Single-cell profiling reveals teclistamab-induced reshaping of nasopharyngeal immunity in multiple myeloma

Abstract Introduction: BCMA × CD3 bispecific antibodies such as teclistamab induce high response rates and durable remissions in relapsed/refractory multiple myeloma (RRMM). However, due to BCMA expression on normal plasma cells, circulating B cells, and subsets of dendritic cells, these therapies cause profound immunosuppression and hypogammaglobulinemia. While intravenous immunoglobulin replacement can mitigate severe infections to some extent, upper respiratory tract infections remain common. These infections often persist, are prolonged, and significantly impair patients' quality of life. Recent studies in healthy individuals have underscored the importance of nasopharyngeal immunity in protecting against respiratory pathogens such as SARS-CoV-2 (Lindeboom R.G.H. et al. Nature, 2024). Yet, the effect of teclistamab on local mucosal immunity, particularly in the nasopharynx, remains entirely unexplored. Methods: To investigate the impact of teclistamab on nasopharyngeal immunity, we performed deep nasal swabs in 36 RRMM patients treated with teclistamab and 13 RRMM patients receiving daratumumab plus pomalidomide, bortezomib and dexamethasone (control group). In addition, we integrated publicly available single-cell data from healthy individuals from the study of Lindeboom et al. (n = 16). In teclistamab-treated patients, longitudinal sampling was performed at baseline, 1 week, 3 weeks, and 6 months of treatment. Nasopharyngeal cells were dissociated by enzymatic digestion (accutase) and multiple washing steps to generate single-cell suspensions. Cells were subsequently processed for single-cell RNA sequencing using 10x Genomics 5′ chemistry. Results: Single-cell RNA sequencing from nasal swabs was feasible, yielding on average 500 high-quality single cells per sample and the technical success rate of our approach was 90%. Based on canonical marker expression, we identified 17 distinct cell populations, including immune cells (monocytes, CD4⁺ and CD8⁺ T cells, Tregs, NK cells) and epithelial subtypes (ciliated, squamous, ionocytes, basal cells). The cellular composition provided a representative snapshot of the nasopharyngeal microenvironment. Next, we compared the cellular composition of teclistamab- and daratumumab-treated patients to that of healthy individuals. Strikingly, both patient groups completely lacked B cells, and dendritic cells in the nasopharynx, whereas these populations were readily detectable in healthy controls. This suggests a profound disruption of the nasopharyngeal immune barrier in treated myeloma patients, not limited to BCMA-directed therapy. Interestingly, longitudinal sampling in teclistamab-treated patients revealed the emergence of CD4⁺ T cells at later time points expressing TOX2, ENTPD1, BTLA, PDCD1, and CTLA4, a transcriptional signature characteristic of exhausted T cells previously described in autoimmune settings (Saggau C. et al. 2024, Immunity). These cells were barely found in daratumumab-treated patients, suggesting a link between T-cell engaging therapies and the emergence of exhausted T cells in the nasopharyngeal mucosa. We also detected CD8⁺ T cells expressing tissue-residency markers (ZNF683, ITGA1, ITGAE, CD69) that exhibited dynamic transcriptional changes over time and differed from those in daratumumab-treated controls. Additionally, differential gene expression in e.g. WFDC2, SLIT2, SOCS3, RARRES2, was observed in ciliated epithelial cells, supporting the notion that bispecific antibody therapy profoundly impacts on the local mucosa and immune compartment in the nasopharynx. Conclusion: We established a feasible approach to assess local nasopharyngeal immunity in real-world clinical cohorts, revealing teclistamab-associated alterations that may contribute to persistent infections. Ongoing analyses, including an increased sample size as well as samples from patients with viral infections and matched peripheral blood mononuclear cells, will be presented at the meeting.