AstraZeneca and MedImmune, its global biologics research and development arm, announced that the US Food and Drug Administration (FDA) has granted Breakthrough Therapy designation (BTD) for durvalumab (MEDI4736), an investigational human monoclonal antibody directed against programmed death ligand-1 (PD-L1), for the treatment of patients with PD-L1 positive inoperable or metastatic urothelial bladder cancer whose tumour has progressed during or after one standard platinum-based regimen.