Seattle Genetics stops all trials of ’33A blood cancer drug after patient deaths

Several earlier-stage trials of the CD33-targeting antibody-drug conjugate were halted by the FDA last December on safety concerns, mainly relating to possible liver toxicity. Now, the CASCADE registration study in acute myeloid leukemia (AML) and another phase 1/2 study in myelodysplastic syndrome have also been stopped, leaving the program looking decidedly shaky and driving the company’s shares down more than 11% premarket.