Effect of CD19-CD28 and glofitamab treatments in vivo on the RNA-Seq profile in tumor tissue from humanized mice over time

The study's objective is to investigate the mode of action of a bispecific CD19-targeted CD28 agonist (RG6333, CD19-CD28) in combination with the glofitamab through bulk RNA sequencing of tumor tissue from humanized mice over time. This analysis aims to describe the molecular and immunological changes induced by the combination therapy, which is designed to potentiate T cell-mediated antitumor activity. Glofitamab, a T cell bispecific antibody, targets CD20-expressing malignant B cells and engages CD3e to deliver a robust TCR signal. To enhance this effect, CD19-CD28 was developed to provide a necessary costimulatory signal by binding to CD19 on tumor-infiltrating T cells. This agent is engineered to require concurrent TCR signaling and CD19 target presence, avoiding the issues associated with previous superagonistic antibodies. In this study, we explore the synergistic potential of CD19-CD28 with glofitamab in activating T cell responses and inducing tumor regression in humanized mouse models. The RNA-Seq analysis identified gene expression signatures and immune pathways activated by the treatment. These findings underscore the promise of CD19-CD28 as an effective combination partner to glofitamab. Overall design: In the study, humanized mice were subcutaneously implanted with human tumor cells, OCY-Ly18, to establish a model for aggressive lymphomas. Upon tumor engraftment, the study included three treatment groups: one group received monotherapy with glofitamab, another group was treated with the combination therapy of the bispecific CD19-targeted CD28 agonist (CD19-CD28) and glofitamab, and a control group was administered a vehicle solution. Tumor tissues were harvested from 3 to 5 (up to 11 at termination) mice per treatment condition at day 19, 21 or 29 (termination) time points. This approach was intended to capture the temporal changes in gene expression induced by the therapeutic agents. The harvested tumors were then processed for bulk RNA sequencing to analyze the gene expression profiles and to elucidate the immunological mechanisms activated by the combination therapy.