MedImmune Inc., part of AstraZeneca plc, started the first patient in its Phase III hairy-cell leukemia (HCL) trial with its first-in-class antibody-drug conjugate moxetumomab pasudotox (MP), a CD22 immunotoxin made up of an anti-CD22 antibody fused to a toxin. The molecule binds to CD22, gets internalized and processed, and then releases the toxin payload to blast the tumor.