Expanding the use of arsenic trioxide: leukemias and beyond

Arsenic has a long history of use in Chinese and Western medicine but fell out of use in the mid-20th century because of the unacceptable side effects that occurred at the doses that were thought to be necessary. The re-emergence of arsenic trioxide (ATO) in clinical use is due largely to purification of this compound from traditional mixtures, and the definition of effective, low-dose regimens for the treatment of acute promyelocytic leukemia (APL). ATO was first purified and used in controlled studies in patients with APL in China in the 1970s. Studies have subsequently also been performed in the United States. Complete response (CR) rates reported in patients with relapsed or refractory APL have varied from 52% to 92%, with similar rates reported in patients with newly diagnosed disease. The mechanism of action of ATO suggests it may be active against other malignancies, and ATO has shown some activity in patients with accelerated phase chronic myelogenous leukemia (CML) and multiple myeloma (MM). Clinical trials are ongoing and planned to define the optimal use of this compound in hematologic malignancies. Preliminary results from studies in patients with primary hepatocellular and gallbladder tumors indicate that ATO may also prove active against some solid tumors.