Cyclosporine promotes the induction of thymic lymphomas in C57BL/6 mice initiated by a single dose of gamma-radiation

Optimized nonclinical safety assessment strategies supporting clinical development of therapeutic monoclonal antibodies targeting inflammatory diseases

An increasing number of immunomodulatory monoclonal antibodies (mAbs) and IgG Fc fusion proteins are either approved or in early-to-late stage clinical trials for the treatment of chronic inflammatory conditions, autoimmune diseases and organ transplant rejection. The exquisite specificity of mAbs, in combination with their multi-functional properties, high potency, long half-life (permitting intermittent dosing and prolonged pharamcological effects), and general lack of off-target toxicity makes them ideal therapeutics. Dosing with mAbs for these severe and debilitating but often non life-threatening diseases is usually prolonged, for several months or years, and not only affects adults, including sensitive populations such as woman of child-bearing potential (WoCBP) and the elderly, but also children. Immunosuppression is usually a therapeutic goal of these mAbs and when administered to patients whose treatment program often involves other immunosuppressive therapies, there is an inherent risk for frank immunosuppression and reduced host defence which when prolonged increases the risk of infection and cancer. In addition when mAbs interact with the immune system they can induce other adverse immune-mediated drug reactions such as infusion reactions, cytokine release syndrome, anaphylaxis, immune-complex-mediated pathology and autoimmunity. An overview of the nonclinical safety assessment and risk mitigation strategies utilized to characterize these immunomodulatory mAbs and Fc fusion proteins to support first-in human (FIH) studies and futher clinical development in inflammatory disease indications is provided. Specific emphasis is placed on the design of studies to qualify animal species for toxicology studies, early studies to investigate safety and define PK/PD relationships, FIH-enabling and chronic toxicology studies, immunotoxicity, developmental, reproductive and juvenile toxicity studies and studies to determine the potential for immunosuppression and reduced host defence against infection and cancer. Nonclinical strategies to facilitate clinical and market entry in the most efficient timeframe are presented.

Successful drug development despite adverse preclinical findings part 1: processes to address issues and most important findings

Unexpected adverse preclinical findings (APFs) are not infrequently encountered during drug development. Such APFs can be functional disturbances such as QT prolongation, morphological toxicity or carcinogenicity. The latter is of particular concern in conjunction with equivocal genotoxicity results. The toxicologic pathologist plays an important role in recognizing these effects, in helping to characterize them, to evaluate their risk for man, and in proposing measures to mitigate the risk particularly in early clinical trials. A careful scientific evaluation is crucial while termination of the development of a potentially useful drug must be avoided. This first part of the review discusses processes to address unexpected APFs and provides an overview over typical APFs in particular classes of drugs. If the mode of action (MoA) by which a drug candidate produces an APF is known, this supports evaluation of its relevance for humans. Tailor-made mechanistic studies, when needed, must be planned carefully to test one or several hypotheses regarding the potential MoA and to provide further data for risk evaluation. Safety considerations are based on exposure at no-observed-adverse-effect levels (NOAEL) of the most sensitive and relevant animal species and guide dose escalation in clinical trials. The availability of early markers of toxicity for monitoring of humans adds further safety to clinical studies. Risk evaluation is concluded by a weight of evidence analysis (WoE) with an array of parameters including drug use, medical need and alternatives on the market. In the second part of this review relevant examples of APFs will be discussed in more detail.

Critical Review of Preclinical Approaches to Evaluate the Potential of Immunosuppressive Drugs to Influence Human Neoplasia

Many immunosuppressive drugs are associated with an increased risk of B-cell lymphoma, squamous cell carcinoma, and Kaposi sarcoma. Thirteen immunosuppressive drugs have been tested in 2-year carcinogenicity studies (abatacept; azathioprine; busulfan; cyclophosphamide; cyclosporine; dexamethasone; everolimus; leflunomide; methotrexate; mycophenolate mofetil; prednisone; sirolimus; and tacrolimus) and in additional models including neonatal and genetically modified mice; chemical, viral, ultraviolet, and ionizing radiation co-carcinogenesis, and in models with transplanted tumor cells. The purpose of this review is to outline the mechanisms by which immunosuppressive drugs can influence neoplasia, to summarize the available preclinical data on the 13 drugs, and to critically review the performance of the models. A combination of primary tumor and metastasis assays conducted with transplanted cells may provide the highest value for hazard identification and can be applied on a case-by-case basis. However, for both small molecules and therapeutic proteins, determining the relative risk to patients from preclinical data remains problematic. Classifying immunosuppressive drugs based on their mechanism of action and hazard identification from preclinical studies and a prospective pharmacovigilance program to monitor carcinogenic risk may be a feasible way to manage patient safety during the clinical development program and postmarketing.

Unexpected tumour findings in lifetime rodent bioassay studies--what to do?

Currently, the majority of substances tested in lifetime bioassays in rodents are not mutagenic and, therefore, at the most weakly carcinogenic, generally by epigenetic mechanisms. It thus appears obvious that only marginal increases of tumour incidences can be expected in lifetime bioassays and that, therefore, every aspect of a potential carcinogenic effect must be thoroughly evaluated. This paper describes a series of key factors, which should be looked at in order to exclude that the lifetime bioassay in question is flawed for design, technical or qualification reasons. It also provides some hints whether there is indeed a real effect and not just a variation of the spontaneous tumour incidences. Tumour findings must be seen in the context of the animal model, the pharmcokinetics and pharmcodynamics of the test substance, as well as any other observation in the present or other studies with the test substance, including non-tumour findings and--in particular--potential precursor lesions and effects on feed intake and survival. The possibility that the observed carcinogenic effects may be species-specific and not relevant for man is discussed. It is also important to check what findings are reported with similar substances or substances with the same pharmacological effect. Data from additional investigations on material of the same study and/or mechanistic studies are often needed to support the final risk assessment.

First report of a B cell lymphoproliferative disorder arising in a patient treated with immune suppressants for severe aplastic anemia

Aplastic anemia is a disorder characterized by pancytopenia and bone marrow hypocellularity. There is some evidence that aplastic anemia may be due to suppression of hematopoiesis by activated T-suppressor cells. Thus, immunosuppressive agents have been used as an alternative to bone marrow transplantation for treatment. We report on a unique case of a patient with aplastic anemia who was treated with a course of immunosuppression including cyclosporine (CSA), anti-thymocyte globulin (ATG), and prednisone. Five months after this treatment, the patient developed a B cell lymphoproliferative disorder which was successfully treated with radiation therapy. Prior reports of CSA-associated lymphoproliferative disorders have appeared in the literature as potential side effects of immunosuppression following transplantation. This is the first report of a lymphoproliferative disorder associated with immunosuppressive treatment of aplastic anemia in a nontransplant setting. Thus, when presenting options for treatment of aplastic anemia, lymphoproliferative disorders should be included as a rare complication of immunosuppressive therapy.

Immune parameters are affected differently after cyclosporine A exposure in Fischer 344 rats and B6C3F1 mice: implications for immunotoxicology

Knowledge of interspecies differences, commonly evaluated in other disciplines such as carcinogenesis, is a prerequisite for an appropriate assessment of immunotoxicological risks. The purpose of this study was to assess interspecies differences following exposure of Fischer 344 rats and B6C3F1 mice to cyclosporine A. These animals were exposed daily to cyclosporine A by oral gavage at 0, 5, 10, 25 mg/kg/day for 14 consecutive days. The results showed that splenocytes lymphoproliferation in response to concanavalin A or phytohemagglutinin, and IgM antibody-forming cells to sheep red blood cells, were affected in both species. Cytotoxic T-lymphocyte activity and mixed lymphocyte response were significantly inhibited in the rat following cyclosporine A exposure while they remained unaffected in the mouse. In contrast, natural killer cell activity was significantly depressed in the B6C3F1 mouse but not in the Fischer 344 rat. The discrepancies between the two species in cytotoxic T-lymphocyte activity and mixed lymphocyte response assays could partially be explained by the constantly higher blood level of cyclosporine A in the rat than in the mouse. When these tests were performed using rat and mouse splenocytes exposed to cyclosporin A in vitro (10(-9) to 10(-5) M) it was possible to correlate in vivo and in vitro data for concanavalin A- and phytohemagglutinin-induced lymphoproliferation and for cytotoxic T-lymphocyte activity but not for mixed lymphocyte response. Natural killer activity was 10-fold more sensitive in mice than in rats in vitro but these results did not clarify the in vivo difference. In conclusion, these results emphasize that the utilization of more than one species should be considered when assessing immunotoxicity.