement from week 1, continuing through week 4. Culver et al. 2017 tied nerve fibre area change to 6 minute walk gains and found 4 mg optimal among 1, 4, and 8 mg.

In practice. Users report burning and tingling easing within the first 1 to 2 weeks, with sensation recovery and reduced numbness around weeks 3 to 4. Some describe outcomes better than IVIG. Some report improvement within hours of a dose but note sustained benefit requires continued daily use. Peak trial effects were measured at 28 days; sustained benefit months after stopping is documented, consistent with the molecular switch model.

Injection experience. PBS reconstitution produces a mild sting resolving within minutes owing to its pH relative to bacteriostatic water; the peptide itself can cause minor site irritation independent of diluent.

Expectations. Nerve regeneration is slow; 28 days of daily dosing is the trial minimum. Longer courses may be warranted for chronic conditions but data beyond 28 days is limited. The user base is niche — predominantly people with diagnosed neuropathy or nerve injury — so anecdotal data is thin compared with BPC-157 or TB-500. Trial evidence covers sarcoidosis and diabetic small-fibre neuropathy, not every nerve injury; extrapolation to conditions such as brachial neuritis is plausible but unstudied.

Trial doses. Heij et al. 2012: 2 mg intravenously three times weekly for 4 weeks. Dahan et al. 2013 and Brines et al. 2015: 4 mg subcutaneously once daily for 28 days. Culver et al. 2017 (Phase 2b): 1, 4, and 8 mg subcutaneously once daily for 28 days, with 4 mg optimal for corneal nerve fibre area (placebo-corrected mean change 697 square micrometres, p = 0.012) and pain reduction. The 4 mg daily subcutaneous dose is the most consistently studied and best-performing.

Standard protocol. 4 mg subcutaneously once daily, morning dosing as in most trials, for 28 days minimum. Diluent: phosphate buffered saline preferred over bacteriostatic water for stability and bioactivity; bacteriostatic water is not necessarily ruinous if the peptide dissolves normally, but PBS is the trial standard. Vial 10 mg; PBS volume per manufacturer instructions; refrigerate after reconstitution.

Titration in practice. Week 1 at 2 mg daily to assess tolerance, weeks 2 to 4 at 4 mg daily.

Other presentations. A 16 mg vial reconstituted with 1.5 mL (150 units) of bacteriostatic water yields 10.67 mg/mL, approximately 106.7 mcg per insulin unit. That format has been run at 2, 3, or 4 mg daily over 4, 8, or 12 week cycles with 2, 4, or 6 week washouts, and at 8 mg daily capped at 4 weeks. Culver et al. 2017 tested 8 mg and did not find it superior to 4 mg, which argues against the higher dose on efficacy grounds. At 8 mg/day a 16 mg vial lasts two days.

Meals. No fasting requirement; timing relative to meals does not appear to affect absorption.

Monitoring. No haematocrit monitoring required, unlike EPO. No renal dose adjustment was needed in trials, but one participant with pre-existing borderline renal insufficiency worsened (causality not established); a standard metabolic panel including renal function before and after a course is reasonable, especially with pre-existing renal concerns. No significant drug interactions were identified in trials; ARA-290 was co-administered with metformin, sulfonylureas, and insulin without issues.

Duration and cycling. 28 days is the consistent trial period; data beyond it is limited. Sustained post-treatment effects — analgesia persisting 3 months after a single week of intravenous dosing, metabolic gains continuing 28 days after stopping — indicate continuous indefinite use may not be necessary. A 28 day course followed by reassessment is the defensible approach; no published data covers long-term continuous use.

Four randomised controlled human trials totalling over 170 patients, all in small fibre neuropathy.

Heij et al. 2012: double-blind, placebo-controlled pilot in 22 sarcoidosis patients; 2 mg IV three times weekly for 4 weeks. Small Fiber Neuropathy Screening List improved 11.5 points versus 2.9 for placebo. Pain and physical functioning QoL dimensions improved. Haemoglobin and blood chemistry unchanged.

Dahan et al. 2013: 38 sarcoidosis patients with small nerve fibre loss; 4 mg SC daily for 28 days, 12 week follow-up. Corneal nerve fibre area +14.5% versus −5.3% placebo. Screening scores −28% versus −9%. Pain interference −36% versus −16%. 6 minute walk +18.7 m versus −15.1 m. 81% clinically meaningful improvement versus 47%. No serious adverse events; no anti-drug antibodies.

Brines et al. 2015: 48 type 2 diabetics with neuropathy; 4 mg SC daily for 28 days, 28 day follow-up. HbA1c −0.21% versus +0.21% placebo, still improving at day 56. Cholesterol:HDL ratio improved, HDL up, triglycerides down. PainDetect −18 to 23%, with significant gains in tingling, thermal pain, and allodynia. Nerve fibre density +2.6 fibres/mm² versus 0.7 in patients with reduced baseline density. One case of worsening renal function in borderline renal insufficiency, causality unestablished.

Culver et al. 2017: Phase 2b, 64 sarcoidosis patients; 1, 4, and 8 mg daily versus placebo for 28 days. 4 mg produced a placebo-corrected corneal nerve fibre area change of 697 µm² (p = 0.012), a significant rise in GAP-43-positive regenerating fibres, correlation with 6 minute walk improvement, and clinically meaningful reduction in moderate-to-severe pain. 4 mg was optimal.

Preclinical: Winicki et al. 2023 — 15 months of ARA-290 in aged Fischer 344 x Brown Norway rats reduced cardiac inflammation, preserved LVEF, blunted age-associated blood pressure rise, enhanced cardiomyocyte autophagy, and reduced frailty markers. Liu et al. 2025 — inhibition of NLRP3 inflammasome activation in Schwann cells after sciatic crush via reduced NF-κB phosphorylation and ROS. 2021 mouse data: osteoclastogenesis inhibited, cortical BMD +5.8%, trabecular +5.2% at one month. Models of colitis, autoimmune neuritis, lupus, renal ischaemia-reperfusion, cisplatin nephrotoxicity, ischaemic stroke, and diabetic wound healing.

Mechanistic anchors: IRR (EPOR–CD131 heterodimer) selectivity with no classical EPOR homodimer activation; JAK2 → NF-κB inhibition lowering TNF-α, IL-1β, IL-6; direct TRPV1 inhibition; sustained signalling despite ~2 minute IV and ~20 minute SC plasma half-life.