Adverse events occurred in 25 ( 61 % ) of 41 patients in the etrolizumab 100 mg group ( five [ 12 % ] of which were regarded as serious ) , 19 ( 48 % ) of 40 patients in the etrolizumab 300 mg plus LD group ( two [ 5 % ] serious ) , and 31 ( 72 % ) of 43 patients in the placebo group ( five [ 12 % ] serious ) .