In a groundbreaking study that offers new hope for women with advanced breast cancer, researchers from UCLA's Jonsson Comprehensive Cancer Center have published final clinical trial results that showed the amount of time patients were on treatment without their cancer worsening was effectively doubled in women with advanced breast cancer who took the experimental drug palbociclib. An investigational drug discovered and being developed by Pfizer Inc., palbociclib targets a key family of proteins responsible for cell growth by preventing them from dividing.