Delivery of the p38 MAPkinase inhibitor SB202190 to angiogenic endothelial cells: development of novel RGD-equipped and PEGylated drug-albumin conjugates using platinum(II)-based drug linker technology

Endothelial cells play an important role in inflammatory disorders, as they control the recruitment of leukocytes into inflamed tissue and the formation of new blood vessels. Activation of p38MAP kinase results in the production of proinflammatory cytokines and the expression of adhesion molecules. P38MAP kinase inhibitors are therefore considered important candidates for the treatment of inflammatory disorders. In the present study, we propose a novel strategy to counteract these processes by delivery of the p38MAP kinase inhibitor SB202190 into angiogenic endothelial cells. A drug-targeting conjugate was developed by conjugation of SB202190 to human serum albumin (HSA) using a novel platinum-based linker. Specificity for angiogenic endothelial cells was introduced by conjugation of cyclic RGD-peptides via bifunctional polyethylene glycol linkers. The final products contained an average of nine SB202190 and six RGDPEG groups per albumin. The platinum-based linker displayed high stability in buffers and culture medium, but released SB202190 slowly upon competition with sulfur-containing ligands like glutathione. RGDPEG-SB-HSA bound to alpha(v3)-integrin expressing endothelial cells (human umbilical cord vein endothelial cells) with low nanomolar affinity and was subsequently internalized. When HUVEC were treated with TNF to induce inflammatory events, pretreatment with RGDPEG-SB-HSA partially inhibited proinflammatory gene expression (IL-8, E-selectin; 30% inhibition) and secretion of cytokines (IL-8, 34% inhibition). We conclude that the developed RGDPEG-SB-HSA conjugates provide a novel means to counteract inflammation disorders such as rheumatoid arthritis.