Induced pluripotent stem cells (iPSCs) can generate any mature (differentiated) cell type. By generating iPSCs from patients, we can generate large numbers of relevant cells by re-differentiation for disease modeling and drug screening. Here, we generate and re-differentiate iPSCs from a patient with chronic myelomonocytic leukemia (CMML), a disease of the blood. Using this novel system, we identify a potential new drug treatment for CMML.