In a similar manner, the activity of the ATR inhibitor VE-821 was potentiated by other replication stress inducers, hydroxyurea and gemcitabine, in AML cell lines and primary samples coinciding with abrogation of ribonucleotide reductase (RNR) expression and inhibition of replication fork progression (41). The gene discussed is ATR; the disease is acute myeloid leukemia.