T cell bispecific antibodies (TCBs) are an emerging class of immunotherapeutics with several TCBs approved by the FDA for the treatment of leukemias, lymphomas, and myelomas. TCBs label tumor cells with one of their ends, and attract immune cells with another end to coerce them into tumor cell killing. However, one major challenge in the development of TCBs are “on-target, off-tumor” toxicities at sites in the body that also express TCB-targeted antigens. A new collaboration of Jennifer Lewis’ group and researchers from the Roche Innovation Centers in Switzerland and Germany now created an immune-infiltrated human kidney organoid-on-chip model that allows kidney toxicity of TCBs.