The U.S. Food and Drug Administration has granted breakthrough therapy designation to AstraZeneca's biggest new drug hope ‍durvalumab as a treatment in bladder cancer, the drugmaker said on Wednesday.

The experimental medicine is a so-called PD-L1 therapy that fights cancer by boosting the immune system.

Breakthrough therapy designation expedites the development and review of medicines intended to treat serious or life-threatening diseases.

Durvalumab is also being developed as a treatment for lung, head and neck, gastric, pancreatic, liver and blood cancers. It faces competition from rival products made by Bristol-Myers Squibb, Merck and Roche.