There was no difference between pirfenidone and placebo in the percentage of patients who experienced a serious adverse event ( SAE ) . An SAE was reported by 35 % and 33 % of pirfenidone and placebo groups , respectively , in CAPACITY 2 and by 31 % and 30 % , respectively , in CAPACITY 1 . While there was a slightly higher incidence of Grade 3 adverse events in the pirfenidone groups in both studies , there was no difference in overall Grade 4 adverse events between pirfenidone and placebo .