Ruxolitinib Phosphate in Treating Patients With Chronic Neutrophilic Leukemia or Atypical Chronic Myeloid Leukemia

Inclusion Criteria: * Subjects must be newly diagnosed or previously diagnosed with CNL or aCML; all patients must have a bone marrow biopsy completed during the screening or baseline period if one has not been done within 90 days of day 1, cycle one * Subjects must have platelet count greater than 25,000 per microliter at baseline and at the start of study (day 1, cycle 1) visit * Subjects must be able to discontinue any drug treatment aimed at lowering disease burden in CNL or aCML; subjects should discontinue hydroxyurea to treat underlying CNL or aCML disease no later than day -7 (one week before starting ruxolitinib); for drugs that have more long-lasting effects on the marrow, such as thalidomide and its analogs, and interferon, subjects should discontinue these no later than day -28 * Subjects must be willing to accept/continue transfusions to treat low hemoglobin levels * Subjects must have a life expectancy of \> 6 months Exclusion Criteria: * Subjects unable to review and sign informed consent form * Females who are pregnant or breastfeeding, and males and females who cannot comply with requirements to avoid fathering a child or becoming pregnant * Subjects with known diagnosis of human immunodeficiency virus (HIV) or chronic active Hepatitis B or C; viral testing is not required; subjects with a history of Hepatitis B and/or C are allowed on trial if the virus is undetected at the time of enrollment * Subjects with inadequate liver (alanine aminotransferase \[AL…