IMPRESS (Investigation for Maximal Peyronie's Reduction Efficacy and Safety Studies) I and II examined the clinical efficacy and safety of collagenase Clostridium histolyticum intralesional injections in subjects with Peyronie disease. Co-primary outcomes in these identical phase 3 randomized, double-blind, placebo controlled studies included the percent change in the penile curvature abnormality and the change in the Peyronie disease questionnaire symptom bother score from baseline to 52 weeks.