A34. Development of novel matrix metalloproteinase inhibitors and their effects on isolated stunned hearts

Abstract

Matrix metalloproteinases (MMPs) are hydrolytic enzymes involved in the breakdown of myocardial connective tissue with disease. We have undertaken the development of novel non-hydroxamate-based MMP inhibitors (MPIs) intended to enhance the potency and safety profiles of the drugs in light of a troubled clinical history of hydroxamate-based inhibitors. MPI basic design consists of a peptidomimetic backbone attached to a zinc-binding group (ZBG). The drug discovery software LUDI was used to design MPIs with specific inhibition profiles. Interactions between novel MPIs and the enzyme was reproduced using the ZBG portion of the inhibitors bound to a tris(pyrazolyl)borate model complex. This model was then integrated into a known MMP crystal structure. Candidate compounds were initially screened and ranked using a LUDI scoring function. Candidate novel MPIs were subsequently tested at three levels: In vitro using recombinant MMPs, in cell culture using neonatal rat cardiac fibroblasts where cytotoxicity was also monitored, and ex vivo using isolated rat hearts. In both recombinant and cell culture assays new ZBGs were found to be 10–100-fold more potent inhibitors compared to acetohydroxamic acid. Cytotoxicity assays demonstrated that most of these novel compounds were non-toxic at concentrations reaching 100 μM. Two compounds: 200 μM thiomaltol (ZBG) and 10 μM PY2 (PY-2 has nanomolar IC50 vs. MMP-3) were tested ex vivo to assess recovery of cardiac function in stunned myocardium. Stunning was induced by 20 min of no flow ischemia. Rate pressure product results indicated that both compounds conferred a significant increase in recovery of contractile function versus controls. We demonstrate that in silico drug design using a chelator-driven approach can produce potent and selective MPIs.