- Steroids, hydroxyurea, vincristine, 6-mercaptopurine, methotrexate, thioguanine and intrathecal chemotherapy are permitted within any timeframe prior to registration; Food and Drug Administration (FDA)-approved TKIs may also be administered until 1 day prior to start of study therapy (C1, D1); IV cyclophosphamide may be administered at doses of 1 g/m^2 or less until up to 7 days prior to registration