A Study Evaluating Tolerability and Efficacy of Navitoclax in Combination With Ruxolitinib in Subjects With Myelofibrosis

Inclusion Criteria:

- Participants with documented diagnosis of primary Myelofibrosis, post polycythemia
Vera Myelofibrosis or post-essential thrombocythemia myelofibrosis

- Participant must be ineligible or unwilling to undergo stem cell transplantation at
time of study entry

- Participant must have received ruxolitinib therapy for at least 12 weeks and be
currently on a stable dose of >= 10 mg BID of ruxolitinib for >= 8 weeks prior to the
1st dose of navitoclax, ECOG of 0,1, or 2.

Exclusion Criteria:

- Splenic irradiation within 6 months prior to screening, or prior splenectomy.

- Leukemic transformation (> 10% blasts in peripheral blood or bone marrow biopsy).

- Participant is currently on medications that interfere with coagulation (including
warfarin) or platelet function with the exception of low dose aspirin (up to 100 mg)
and Low-molecular-weight heparin.