A trial of recombinant α₂ interferon in the myelodysplastic syndromes: I. Clinical results

Interferon has been reported to have differentiation promoting effects in certain model systems. Because of this and other potentially beneficial effect, a trial of recombinant α₂ interferon was undertaken in myelodysplastic syndromes. The study population consisted of 14 patients, subclassified as two refractory anemia (RA), one RA with ring sideroblasts (RARS), nine RA with excess blasts (RAEB), and two chronic myelomonocytic leukemia (CMMoL). The planned dosage schedule was 2.0 MU/M² t.i.w. sc x 2 weeks q 4 weeks for at least two cycles. No patient achieved the prospective remission criteria, which included sustained blood count improvements. Transient improvements of platelet counts of >50% in baseline were noted in six patients, and a transient antileukemic effect was noted in one patient with CMMoL. Myelodysplastic syndrome patients were found to be sensitive to the count suppressing effects of α₂ interferon with >25% suppression of granulocytes, platelets, or reticulocytes transiently noted in 11 patients and decreasing bone marrow cellularity noted in two while on treatment. Because of these effects, dosage adjustments were frequently instituted in the RA, RARS, and RAEB patients. The average dosages and durations of treatment received were thus 1.48 MU/M² x 19.4 injections for patients with RA, RARS, and RAEB and 2.25 MU/M² x 27 injections for the CMMoL patients. Progression to acute myeloid leukemia or RAEB in transformation was noted in five patients, and increasing leukocytosis was noted in one CMMoL patient while on protocol. It cannot be determined at this time whether these transformations were accelerated by α² interferon or represent selection bias in this study population. Although some evidence of beneficial effects was noted, α² interferon in this dosage and schedule is not a useful treatment for myelodysplastic syndromes.