Inclusion Criteria:  Primary MF, post-PVMF or post-ETMF according to the DIPSS risk categories of intermediate-2 or high-risk MF Average platelet count of <50,000/µL at Screening based on 2 measurements taken on different days; both measurements must be <50,000/µL. ECOG performance status ≤2. Life expectancy >6 months. Spleen volume of at least 450 cm3 measured by MRI (or by CT for applicable subjects). Total Symptom Score (TSS) ≥10 on the Myelofibrosis Symptom Assessment Form (MFSAF) version 4.0. Peripheral blast count <10%. No MF-directed treatment for at least 2 weeks prior to initiation of NS-018, including JAK inhibitor, erythropoietic, thrombopoietic agent, or any use of corticosteroids for MF symptom or blood count management. Low dose corticosteroids <10 mg/day prednisone or equivalent is allowed for non-MF purposes.  Exclusion Criteria:  Active, uncontrolled systemic infection. Any prior treatment with more than one JAK inhibitor.  Subject has received prior JAK inhibitor treatment and meets one of the following criteria:  A duration of the treatment is 180 days or more. Loss of spleen response (response defined as at least 50% decrease in spleen length by palpation; loss of response defined as >50% increase in spleen length from the best response). Previous treatment with NS-018. Subjects actively receiving a concurrent investigational agent. Subjects with any unresolved AE greater than Grade 1 other than hematological AEs from previous anticancer therapy. Currently taking medication that is substantially metabolized by cytochrome P450 (CYP) 1A2 or CYP3A4 (see Appendix 5) or taking medication known to be strong inhibitors or inducers of CYP3A4 (see Appendix 5). Radiation therapy for splenomegaly within 6 months prior to study entry (screening). History of splenectomy or planning to undergo splenectomy. Subjects with a serious cardiac condition within the past 6 months such as uncontrolled arrhythmias, myocardial infarction, angina or heart disease Subjects diagnosed with another malignancy within 2 years prior to an enrollment. Subjects who have had surgery (other than placement of vascular access and bone marrow biopsy) within 4 weeks of study entry (screening), or subjects with incomplete recovery from any prior surgical procedures.