Therapy with Anagrelide in patients affected by essential thrombocythemia: preliminary results

Anagrelide, an imidazo-quinazolin compound first proposed as a potent inhibitor of platelet function, was subsequently recognized as a drug able to lower the platelet number both in normal subjects and in myeloproliferative syndromes with thrombocytosis. We report our experience with Anagrelide therapy in 20 patients affected by essential thrombocythemia (E.T.).

Twenty consecutive patients with E.T. entered the study from June, 89 to July, 91. Therapy schedule was as follows: 0.5 mg every 12 hours for 7 days; subsequently the daily dose was increased by 0.5 mg/day every week until a response was obtained (a decrease of the platelet count to less than 500 x 10(9)/l = complete response; to less than 600 x 10(9)/l = partial response).

Of 19 evaluable patients, complete response (CR) was obtained in 13 (68%) and partial response (PR) in 3 (16%). For all responders, the mean time to response was 5.2 months: mean daily dose of Anagrelide 2 mg. Side effects were recorded in 8/20 patients (40%): tachycardia (n = 4), gastrointestinal distress (n = 3), perimalleolar edema (n = 1). In 6 cases therapy was discontinued definitively.

Response rate to therapy with Anagrelide is similar to that with alkylating agents and alpha 2b-recombinant interferon; furthermore, Anagrelide is a drug without cytotoxic properties. The mean daily dose able to obtain a response is 2 mg, but maintenance therapy at similar doses is always necessary. In conclusion, we can say that Anagrelide is an effective drug in the treatment of patients with E.T., but its side effects must be seriously considered. A larger study may show whether it should be considered as a "first-line" drug for all patients with E.T.