Corrination mitigates peptide aggregation as exemplified for Glucagon

Pharmaceutical development of glucagon for use in acute hypoglycemia has proved challenging, due in large part to poor solubility, poor stability and aggregate formation. Herein, we describe highly soluble, low aggregating, glucagon conjugates generated through use of the commercially available vitamin B precursor dicyanocobinamide ('corrination'), which retain full stimulatory action at the human glucagon receptor. The modified glucagon analogs were tested in a chemical stability assay in 50mM phosphate buffer and the percentage of original concentration retained was determined after two weeks of incubation at 37 ˚C. Aggregate formation assays were also performed after 48hours of agitation at 37 ˚C using a thioflavin (ThT) fluorescence-based assay. All corrinated compounds retained original concentration to a higher degree than glucagon controls and showed markedly decreased aggregation compared to their respective noncorrinated analogues. Based on the statistically significant increase in chemical stability coupled with the notably decreased tendency to form aggregates, analogues 2 and its corrinated conjugate 5 were used for a functional assay study performed after agitation at 37 ˚C for 24-hr after which in agonism was measured at the human glucagon receptor agonism using a cAMP FRET assay. Corrinated 5 exhibited a 6.6-fold increased potency relative to glucagon, which was shown to have a 165-fold reduction in potency. The relative potency of 5 was also improved compared to that of 2 with EC values of 5.5nM and 9.6nM for 5 and 2, respectively. In conclusion, corrination of peptides mitigrates aggregation, presenting a compound with prolonged stability and agonism as demonstrated for glucagon.