DRUG DESIGNATION: Pfizer says U.S. regulators have classified its experimental pill for advanced, often-deadly breast cancer as a breakthrough therapy. That's done to speed up development and review of treatments seen as big advances.

THE RESEARCH: Palbociclib is in late-stage testing as an initial treatment for the biggest subgroup of postmenopausal women with advanced breast cancer — those in whom tumor growth is fueled by the hormone estrogen but not by a growth-promoting protein called HER2.

MORE TESTING: Pfizer, which has made research on cancer medicines a priority, also is testing palbociclib as a treatment for other cancers.