The incidence of grade 3 or more adverse events ( 25 [ 47 % ] vs 14 [ 54 % ] ) and serious adverse events ( 12 [ 23 % ] vs five [ 19 % ] ) was similar in each group despite longer median treatment duration with siltuximab than with placebo ( 375 days [ range 1-1031 ] vs 152 days [ 23-666 ] ) .