4-OXO RETINOIC ACID FOR REFRACTORY ACUTE PROMYELOCYTIC LEUKEMIA IN CHILDREN WITH ALL-TRANS-RETINOIC ACID THERAPY

Therapy with all-trans retinoic acid (ATRA) achieves complete remissio n in a high proportion of patients with acute promyelocytic leukemia ( APL), but the efficacy is reported to relate to plasma ATRA level afte r oral administration. The pharmacokinetics of ATRA and 4-oxo all-tran s retinoic acid (4-oxo ATRA), a metabolite of ATRA, were studied in fo ur children with APL at the time of initial oral administration. After administration of ATRA at a dose of 30 mg/m(2), the peak plasma ATRA level was 20-741 ng/ml and was reached at 60-120 min. The patient with the lowest peak plasma level did not achieve complete remission and h ad a very high 4-oxo ATRA level compared to the patients with complete remission. These findings suggest that accelerated metabolism of ATRA plays a role in the failure of this agent in the patients without rem ission.