Polycythemia vera responds to imatinib mesylate.

We report 2 patients with polycythemia vera who were demonstrated to be -negative and were unable to tolerate either hydroxyurea or interferon-alpha but who had excellent clinical responses to imatinib mesylate (STI-571). This effect is consistent with the inhibitory effect of imatinib mesylate on c-kit's tyrosine kinase activity as demonstrated by its effectiveness in patients with gastrointestinal stromal tumors.