Physicochemical and pharmacological characterization of novel vasoactive intestinal peptide derivatives with improved stability

Previously, [R15,20,21, L17]-VIP-GRR (IK312532), a long-acting VIP derivative, was proposed as potential drug candidate for the treatment of asthma/COPD. The present work is aimed to elucidate solution-state stability of IK312532 and to develop further stabilized derivative with equipotent or higher biological functions. A stability study on IK312532 was carried out in solution state, and degradation mechanism was deduced by UPLC–MS and amino acid analyses. Three novel VIP derivatives were designed and chemically synthesized on the basis of stability data, being subjected to physicochemical and pharmacological characterization. Solution-state stability studies revealed the gradual degradation of IK312532, following pseudo-first-order kinetics. Chemical modification of IK312532, mainly position at 24, resulted in marked improvement of stability, although the chemical modification had no influence on the secondary structure, receptor binding, and activation of adenylate cyclase in rat lung cells. Novel derivatives also exhibited more potent neurite outgrowth in rat pheochromocytoma PC12 cells when compared to VIP and IK312532, possibly due to improved stability. Deamination of Asn at position 24 might be responsible for degradation of VIP derivative, and stability and chemical modification studies led us to the successful development of novel VIP derivatives with higher stability and biological functions.