To evaluate cumulative and incremental changes in penile curvature after each treatment cycle of collagenase clostridium histolyticum (CCH) in men with Peyronie's disease (PD).

Data from 2 phase 3, randomized, placebo-controlled trials were analyzed post hoc. Treatment was administered in up to 4 treatment cycles (per cycle: 2 injections, 1-3 days apart, of CCH 0.58 mg or placebo; subsequent penile modeling) at 6-week intervals. Penile curvature was measured at baseline and after each treatment cycle (weeks 6, 12, 18, and 24). Successful response was defined as ≥20% reduction from baseline penile curvature.

Overall, 832 men (CCH, n = 551; placebo, n = 281) were included in the analysis. After each cycle, mean cumulative percent reduction from baseline penile curvature was significantly greater with CCH vs placebo (P <.001). Following one cycle, 29.9% of CCH recipients exhibited a successful response. Among nonresponders, additional cycles of injections led to further successful responses: 60.8% of first cycle failures achieved response after fourth cycle (8 injections), 42.7% of cycle 1-2 failures achieved response after fourth cycle, and 23.5% of cycle 1-3 failures achieved response after fourth cycle.

Data showed incremental benefits from each of the 4 CCH treatment cycles. Completion of a full series of 4 CCH treatment cycles may optimize improvements in penile curvature in men with PD, including among those who did not clinically respond to previous treatment cycles.