Current nonclinical approaches for immune assessments of immuno-oncology biotherapeutics.

Harnessing the immune system to kill tumors has been revolutionary and, as a result, has had an enormous benefit for patients in extending life and resulting in effective cures in some. However, activation of the immune system can come at the cost of undesirable adverse events such as cytokine release syndrome, immune-related adverse events, on-target/off-tumor toxicity, neurotoxicity and tumor lysis syndrome, which are safety risks that can be challenging to assess non-clinically. This article provides a review of the biology and mechanisms that can result in immune-mediated adverse effects and describes industry approaches using in vitro and in vivo models to aid in the nonclinical safety risk assessments for immune-oncology modalities. Challenges and limitations of knowledge and models are also discussed.

Comprehensive BCMA Expression Profiling in Adult Normal Human Brain Suggests a Low Risk of On-target Neurotoxicity in BCMA-targeting Multiple Myeloma Therapy.

B-cell maturation antigen (BCMA) is a target for the treatment of multiple myeloma with cytolytic therapies, such as chimeric antigen receptor T-cells or T-cell redirecting antibodies. To better understand the potential for "on-target/off-tumor" toxicity caused by BCMA-targeting cytolytic therapies in the brain, we investigated normal brain BCMA expression. An immunohistochemistry (IHC) assay using the E6D7B commercial monoclonal antibody was applied to 107 formalin-fixed, paraffin-embedded brain samples (cerebrum, basal ganglia, cerebellum, brainstem; 63 unique donors). Although immunoreactivity was observed in a small number of neurons in brain regions including the striatum, thalamus, midbrain, and medulla, this immunoreactivity was considered nonspecific and not reflective of BCMA expression because it was distinct from the membranous and Golgi-like pattern seen in positive control samples, was not replicated when a different IHC antibody (D6 clone) was used, and was not corroborated by in situ hybridization data. Analysis of RNA-sequencing data from 478 donors in the GTEx and Allen BrainSpan databases demonstrated low levels of BCMA RNA expression in the striatum of young donors with levels becoming negligible beyond 30 years of age. We concluded that BCMA protein is not present in normal adult human brain, and therefore on-target toxicity in the brain is unlikely.

Nonclinical safety assessment of engineered T cell therapies.

Over the last decade, immunotherapy has established itself as an important novel approach in the treatment of cancer, resulting in a growing importance in oncology. Engineered T cell therapies, namely chimeric antigen receptor (CAR) T cells and T cell receptor (TCR) T cell therapies, are platform technologies that have enabled the development of products with remarkable efficacy in several hematological malignancies and are thus the focus of intense research and development activity. While engineered T cell therapies offer promise in addressing currently intractable cancers, they also present unique challenges, including their nonclinical safety assessment. A workshop organized by HESI and the US Food and Drug Administration (FDA) was held to provide an interdisciplinary forum for representatives of industry, academia and regulatory authorities to share information and debate on current practices for the nonclinical safety evaluation of engineered T cell therapies. This manuscript leverages what was discussed at this workshop to provide an overview of the current important nonclinical safety assessment considerations for the development of these therapeutic modalities (cytokine release syndrome, neurotoxicity, on-target/off-tumor toxicities, off-target effects, gene editing or vector integration-associated genomic injury). The manuscript also discusses approaches used for hazard identification or risk assessment and provides a regulatory perspective on such aspects.

Summary of a workshop on preclinical and translational safety assessment of CD3 bispecifics.

Currently, there is a multitude of CD3 bispecifics with different molecular designs and binding properties in preclinical and clinical development for the treatment of liquid or solid tumors. The key safety concerns with CD3 bispecifics are excessive release of cytokines, which may translate to potentially life-threating cytokine release syndrome (CRS), target organ toxicity due to redirection of T-cells to normal tissues expressing the tumor-associated antigen (TAA) (off-tumor/on-target cytotoxicity), and, in some instances, neurotoxicity. Another key challenge is to arrive at a safe clinical starting dose and an efficient escalating strategy that allows patients in early dose cohorts the potential for clinical benefit in Phase 1 trials. To expand the therapeutic index and bring more treatment options to patients, there are intense efforts to overcome these challenges through improvements in molecular design, preclinical safety assessment strategies, and clinical management practices. A recent workshop at the U.S. Food and Drug Administration (FDA) with industry, academic, and regulatory agency representation was held to discuss the challenges and explore where such improvements to the development of CD3 bispecifics can be implemented. Here, the content of the presentations and the discussion that occurred during this workshop are summarized.

Developmental immunotoxicity (DIT) testing of pharmaceuticals: current practices, state of the science, knowledge gaps, and recommendations.

The development and regulatory approval of immunomodulatory pharmaceuticals to treat many human diseases has increased significantly over the last two decades. As discussed by FDA and ICH guidelines, all human pharmaceuticals in development should be evaluated for potential adverse effects on the immune system. Developmental immunotoxicology (DIT) focuses on the concern that early-life (during pre-/post-natal development) exposure to agents which target the immune system may result in enhanced susceptibility to immune-related disease (e.g., infection, autoimmunity, and cancer, particularly leukemia) compared to adults, unique effects not observed in adults, or more persistent effects in comparison to those following adult exposure. This article provides a substantive review of the literature and presents detailed considerations for DIT testing strategies with a specific focus on pharmaceuticals and biopharmaceuticals. In this regard, differences between small molecule and large molecule therapeutics will be considered, along with recommendations for best practices in the assessment of DIT during drug development. In addition, gaps in the DIT knowledge base and current testing strategies are identified. Finally, a summary of an ILSI-HESI-ITC sponsored Workshop conducted in 2010, entitled 'Developmental Immunotoxicity Testing of Pharmaceuticals' will be presented. This Workshop consisted of participants from the pharmaceutical, biotechnology, academic, and regulatory sectors, where many of the issues relating to DIT outlined in this review were discussed, key points of consensus reached, and current gaps in the science identified.

Characterization of a potential animal model of an idiosyncratic drug reaction: nevirapine-induced skin rash in the rat.

Idiosyncratic drug reactions are difficult to study in humans due to their unpredictability. Unfortunately, this characteristic also hinders the development of animal models needed for mechanistic studies. Nevirapine, used to treat human immunodeficiency virus (HIV) infections, results in a severe idiosyncratic skin rash in some patients. We found that nevirapine can also cause a significant rash in some strains of rats. At a dose of 150 mg/kg/day, the incidence in female Sprague-Dawley rats was 6/28 (21%), in female Brown Norway rats 32/32 (100%), and in female Lewis rats 0/6 (0%) while no male Sprague-Dawley or Brown Norway rats developed a rash. Female SJL mice 0/7 also did not develop nevirapine-induced skin lesions. The first sign of a reaction in Brown Norway rats was red ears at days 7-10 followed by a rash with scabbing mainly on the back; this was a shorter time to onset than in Sprague-Dawley rats. Light microscopy of the skin revealed a primarily mononuclear inflammatory infiltrate and lesions typical of self-trauma. Immunohistochemistry results suggest that the infiltrate was composed of CD4 and CD8 T cells as well as macrophages. A lower dose of either 40 or 75 mg/kg/day did not lead to a rash and, in fact, 2 weeks of the lower doses induced tolerance to the 150 mg/kg/day dose in female Brown Norway rats. A dose of 100 mg/kg/day resulted in rash in 2/4 (50%) of female Brown Norway rats. Rechallenge of Brown Norway rats that had been allowed to recuperate after a nevirapine-induced rash led to red ears in less than 24 h followed by hair loss and occasional skin lesions. Although the skin rash was less evident on rechallenge, microscopically, the cellular infiltrate was more prominent, especially surrounding the hair follicles. Moreover, there were lesions of interface dermatitis with apoptosis and satellitosis, indicative of a cell-mediated immune attack on the epidermis. While systemic signs of illness did not accompany the rash on primary exposure, on rechallenge, the animals appeared generally unwell and this forced sacrifice after 2 weeks or less of treatment. Importantly, splenocytes isolated from rechallenged animals were able to transfer susceptibility to nevirapine-induced skin rash to naïve female Brown Norway recipients, which was illustrated by a faster time to onset of rash in the recipients. The characteristics of this adverse reaction are similar to that seen in humans; that is, it is idiosyncratic in that it only occurs in some strains of animals, is delayed in onset, is more common in females, is dose-dependent, and appears to be immune-mediated. Therefore, it may represent a good animal model for the study of idiosyncratic drug reactions.