Representative examples for preexisting and transient treatment-emerging antibodies binding to FVIII, PEG-FVIII, or PEG. (A) Preexisting IgG antibodies binding to FVIII and preexisting IgG antibodies binding to PEG-FVIII. Presented is patient 44 (see Tables 2 and 3). (B) Treatment-emerging transient IgG antibodies binding to FVIII and treatment-emerging transient IgG antibodies binding to PEG-FVIII. Presented is patient 32 (see Tables 2 and 3). (C) Preexisting IgM and IgG antibodies binding to PEG-FVIII and preexisting IgM antibodies binding to PEG. Presented is patient 50 (see Tables 2 and 3). (D) Treatment-emerging transient IgM antibodies binding to PEG. Presented is patient 45 (see Tables 2 and 3). Patients presented in panels A,C-D participated in study NCT02585960 (see Table 1). This study included an assessment of the PK profile of the study drug (single infusion of 60 ± 5 IU/kg rurioctocog alfa pegol) between screening and baseline to enable subsequent PK-guided prophylaxis targeting FVIII trough levels of either 1% to 3% or 8% to 12%.³⁷ Therefore, patients were already exposed to the study drug before baseline. The patient presented in panel B participated in studies NCT02210091 (study A) and NCT01945593 (study B; see Table 1).