Toxicologic Pathology Forum: Considerations Regarding Determination of Adversity for Immunopathology Findings in Nonclinical Toxicology Studies with Immune-Modulating Therapeutics

The evaluation of changes in the immune system serves to determine the efficacy and potential immunotoxicologic effects of new products under development. Toxicologic pathologists play critical roles in identifying immune system changes that drive the immunosafety determination. Standard pathology evaluations of therapies and chemicals remain similar; however, biopharmaceutical therapies have moved from simply affecting the immune system to being specifically developed to modify the immune system, which can impact interpretation. Recent explosive growth in immunomodulatory therapies presents a challenge to the toxicologic pathologist, toxicologist, and regulatory reviewer in terms of evaluating the clinical relevance and potential adversity of immune system changes. Beyond the recognition of such changes, there is an increasing expectation to evaluate, describe, and interpret how therapies affect complex immune system pathways for both immunomodulatory therapies and non-immunomodulatory drugs with off-target immunotoxic effects. In this opinion piece, considerations regarding immune system evaluation, the current landscape of immunomodulatory therapies, a brief description of immunotoxicologic (and immunopathologic) endpoints, the importance of integrating such immunosafety data, and relevance to adversity determination are discussed. Importantly, we describe how the current paradigm of determining adversity for immune system changes may be challenging or insufficient and propose a harmonized and flexible approach for assessing adversity.