A Phase II Study of Interleukin-2 in 49 Patients with Relapsed or Refractory Acute Leukemia

In this report we present the results of a multicenter phase II study of high-dose recombinant Interleukin-2 (rIL-2) in patients with refractory or relapsed acute leukemia. Forty-nine patients with acute myeloid leukemia (AML: 30 patients) or acute lymphoblastic leukemia (ALL: 19 patients) were included. Median age was 30 years (range: 4-71). Four patients were treated for primary refractory disease and 45 for relapsed disease (16 patients > 2nd relapse). Twenty-four patients (49%) had previously received bone marrow transplantation (allogeneic: 5, autologous: 19). Patients were scheduled to receive three 5-day cycles of rIL-2 given every other week. rIL-2 was administered as bolus I.V. infusion of 8 x 10(6) UI/m2 every 8 hours during cycle I and every 12 hours during cycles 2 and 3. Patients received a mean of 76% of rIL-2 planned dose. Main toxicity was hematologic (grade IV thrombopenia: 84%). Hemodynamic and metabolic toxicities lead to treatment discontinuation in 10 patients (20%). Strong immune activation was achieved including a significant increase in activated T-cells and Lymphokine-Activating-Killer cell (LAK) activity. Twenty-seven out of 30 AML patients could be evaluated for response: 2(7%) achieved complete remission (CR) which lasted 3 and 4 months. No response was observed in the 18 assessable ALL patients, most of whom (77 %) presented absolute drug resistance. These results show that this high dose rIL-2 regimen induces significant biological effects and provides some anti-leukemic activity in patients with advanced leukemia. Considering the severe toxicity observed and the limited remission rate achieved here, rIL-2 does not appear to be a valuable therapeutic option for such patients. However, the undoubted anti-leukemic activity of this cytokine invites further investigation especially in the minimal residual disease situation.