David has long been interested in the response of the blood vessels to injury and the influence clotting and inflammation play in the ensuing proliferation and migration of vascular smooth muscle cells (VSMC) that may explain the reocclusion of vessels after percutaneous intervention. He proposed that an alternative physiological anticoagulant system, the product of which, activated protein C (aPC) could modulate the responses.
His research towards a Doctor of Medicine, awarded by Imperial College, London, in 2000, found a controllable level of anti-coagulation can be achieved if aPC when combined with low molecular weight heparin (LMWH). It bound to specific to sites on cultured human and rat vascular smooth muscle cells (VSMC) with properties similar to those described for the endothelial protein C receptor (EPCR). However, unlike the aPC/EPCR complex, the anticoagulant activity of aPC when bound to VSMC is maintained.