Regulatory forum opinion piece*: immunotoxicology assessments in nonhuman primates--challenges and opportunities.

The immune system has been recognized for decades as a potential "target organ" of toxicity. Immune system activation can result in cytokine release resulting in severe systemic toxicity. Immunosuppression can result in impaired host defense and an increase in opportunistic infection, reemergence of latent infection, poor responses to vaccination, or increased risk of certain cancers. Several regulatory documents have addressed various aspects of immunotoxicity assessments. Nonhuman primates (NHPs) and in particular macaques are often the only relevant species for biotechnology-derived investigational new drugs based on cross-reactivity with human and NHP targets. This article reviews the challenges and opportunities associated with monitoring immune function in NHPs in the context of regulatory expectations. The article emphasizes how a comprehensive assessment of immunotoxicity remains a challenge due to interanimal variability associated with certain parameters (e.g., T-dependent antibody response)and it identifies gaps, such as the stage of development of certain assays (e.g., cytotoxic T-cell function). Despite these challenges, a thorough assessment of target biology-driven theoretical risks, in combination with proper integration of all information from the standard toxicology studies, and the refinement of certain assays should enable proper risk assessment. To this effect, emphasis should be placed on leveraging predictive in vitro assays using human cells.

Summary of a workshop on nonclinical and clinical immunotoxicity assessment of immunomodulatory drugs.

The number of anti-inflammatory and immunomodulatory drugs being developed in the pharmaceutical industry has increased considerably in the past decade. This increase in research and development has been paralleled by questions from both regulatory agencies and industry on how best to assess decreased host resistance to infections or adverse immunostimulation caused by immunomodulatory agents such as anti-cytokine antibodies (e.g., the tumor necrosis factor-alpha inhibitors), anti-adhesion molecule antibodies (e.g., anti-alpha-4 integrin inhibitors) and immunostimulatory molecules (e.g., anti-CD28 antibodies). Although several methods have been developed for nonclinical assessment of immunotoxicity, highly publicized adverse events have brought to light significant gaps in the application of nonclinical immunotoxicity testing in assessing potential risk in humans. Confounding this problem is inconsistent application of immunotoxicology methods for risk assessment within the scientific community, limited understanding of appropriate immunotoxicity testing strategy for immunomodulators and inconsistent testing requests by regulatory agencies. To address these concerns, The Immunotoxicology Technical Committee (ITC) of the International Life Science Institute (ILSI) Health and Environmental Sciences Institute (HESI) organized a workshop on Immunomodulators and Clinical Immunotoxicology in May 2007. The Workshop was convened to identify key gaps in nonclinical and clinical immunotoxicity testing of anti-inflammatory and immunomodulatory agents and to begin to develop consistent approaches for immunotoxicity testing and risk assessment. This paper summarizes the outcome of the HESI ITC Immunomodulators and Clinical Immunotoxicology Workshop. Topics not discussed at the Workshop were outside the scope of this report. Although more work is needed to develop consistent approaches for immunotoxicity assessment of immunomodulators, this Workshop provided the foundation for future discussion.