ARA-290 (Cibinetide) vs LL-37 (Human Cathelicidin)

ARA-290 (Cibinetide)

ARA-290, also called cibinetide, is an 11-residue synthetic peptide modelled on the helix B surface of erythropoietin. Erythropoietin is best known as the hormone that drives red blood cell production, but it also acts on other tissues, and ARA-290 was designed to probe that second set of actions without the effect on blood. Its N-terminal glutamine is cyclised to pyroglutamate, which is why it also appears in the literature as pyroglutamate helix B surface peptide. Most studies are in cell and rodent models of nerve injury, inflammation and metabolic disease. It has also been tested in small, early-phase human trials, including in neuropathy associated with sarcoidosis and with diabetes, and human data remain limited.

LL-37 (Human Cathelicidin)

LL-37 is a 37-residue peptide cleaved from hCAP18, the only human cathelicidin; its name refers to its two leading leucines and its length. It is made by neutrophils and by epithelial cells of the skin, gut and airways, and the gene that encodes it is regulated in part by vitamin D. Laboratory studies have examined its activity against bacteria, fungi and some viruses, and its signalling to host immune and epithelial cells. Its research record runs in two directions: it is studied as a host-defence molecule and also as a contributor to inflammatory skin conditions such as psoriasis and rosacea. Most published work is in vitro or in animals, and interventional human studies are few and small.

How ARA-290 (Cibinetide) acts

Erythropoietin acts on red-cell precursors through a homodimer of its receptor (EPOR). A different receptor, proposed to be EPOR paired with the beta-common receptor subunit (CD131), has been suggested to mediate its actions outside the blood-forming system. ARA-290 reproduces the helix B face of erythropoietin, which is thought to engage this proposed complex but not the classical homodimer, and it has been reported not to stimulate red-cell production in animal studies. Cell and rodent work has examined its influence on inflammatory cytokine signalling and apoptosis. The make-up and role of the proposed receptor remain debated.

How LL-37 (Human Cathelicidin) acts

In dilute aqueous solution LL-37 is largely disordered; on contact with lipid membranes it has been reported to fold into an amphipathic α-helix. Its side chains give it a net charge of about +6 at neutral pH, which draws it to the negatively charged surfaces of bacterial membranes, and it is thought to permeabilise those membranes. It also binds bacterial lipopolysaccharide. On host cells it has been reported to act through several receptors, among them formyl peptide receptor 2 and the P2X7 purinergic receptor, and to transactivate the epidermal growth factor receptor in keratinocytes. Complexes of LL-37 with self-DNA or RNA have been reported to activate Toll-like receptor signalling in dendritic cells, a pathway examined in psoriasis research.

The records side by side

• Type: ARA-290 (Cibinetide), Synthetic undecapeptide; LL-37 (Human Cathelicidin), Antimicrobial peptide (cathelicidin)
• Length: ARA-290 (Cibinetide), 11 amino acids; LL-37 (Human Cathelicidin), 37 amino acids
• Molecular weight: ARA-290 (Cibinetide), 1257.3 g/mol; LL-37 (Human Cathelicidin), 4493 g/mol
• Molecular formula: ARA-290 (Cibinetide), C51H84N16O21; LL-37 (Human Cathelicidin), C205H340N60O53

Reading a comparison

A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.