* PK-Guided dosing - Non-intervention group (12M): Subjects with emicizumab concentration of 25-39 μg/mL will continue on their current dose regimen and will be followed according to the same assessment schedule as the Intervention Group. Only subjects with emicizumab plasma concentration \< 25 μg/mL will be adjusted in dosing regimen according to local protocol. These subjects will be followed for selective safety data only. primaryPurpose: TREATMENT masking: NONE count: 95 type: ESTIMATED name: Emicizumab - PK-guided dose reduction name: Emicizumab - Dosis continuation group name: Emicizumab - Dose adjustment group measure: Proportion of patients without treated bleeds measure: Proportion of patients without treated bleeds measure: Proportion of patients without spontaneous joint- or muscle bleeds measure: Annualized bleeding rate (ABR) of treated bleeds, including joint bleeds and sport-induced bleeds measure: To compare cost-effectiveness between conventional dosing and individualized PK-guided dosing of emicizumab measure: To assess the cumulative number of coagulation factor (sc. and/or iv.) of per year. measure: To assess the performance of the population PK model measure: To investigate whether direct joint health remains stable measured by physical examination when switching to lower-dosed emicizumab compared to conventional treatment measure: To investigate whether direct joint health remains stable measured by ultrasound when switching to lower-dosed emicizumab compared to conventional treatment measure: To investigate if indirect joint health, as measured by biomarkers, remains stable when switching to lower doses of emicizumab compared to conventional treatment. measure: To investigate if indirect joint health, as measured by biomarkers, remains stable when switching to lower doses of emicizumab compared to conventional treatment. measure: To investigate whether Health Related Quality of Life (HR-QoL) are similar in patients receiving conventional dosing compared with PK-guided dosing of emicizumab. measure: To investigate whether Health Related Quality of Life (HR-QoL) are similar in patients receiving conventional dosing compared with PK-guided dosing of emicizumab. measure: To investigate whether sports participation are similar in patients receiving conventional dosing compared with PK-guided dosing of emicizumab. measure: To investigate whether thrombin generation parameters can be used as a pharmacodynamic (PD) biomarker for emicizumab treatment efficacy. measure: To assess and monitor pain during emicizumab administration sex: MALE minimumAge: 1 Year stdAges: CHILD stdAges: ADULT stdAges: OLDER_ADULT facility: Radboud University Medical Center status: RECRUITING city: Nijmegen state: Gelderland zip: 6525 GA country: Netherlands name: Saskia Schols, Dr, MD role: CONTACT phone: +310 24 361 8823 email: Saskia.Schols@radboudumc.nl name: Saskia Schols, Dr, MD role: SUB_INVESTIGATOR lat: 51.8425 lon: 5.85278 facility: Maastricht University Medical Center status: RECRUITING city: Maastricht state: Limburg country: Netherlands name: Floor Moenen, Dr, MD role: CONTACT phone: +31433876543 email: floor.moenen@mumc.nl name: Floor Moenen, Dr, MD role: SUB_INVESTIGATOR lat: 50.84833 lon: 5.68889 facility: Amsterdam University Medical Center status: RECRUITING city: Amsterdam state: Noord-Holland zip: 1105 AZ country: Netherlands name: Michiel Coppens, Dr, MD role: CONTACT phone: +31(0)20 566 5964 email: m.coppens@amsterdamumc.nl name: Michiel Coppens, Dr, MD role: SUB_INVESTIGATOR lat: 52.37403 lon: 4.88969 facility: HagaZiekenhuis status: RECRUITING city: Den Haag state: Zuid-Holland zip: 2545 CH country: Netherlands name: Paula Ypma, MD role: CONTACT phone: +310702102620 email: haematologie@hagaziekenhuis.nl name: Paula Ypma, MD role: SUB_INVESTIGATOR lat: 52.07667 lon: 4.29861 facility: Leids Universitair Medisch Centrum status: RECRUITING city: Leiden state: Zuid-Holland zip: 2300 RC country: Netherlands name: Paul den Exter, Dr, MD role: CONTACT phone: +31 (0)71 526 1850 email: p.l.den_exter@lumc.nl name: Paul den Exter, Dr, MD role: SUB_INVESTIGATOR lat: 52.15833 lon: 4.49306 facility: Erasmus University Medical Center status: RECRUITING city: Rotterdam state: Zuid-Holland zip: 3000CA country: Netherlands name: Marjon Cnossen, Dr., MD role: CONTACT phone: +31107040113 email: m.cnossen@erasmusmc.nl name: Marjon Cnossen, Dr. MD role: SUB_INVESTIGATOR lat: 51.9225 lon: 4.47917 facility: University Medical Center Groningen status: RECRUITING city: Groningen zip: 9700 RB country: Netherlands name: Louise Hooimeijer, MD role: CONTACT phone: +310-503612740 email: h.l.hooimeijer@umcg.nl name: Louise Hooimeijer, MD role: SUB_INVESTIGATOR lat: 53.21917 lon: 6.56667 facility: University Medical Center Utrecht status: RECRUITING city: Utrecht country: Netherlands name: Kathelijn Fischer, Dr, MD role: CONTACT phone: +31887558450 email: K.Fischer@umcutrecht.nl name: Konrad van der Zwet, MD role: CONTACT phone: +31650124691 email: dosemi@umcutrecht.nl name: Kathelijn Fischer, Dr, MD role: PRINCIPAL_INVESTIGATOR name: Konrad van der Zwet, MD role: SUB_INVESTIGATOR name: Lize F.D. van Vulpen, Dr, MD role: SUB_INVESTIGATOR name: Roger E.G. Schutgens, Prof, MD role: SUB_INVESTIGATOR name: Paul van der Valk, MD role: SUB_INVESTIGATOR name: Karin P.M. van Galen, Dr, MD role: SUB_INVESTIGATOR name: Nanda Uitslager, Msc role: SUB_INVESTIGATOR lat: 52.09083 lon: 5.12222 hasResults: False