Investigative safety strategies to improve success in drug development

Understanding and reducing attrition rate remains a key challenge in drug development. Preclinical and clinical safety issues still represent about 40% of drug discontinuation, of which cardiac and liver toxicities are the leading reasons. Reducing attrition rate can be achieved by various means, starting with a comprehensive evaluation of the potential safety issues associated to the primary target followed by an evaluation of undesirable secondary targets. To address these risks, a risk mitigation plan should be built at very early development stages, using a panel of in silico, in vitro, and in vivo models. While most pharmaceutical companies have developed robust safety strategies to de-risk genotoxicity and cardiotoxicity issues, partly driven by regulatory requirements; safety issues affecting other organs or systems, such as the central nervous system, liver, kidney, or gastro-intestinal system are less commonly addressed during early drug development. This paper proposes some de-risking strategies that can be applied to these target organ systems, including the use of novel biomarkers that can be easily integrated in both preclinical and clinical studies. Experiments to understand the mechanisms’ underlying toxicity are also important. Two examples are provided to demonstrate how such mechanistic studies can impact drug development. Novel trends in investigative safety are reviewed, such as computational modeling, mitochondrial toxicity assessment, and imaging technologies. Ultimately, understanding the predictive value of non-clinical safety testing and its translatability to humans will enable to optimize assays in order to address the key objectives of the drug discovery process, i.e., hazard identification, risk assessment, and mitigation

A Non-Cytosolic Protein of Trypanosoma evansi Induces CD45-Dependent Lymphocyte Death

In a recent study dealing with a mouse model of Trypanosoma evansi-associated disease, a remarkable synchrony between the parasitaemia peak and the white-blood-cell count nadir was noticed. The present study was designed to establish whether there is a direct causal link between the parasite load during its exponential phase of growth and the disappearance of peripheral blood leukocytes. In vitro experiments performed with trypanosomes and purified peripheral blood mononucleated cells revealed the existence of a lymphotoxin embedded in the T. evansi membrane: a protein sensitive to serine proteases, with a molecular mass of less than 30 kDa. Lymphocytes death induced by this protein was found to depend on the intervention of a lymphocytic protein tyrosine phosphatase. When lymphocytes were exposed to increasing quantities of a monoclonal antibody raised against the extracellular portion of CD45, a transmembrane protein tyrosine phosphatase covering over 10% of the lymphocyte surface, T. evansi membrane extracts showed a dose-dependent decrease in cytotoxicity. As the regulatory functions of CD45 concern not only the fate of lymphocytes but also the activation threshold of the TCR-dependent signal and the amplitude and nature of cytokinic effects, this demonstration of its involvement in T. evansi-dependent lymphotoxicity suggests that T. evansi might manipulate, via CD45, the host's cytokinic and adaptive responses

ChemR23 Dampens Lung Inflammation and Enhances Anti-viral Immunity in a Mouse Model of Acute Viral Pneumonia

Viral diseases of the respiratory tract, which include influenza pandemic, children acute bronchiolitis, and viral pneumonia of the elderly, represent major health problems. Plasmacytoid dendritic cells play an important role in anti-viral immunity, and these cells were recently shown to express ChemR23, the receptor for the chemoattractant protein chemerin, which is expressed by epithelial cells in the lung. Our aim was to determine the role played by the chemerin/ChemR23 system in the physiopathology of viral pneumonia, using the pneumonia virus of mice (PVM) as a model. Wild-type and ChemR23 knock-out mice were infected by PVM and followed for functional and inflammatory parameters. ChemR23−/− mice displayed higher mortality/morbidity, alteration of lung function, delayed viral clearance and increased neutrophilic infiltration. We demonstrated in these mice a lower recruitment of plasmacytoid dendritic cells and a reduction in type I interferon production. The role of plasmacytoid dendritic cells was further addressed by performing depletion and adoptive transfer experiments as well as by the generation of chimeric mice, demonstrating two opposite effects of the chemerin/ChemR23 system. First, the ChemR23-dependent recruitment of plasmacytoid dendritic cells contributes to adaptive immune responses and viral clearance, but also enhances the inflammatory response. Second, increased morbidity/mortality in ChemR23−/− mice is not due to defective plasmacytoid dendritic cells recruitment, but rather to the loss of an anti-inflammatory pathway involving ChemR23 expressed by non-leukocytic cells. The chemerin/ChemR23 system plays important roles in the physiopathology of viral pneumonia, and might therefore be considered as a therapeutic target for anti-viral and anti-inflammatory therapies

Immune depression of the SJL/J mouse, a radioresistant and immunologically atypical inbred strain.

peer reviewedAs the inbred mouse strain SJL/J displays increased resistance to several pathogens and as its immune system shows multiple specificities, it is tempting to infer a causal link between these observations. The first question that comes to mind is whether adaptive immunity plays a role, and a way to answer this question is to see if the resistance phenotype persists when adaptive immunity is depressed. Although it has long been known that irradiation causes repression of leukopoiesis in mice, the technical data available in the literature are of no help in the case of strain SJL/J, because it displays exceptional radioresistance. Here we show that exposure of SJL/J to ∼9Gy, an intensity corresponding to the lethal dose 50 for the species Mus musculus, leads to serious but reversible alteration of leukopoiesis. This conclusion stems from an examination of the effects, 1-11 days post-exposure, of whole-body gamma-ray irradiation on leukocyte populations in the thymus and peripheral blood of young adult females. Immunodepression was most severe 4 days post-exposure. As in other strains, leukocyte populations displayed differential radiosensitivity, B (CD19(+)) cells being most sensitive, T (CD4(+)/CD8(+)) cells moderately sensitive, and natural killer (NK1.1(+)) cells most resistant. Surprisingly, however, the helper/inducer T lymphocytes proved more resistant than the cytotoxic/suppressor T lymphocytes, contrarily to what is observed in other strains. The procedure described will make it possible to refute or establish reliably the existence of causal links between SJL-specific phenotypic traits and immune aberrations and to elucidate further the respective roles of innate and acquired immunity in determining the resistance of this strain to an array of viral diseases

Characterization of the resistance of SJL/J mice to pneumonia virus of mice, a model for infantile bronchiolitis due to a respiratory syncytial virus

Respiratory syncytial virus (RSV), a prominent cause of airway morbidity in children, maintains an excessive hospitalization rate despite decades of research. Host factors are assumed to influence the disease severity. As a first step toward identifying the underlying resistance mechanisms, we recently showed that inbred mouse strains differ dramatically as regards their susceptibility to pneumonia virus of mice (PVM), the murine counterpart of RSV. PVM infection in mice has been shown to faithfully mimic the severe RSV disease in human infants. This study aimed at dissecting the remarkable PVM-resistance shown by the SJL/J strain. To characterize its genetic component, we assessed clinical, physiopathological, and virological resistance/susceptibility traits in large first (F1) and second (F2) generations obtained by crossing the SJL/J (resistant) and 129/Sv (susceptible) strains. Then, to acquire conclusive in vivo evidence in support of the hypothesis that certain radiosensitive hematopoietic cells might play a significant role in PVM-resistance, we monitored the same resistance/susceptibility traits in mock- and γ-irradiated SJL/J mice. Segregation analysis showed that (i) PVM-resistance is polygenic, (ii) the resistance alleles are recessive, and (iii) all resistance-encoding alleles are concentrated in SJL/J. Furthermore, there was no alteration of SJL/J PVM resistance after immunosuppression by γ-irradiation, which suggests that adaptive immunity is not involved. We conclude that host resistance to pneumoviruses should be amenable to genetic dissection in this mouse model and that radioresistant lung epithelial cells and/or alveolar macrophages may control the clinical severity of pneumovirus-associated lung disease

Paving the Route to Plasma miR-208a-3p as an Acute Cardiac Injury Biomarker: Preclinical Rat Data Supports Its Use in Drug Safety Assessment.

Drug-induced cardiac injury (DICI) detection remains a major safety issue in drug development. While circulating microRNAs (miRs) have emerged as promising translational biomarkers, novel early detection biomarkers of cardiotoxicity are needed. This work aims at evaluating whether a panel of putative cardiac injury plasma miRs could serve as early DICI biomarkers in a 4-day rat preclinical model. Out of a panel of 68 selected targets, we identified plasma miR-208a-3p as being significantly upregulated after single administration with either isoproterenol (ISO) or allylamine (AAM). This provides the first evidence of miR-208a-3p detection after AAM administration. Moreover, similarly to cardiac troponins (cTn), plasma miR-208a-3p expression profile appears to be compound-specific with most significant early changes occurring in ISO-treated rats. Overall, miR-208a-3p performance in detecting the severity of myocardial injury, as well as the magnitude of miR-208a-3p increase after ISO or AAM administration, were comparable to that of cTn. Our results highlight the importance of assessing the whole time-dependent profiles of miR expression. Hence, time course evaluation revealed plasma miR candidates whose expression was not stable across the duration of the study in the vehicle group, restricting their utility as cardiac injury-specific biomarkers. In light of these findings, miR-208a-3p has a potential to complement the existing biomarkers of cardiac injury specifically in the context of evaluating toxicity in a time-dependant manner. Assessment of miR-208a-3p in other DICI settings would strengthen its robustness as an early detection biomarker leading to a warranted extensive and rigorous validation.info:eu-repo/semantics/publishe