Abstract: Objective To explore the efficacy and safety of ruxolitinib in the treatment of myelofibrosis （MF）. Methods This study enrolled 60 cases with MF，aged over 18 years and diagnosed with PMF，PPV，or PET in Nanfang Hospital from June 2017 and May 2019.All patients received ruxolitinib over 12 months. The symp⁃ toms were evaluated by MPN Symptom Assessment Form⁃Total symptom score（MPN⁃SAF⁃TSS）and B⁃ultrasound was used to assess the size of spleen. The improvement of bone marrow fibrosis，JAK2V617 gene mutation burden and adverse events were observed and the effect of ruxolitinib on lymphocytes was analyzed. Results The total symptom score reduced at least 50% in 51.67% of the patients. The median length and thickness of the spleen were shortened and reduced from（16.65 ± 3.42）cm and（5.86 ± 1.54）cm at baseline to（14.93 ± 3.02）cm and（5.32 ± 1.29）cm respectively（P < 0.001）. A total of 92.86% of the patients were with stable or improved bone marrow fibrosis；45 patients with JAK2V617F gene mutation and the median mutation burden decreased by 0.90%（P = 0.600）. The most common hematologic adverse events were anemia（68.09%）and thrombocytopenia（40.43%）and infection（23.33%）was the frequently⁃seen non⁃hematologic adverse event. CD3+，CD4+，CD8+，and NK cells were reduced after the treatment，and the difference in terms of NK cells before and after the treatment was statistically significant（P = 0.020）. Conclusion Ruxolitinib is safe and effective for the treatment of patients with myelofibrosis.

Key words:

ruxolitinib, myelofibrosis, efficacy, safety, immune