Cell Therapeutics announces positive results from OPAL study of tosedostat Cell Therapeutics and Chroma Therapeutics announced that Lancet Oncology has published results from the OPAL Phase 2 study of tosedostat in elderly patients with relapsed or refractory acute myeloid leukemia. Tosedostat is an oral aminopeptidase inhibitor which has been shown to deprive tumor cells of the amino acid building blocks they need to make proteins necessary for tumor cell survival. The trial showed that once-daily oral tosedostat resulted in a disease control rate of 51%. Subset analyses suggested the greatest benefit occurred in the difficult-to-treat patients with prior myelodysplastic syndrome or those that had received prior hypomethylating therapy. Adverse events were mild, predictable and manageable.