Supplementary Material for: Peeling Back the Layers: Recurrent Talquetamab Skin Toxicity After Supportive Stem Cell Boost in Multiple Myeloma

Bispecific antibodies have meaningfully expanded the therapeutic armentarium in multiple myeloma. Talquetamab is a CD3+ T cell redirecting antibody targeting GPRC5D, which is expressed on multiple myeloma plasma cells as well as in keratinized tissues. Due to the expression pattern, toxicity of talquetamab involves skin toxicity.
Here we report the case of a patient who was treated with talquetamab after relapse after CAR-T therapy. The patient developed a severe recurrence of talquetamab-mediated skin toxicity after the administration of a supportive hematopoietic stem cell boost to treat persistent late cytopenias after CAR-T therapy. This case underscores the complex dynamics between novel immunotherapies like talquetamab and stem cell-based interventions in the context of MM treatment, shedding light on the need for personalized approaches to maximize the benefits of these therapies while minimizing their associated adverse effects.