Predictive scaling of fiber-based protein A capture chromatography using mechanistic modeling.

Protein A affinity chromatography is an important step in the purification of monoclonal antibodies (mAbs) and mAb-derived biotherapeutics. While the biopharma industry has extensive expertise in the operation of protein A chromatography, the mechanistic understanding of the adsorption/desorption processes is still limited, and scaling up and scaling down can be challenging because of complex mass transfer effects in bead-based resins. In convective media, such as fiber-based technologies, complex mass transfer effects such as film and pore diffusions do not occur which facilitates the study of the adsorption phenomena in more detail and simplifies the process scale-up. In the present study, the experimentation with small-scale fiber-based protein A affinity adsorber units using different flow rates forms the basis for modeling of mAb adsorption and elution behavior. The modeling approach combines aspects of both stoichiometric and colloidal adsorption models, and an empirical part for the pH. With this type of model, it was possible to describe the experimental chromatograms on a small scale very well. An in silico scale-up could be carried out solely with the help of system and device characterization without feedstock. The adsorption model could be transferred without adaption. Although only a limited number of runs were used for modeling, the predictions of up to 37 times larger units were accurate.

Multiproduct Resin Reuse for Clinical and Commercial Manufacturing-Methodology and Acceptance Criteria.

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). Resin and column performance 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.Product carryover defined as the carryover of the previously processed product (A) into a dose of the subsequently processed product (B) (COA→B), should be acceptable from a predictive patient safety standpoint. A methodology for determining COA→B from first principles and setting acceptance limits for cleaning validation is described.Cleaning effectiveness is evaluated by performing a blank elution run after inter-campaign cleaning and prior to product changeover. The acceptance limits for product carryover (COA→B) 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.LAY ABSTRACT: 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 carryover, and cleaning effectiveness are continually monitored to ensure that product quality is not affected by multiproduct resin reuse.General considerations for designing small-scale chromatographic studies for process development are 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 impacting 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.

The Zds proteins control entry into mitosis and target protein phosphatase 2A to the Cdc25 phosphatase.

The Wee1 kinase restrains entry into mitosis by phosphorylating and inhibiting cyclin-dependent kinase 1 (Cdk1). The Cdc25 phosphatase promotes entry into mitosis by removing Cdk1 inhibitory phosphorylation. Experiments in diverse systems have established that Wee1 and Cdc25 are regulated by protein phosphatase 2A (PP2A), but a full understanding of the function and regulation of PP2A in entry into mitosis has remained elusive. In budding yeast, entry into mitosis is controlled by a specific form of PP2A that is associated with the Cdc55 regulatory subunit (PP2A(Cdc55)). We show here that related proteins called Zds1 and Zds2 form a tight stoichiometric complex with PP2A(Cdc55) and target its activity to Cdc25 but not to Wee1. Conditional inactivation of the Zds proteins revealed that their function is required primarily at entry into mitosis. In addition, Zds1 undergoes cell cycle-dependent changes in phosphorylation. Together, these observations define a role for the Zds proteins in controlling specific functions of PP2A(Cdc55) and suggest that upstream signals that regulate PP2A(Cdc55) may play an important role in controlling entry into mitosis.

Rational design of a fully active, long-acting PEGylated factor VIII for hemophilia A treatment.

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.