Data collection
We collected data from haemophilia B patients (endogenous FIX activity
level ≤ 5 IU/dL) treated with rFIX-Fc (eftrenonacog alfa, Alprolix®)
included in the OPTI-CLOT TARGET study (NTR7523)17 or
United Kingdom (UK)-EHL Outcome Registry (NCT02938156). Briefly,
haemophilia patients in the OPTI-CLOT TARGET study received nine months
of PK-guided dosing to investigate the reliability and feasibility of
the Bayesian forecasting procedure. FIX samples for PK profiling were
obtained pre-infusion and approximately 15-30 minutes, 4, 24, 72-120 and
168h after infusion. During PK-guidance, a minimum of four FIX activity
(at nonspecific time points after infusion) levels per patient was
collected in a minimum of two visits to validate predicted FIX. The
UK-EHL Outcome Registry contains patient characteristics and treatment
information, including FIX infusions (timing and doses) and FIX activity
level measurements. During PK profiling, FIX activity levels were
measured at pre-infusion and approximately 15 minutes, 24, 72, 120 and
168h after infusion. Additional FIX activity levels were sampled during
visits at 10 days, 3, 6, 12 and 18 months after initiation of rFIX-Fc
treatment. In both studies, no wash-out was required during PK profiling
if three prior infusions were documented. Informed consent was obtained
from all patients and/or caregivers.