Sentence: On February 3 , 2015 , the FDA granted accelerated approval to palbociclib ( IBRANCE , Pfizer Inc. ) , an inhibitor of cyclin-dependent kinases 4 and 6 ( CDK4 and CDK6 ) , for use in combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive , HER2-negative advanced breast cancer as initial endocrine-based therapy for their metastatic disease .
Drug combination annotation:
[{'class': 'POS', 'spans': ['palbociclib', 'letrozole'], 'is_context_needed': False}]