RecruitingPhase 1Drug trialIvosidenib and Ruxolitinib in Patients With Advanced Myeloproliferative Neoplasms (MPNs) That Have an IDH1 Gene MutationThe purpose of this research is to gather information on the safety and effectiveness determining maximum tolerated dose (MTD) of ruxolitinib in combination with ivosidenib in IDH1-mutated advanced-phase Ph-negative MPNs while evaluate the efficacy of ruxolitinib in combination with ivosidenib in IDH1-mutated advanced-phase Ph-negative MPNs.