Myelodysplastic syndrome occurring after enfortumab vedotin treatment for metastatic urothelial carcinoma

Introduction Enfortumab vedotin is an antibody‐drug conjugate targeting Nectin‐4 for the treatment of advanced urothelial carcinoma in patients previously treated with platinum‐containing chemotherapy and immune checkpoint inhibitors. Common adverse events include rashes, peripheral neuropathy, and hyperglycemia. However, there are no reports on the development of myelodysplastic syndrome during enfortumab vedotin therapy in clinical settings. Case presentation A 72‐year‐old male patient experienced prolonged and severe thrombocytopenia 18 weeks after the start of enfortumab vedotin therapy for metastatic urothelial carcinoma, requiring daily platelet transfusions. Bone marrow examination and chromosomal analysis confirmed the diagnosis of myelodysplastic syndrome. Treatment with eltrombopag proved to be effective. Conclusion This is the first report of the development of myelodysplastic syndrome during enfortumab vedotin therapy in a clinical setting. Although rare, myelodysplastic syndrome can occur during enfortumab vedotin therapy.