Abstract LB349: The use of PBMC humanized mice to test the efficacy and safety of antibody and cell-based cancer immunotherapeutics
Authors: Rose Destanie , Lee Won , Yang Guoxiang , Yang Jiwon , Cheng Mingshan , He Wenqian , Buetow Bernard , Vitsky Allison , Liu Maggie , Jessen Bart , Keck James 
Published: April 2023

Abstract
In the fight against cancer, immunotherapies are one of the largest growing therapeutics in development. Immunotherapeutics are designed to boost or harness the power of the immune system to prevent, control, or eliminate cancer; while many immune therapies have been found to be safe others have induced severe toxicities. For instance, even compounds that target the same molecule/antigen can have dramatically differing safety profiles. Current preclinical models evaluating these therapies are underequipped to assess the safety of these compounds: in vitro assays fail to predict systemic responses and traditional animal models often fail to correlate with human responses. To better meet the needs of assessing preclinical toxicity we developed a PBMC-humanized mouse model to test a variety of therapeutics, including both monoclonal and bispecific antibodies and induce human cytokine release responses which can manifest within hours or days later resulting in tissue damage and lethality of the mice. To date we have tested a variety of therapeutics, including Blinatumomab, Rituximab, EGFRxCD3 BiTE, CAR-T, and others in our platform while evaluating the ability of the therapeutic to induce human cytokines, bodyweight loss, clinical symptom assessment, and survival in the context of toxicity alone or along with the evaluation with efficacy. We found that many of the therapeutics tested in our platform showed similarities to clinical data in humans. For example, urelumab and utomilumab are both fully humanized monoclonal antibodies against 4-1BB (CD137). However, during clinical trials, urelumab was shown to induce severe liver toxicities while utomilumab was well tolerated. In our huPBMC mouse model, we likewise showed that huPBMC mice dosed with 10 mpk of urelumab experienced body weight loss, showed liver necrosis, and met the clinical criteria for early euthanasia compared to mice treated with 10 mpk utomilumab and PBS treated controls. Serum levels of enzymes associated with liver damage: AST, ALT and GLDH were significantly higher in urelumab treated mice and terminal serum cytokine analysis revealed similarities with those found to be increased in urelumab clinical trials, including elevated IFNγ, IP-10, MIG, and MIP-1α and MIP-1β. Further, HuPBMC mice are also capable of detecting variability among donors. We have screened well over 60 human PBMC donors in huPBMC mice treated with OKT3 and αCD28 and while we always see an increase in cytokines such as IFNγ - the range of induction varies greatly among donors. Further, we see PBMC-donor variability in body weight loss and survival rate after OKT3 and αCD28 treatments. We demonstrate that the PBMC humanized mouse model shows clinical relevance. The use of these models for preclinical safety assessments has the potential to become an important part of novel immunotherapeutic development for patient safety and reducing drug development costs.
Citation Format: Destanie Rose, Won Lee, Guoxiang Yang, Jiwon Yang, Mingshan Cheng, Wenqian He, Bernard Buetow, Allison Vitsky, Maggie Liu, Bart Jessen, James Keck. The use of PBMC humanized mice to test the efficacy and safety of antibody and cell-based cancer immunotherapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB349.