Efficacy of Ruxolitinib in Patients With Chronic Neutrophilic Leukemia and Atypical Chronic Myeloid Leukemia

J Clin Oncol. 2020 Apr 1;38(10):1006-1018. doi: 10.1200/JCO.19.00895. Epub 2019 Dec 27.


Purpose: Colony-stimulating factor-3 receptor (CSF3R)-T618I is a recurrent activating mutation in chronic neutrophilic leukemia (CNL) and to a lesser extent in atypical chronic myeloid leukemia (aCML) resulting in constitutive JAK-STAT signaling. We sought to evaluate safety and efficacy of the JAK1/2 inhibitor ruxolitinib in patients with CNL and aCML, irrespective of CSF3R mutation status.

Methods: We conducted a phase II study of ruxolitinib in 44 patients (21 CNL and 23 aCML). The primary end point was overall hematologic response rate (ORR) by the end of 6 continuous 28-day cycles for the first 25 patients enrolled. We considered a response as either partial (PR) or complete response (CR). We expanded accrual to 44 patients to increase our ability to evaluate secondary end points, including grade ≥ 3 adverse events, spleen volume, symptom assessment, genetic correlates of response, and 2-year survival.

Results: ORR was 32% for the first 25 enrolled patients (8 PR [7 CNL and 1 aCML]). In the larger cohort of 44 patients, 35% had a response (11 PR [9 CNL and 2 aCML] and 4 CR [CNL]), and 50% had oncogenic CSF3R mutations. The mean absolute allele burden reduction of CSF3R-T618I after 6 cycles was greatest in the CR group, compared with the PR and no response groups. The most common cause of death is due to disease progression. Grade ≥ 3 anemia and thrombocytopenia were observed in 34% and 14% of patients, respectively. No serious adverse events attributed to ruxolitinib were observed.

Conclusion: Ruxolitinib was well tolerated and demonstrated an estimated response rate of 32%. Patients with a diagnosis of CNL and/or harboring CSF3R-T618I were most likely to respond.

Trial registration: ClinicalTrials.gov NCT02092324.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Alleles
  • Antineoplastic Agents / therapeutic use
  • Female
  • Gene Frequency
  • Humans
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / genetics
  • Leukemia, Neutrophilic, Chronic / drug therapy*
  • Leukemia, Neutrophilic, Chronic / genetics
  • Male
  • Middle Aged
  • Nitriles
  • Protein Kinase Inhibitors / adverse effects
  • Protein Kinase Inhibitors / therapeutic use
  • Pyrazoles / adverse effects
  • Pyrazoles / therapeutic use*
  • Pyrimidines
  • Receptors, Colony-Stimulating Factor / genetics
  • Survival Rate


  • Antineoplastic Agents
  • CSF3R protein, human
  • Nitriles
  • Protein Kinase Inhibitors
  • Pyrazoles
  • Pyrimidines
  • Receptors, Colony-Stimulating Factor
  • ruxolitinib

Associated data

  • ClinicalTrials.gov/NCT02092324