A Study of Ruxolitinib in Combination With Nilotinib in Patients With Chronic Phase CML

Inclusion Criteria: * Patients ≥ 18 years of age * ECOG (Eastern Cooperative Oncology Group) Performance Status 0, 1, or 2 * Must have a diagnosis of Philadelphia chromosome positive (Ph+) chronic myeloid leukemia (CML) in chronic phase, with no previous evidence of accelerated or blast-phase disease. * Must be actively receiving treatment for their CML with a tyrosine kinase inhibitor (TKI): imatinib, dasatinib, nilotinib or bosutinib, and must be on stable dose for \> 1 year. * Must have an ongoing complete hematologic response (CHR) on a TKI * Must have an ongoing complete cytogenetic response (CCyR) on a TKI * Must be in a major molecular remission (MMR) on a TKI for a minimum of 1 year leading up to enrollment. * Adequate end organ function * Adequate electrolytes * Adequate platelet count * Adequate neutrophil count * Written informed consent prior to any screening procedures Exclusion Criteria: * Patients in complete molecular remission (CMR) on a TKI. * Patients who have failed nilotinib or not tolerated nilotinib in the past * Certain cardiovascular disorders * Currently receiving treatment with strong CYP3A4 inhibitors which cannot be discontinued prior to starting study drug * Actively receiving herbal medicines that are strong CYP3A4 inhibitors and/or inducers and treatment cannot be discontinued prior to starting study drug * Currently receiving treatment with any medications that have the potential to prolong the QT interval that cannot be discontinued prior to starting study drug * Impaired gastrointestinal (GI) function or GI disease that may significantly alter the absorption of the drug * Acute or chronic pancreatic disease within the last year * Cytopathologically confirmed Central Nervous System (CNS) infiltration * Another primary malignancy that requires systemic chemotherapy or radiation * Acute or chronic liver disease or severe renal disease considered unrelated to the cancer * History of significant congenital or acquired bleeding disorder unrelated to cancer * Major surgery within 4 weeks prior to Day 1 of the study or who have not recovered from prior surgery * Past treatment with ruxolitinib * Treatment with other investigational agent within 30 days of Day 1 * Inability to grant consent or history of non-compliance to medical regimens * Women who are breastfeeding * Women of child-bearing potential, unless they are using highly effective contraception