Sentence: Tissue from preclinical models and patients ' biopsies were collected pre-treatment and on Cycle ( C ) 1 , Day ( D ) 9 to characterize the effect of gemcitabine and salirasib on activated Ras protein levels .
Drug combination annotation:
[{'class': 'POS', 'spans': ['gemcitabine', 'salirasib'], 'is_context_needed': True}]