ORIGINAL ARTICLE Treatment Pharmacokinetic study of a high-purity factor IX concentrate (Factor IX Grifols Ò ) with a 6-month follow up in previously treated patients with severe haemophilia B J. A. AZNAR,* N. CABRERA,* M. MATYSIAK,  K. ZAWILSKA, à L. GERCHEVA,§ A. ANTONOV, – M. MONTAN ˜ E ´ S,** A. M. PA ´ EZ** and T. LISSITCHKOV    *Hospital Universitario La Fe, Unidad de Coagulopatı ´as Conge ´nitas, Valencia, Spain;  Pediatric Hematology and Oncology Department, University Medical School, Warsaw, Poland; àDepartment of Internal Medicine and Hematology, J. Strusia Hospital, Poznan, Poland; §Department of Hematology, Sveta Marina University Hospital, Varna, Bulgaria; –Department of Hematology, University Hospital, Medical University, Pleven, Bulgaria; **Department of Clinical Trials and Pharmacovigilance, Instituto Grifols S.A, Parets del Valle `s, Barcelona, Spain; and   National Center of Hematology, Sofia, Bulgaria Summary. Optimal replacement treatment in hae- mophilia B patients requires a good understanding of the pharmacokinetics of factor IX (FIX). The aim of this study was to compare the pharmacokinetic profile of Factor IX Grı´fols Ò , a highly purified human FIX concentrate with two specific pathogen inactivation/removal steps, to that of available FIX preparations. The study was an open, non-random- ized trial including 25 male subjects older than 12 years of age with severe haemophilia B. Pharma- cokinetic profile of the FIX preparation regularly used by the subjects was determined as control. Pharmacokinetic profile of Factor IX Grifols Ò was determined twice, one 7–15 days after control assessment and second after a 6 months period had elapsed. Results showed that all products had peak plasma levels of FIX:C within 30 min. Mean recovery was 1.3 ± 0.3 IU dL )1 per IU kg )1 for Factor IX Grifols Ò and 1.0 ± 0.3 IU dL )1 per IU kg )1 for con- trol products (P < 0.001). The mean terminal half-life (t 1/2 ) for Factor IX Grifols Ò was 26.7 h and 26.8 h for control product. Pharmacokinetic parameters after 6 months of treatment with Factor IX Grifols Ò did not statistically differ from the parameters obtained with the first infusion. There were no adverse events related to Factor IX Grifols Ò for the duration of the study. In conclusion, Factor IX Grifols Ò has adequated phar- macokinetic properties comparable to the control plasma-derived FIX and these parameters remain stable after 6 months of treatment. Factor IX Grifols Ò can be an effective and safe plasma-derived FIX concentrate for replacement therapy in haemophilia B patients. Keywords: factor IX, factor IX Grifols Ò , Grifols, haemophilia, haemophilia B, pharmacokinetics Introduction Haemophilia B is an X-linked chronic coagulation disorder characterized by a factor IX (FIX) deficiency with an incidence of approximately 1 case per 30 000 males, accounting for 12% of the total cases of haemophilia [1]. Factor IX is a 68 kDa plasma serine protease synthesized in the liver [2]. Factor IX is activated by factor XIa or factor VIIa to form FIXa, which in turn, together with other cofactors, activates factor X to form factor Xa, the first member of the final common coagulation pathway [2]. Patients with haemophilia B experience bleeding episodes with a frequency usually correlating with the baseline level of FIX activity. The disease causes recurrent spontaneous haemorrhages in joints, muscles, brain and other internal organs as well as continuous bleeding after minor surgery or trauma- tisms. Articular haemorrhages are common in Correspondence: Dr Jose ´ Antonio Aznar, Hospital Universitario La Fe, Unidad de Coagulopatı´as Conge ´nitas, Avenida Campanar 21, 46009 Valencia, Spain. Tel.: 34 96 386 8752; fax +34 96 386 8752; e-mail: aznar_jan@gva.es Accepted after revision 27 April 2009 Haemophilia (2009), 15, 1243–1248 DOI: 10.1111/j.1365-2516.2009.02052.x Ó 2009 Blackwell Publishing Ltd 1243