ARA-290

This foundational study characterized the pyroglutamate helix B surface peptide (pHBSP, later named ARA-290 / Cibinetide), an 11-amino-acid peptide derived from the aqueous face of helix B within the erythropoietin molecule. The authors confirmed that pHBSP does not bind the homodimeric EPO receptor and thus lacks hematopoietic activity, while selectively engaging the heterodimeric innate repair receptor (EPOR/β-common receptor). In a rat model of myocardial ischemia–reperfusion injury, single-dose pHBSP administration was associated with a significant reduction in infarct size compared to vehicle control. The findings supported the hypothesis that the tissue-protective signaling of EPO can be dissociated from its erythropoietic activity via short helix-B-derived peptides.

The natural hormone erythropoietin (EPO) does two things: it tells the bone marrow to make red blood cells, and it protects injured tissue from further damage. These researchers showed that those two jobs are handled by two different receptors. They designed a small 11-amino-acid peptide copied from one specific surface of the EPO molecule (helix B) and showed it only activates the tissue-protecting receptor, not the red-blood-cell receptor. In rats with simulated heart attacks, the peptide was associated with smaller areas of damaged heart tissue compared with control animals. This study established the design principle behind ARA-290.

This Phase 2 randomized, double-blind, placebo-controlled investigation enrolled patients with sarcoidosis-associated small fiber neuropathy. Subjects received 28 days of daily subcutaneous ARA-290 (4 mg) or matched placebo. The ARA-290 group showed significant improvements in cold and heat pain thresholds and thermal sensory limen versus placebo, alongside improved scores on the 6-minute walk test. Notably, in vivo corneal confocal microscopy demonstrated a significant increase in corneal small-nerve-fiber density in the ARA-290 arm, providing objective evidence of small-fiber regrowth over the dosing window. The authors concluded that selective IRR activation was associated with reduced neuropathic symptoms and measurable changes in nerve fiber abundance in this patient cohort.

Sarcoidosis is an inflammatory condition that can damage the smallest nerve fibers in the skin and eyes, causing chronic pain and reduced sensation. Researchers tested ARA-290 in adults with this kind of nerve damage. Half received the peptide and half received a placebo for 28 days. People who got ARA-290 reported less pain and walked further in a six-minute walk test. Researchers also used a specialized eye microscope to count the tiny nerve fibers in the cornea (the front of the eye) and found that the ARA-290 group had measurably more nerve fibers at the end of the study. This was one of the first human trials to show that activating the innate repair receptor was associated with both symptom changes and an objective change in nerve fiber counts.