ARA-290

Erythropoietin has two distinct activities: red cell production through the classical EPOR homodimer, and tissue protection through a heterodimer of EPOR and the beta-common receptor known as the innate repair receptor. ARA-290 corresponds to the helix B surface region of EPO, which is the part that engages the repair receptor but not the homodimer, so it produces the cytoprotective and anti-inflammatory effect with no rise in haematocrit. In human trials it increased corneal nerve fibre area and intra-epidermal nerve fibre density, reduced neuropathic pain scores, and improved metabolic control in diabetic patients with small fibre neuropathy. This is a genuinely well-characterised mechanism with randomised human data behind it - unusual for this class.

Targets: Innate repair receptor (EPOR / beta-common receptor heterodimer), Small nerve fibre regeneration, Macrophage and mast cell inflammatory signalling

• · The sarcoidosis small-fibre-neuropathy trial tested 1, 4 and 8 mg daily for 28 days, and 4 mg was the dose that produced significant corneal nerve fibre regrowth. 4 mg daily is therefore the reference protocol.
• · Used by people rationing an expensive peptide. 1 mg did not separate from placebo on the nerve endpoints in trial, so this is a cost compromise rather than an evidence-based choice.

Work out your exact syringe units →

• commonInjection-site reaction— The dominant adverse event in trials.
• uncommonHeadache
• uncommonTemporary increase in neuropathic sensations early in treatment— Sometimes described as reinnervation tingling as fibres regrow.

• None established from the trial data - notably, ARA-290 does not raise haematocrit, so the thrombotic concerns that apply to EPO itself do not carry over.

• cautionErythropoiesis-stimulating agents — Different receptor targets, but no data on co-administration.

• · Haemoglobin and haematocrit at baseline if you want reassurance, though trials consistently showed no erythropoietic effect.
• · Track neuropathic symptoms with a structured scale rather than impressions - the effect sizes are real but modest.

Investigational; not approved anywhere. Sold as a research chemical and generally expensive relative to other peptides in this class.

• Dahan et al., ARA 290 in sarcoidosis patients with symptoms of small fibre neuropathy, randomised double-blind pilot study (trial)
• Culver et al., cibinetide improves corneal nerve fibre measures in sarcoid small fibre neuropathy, Investigative Ophthalmology & Visual Science (trial)
• Brines & Cerami, the innate repair receptor and non-erythropoietic EPO derivatives (review) (review)

Erythropoietin does two entirely separate jobs through two different receptor assemblies. Red cell production runs through the EPOR homodimer, which binds EPO with very high affinity. Tissue protection runs through a heterodimer of EPOR and the beta-common receptor - the same beta-common subunit shared by the GM-CSF, IL-3 and IL-5 receptors - and this assembly, called the innate repair receptor, binds EPO with much lower affinity. That affinity gap is the whole story: the concentrations of EPO needed for tissue protection are far higher than those needed for erythropoiesis, which is why you cannot use EPO as a repair drug without also thickening the blood. ARA-290 solves this structurally. It reproduces the aqueous face of helix B, which is the part of EPO that contacts the innate repair receptor. It is not the part that contacts the EPOR homodimer. So it engages the repair receptor without touching erythropoiesis - and the trials confirm it, with no haematocrit rise across every study. Downstream, innate repair receptor activation suppresses macrophage and mast cell inflammatory activation and switches on cytoprotective and anti-apoptotic signalling in stressed tissue. In small fibre neuropathy, the clinical consequence is measurable: corneal nerve fibre area increased by a placebo-corrected 697 square micrometres in the 4 mg arm at 28 days, and regenerating intraepidermal GAP-43-positive fibres increased in the same arm. Those are objective imaging endpoints, not questionnaires, and the changes in corneal nerve fibre area correlated with both the GAP-43 measure and six-minute walk distance. The dose-response is the other genuinely useful piece. One milligram did not separate from placebo. Four milligrams did. Eight milligrams did not do better than four - the point estimate was lower. That is an inverted-U, which is common in receptor pharmacology and means that in this compound more is actively not better. It is the reason 4 mg is the reference dose rather than a starting point. And because plasma clearance is measured in minutes while the effect takes 28 days to appear, this is unambiguously a compound where you are initiating a biological programme rather than maintaining a drug level.

The most common and most expensive mistake is dose rationing. People buy an 8 mg vial, dose 1 mg daily to make it last, and conclude the compound does not work. One milligram was tested and did not separate from placebo. You have not run a low dose - you have run a dose the trial showed to be ineffective. The mirror-image mistake is escalating past 4 mg when 4 mg is not working. The 8 mg arm underperformed the 4 mg arm. This is an inverted-U dose-response and going up is going down. The third failure is judging it too early or on the wrong endpoint. Nerve fibre regrowth took 28 days to become measurable in the trials, and it was measured with corneal confocal microscopy, not with how the feet felt. Pain improved in all arms including placebo, which is exactly what you would expect in a neuropathic pain trial and exactly why subjective improvement on ARA-290 should not be over-read. The fourth is the reinnervation tingling. As small fibres regrow, some people report a temporary increase in neuropathic sensations early on. It is not a warning sign and it usually settles, but it catches people out because it looks like the opposite of what they paid for. The fifth is product identity, and there is an elegant test for it here that exists for no other peptide in this class: ARA-290 should not move your haematocrit. If it does, you did not buy ARA-290.

1. 4 mgDays 1-28 — 4 mg once daily subcutaneously is the reference dose, and it is a reference rather than a starting point. This is the dose that produced the significant corneal nerve fibre area increase in the phase 2b trial. There is no reason to work up to it - the trial started people here.
2. 1 mgAlternative if rationing — 1 mg daily is what people use when the cost is prohibitive. Be clear about what you are buying: 1 mg did not separate from placebo on the nerve endpoints. This is a cost compromise, not a low dose that works more slowly.
3. 8 mgDo not escalate — 8 mg daily was tested and did not beat 4 mg - the point estimate for corneal nerve fibre area was lower. This is an inverted-U dose-response. Going higher because 4 mg did not work is the exact wrong move.
4. —After day 28 — Stop and reassess. Every trial ran 28 days. Some people with neuropathy repeat courses every few months; there is no data on repeated courses, but there is also no accumulation concern given the minutes-long clearance.

• Innate repair receptor (EPOR / beta-common receptor heterodimer) — Selective for the heterodimer; ARA-290 does not activate the EPOR homodimer, which is confirmed clinically by the absence of any haematocrit change across all trials

  Cytoprotective and anti-apoptotic signalling in stressed tissue, suppression of macrophage and mast cell inflammatory activation, and small nerve fibre regeneration.

• EPOR homodimer (classical erythropoietin receptor) — No meaningful activity - this is a designed negative

  No erythropoiesis, therefore none of the thrombotic and hypertensive risk that limits EPO itself.

• TRPV1 channel — Reported in preclinical work as a route by which ARA-290 relieves pathophysiological pain

  A proposed contributor to the analgesic effect, distinct from the regenerative effect on nerve fibres. Preclinical only.

• Macrophage activation — Downstream of innate repair receptor signalling

  Reduced inflammatory activation, demonstrated in transplanted islet protection models.

• ARA 290 in sarcoidosis patients with symptoms of small fibre neuropathy (randomised, double-blind, placebo-controlled pilot) Phase 2 pilot · n=22 · 4 weeks · 2012

  2 mg intravenously three times weekly for four weeks in 12 patients versus 10 on placebo. Significant improvement at week 4 in the Small Fibre Neuropathy Screening List score, -11.5 versus -2.9 for placebo (p<0.05), with improvements in the pain and physical functioning dimensions of quality of life. Well tolerated with no safety signal.

• Cibinetide phase 2b trial in sarcoidosis-associated small nerve fibre loss Phase 2b · n=64 · 4 weeks · 2017

  Randomised, 28 days, cibinetide 1, 4 or 8 mg daily versus placebo. Primary endpoint was change in corneal nerve fibre area. Placebo-corrected mean change was 109 (not significant) at 1 mg, 697 (95% CI 159-1236, p=0.012) at 4 mg, and 431 (not significant) at 8 mg. Intraepidermal GAP-43-positive regenerating fibres increased in the 4 mg group (p=0.035), and change in corneal nerve fibre area correlated with GAP-43 change and with six-minute walk distance.

• ARA 290 in type 2 diabetes with neuropathic symptoms (randomised, double-blind, placebo-controlled) Phase 2 · 8 weeks · 2015

  4 mg subcutaneously daily for 28 days followed by 28 days of observation. Improved HbA1c sustained through the observation period, improved cholesterol-to-HDL ratio and triglycerides, significant improvement in PainDetect neuropathic symptom scores, and increased corneal nerve fibre density in subjects whose baseline was more than one standard deviation below normal. No safety concerns.

• Phase 2 trial of cibinetide for diabetic macular oedema Phase 2 · 2020

  Evaluated cibinetide in diabetic macular oedema. Included here because it shows the development programme extended beyond neuropathy; outcome details were not resolved in the preparation of this entry.

Days 1-7: nothing measurable. Injection-site reaction is the dominant adverse event in the trials, and some people report a transient increase in neuropathic sensations as fibres begin regenerating. Weeks 2-4: pain and autonomic symptoms begin shifting. Be sceptical here - placebo arms in these trials also improved on pain. Day 28: the trial endpoint, and the point at which nerve fibre regrowth became objectively measurable. If you have access to corneal confocal microscopy, this is when to repeat it. Day 56: in the type 2 diabetes trial, the HbA1c improvement was still present 28 days after the last dose. That persistence is consistent with a compound that starts a repair programme rather than one that suppresses a symptom. Beyond: no data on repeated courses. People with chronic neuropathy repeat every few months on their own judgement.

ARA-290 is the compound in this class least in need of a stack, because it has its own randomised evidence and a specific target. If you are running it for small fibre neuropathy, the things worth adding are the ones that address the cause - glycaemic control if diabetic, immunosuppression if sarcoid - not other peptides. The pairing that makes mechanistic sense is with anything reducing the underlying inflammatory driver, since innate repair receptor signalling suppresses macrophage and mast cell activation. KPV is a plausible partner on that logic, though nobody has tested it. With erythropoiesis-stimulating agents there is a theoretical interaction worth thinking about: ARA-290 occupies the beta-common heterodimer while an ESA drives the homodimer. Different assemblies, and no co-administration data exists in either direction. Do not stack it with BPC-157 in the expectation of additive nerve regeneration. BPC-157's nerve claims are rodent sciatic models; ARA-290's are randomised human trials with imaging endpoints. Adding the weaker evidence does not strengthen the stronger. One practical note: ARA-290 is expensive per milligram and dosed in milligrams, not micrograms. A stack that includes it is a stack built around it.

Against every other compound in this class for nerve pain: ARA-290 is the one with randomised, double-blind, placebo-controlled human trials using objective nerve-fibre imaging endpoints. That is a different tier of evidence from BPC-157's rodent sciatic models, and the writing on this site should not flatten the two. Against gabapentin, pregabalin and duloxetine for neuropathic pain: those are approved, cheap and suppress symptoms without touching the nerve. ARA-290 has imaging evidence of actual fibre regrowth, which none of them can claim, but it is investigational, expensive, and its pain effect in trials was not dramatically better than placebo. The honest framing is that they solve different halves of the problem. Against erythropoietin itself: EPO would also engage the innate repair receptor, at doses that would raise your haematocrit into thrombosis territory. ARA-290 exists specifically to remove that trade-off and the trials confirm it succeeded. Against doing nothing while glycaemic control is poor: if the neuropathy is diabetic and the HbA1c is uncontrolled, the compound is being asked to repair nerve faster than the disease damages it. Fix the driver.

$200–$600/month. Dosed in milligrams rather than micrograms - 4 mg daily is 112 mg over a 28-day course, which is why this is one of the most expensive peptides in the class per course. Order-of-magnitude estimate, not price-checked in the preparation of this entry.

• ?No published human pharmacokinetics - no tmax, bioavailability, volume of distribution, protein binding or clearance figure beyond 'minutes'.
• ?Participant numbers for the type 2 diabetes trial and the diabetic macular oedema trial were not stated in the abstracts available in this session.
• ?The reference protocol in the Core record is subcutaneous 4 mg daily; the sarcoidosis pilot used 2 mg intravenously three times weekly. Both worked, and the relative efficiency of the two routes has not been compared.
• ?No data exists on repeated courses, which is what people with chronic neuropathy actually do.
• ?The mechanism by which ARA-290 improved HbA1c and lipids is not established and was an incidental finding.
• ?The TRPV1 contribution to analgesia is preclinical only.
• ?ARA-290 has never completed phase 3 and has no approval anywhere, so all of the above is phase 2 evidence.
• ?Cost figures are estimates and were not price-verified in this session.

• Safety and efficacy of ARA 290 in sarcoidosis patients with symptoms of small fiber neuropathy: a randomized, double-blind pilot study Heij L, Niesters M, Swartjes M, Hoitsma E, Drent M, Dunne A, Grutters JC, Vogels O, Brines M, Cerami A, Dahan A, Molecular Medicine, 2012 · PMID 23168581

  The first randomised placebo-controlled human evidence. Small at 22 patients but properly controlled, and the source of the SFNSL result.

• Cibinetide Improves Corneal Nerve Fiber Abundance in Patients With Sarcoidosis-Associated Small Nerve Fiber Loss and Neuropathic Pain Culver DA, Dahan A, Bajorunas D, Jeziorska M, van Velzen M, Aarts LPHJ, Tavee J, Tannemaat MR, Dunne AN, Kirk RI, Petropoulos IN, Cerami A, Malik RA, Brines M, Investigative Ophthalmology & Visual Science, 2017 · PMID 28475703

  The most important trial for dose selection. It is the source of the 4 mg reference dose and of the finding that 8 mg is not better - the inverted-U dose-response.

• ARA 290, a nonerythropoietic peptide engineered from erythropoietin, improves metabolic control and neuropathic symptoms in patients with type 2 diabetes Brines M, Dunne AN, van Velzen M, Proto PL, Ostenson CG, Kirk RI, Petropoulos IN, Javed S, Malik RA, Cerami A, Dahan A, Molecular Medicine, 2015 · PMID 25387363

  Source of the HbA1c, lipid and PainDetect findings, and of the 4 mg subcutaneous daily for 28 days protocol most people copy.

• Corneal nerve fiber size adds utility to the diagnosis and assessment of therapeutic response in patients with small fiber neuropathy Brines M et al., Scientific Reports, 2018 · PMID 29549285

  Methodological backing for corneal confocal microscopy as the objective endpoint, which is what makes the ARA-290 results more credible than a questionnaire-based literature.

• A Phase 2 Clinical Trial on the Use of Cibinetide for the Treatment of Diabetic Macular Edema Lois N et al., Journal of Clinical Medicine, 2020 · PMID 32674280

  Shows the breadth of the clinical programme beyond neuropathy.