Multi-Omic Single-Cell Dissection of Leukemic T-Cell Lymphoma Following CAR T-Cell Therapy

A 63-year-old male who received ciltacabtagene autoleucel (cilta-cel) CAR-T cells and the GPRC5DxCD3 bispecific talquetamab for early relapse of his multiple myeloma (MM) developed a leukemic peripheral T-cell lymphoma (PTCL) with cutaneous and intestinal involvement. Longitudinal single-cell RNA and T-cell receptor sequencing of peripheral blood and bone marrow revealed two hyperexpanded CAR-carrying, exhausted effector-memory T-cell clones with marked immunophenotypic as well as transcriptional alterations and different susceptibilities towards treatment with dexamethasone. Spatial transcriptomes of skin lesions confirmed the aberrant CAR-expressing T cells. Whole genome sequencing revealed three distinct integration sites, within the introns of ZGPAT, KPNA4, and polycomb-associated non-coding RNAs. Pre/post-CAR-T whole-genome analyses implicated clonal outgrowth of a TET2-mutated precursor propelled by additional sub-clone specific LOH and other secondary mechanisms