A senator who has been a leading critic of Philippine President Rodrigo Duterte’s deadly anti-drug crackdown was arrested Friday on drug charges but professed her innocence and vowed she would not be intimidated by a leader she called a “serial killer.” Sen. Leila de Lima was arrested a day after the Regional Trial Court in Muntinlupa city in the Manila metropolis issued the warrant for her and other officials who have been charged by state prosecutors for allegedly receiving bribes from detained drug lords.