Distribution of participants with severe HA by CFC exposure and reason for study exit. Of 171 patients, 164 (95.9%) had CFC exposure at some time during the study; 113 of 164 (68.9%) had CFC exposure through prophylaxis, including 7 who also had FVIII mimetic prophylaxis; and 51 of 164 (31.1%) only had on-demand CFC exposure, including 7 who also had FVIII mimetic prophylaxis. Of 171 patients, 7 (4.1%) had no CFC exposure. In addition, of 113 patients who were on CFC prophylaxis, 85 exited because of 50 EDs (2 also were prescribed an FVIII mimetic); 22 exited because of FVIII inhibitor (none were also prescribed an FVIII mimetic); and 6 exited because of study closure (5 were also prescribed an FVIII mimetic).