Randomized phase II trial of the nucleolin targeting aptamer AS1411 combined with high-dose cytarabine in relapsed/refractory acute myeloid leukemia (AML)

Abstract

7019 Background: Aptamers are small synthetic oligonucleotides that form stable nuclease-resistant 3D structures and bind target proteins with specificity and affinity similar to antibodies. These “chemical antibodies” represent a new class of therapeutics. The AS1411 aptamer binds nucleolin on the surface of cancer cells and induces apoptosis. AS1411 has synergistic effects in combination with cytarabine on AML cell lines in vitro and in vivo. A phase I trial of AS1411 monotherapy in 30 patients with advanced cancer showed objective responses without serious toxicities. Methods: This open-label randomized phase II trial compared AS1411 plus high-dose cytarabine (HiDAC) with HiDAC alone in patients with primary refractory or relapsed AML who had received up to 3 previous lines of chemotherapy. Patients in cohort I were randomized 2:1 to receive AS1411 10 mg/kg/day as continuous IVI on days 1–7 + HiDAC 1.5 g/m2/ twice daily on days 4–7 or HiDAC alone for 4 days. Following safety assessment, a second cohort was randomized in a similar manner, with AS1411 escalated to 40 mg/kg/day. Objectives were comparison of response rates (CR+CRp), safety and tolerability between treatment groups. Results: Accrual has been completed, with 71 patients randomized: 22 to AS1411 10 mg/kg/day + HiDAC (AS1411–10), 26 to AS1411 40 mg/kg/day + HiDAC (AS1411–40) and 23 to HiDAC alone (control). Safety findings are currently available for 44 patients (AS1411–10, 21; AS1411–40, 9; control, 14). The main grade 3/4 toxicities were hematologic, notably febrile neutropenia, neutropenia, and thrombocytopenia; and infections. Safety findings were similar across groups, except that grade 3 hypokalemia was more frequent with AS1411–40. Deaths within 28 days of treatment were: AS1411–10, 1/21; AS1411–40, 1/9; and control, 2/14. Response data are currently available for 39 patients; response rates were: AS1411–10, 16% (3/19); AS1411–40, 14% (1/7); and control, 0% (0/13). Conclusions: Data from this first phase II trial of an aptamer in oncology are encouraging. The combination of AS1411 at 10 or 40 mg/kg/day with HiDAC appears well tolerated and shows promising signs of activity in patients with relapsed/refractory AML. [Table: see text]