Effects of imatinib mesylate in patients with polycythemia vera: results of a phase II study.

The antiproliferative effects of the tyrosine kinase inhibitor imatinib mesylate were reported in single cases with polycythemia vera (PV). We, therefore, conducted a clinical phase II study to assess the rate and quality of response in patients with PV. Thirty-one patients, with a median age of 64 years (range, 45-84 years), were included. All but one patient were on phlebotomy; 14 (45%) had previously received cytoreductive therapy. Imatinib was started with 400 mg/day. In 26% of patients, dose escalation up to 800 mg was performed. After a median treatment duration of 8.3 months (range, 0.1-62.1 months), the overall response rate was 55%. No complete remission (normalization of all parameters: hematocrit, white blood cell (WBC) count, platelet count, and spleen size determined by ultrasound examination) was reached because the spleen remained enlarged in all patients. Thirteen patients (42%) achieved partial remission (≥25% reduction of at least one of the previously mentioned parameters); in 10 of these, the respective reduction was ≥50%. In four patients (13%) with minor response, the reduction was <25%. No change or progressive disease was seen in 14 patients (45%). The nonresponders had a longer previous disease duration and had received more antecedent cytoreductive therapy (p = 0.009). Compared to baseline characteristics, imatinib induced the reduction of phlebotomies (p = 0.003), of WBC count (p = 0.002), and of platelet count (p = 0.04). Three patients became free from phlebotomies. In six investigated patients, no significant reduction of the JAK2V617F burden was observed despite clinical improvement. The results show that imatinib has moderate cytoreductive effects in PV.
AuthorsKirsten Merx, Alice Fabarius, Philipp Erben, Martin Griesshammer, Andreas Reiter, Wolf-Karsten Hofmann, Rüdiger Hehlmann, Andreas Hochhaus, Eva Lengfelder
JournalAnnals of hematology (Ann Hematol) Vol. 92 Issue 7 Pg. 907-15 (Jul 2013) ISSN: 1432-0584 [Electronic] Germany
PMID23525684 (Publication Type: Clinical Trial, Phase II, Journal Article)
Chemical References
  • Benzamides
  • Piperazines
  • Protein Kinase Inhibitors
  • Pyrimidines
  • Imatinib Mesylate
  • JAK2 protein, human
  • Janus Kinase 2
  • Aged
  • Aged, 80 and over
  • Benzamides (adverse effects, therapeutic use)
  • Bone Marrow (enzymology, pathology)
  • Combined Modality Therapy
  • Female
  • Gastrointestinal Diseases (chemically induced)
  • Humans
  • Imatinib Mesylate
  • Janus Kinase 2 (antagonists & inhibitors, genetics)
  • Leukocyte Count
  • Male
  • Middle Aged
  • Mutation, Missense
  • Organ Size (drug effects)
  • Pain (chemically induced)
  • Phlebotomy
  • Piperazines (adverse effects, therapeutic use)
  • Point Mutation
  • Polycythemia Vera (blood, drug therapy, enzymology, pathology, therapy)
  • Prospective Studies
  • Protein Kinase Inhibitors (adverse effects, therapeutic use)
  • Pyrimidines (adverse effects, therapeutic use)
  • Spleen (pathology)
  • Treatment Outcome

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