Key Points• GlycoPEGylated demonstrates the same efficacy and prolonged effect in animal models as native FVIII.• Circulatory half-life of glycoPEGylated FVIII (N8-GP) is prolonged by approximately twofold in several species.Frequent infusions of intravenous factor VIII (FVIII) are required to prevent bleeding associated with hemophilia A. To reduce the treatment burden, recombinant FVIII with a longer half-life was developed without changing the protein structure. FVIII-polyethylene glycol (PEG) conjugates were prepared using an enzymatic process coupling PEG (ranging from 10 to 80 kDa) selectively to a unique O-linked glycan in the FVIII B-domain. Binding to von Willebrand factor (VWF) was maintained for all conjugates. Upon cleavage by thrombin, the B-domain and the associated PEG were released, generating activated FVIII (FVIIIa) with the same primary structure and specific activity as native FVIIIa. In both FVIII-and VWF-deficient mice, the half-life was found to increase with the size of PEG. In vivo potency and efficacy of FVIII conjugated with a 40-kDa PEG (N8-GP) and unmodified FVIII were not different. N8-GP had a longer duration of effect in FVIII-deficient mouse models, approximately a twofold prolonged half-life in mice, rabbits, and cynomolgus monkeys; however, the prolongation was less pronounced in rats. Binding capacity of N8-GP on human monocyte-derived dendritic cells was reduced compared with unmodified FVIII, resulting in several-fold reduced cellular uptake. In conclusion, N8-GP has the potential to offer efficacious prevention and treatment of bleeds in hemophilia A at reduced dosing frequency. (Blood. 2013;121(11):2108-2116

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Biomarkers detect increased cartilage and bone degradation, and altered inflammatory activity in haemophilia patients with arthropathy. These biomarkers could potentially be used to identify patients with progressing joint disease.

Background Hemophilic arthropathy is a severe complication of hemophilia. It is caused by recurrent bleeding into joint cavities, which leads to synovial inflammation, fibrosis, cartilage degradation and bone remodeling. Extracellular matrix remodeling of affected tissues is a hallmark of these pathological processes. Objectives The aim of this study was to use serological biomarkers of collagen turnover to evaluate extracellular matrix remodeling in a factor VIII-deficient rat model of hemophilic arthropathy. Methods F8 rats and wild-type littermate controls were subjected to repeated knee bleeds induced by needle puncture on days 0 and 14. Development of arthropathy was confirmed by histology after termination on day 28. Serum samples were collected at baseline and throughout the study and analyzed for biomarkers of collagen turnover, including collagens of the basement membrane (type IV collagen), the interstitial matrix (collagen types III, V and VI) and cartilage (type II collagen). Results In F8 rats, induced knee bleeding and subsequent development of arthropathy caused significant alterations in collagen turnover, measured as changes in serological biomarkers of basement membrane turnover, interstitial matrix turnover and cartilage degradation. Biomarkers of type II collagen degradation correlated significantly with cartilage degradation and degree of arthropathy. Hemophilic rats had a 50% higher turnover of the basement membrane than wild-type littermates at baseline. Conclusions Joint bleeding and hemophilic arthropathy cause changes in turnover of extracellular matrix collagens in hemophilic rats. Biomarkers of collagen turnover may be used to monitor joint bleeding and development of blood-induced joint disease in hemophilia.

Recombinant human interleukin-11 (rhIL-11), a glycoprotein 130 (gp130)-signaling cytokine approved for treatment of thrombocytopenia, also raises von Willebrand factor (VWF) and factor VIII (FVIII) by an unknown mechanism. Desmopressin (1-deamino-8-D-arginine vasopressin [DDAVP]) releases stored VWF and FVIII and is used for treatment of VWF and FVIII deficiencies. To compare the effect of these 2 agents, heterozygous von Willebrand disease (VWD) and normal dogs were treated with either rhIL-11 (50 g/kg/d subcutaneously ؋ 7 days) or DDAVP (5 g/kg/d intravenously ؋ 7 days). The rhIL-11 produced a gradual and sustained elevation of VWF and FVIII levels in both heterozygous VWD and normal dogs while DDAVP produced a rapid and unsustained increase. Importantly, rhIL-11 treatment produced a 2.5-to 11-fold increase in VWF mRNA in normal canine heart, aorta, and spleen but not in homozygous VWD dogs, thus identifying a mechanism for elevation of plasma VWF in vivo. Moreover, dogs pretreated with rhIL-11 retain a DDAVP-releasable pool of VWF and FVIII, suggesting that rhIL-11 does not signifi-