Ivosidenib and Ruxolitinib in Patients With Advanced Myeloproliferative Neoplasms (MPNs) That Have an IDH1 Gene Mutation

Inclusion Criteria: * Advanced-Phase IDH1-mutated Ph-negative MPNs (both untreated and relapsed/refractory) including any of the following: * polycythemia vera with (PV) ≥ 5% peripheral or bone marrow blasts at time of screening * essential thrombocythemia (ET) with ≥ 5% peripheral or bone marrow blasts at time of screening * primary myelofibrosis (PMF) with ≥ 5% peripheral or bone marrow blasts at time of screening * Atypical CML with ≥ 5% peripheral or bone marrow blasts at time of screening * MPN-NOS with ≥ 5% peripheral or bone marrow blasts at time of screening * MDS/MPN Overlap Syndromes including CMML with ≥ 5% peripheral or bone marrow blasts at time of screening * post-PV myelofibrosis with ≥ 5% blasts peripheral or bone marrow blasts at time of screening * post-ET myelofibrosis with ≥ 5% blasts peripheral or bone marrow blasts at time of screening * primary and secondary myelofibrosis with inadequate response to JAK inhibitor regardless of blast percentage. Inadequate response to JAK inhibitor will be defined as lack of achieving any clinical improvement criteria within 12 weeks of of JAK inhibitor initiation. * Patients can be on cytoreduction at time of study enrollment with hydroxyurea or steroids. * Age ≥18 years. * ECOG performance status ≤2 * Patients must have normal organ and marrow function as defined below: * Creatinine clearance ≥60 mL/min, determined by the Cockroft-Gault formula, OR serum creatinine ≤ 1.5 x ULN * AST and ALT ≤3 …