Small-dose Harringtonine induces complete remission in patients with acute promyelocytic leukemia.

Small-dose Harringtonine (1-3 mg infused during 4-5 hr) was used as a single agent to treat 10 patients with acute promyelocytic leukemia. Every patient received one to three courses, each lasting 13-81 days (mean 33 days). The interval between courses (i.e., interruptions) was 5-11 days. During treatment, marrow aplasia occurred in one patient and hypoplasia in three. Pancytopenia occurred in all 10 patients. Complete remission was achieved in seven patients (70%) and cytoreduction in two. In vitro studies showed that, although Harringtonine produced a decrease in leukemic cells in all five series of marrow cultures from five patients, there was only one wherein the decrease was accompanied by a simultaneous absolute increase in differentiated myeloid cells. Considerable discrepancy existed between the culture results and clinical responses. These results seem to suggest that the therapeutic effect of Harringtonine on acute promyelocytic leukemia originates chiefly from cytotoxicity.