Using RNAseq analysis of 61 pre-treatment specimen from newly diagnosed pediatric AML patients, CD33M and CD33m isoforms were found to be co-expressed in AML cells, however the presence of CD33m did not abate the efficacy of GO in these patients (24), indicating a complex relationship between CD33 isoforms expression and response to anti-CD33M therapy. The gene discussed is CD33; the disease is acute myeloid leukemia.