ABSTRACT
Although current antiplatelet therapies provide potent antithrombotic effects, their efficacy is limited by a heightened risk of bleeding and failure to affect vascular remodeling after injury. New lines of research suggest that thrombosis and hemorrhage may be uncoupled at the interface of pathways controlling thrombosis and inflammation. Here, as one remarkable example, studies using a novel and highly selective pharmacologic inhibitor of the spleen tyrosine kinase Syk [PRT060318; 2-((1R,2S)-2-aminocyclohexylamino)-4-(m-tolylamino)pyrimidine-5-carboxamide] coupled with genetic experiments, demonstrate that Syk inhibition ameliorates both the acute and chronic responses to vascular injury without affecting hemostasis. Specifically, lack of Syk (murine radiation chimeras) attenuated shear-induced thrombus formation ex vivo, and PRT060318 strongly inhibited arterial thrombosis in vivo in multiple animal species while having minimal impact on bleeding. Furthermore, leukocyte-platelet-dependent responses to vascular injury, including inflammatory cell recruitment and neointima formation, were markedly inhibited by PRT060318. Thus, Syk controls acute and long-term responses to arterial vascular injury. The therapeutic potential of Syk may be exemplary of a new class of antiatherothrombotic agents that target the interface between thrombosis and inflammation.
Subject(s)
Intracellular Signaling Peptides and Proteins/physiology , Protein-Tyrosine Kinases/physiology , Vascular System Injuries/physiopathology , Wound Healing/genetics , Animals , Cyclohexylamines/pharmacology , Cyclohexylamines/therapeutic use , Disease Models, Animal , Drug Evaluation, Preclinical , Female , Intracellular Signaling Peptides and Proteins/antagonists & inhibitors , Intracellular Signaling Peptides and Proteins/genetics , Male , Mice , Mice, Knockout , Platelet Aggregation/drug effects , Platelet Aggregation Inhibitors/pharmacology , Protein Kinase Inhibitors/pharmacology , Protein-Tyrosine Kinases/antagonists & inhibitors , Protein-Tyrosine Kinases/genetics , Pyrimidines/pharmacology , Pyrimidines/therapeutic use , Swine , Syk Kinase , Thrombosis/drug therapy , Thrombosis/genetics , Thrombosis/pathology , Vascular System Injuries/genetics , Vascular System Injuries/rehabilitationABSTRACT
Platelet-derived growth factor (PDGF) is a potent stimulant of smooth muscle cell migration and proliferation in culture. To test the role of PDGF in the accumulation of smooth muscle cells in vivo, we evaluated ApoE -/- mice that develop complex lesions of atherosclerosis. Fetal liver cells from PDGF-B-deficient embryos were used to replace the circulating cells of lethally irradiated ApoE -/- mice. One month after transplant, all monocytes in PDGF-B -/- chimeras are of donor origin (lack PDGF), and no PDGF-BB is detected in circulating platelets, primary sources of PDGF in lesions. Although lesion volumes are comparable in the PDGF-B +/+ and -/- chimeras at 35 weeks, lesions in PDGF-B -/- chimeras contain mostly macrophages, appear less mature, and have a reduced frequency of fibrous cap formation as compared with PDGF-B +/+ chimeras. However, after 45 weeks, smooth muscle cell accumulation in fibrous caps is indistinguishable in the two groups. Comparison of elicited peritoneal macrophages by RNase protection assay shows an altered cytokine and cytokine receptor profile in PDGF-B -/- chimeras. ApoE -/- mice were also treated for up to 50 weeks with a PDGF receptor antagonist that blocks all three PDGF receptor dimers. Blockade of the PDGF receptors similarly delays, but does not prevent, accumulation of smooth muscle and fibrous cap formation. Thus, elimination of PDGF-B from circulating cells or blockade of PDGF receptors does not appear sufficient to prevent smooth muscle accumulation in advanced lesions of atherosclerosis.
Subject(s)
Apolipoproteins E/genetics , Blood Platelets/physiology , Platelet-Derived Growth Factor/antagonists & inhibitors , Platelet-Derived Growth Factor/genetics , Receptors, Platelet-Derived Growth Factor/antagonists & inhibitors , Animals , Apolipoproteins E/deficiency , Apolipoproteins E/physiology , Arteriosclerosis/genetics , Arteriosclerosis/pathology , Arteriosclerosis/prevention & control , Becaplermin , Blood Platelets/drug effects , Mice , Mice, Knockout , Piperazines/pharmacology , Platelet-Derived Growth Factor/deficiency , Platelet-Derived Growth Factor/physiology , Polymerase Chain Reaction , Proto-Oncogene Proteins c-sis , Quinazolines/pharmacologyABSTRACT
Monoamidine FXa inhibitors 3 were designed and synthesized. SAR studies and molecular modeling led to the design of conformationally constrained diaryl ethers 4 and 5, as well as benzopyrrolidinone 7 as potent FXa inhibitors. The monoamidines show high efficacy in a DVT model, but lack desirable oral bioavailability. The benzopyrrolidinone-based aminoisoquinolines 8 do not show significant improvement in oral bioavailability.
Subject(s)
Benzamidines/chemical synthesis , Benzamidines/pharmacology , Factor Xa Inhibitors , Isoquinolines/chemical synthesis , Isoquinolines/pharmacology , Serine Proteinase Inhibitors/chemical synthesis , Serine Proteinase Inhibitors/pharmacology , Administration, Oral , Animals , Benzamidines/chemistry , Benzamidines/pharmacokinetics , Biological Availability , Drug Design , Isoquinolines/chemistry , Isoquinolines/pharmacokinetics , Rats , Rats, Sprague-Dawley , Serine Proteinase Inhibitors/chemistry , Serine Proteinase Inhibitors/pharmacokinetics , Structure-Activity RelationshipABSTRACT
Substituted acrylamides were used as templates that bridge P1 and P4 binding elements, resulting in a series of potent (sub-nanomolar) and selective factor Xa inhibitors. In this template, cis-geometry of P1 and P4 ligands is highly preferred. SAR on the substituting groups, as well as on modification of P1 and P4 moieties is described. Compounds in this series show good in vivo efficacy in animal models.
