Low doses of high-potency antithymocyte globulin (ATG) in severe aplastic anemia: experience with the Mexican ATG.

Twenty patients with severe aplastic anemia (SAA) were treated with low doses (1-5 mg/kg/day) of a high-potency antithymocyte globulin (ATG) produced in Mexico, shown to have at least a 10-fold potency as compared with other globulins of commercial sources. Patients received ATG within a 10-day period, every other day (5 doses) at a dose of 1 mg/kg/day (4 courses), 2 mg/kg/day (12 courses) or 5 mg/kg/day (8 courses). Four patients received 2 consecutive courses of different doses of ATG. A response rate of 42% was recorded in the group, assessed by means of increases in reticulocytes, granulocytes or platelets. One patient showed a complete remission. The 570-day survival of the group was 51%. It is concluded that the domestically produced ATG is useful in the treatment of some patients with SAA in Mexico.

A prospective trial of the treatment of acute megakaryoblastic leukaemia.

Acute megakaryoblastic leukaemia, the M-7 variant of acute leukaemia according to the French-American-British (FAB) co-operative group, comprises 8.4% of all cases of acute leukaemia in the city of Puebla, Mexico. The malignancy can be identified by means of monoclonal antibodies or electron microscopy. Using two monoclonal antibodies, Hp1-1d that binds the glycoprotein IIb/IIIa complex (CDw 41) and W1-23 that recognizes the factor VIII:von Willebrand fraction, we have found 19 cases of M-7 leukaemia. Fourteen of these were entered in a prospective therapeutic trial, seven were treated with low-dose (LD) Ara-C (10 mg/m2, delivered subcutaneously every 12 h in 21-day courses). The median age was 14 years, four were female and three male. The remaining seven patients were treated with HOP (adriamycin 25 mg/m2 + vincristine 1.4 mg/m2 orally, daily, for the same period. The median age was 20 years, three were females and four males. Patients were followed for periods of 1-24 months. Six of seven patients in each group achieved remission; however, 18-month disease-free survival was 14% for the LD Ara-C group and 42% for the HOP-treated group. All patients in the LD Ara-C group were dead at 24 months; three patients in the HOP group survived at 12, 14 and 18 months. Differences between these two groups are probably not significant due to the small number of patients involved.