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Nonclinical testing of human pharmaceuticals is conducted to assess the safety of compounds to be studied in human clinical trials and for marketing of new drugs. Although there is no exact number and type of nonclinical studies required for safety assessments, as there is inherent flexibility for each new compound, the traditional approach is outlined in various FDA and ICH guidance documents and involves a combination of in vitro assays and whole animal testing methods. Recent advances in science have led to the emergence of numerous new approach methodologies (NAMs) for nonclinical testing that are currently being used in various aspects of drug development. Traditional nonclinical testing methods can predict clinical outcomes, although improvements in these methods that can increase predictivity of clinical outcomes are encouraged and needed. This paper discusses FDA/CDER's view on the opportunities and challenges of using NAMs in drug development especially for regulatory purposes, and also includes examples where NAMs are currently being used in nonclinical safety assessments and where they may supplement and/or enhance current testing methods. FDA/CDER also encourages communication with stakeholders regarding NAMs and is committed to exploring the use of NAMs to improve regulatory efficiency and potentially expedite drug development.

After evaluating a safety signal regarding pancreatitis and pancreatic cancer in patients using incretin-based drugs, the Food and Drug Administration and the European Medicines Agency conclude that assertions of a causal association are inconsistent with the data. With approximately 25.8 million diabetic patients in the United States and 33 million in the European Union alone, the growing prevalence of diabetes worldwide poses a major public health challenge. Both the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) are committed to ensuring the safety of drug products marketed for the treatment of diabetes, and postmarketing reports of pancreatitis and pancreatic cancer in patients taking certain antidiabetic medications have been of concern to both agencies. Working in parallel, the agencies have reviewed nonclinical toxicology studies, clinical trial data, and epidemiologic data pertaining to blood glucose-lowering ...

The mannose-binding lectin (MBL), a circulating pattern recognition molecule, recognizes a wide range of infectious agents with resultant initiation of the complement cascade in an Ab-independent manner. MBL recognizes infectious non-self and altered self in the guise of apoptotic and necrotic cells. In this study, we demonstrate that mice lacking MBL, and hence are devoid of MBL-dependent lectin pathway activation but have fully active alternative and classical complement pathways, are protected from cardiac reperfusion injury with resultant preservation of cardiac function. Significantly, mice that lack a major component of the classical complement pathway initiation complex (C1q) but have an intact MBL complement pathway, are not protected from injury. These results suggest that the MBL-dependent pathway of complement activation is a key regulator of myocardial reperfusion ischemic injury. MBL is an example of a pattern recognition molecule that plays a dual role in modifying inflammatory responses to sterile and infectious injury.

Background—Myocardial ischemia and reperfusion-induced tissue injury involve a robust inflammatory response, but the proximal events in reperfusion injury remain incompletely defined. Toll-like receptor 4 (TLR4) is a proximal signaling receptor in innate immune responses to lipopolysaccharide of Gram-negative pathogens. TLR4 is also expressed in the heart and vasculature, but a role for TLR4 in the myocardial response to injury separate from microbial pathogens has not been examined. This study assessed the role of TLR4 in myocardial infarction and inflammation in a murine model of ischemia-reperfusion injury.Methods and Results—Myocardial ischemia-reperfusion (MIR) was performed on 2 strains of TLR4-deficient mice (C57/BL10 ScCr and C3H/HeJ) and controls (C57/BL10 ScSn and C3H/OuJ). Mice were subjected to 1 hour of coronary ligation, followed by 24 hours of reperfusion. TLR4-deficient mice sustained significantly smaller infarctions compared with control mice given similar areas at risk. Fewer neutrophils infiltrated the myocardium of TLR4-deficient Cr mice after MIR, indicated by less myeloperoxidase activity and fewer CD45/GR1-positive cells. The myocardium of TLR4-deficient Cr mice contained fewer lipid peroxides and less complement deposition compared with control mice after MIR. Serum levels of interleukin-12, interferon-γ, and endotoxin were not increased after ischemia-reperfusion. Neutrophil trafficking in the peritoneum was similar in all strains after injection of thioglycollate.Conclusions—TLR4-deficient mice sustain smaller infarctions and exhibit less inflammation after myocardial ischemia-reperfusion injury. The data suggest that in addition to its role in innate immune responses, TLR4 serves a proinflammatory role in murine myocardial ischemia-reperfusion injury.

Growing evidence from patients with heart failure and from experimental animal models implicates effectors of innate immunity in the pathogenesis of this syndrome. The expression of the innate immunity signaling protein, Toll-like receptor 4 (TLR4), is increased in cardiac myocytes in situ and in failing myocardium, but the mechanism by which TLRs may be activated in the failing heart remains unclear. We report that TLR2, which is expressed in cardiac myocytes, participates in the response of these cells to oxidative stress, a major contributor to the pathogenesis of cardiac dysfunction. Hydrogen peroxide increased nuclear factor kappaB (NF-kappaB) activation in Chinese hamster ovary fibroblasts that overexpress TLR2 but not in normal or TLR4-overexpressing Chinese hamster ovary cells, an effect that was abrogated by an alpha-TLR2 antibody. In neonatal rat ventricular myocytes, the alpha-TLR2 antibody inhibited hydrogen peroxide-induced nuclear translocation of NF-kappaB and activator protein-1 (AP-1). Inhibition of TLR2 had no effect on tumor necrosis factor alpha-induced NF-kappaB or AP-1 activation, on the DNA binding of the basal transcription factor Oct-1, or on hydrogen peroxide-induced phosphorylation of p38 MAP kinase. Importantly, oxidative stress-induced cytotoxicity was enhanced by blocking TLR2. Given the importance of cytotoxicity and apoptosis to the pathology of the ischemic heart, an anti-apoptotic effect of TLR2 in cardiac myocytes exposed to elevated levels of ROS may limit further cardiac dysfunction.

IntroductionThrombosis underlies most acute manifestations of atherosclerosis and likely is an important contributor to the evolution of atherosclerotic lesions. In the coronary arteries, thrombosis precipitates most episodes of unstable angina and acute myocardial infarction (both Q-wave and non Q- wave). But, of course, atherosclerosis is a systemic disease that affects many arterial beds. Thus, the thrombotic complications of atherosclerosis also cause many strokes and acute exacerbations of peripheral vascular disease that place limbs in jeopardy.Many studies have clarified the microanatomy of fatal coronary thrombosis. Flow limiting stenoses were formerly considered the cause of the acute coronary syndromes. Recent clinical observations, however, have taught us that most myocardial infarctions result from thrombi that occur on the substrate of a lesion that does not cause a critical narrowing of a coronary artery. We now appreciate that a physical disruption of the atheromatous plaque most often provokes thrombus formation. Plaque disruption takes two major forms: a frank fissuring of the plaque’s fibrous cap and a superficial erosion of the intimal surface (Table 1). In the case of a ruptured cap, blood coagulation factors come into contact with the plaque’s lipid core, which is rich in tissue factor and considered the major procoagulant in this situation. In the case of superficial erosion, platelets can contact subendothelial basement membrane and collagen within the plaque, which may trigger platelet aggregation. Additionally, smooth muscle cells underlying the endothelium can also express tissue factor, further contributing to thrombus formation.Excellent evidence suggests that plaque rupture occurs frequently, even in asymptomatic individuals. Consequently, most arterial thrombi do not produce clinical manifestations. Presumably, most mural thrombi either fail to occlude the vessel, as they do not propagate, or are evanescent. A healing mural thrombus, although clinically silent, may still contribute to plaque growth. Platelets contain potent fibrogenic mediators, such as platelet-derived growth factor (a smooth muscle cell chemoattractant) and transforming growth factor (TGF)-β (a strong stimulus to smooth muscle collagen gene expression). Thrombin and activated factor X can stimulate smooth muscle cell proliferation by direct and/or indirect routes. These mediators may link healing mural thrombi in arteries to intimal growth and the formation of stenotic lesions.Why do some plaque disruptions lead to an occlusive thrombus that may cause sudden death, while other disruptions pass unnoticed? The locally prevailing hemostatic and fibrinolytic balance likely proves decisive in determining the fate of a given disruption of an atheroma. Much evidence has recently accumulated regarding the factors that regulate these regional balances. This chapter will selectively summarize certain of those recent findings. It will also provide some mechanistic insight into how contemporary therapies may act to reduce the thrombotic complications that cause the most dreaded and dramatic complications of atherosclerosis.

Abstract —Plasminogen activator inhibitor type-1 (PAI-1) is a major physiological inhibitor of fibrinolysis, with its plasma levels correlating with the risk for myocardial infarction and venous thrombosis. The regulation of PAI-1 transcription by endothelial cells (ECs), a major source of PAI-1, remains incompletely understood. Adipocytes also produce PAI-1, suggesting possible common regulatory pathways between adipocytes and ECs. Peroxisomal proliferator-activated receptor-γ (PPAR)γ is a ligand-activated transcription factor that regulates gene expression in response to various mediators such as 15-deoxy- Δ12,14 -prostaglandin J 2 (15d-PGJ 2 ) and oxidized linoleic acid (9- and 13-HODE). The present study tested the hypotheses that human ECs express PPARγ and that this transcriptional activator regulates PAI-1 expression in this cell type. We found that human ECs contain both PPARγ mRNA and protein. Immunohistochemistry of human carotid arteries also revealed the presence of PPARγ in ECs. Bovine ECs transfected with a PPAR response element (PPRE)–luciferase construct responded to stimulation by the PPARγ agonist 15d-PGJ 2 in a concentration-dependent manner, suggesting a functional PPARγ in ECs. Treatment of human ECs with 15d-PGJ 2 , 9( S )-HODE, or 13( S )-HODE augmented PAI-1 mRNA and protein expression, whereas multiple PPARα activators did not change PAI-1 levels. Introduction of increasing amounts of a PPARγ expression construct in human fibroblasts enhanced PAI-1 secretion from these cells in proportion to the amount of transfected DNA. Thus, ECs express functionally active PPARγ that regulates PAI-1 expression in ECs. Our results establish a role for PPARγ in the regulation of EC gene expression, with important implications for the clinical links between obesity and atherosclerosis.

Activated macrophages release cytokines and growth factors that may contribute to the growth of vascular smooth muscle cells in injured blood vessels. In the present study, we investigated the interactions between interleukin-1 beta (IL-1 beta) and basic fibroblast growth factor (FGF-2) in primary rat aortic smooth muscle cells, relative to their effects on DNA synthesis and cell proliferation. We report that femtomolar levels of IL-1 beta, which alone were non-mitogenic or weakly mitogenic, synergistically increased FGF-2-induced [3H]thymidine incorporation and cell proliferation. The potentiating effect of IL-1 beta extended to PDGF-AB and EGF, but not to IGF-1-induced thymidine incorporation. An antagonist of the IL-1 receptor, IL-1ra, blocked the co-mitogenic effect of IL-1 beta. Stimulation of cells with FGF-2 and IL-1 beta increased both DNA content and proliferation, an observation that was consistent with the thymidine incorporation experiments. An inhibitor of NO synthase, N5-iminoethyl L-ornithine (L-NIO), did not block the co-mitogenic effect of IL-1 beta, despite effective inhibition of NO synthase activity, suggesting that the synergistic interaction between IL-1 beta and FGF-2 was independent of the NO/cGMP pathway. The mechanism of co-mitogenesis appeared to be independent of the intermediacy of PDGF-AA, IL-6, and prostanoids, and was not associated with increased levels of c-fos mRNA, FGF receptor-1 protein, or FGF-2-induced early and delayed tyrosine phosphorylation events. We conclude that IL-1 beta interacts with FGF-2 to amplify the proliferation of primary rat aortic smooth muscle cells, an effect that may be important in vascular smooth muscle cell proliferation following vascular injury.