Bioprocessing of High Concentration Protein Solutions: Quality by Digital Design Approach

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There is a need for underpinning research to support industrial development of novel protein therapeutics for more convenient delivery by subcutaneous injection (SC). This is an increasing priority for biopharmaceutical companies such that patients can administer the medicines at home, rather than having to visit hospital for a lengthy infusion. The challenge for bioprocessing research is to dissolve the dose of protein required in a small volume, usually 1 ml, that can be self injected. The protein therefore must be soluble up to 300 mg/ml, and it is desirable that the liquid can be stored at 2-8 C for 2 years or more without precipitation, aggregation or other instability. In addition, the liquid must not be too viscous, otherwise the injection will require too high a pressure or may take too long to administer. There is also a need to prevent damage to the protein during the process of forcing the liquid through a narrow needle, into the tissue under the skin. The proposed research will develop methods for use by industry to screen protein formulations for viscosity and other flow properties, using small quantities of protein. This will enable methods for viscosity reduction to be developed. It is known that similar proteins differ widely (by a factor of two or more) in their viscosity at similar concentrations, and that alterations in co-solvent can reduce the viscosity of a formulation. To achieve this, we propose to apply comprehensive rheological characterisation, RheoChip rheometry, and advanced modelling as a platform, which can be used by industry to select the protein and formulation for development of the final dosage form, at an earlier stage than it is possible today. This should save time and cost in development of many new protein medicines. The research will build on existing methods, which are already well established for rheological characterisation of water soluble polymers and BSA solutions, and adapt and apply them to the bioprocessing and injectability of high concentration protein biopharmaceutical solutions. Comprehensive rheological characterisation of protein solutions has not yet been published. In addition, there is the potential for this new knowledge to be applied in industry to improve the production of biopharmaceutical proteins, as high concentrations may be reached during bioprocessing, e.g. freeze drying, tangential flow filtration (TFF) etc. and there can be difficulties in processing viscous solutions, e.g. nanofiltration for virus removal may be impractical. The deliverables of the project will be the form of instrumentation, rheological characterisation methods more relevant than current viscosity measurement, and computational tools. The project has five work packages (WPs). WP1 and WP2 will focus on development of new enabling technologies. The output of WP1 will be the first high throughput characterisation platform for screening protein formulations under the flow conditions encountered in bioprocessing while requiring minimal sample. WP2 will construct a computational platform for predictive modelling of concentrated protein fluid flows. WP3 and WP4 will critically validate these enabling technologies using both model and industrially relevant protein solutions under the complex flows, including TFF and SC injection. The output will be an integrated approach for design and optimisation of (nonlinear) scale-up protein production, based on high throughput rheological data obtained from Rheo-chip and predictive modelling of protein flows and protein stability during processing. WP5 will correlate the rheological properties and flow behaviour of concentrated protein solutions with the effects of excipients and/or formulation conditions on the conformational stability and self-association in dilute solution. This will help to establish the molecular determinants of high viscosities and flow induced protein aggregation leading to rational design of high throughput screens.