To Evaluate the Efficacy and Safety of Parsaclisib and Ruxolitinib in Participants With Myelofibrosis (LIMBER-313)

Inclusion Criteria: * Diagnosis of PMF, PPV-MF, or PET-MF. * DIPSS risk category of intermediate-1, intermediate-2, or high. * Palpable spleen of ≥ 5 cm below the left costal margin on physical examination at the screening visit. * Active symptoms of MF at the screening visit, as demonstrated by the presence of a TSS of ≥ 10 using the Screening Symptom Form. * Participants with an ECOG performance status score of 0, 1, or 2. * Screening bone marrow biopsy specimen and pathology report(s) available that was obtained within the prior 2 months or willingness to undergo a bone marrow biopsy at screening/baseline; willingness to undergo bone marrow biopsy at Week 24 and every 24 weeks there after. Screening/baseline biopsy specimen must show diagnosis of MF. * Life expectancy of at least 24 weeks. * Willingness to avoid pregnancy or fathering children. Exclusion Criteria: * Prior use of any JAK inhibitor. * Prior therapy with any drug that inhibits PI3K (examples of drugs targeting this pathway include but are not limited to INCB040093, idelalisib, duvelisib, buparlisib, copanlisib, and umbralisib). * Use of experimental drug therapy for MF or any other standard drug (eg, danazol, hydroxyurea) used for MF within 3 months of starting study drug and/or lack of recovery from all toxicities from previous therapy to ≤ Grade 1. * Inability to swallow food or any condition of the upper gastrointestinal tract that precludes administration of oral medications. * Recent history of inadeq…