Rondaptivon pegol increases the half-lives of the substituted FVIII products. Patients with severe hemophilia (patients 1-8) followed the full rondaptivon pegol study protocol: 3 mg on days 1, 4, and 7 and weekly doses of 2 to 9 mg until day 28. FVIII activity was measured by 1-stage clotting assay, and half-lives were estimated by WAPPS population pharmacokinetics models. ∗Patient 9 followed an abbreviated regimen of only 3 doses of 3 mg rondaptivon pegol. Error bars depict 95% credible intervals. Patients are ordered by the FVIII half-life achieved during treatment with rondaptivon pegol.