Target arm affinities determine preclinical efficacy and safety of anti-HER2/CD3 bispecific antibody.

Systemic cytokine release and on-target/off-tumor toxicity to normal tissues are the main adverse effects limiting the clinical utility of T cell-redirecting therapies. This study was designed to determine how binding affinity for CD3 and tumor target HER2 impact the efficacy and nonclinical safety of anti-HER2/CD3 T cell-dependent antibodies (TDBs). Affinity was found to be a major determinant for the overall tolerability. Higher affinity for CD3 associated with rapidly elevated peripheral cytokine concentrations, weight loss in mice, and poor tolerability in cynomolgus monkeys. A TDB with lower CD3 affinity was better tolerated in cynomolgus monkeys compared with a higher CD3-affinity TDB. In contrast to tolerability, T cell binding affinity had only limited impact on in vitro and in vivo antitumor activity. High affinity for HER2 was critical for the tumor-killing activity of anti-HER2/CD3 TDBs, but higher HER2 affinity also associated with a more severe toxicity profile, including cytokine release and damage to HER2-expressing tissues. The tolerability of the anti-HER2/CD3 was improved by implementing a dose-fractionation strategy. Fine-tuning the affinities for both the tumor target and CD3 is likely a valuable strategy for achieving maximal therapeutic index of CD3 bispecific antibodies.

In vitro assessment of chemotherapy-induced neuronal toxicity.

Neurotoxicity is a major concern during drug development, and together with liver and cardio-toxicity, it is one of the main causes of clinical drug attrition. Current pre-clinical models may not sufficiently identify and predict the risk for central or peripheral nervous system toxicity. One such example is clinically dose-limiting neuropathic effects after the administration of chemotherapeutic agents. Thus, the need to establish novel in vitro tools to evaluate the risk of neurotoxicities, such as neuropathy, remains unmet in drug discovery. Though in vitro studies have been conducted using primary and immortalized cell lines, some limitations include the utility for higher throughput methodologies, method reproducibility, and species extrapolation. As a novel alternative, human induced-pluripotent stem cell (iPSC)-derived neurons appear promising for testing new drug candidates. These iPSC-derived neurons are readily available and can be manipulated as required. Here, we describe a novel approach to assess neurotoxicity caused by different classes of chemotherapeutics using kinetic monitoring of neurite dynamic changes and apoptosis in human iPSC-neurons. These studies show promising changes in neurite dynamics in response to clinical inducers of neuropathy, as well as the ability to rank-order and gather mechanistic insight into class-specific compound induced neurotoxicity. This platform can be utilized in early drug development, as part of a weight of evidence approach, to screen drug candidates, and potentially reduce clinical attrition due to neurotoxicity.