Anagrelide (ANA) is a drug with specific platelet-lowering activity, used primarily in ET, registered as a second-line drug in
essential thrombocythemia (ET) in Europe and in some countries as first-line
therapy, in USA licensed by FDA for
thrombocythemia in myeloproliferative
neoplasms (MPN). The platelet-lowering efficacy is similar to that of hydroxycarbamide (HC), around 70 % complete response and 90 % partial response. Side effects are common, especially
headache and
tachycardia, but usually subside or disappear within a few weeks. Around 20 % of patients stop ANA
therapy due to side effects or insufficient response. Studies of treatment patterns in Europe show that ANA is preferentially given to younger patients, probably because of the concern for a possible leukemogenic effect of the common first-line drug, HC. Only two randomized studies have compared the efficacy of ANA and HC in preventing
thrombosis and haemorrhage, the larger of them showing a slightly better efficacy of HC, the other showing non-inferiority of ANA to HC. A recent observational 5-year study of 3600 patients shows a low and basically similar efficacy of ANA and other cytoreductive
therapies in ET. ANA does not appear to inhibit
fibrosis development, and probably due to its anticoagulation properties, the combination of ASA and ANA produces an increased rate of haemorrhage. Combination of ANA with HC or
interferon (IFN) is feasible and effective in patients with insufficient platelet response to mono-
therapy.