Regression of Atherosclerosis in ApoE−/− Mice Via Modulation of Monocyte Recruitment and Phenotype, Induced by Weekly Dosing of a Novel 'Cytotopic' Anti‐Thrombin Without Prolonged Anticoagulation

Background Anticoagulants induce atherosclerosis regression in animal models but exploiting this clinically is limited by bleeding events. Here we test a novel thrombin inhibitor, PTL060, comprising hirulog covalently linked to a synthetic myristoyl electrostatic switch to tether to cell membranes. Methods and Results ApoE−/− mice were fed chow or high‐fat diets, before transplantation of congenic aortic segments or injection of PTL060, parental hirulog, control saline, or labeled CD11b positive cells. Aortic transplants from transgenic mice expressing anticoagulants on endothelium did not develop atherosclerosis. A single intravenous injection of PTL060, but not hirulog inhibited atheroma development by >50% compared with controls when assessed 4 weeks later. Mice had prolonged bleeding times for only one seventh of the time that PTL060 was biologically active. Repeated weekly injections of PTL060 but not hirulog caused regression of atheroma. We dissected 2 contributory mechanisms. First, the majority of CCR2+ (C‐C chemokine receptor type 2+) monocytes recruited into plaques expressed CCR7 (C‐C chemokine receptor type 7), ABCA1 (ATP‐binding cassette transporter – 1), and interleukin‐10 in PTL060 mice, a phenotype seen in