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The Food and Drug Administration (FDA) regulates pharmaceutical drug products to ensure a continuous supply of high-quality drugs in the USA. Continuous processing has a great deal of potential to address issues of agility, flexibility, cost, and robustness in the development of pharmaceutical manufacturing processes. Over the past decade, there have been significant advancements in science and engineering to support the implementation of continuous pharmaceutical manufacturing. These investments along with the adoption of the quality-by-design (QbD) paradigm for pharmaceutical development and the advancement of process analytical technology (PAT) for designing, analyzing, and controlling manufacturing have progressed the scientific and regulatory readiness for continuous manufacturing. The FDA supports the implementation of continuous manufacturing using science-and risk-based approaches.

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Synthetic polymers have long been used to modify various properties of proteins such as activity and solubility. Polyethylene glycol (PEG) has been widely used to form adducts with enzymes and antibodies. In this study, the polyoxazoline family of water-soluble polymers was used to synthesize adducts containing a synthetic peptide recognized by a monoclonal antibody (MAb) directed against human protein C (hPC). This is the first application of direct conjugation of unterminated or "living" polymer to a peptide. The avidity of the antibody for the various adducts was characterized with respect to size and hydrophilicity of methyl- and ethyl-substituted polyoxazoline polymers (POX). Avidity of the adducts was not found to be dependent upon the hydrophilicity and was slightly decreased due to polymer modification. The methyl-POX-peptide adducts were found to be highly water soluble, while the ethyl-POX-peptide adducts showed sporadic problems with aqueous solubility. Because the polymer-peptide adducts retained avidity for the antibody, polyoxazoline polymers may have potential application to protein-adduct chemistry.

Encrustation is a risk factor that can cause product and process failure in continuous crystallization processes. Mitigation, prevention, and control of encrustation have been extensively researched. Various risk mitigation strategies proposed in the literature, such as coating of crystallizer walls, use of additives to control encrustation kinetics, and periodic steady-state operation show promising results in delaying or preventing encrustation. Because of the increased interest in the use of continuous crystallization in industrial applications, it is important to understand this risk factor further. This review presents recent developments on dynamic models, mechanisms, and risk factors for encrustation in continuous crystallization processes. Various design and control strategies to mitigate the encrustation risk are also summarized. Appropriate control strategies should be implemented during continuous crystallization to avoid the impact of encrustation on drug substance quality.