Introduction Cancer Immune Therapies have shown unprecedented results in improving tumor control.^1–3 However, many patients are still refractory to treatment. A deeper understanding of the mode of action of the different CITs sub-classes may help improving therapeutic approaches to reach better anti-tumor response. For this reason, we developed a multi-photon intra-vital microscopy (MP-IVM) approach to study in vivo, at single cell level, the tumor microenvironment upon treatment with CD20-targeting T-cell bispecific antibodies (TCB) [4] in a preclinical model of diffuse large B cell lymphomas (DLBCL).

Methods To selectively monitor clinical lead molecules in the context of human T cell responses, we developed a skinfold chamber model [5] in last generation humanized mice [6] that allows visualization, by MP-IVM, of labelled human T cells co-injected intra-dermally with WSU-DLCL2, a human DLBCL. We have used this model to investigate T cells recruitment to tumors upon CD20-TCB therapy: by intra-venously injecting labeled T cells in mice treated with selected blocking antibodies, we were able to identify dedicated pathways induced by CD20-TCB and regulating T cell influx into the tumor bed. Furthermore, we developed a user-independent quantification platform to assess changes in the dynamics of T cell motility and time of interaction with tumor cells.

Results/Discussion We have developed an experimental preclinical model that aims to reduce xenoreaction (human T cell reaction against mouse tissue) by utilizing T cells derived from humanized mice, educated within murine thymus. We demonstrate that such model is optimal to quantify human T cell dynamics in vivo. We show that CD20-TCB localizes in the tumor and acts on tumor-resident T cell motility within 1 hour post i.v. injection (defined as functional PK), causing a sharp reduction in their speed (from 4 to 2 µm/min) and an increase in tumor/T cell interaction time; those changes last up to 72h post-treatment. In addition, we prove how the initial tumor/T cell interaction mediated by CD20-TCB lead to peripheral T cells recruitment into the tumor. This mechanism is dependent on the presence of tumor-resident T cells and on IFNg-CXCL10 pathway. Inhibiting any of these two parameters resulted in reduced T cells infiltration from the periphery and reduced anti-tumor efficacy.

Conclusion We developed a reliable imaging and analysis pipeline to investigate in vivo T cell dynamics and recruitment and applied it to the study of CD20-TCB treatment of DLBCL model. Our approach has shed new lights into the MoA of this new class of immune-therapeutics, demonstrating that the IFNγ-CXCL10 pathway is involved in T cell recruitment upon CD20-TCB treatment.

Disclosure Information F. Cremasco: A. Employment (full or part-time); Significant; Roche Glycart AG. E. Menietti: A. Employment (full or part-time); Significant; Roche Glycart AG. D. Speziale: A. Employment (full or part-time); Significant; Roche Glycart AG. J. Sam: A. Employment (full or part-time); Significant; Roche Glycart AG. S. Sammicheli: A. Employment (full or part-time); Significant; Roche Glycart AG. S. Chen: A. Employment (full or part-time); Significant; Roche Glycart AG. M. Richard: A. Employment (full or part-time); Significant; Roche Glycart AG. C. Klein: A. Employment (full or part-time); Significant; Roche Glycart AG. P. Umana: A. Employment (full or part-time); Significant; Roche Glycart AG. M. Bacac: A. Employment (full or part-time); Significant; Roche Glycart AG. S. Colombetti: A. Employment (full or part-time); Significant; Roche Glycart AG. M. Perro: A. Employment (full or part-time); Significant; Roche Glycart AG.