Inhibitor development is a serious complication in patients with haemophilia A and B. Historically, a lack of optimal therapies and factor products for treating inhibitor patients resulted in many patients developing chronic haemophilic arthropathies and flexion contractures of the involved joints. The introduction of immune-tolerance protocols to eradicate high-titre inhibitors has greatly diminished the incidence of these types of complications but as in the case reported here, immune tolerance is not always successful. Various elective surgical procedures were often delayed or not even considered in patients with inhibitor because of the variability in achieving adequate haemostasis and the thrombotic risks involved with the use of activated prothrombin-complex concentrates (APCCs) over extended periods of time. The development of recombinant factor VIIa (rFVIIa; NovoSeven) and its demonstrated safety and efficacy in treating inhibitor patients has opened new possibilities for addressing severe arthropathy with flexion contracture. This case report demonstrates that the use of rFVIIa in such a situation must include dosing flexibility that is both patient-specific and related to the potential for bleeding; the ability to maintain clinical haemostasis with a prophylactic dose of rFVIIa given as little as once daily; and the capacity for higher doses of rFVIIa, particularly in children because their kinetic profiles differ from adults.

Activated recombinant human coagulation factor VII (rFVIIa) is a promising new therapeutic agent for patients with hemophilia A or B with inhibitors who experience serious bleeding episodes or who need coverage during surgical procedures. This open-label, uncontrolled, emergency-use study evaluated the efficacy and safety of rFVIIa in 11 hemophiliac patients and 1 FVII-deficient patient with life-threatening intracranial hemorrhage previously unresponsive to one or more alternative therapies. rFVIIa effectively controlled intracranial hemorrhage in 10 of the 12 patients. Patients with hemophilia A or B received an average of 96.9 rFVIIa injections over 14.7 days with a mean total administration of 153.3 mg, corresponding to 8.1 mg/kg. Most reported adverse events were considered to be unrelated to rFVIIa therapy. These findings suggest that rFVIIa is an effective and well-tolerated therapeutic option in the management of central nervous system bleeding in patients with hemophilia A or B with inhibitors.

SummaryA technique for the detection of von Willebrand factor multimers separated by discontinuous SDS agarose electrophoresis has been developed using non-radioactive com-v pounds. The multimeric patterns were visualized by monospecific anti-human vWF:Ag followed by incubation with biotinylated antibody. After addition of avidin-biotin-peroxidase complex, the peroxidase activitiy was detected by 4-chloro-l-naphthol, giving sharp bands with a clear background.By this method, the differences of vWF : Ag multimers could be easily observed between normal plasma and the plasmas from variant type vWD (IIA, IIB, platelet-type). Large and intermediate multimers were absent in the plasma with vWD type IIA, while only large multimers were absent in the plasma with vWD IIB and platelet-type. The absence of large multimers was also observed in two commercial F VIII preparations having the ratio of vWF/vWF : Ag 0.18 and 0.63. The preparation with the ratio of 0.63 showed the presence of larger intermediate multimers.Electrophoresis in SDS 1.5% agarose gel revealed triplet structure of each small multimer, and a relative increase of the smallest subband was observed in vWD IIA plasma, platelet-type vWD plasma and commercial F VIII preparations.The procedures described are easy and safe to perform and are useful for screening or classifying cases with vWD in general laboratories.

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Factor VIII is a large protein molecule of molecular weight 2,000,000 or larger that elutes in the void volume on agarose gel chromatography. It has been shown previously that high concentrations of alkali halides and, more specifically, 0.25 M Ca2+ dissociate the molecule into a large carrier protein and a small fragment that retains the factor VIII activity. Factor VIII was prepared from normal canine plasma collected in sodium oxalate and heparin and adsorbed with BaSO4. Results with Ca2+ dissociation were the same as those obtained with fractions prepared from canine plasma collected in sodium citrate. The addition of 0.1 M e-aminocaproic acid in the dissociation step had no effect. Fractionation of canine hemophilic plasma produced preparations without activity, and no activity was found when these inert preparations were dissociated with Ca2+. These results indicate that the Ca2+ dissociation is a true dissociation and not caused by enzymatic degradation by plasmin, thrombin, or activated factors VII, IX, or X. The apparent molecular weight of the small active fragment of factor VIII determined by gel chromatography was about 100,000. Finally, when the large carrier protein and the small active fragment of factor VIII were separated by gel chromatography, mixed, and dialyzed free of Ca2 , they recombined to form a large active molecule that appeared in the void volume on agarose gel chromatography.Antihemophilic factor (AHF, factor VIII) is a glycoprotein which when highly purified has a molecular weight of about 2 X 106, as determined by ultracentrifugal techniques (1-4) and gel chromatographic studies (2-5). Its large size is also confirmed by its inability to enter standard polyacrylamide gels and its slow migration in agar during immunodiffusion.AHF is present in plasma at a concentration of <10 ,g/ml and has been purified 3,000-10,000 times by various procedures.Beginning with the work of Thelin and Wagner (1) in the early 1960s, evidence accumulated suggesting that under suitable conditions this macromolecule could be dissociated, with release of an active small-molecular-weight fragment(s). Weiss and coworkers (6) have shown that at high ionic strength, subunits of AHF can be separated by agarose gel chromatography. Most recently, Owen and Wagner (7) achieved dissociation of canine AHF with alkali halides, detergents, and most specifically 0.25 M Ca2+. Their data suggested that a small active AHF fragment(s) binds to a large carrier protein by both electrostatic and hydrophobic interactions. Rechromatography of the isolated small fragment after removal of calcium showed no reaggregation. The reversibility of the AHF dissociation was tested by incubating canine AHF in 0.25 M Ca2+, removing the Ca2+ by dialysis, Abbreviation: AHF, antihemophidic factor. and chromatographing the material on agarose 15m. The AHF activity was again eluted as a single peak in the void volume, suggesting that partially purified preparations are capable of recombination.This paper presents further studies on the ac...