A long-acting factor VIII (FVIII) as a replacement therapy for hemophilia A would significantly improve treatment options for patients with hemophilia A. To develop a FVIII with an extended circulating half-life, but without a reduction in activity, we have engineered 23 FVIII variants with introduced surface-exposed cysteines to which a polyethylene glycol (PEG) polymer was specifically conjugated. Screening of variant expression level, PEGylation yield, and functional assay identified several conjugates retaining full in vitro coagulation activity and von Willebrand factor (VWF) binding. PEGylated FVIII variants exhibited improved pharmacokinetics in hemophilic mice and rabbits. In addition, pharmacokinetic studies in VWF knockout mice indicated that larger molecular weight PEG may substitute for VWF in protecting PEGylated FVIII from clearance in vivo. In bleeding models of hemophilic mice, PEGylated FVIII not only exhibited prolonged efficacy that is consistent with the improved pharmacokinetics but also showed efficacy in stopping acute bleeds comparable with that of unmodified rFVIII. In summary site-specifically PEGylated FVIII has the potential to be a long-acting prophylactic treatment while being fully efficacious for on-demand treatment for patients with hemophilia A. (Blood. 2010;116(2):270-279)

Previous studies have suggested that cyclin-dependent kinases control the cell cycle by directly phosphorylating proteins involved in specific events, such as nuclear lamins, microtubule-associated proteins and histones. In contrast, our results demonstrate that the Clb2-Cdc28 cyclin-dependent kinase complex controls specific cell-cycle events through a pathway that involves a GTPase and at least two different kinases. This suggests that cyclin-dependent kinases may control many cell-cycle events through GTPase-linked signaling pathways that resemble the intricate signaling pathways known to control many other cellular events.

Protein phosphatase 2A (PP2A) is a key regulator of mitosis, but the roles that it plays are poorly understood. New evidence in budding yeast shows that the Zds proteins form a tight stoichiometric complex with PP2A and target its activity to the Cdc25 phosphatase, which is a key regulator of entry into mitosis.

Chromatography resins used for purifying biopharmaceuticals are generally dedicated to a single product. In good manufacturing practice (GMP) facilities that manufacture a limited amount of any particular product, this practice can result in the resin being used for a fraction of its useful life. A methodology for extending resin reuse to multiple products is described. With this methodology, resin and column performance, product carryover, and cleaning effectiveness are continually monitored to ensure that product quality is not affected by multiproduct resin reuse (MRR). is evaluated in terms of (a) system suitability parameters, such as peak-shape and transition, and height equivalent theoretical plate (HETP) data; (b) key operating parameters, such as flow rate, inlet pressure, and pressure drop across the column; and (c) process performance parameters, such as impurity profiles, product quality, and yield. Historical data are used to establish process capability limits (PCLs) for these parameters. Operation within the PCLs provides assurance that column integrity and binding capacity of the resin are not affected by MRR. defined as the carryover of the previously processed product (A) into a dose of the subsequently processed product (B) (CO), should be acceptable from a predictive patient safety standpoint. A methodology for determining CO from first principles and setting acceptance limits for cleaning validation is described. is evaluated by performing a blank elution run after inter-campaign cleaning and prior to product changeover. The acceptance limits for product carryover (CO) are more stringent for MRR than for single-product resin reuse. Thus, the inter-campaign cleaning process should be robust enough to consistently meet the more stringent acceptance limits for MRR. Additionally, the analytical methods should be sensitive enough to adequately quantify the concentration of the previously processed product (A) and its degradants in the eluent.General considerations for designing small-scale chromatographic studies for process development are also described. These studies typically include process-cycling runs with multiple products followed by viral clearance studies with a panel of model viruses. Small-scale studies can be used to optimize cleaning parameters, predict resin performance and product quality, and estimate the number of multiproduct purification cycles that can be run without affecting product quality. The proposed methodology is intended to be broadly applicable; however, it is acknowledged that alternative approaches may be more appropriate for specific scenarios. Chromatography resins used for purifying biopharmaceuticals are generally dedicated to a single product. In good manufacturing practice (GMP) facilities that make a limited amount of any particular product, this practice can result in the resin being used for a fraction of its useful life. A methodology for extending resin reuse to multiple products is described. With this methodology, resin and column performance, product...

Prophylactic therapy with rFVIII has been shown to have a significant positive impact on the treatment of Hemophilia A. One of the impediments to effective prophylaxis is the requirement for frequent injections necessitated by the 12–14 hour circulating half-life of FVIII. We have evaluated a number of approaches to modify FVIII to reduce the need for frequent injections. In one approach, the active form of FVIII was stabilized by addition of a disulfide linkage between the A2 and A3 domains. As previously reported1, these molecules exhibited prolonged FVIII activity in a number of in vitro assays following activation. In vivo characterization of these molecules is in progress. Other approaches focused on increasing the circulating half-life of FVIII. In an attempt to reduce FVIII clearance by the liver receptor LRP, site-directed mutations in the reported LRP binding region of the FVIII A2 domain were generated. Twenty mutants, with single amino acid changes, were analyzed in mouse and rabbit recovery studies and no significant increase in recovery was observed. Since the point mutants may not have covered a large enough surface of the LRP binding domains, polyethlylene glygol (PEG) modification was used to disrupt a larger surface area. Previously, attachment of PEG moieties to FVIII had been shown to lead to an increase in plasma half-life in animal models; however, standard pegylation chemistries result in significant product heterogeneity and thus may not be suitable for commercial production. We have developed a novel method, based on protein engineering, to introduce PEG to specific cysteine residues on the surface of FVIII. Using this method, different molecular weight PEGs have been conjugated to sites in the A1, A2 or A3 domains of FVIII. Analysis of the pegylated proteins confirms that the attachment of PEG is highly specific to the engineered site. The pegylated products retain activity based on the two stage chromogenic assay, but exhibit reduced activity when analyzed by the one stage coagulation assay. Pharmacokinetic studies, performed in mouse and rabbit, show that pegylation increases half-life in a manner that is proportional to PEG molecular weight. Using a number of injury models in hemophilic mice, the pegylated molecules have been shown to be efficacious in stopping bleeds. The prospects for using site-specific pegylation of FVIII to produce a therapeutic for treatment of hemophilia A will be discussed.