Conclusions: This phase II trial suggested that addition of AS1411 to cytarabine may enhance anti-leukemic activity and that the combination has an acceptable safety profile in patients with relapsed and refractory AML. Follow-up suggests substantial survival durations in some patients responding to AS1411 + cytarabine. A phase IIb study is now evaluating responses, duration of responses and survival in AML patients randomized to AS1411 + cytarabine or cytarabine alone.