Preclinical evaluation of efficacy and cytokine release of bispecific T cell engagers in humanized NSG mice

Abstract Bispecific T cell engagers (BiTEs) are a growing class of cancer therapy that redirects effector T cells against target-expressing tumors. Mouse models to assess efficacy and cytokine release associated with T cell engagement are needed. JAX humanized NOD scid gamma (Hu-NSG™) mice are engrafted with cord blood-derived CD34+ HSC and have shown robust T cell reconstitution. In this report we evaluated two novel BiTEs, EGFR-CD3 and BCMA-CD3, in Hu-NSG™ mice implanted with MDA-MB-231 human breast cancer cells and NCI-H929 multiple myeloma, respectively. Following the initial dosing, we measured human cytokines and analyzed T cell activation by flow cytometry. Clinical observations and body weight change were also monitored. Treatment with EGFR-CD3 for 2 weeks resulted in complete tumor regression when the dosing was initiated around 100 mm3. 50% of the treated-tumors remained nonpalpable for 10 weeks after dosing ceased. EGFR-CD3 also inhibited tumor growth in mice bearing tumors of ~400 mm3 average in volume. In both cases human IFN-γ, IL-6, and IL-10 levels were elevated from the first dose before returning to the baseline and the frequency of CD69+ cells in T cell subsets increased after the treatment. BCMA-CD3 treatment also induced T cell activation and elevated levels of human IFN-γ, TNF-a, IL-6, and IL-10. NCI-H929 tumor growth inhibition by BCMA-CD3 showed donor to donor variability. We observed that significant growth inhibition in one donor while the other donor did not respond. Together, our Hu-NSG™ platform enables preclinical evaluation of drug efficacy and cytokine release induced by BiTEs and has the potential to be applied to other immunotherapies.