Ikaros degradation by mezigdomide reduces T-cell dysfunction and improves the efficacy of antimyeloma T-cell therapies.

T cell dysfunction is an important contributor to both multiple myeloma (MM) disease progression and failure of anti-myeloma chimeric antigen receptor (CAR) T cell and bispecific T cell engager (TCE) therapies. Overcoming T cell dysfunction is therefore key to improving MM patient outcomes. Immunomodulatory drugs (IMiDs) and cereblon E3 ligase modulatory drugs (CELMoDs) have been observed to activate T cells, and more recently reduce T cell dysfunction, however the underlying mechanisms behind this are incompletely understood. Here, using bone marrow samples from MM patients, we demonstrate a significant reduction in dysfunctional T cell populations expressing exhaustion markers such as TIGIT, upon treatment with Mezigdomide. We further demonstrate the ability of Mezigdomide to improve T cell function and cytotoxicity in primary T cell models of T cell dysfunction and bispecific TCE therapy in vitro. Using concurrent ATAC-seq, ChIP-seq, HiC and RNA-seq in primary T cells treated with Mezigdomide, we demonstrate the novel role of transcription factor Ikaros in regulating an important T cell exhaustion gene TIGIT. Finally, we demonstrate the ability of Mezigdomide to enhance survival outcomes from anti-BCMA CAR-T therapy in vivo. Overall, our data show that Mezigdomide treatment improves anti-myeloma T cell therapy efficacy and reduces T cell dysfunction by abrogating Ikaros-mediated upregulation of exhaustion genes.