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Bispecific antibodies (bsAbs) are an important class of emerging therapeutics with applications in cancer, hemophilia, diabetes, Alzheimer's, and infectious disease treatment. The presence of two distinct antigen binding sites enables more robust and tailored targeting than is possible with conventional monoclonal antibodies (mAbs), leading to enhanced efficacy and lower dosage requirements. However, the translation and commercialization of bsAbs has been hindered by production challenges, including low yield, chain mispairing, instability, and impaired binding activity. Therefore, this project proposes a manufacturing process to produce 100 kg of bispecific antibodies on an annual basis starting from purified monoclonal antibodies. Controlled functional arm exchange, which has been empirically shown to have excellent yield and selectivity (>90%), is used as the method of production.

First, a kinetic model was built in MATLAB to simulate and optimize key parameters for the functional arm exchange reactions. α-Respiratory syncytial virus and α-HIV envelope glycoprotein gp120 antibodies are used to model the parental mAbs, but the design can be easily adapted for other antibody combinations by changing the specific rate constants. Using optimized conditions from the kinetic model, a batch process was developed consisting of reduction of parental mAbs into half-mAbs by cysteamine, followed by removal of the reducing agent through diafiltration and concurrent re-oxidation of the antibodies to form heterodimeric bsAbs. The bsAbs are then purified using protein A chromatography with pH gradient elution to remove unreacted parental mAbs and high molecular weight aggregates, and are finally packaged into 5 L biotainers for storage at -20oC. The process has an overall yield of 82.3% (90.4% for functional arm exchange and 91.1% for purification), and the desired bsAb product reaches 98.1% purity, meeting the required threshold. Several measures were taken to maintain sterility and consistency throughout the design in compliance with cGMP guidelines, including single-use equipment with integrated process control and peristaltic pumps with flexible tubing. The final bsAbs will be sold to a separate manufacturing facility for formulation, packaging, and labeling as an injectable dose format.

The process is run in ten batches of 11.1 kg each, which allows the 100 kg annual target to be achieved with an allowance for one contingency batch per year. This equates to approximately 3.3 million bsAb doses, enough to treat 15,000-18,000 patients through a 9-10 month standard treatment course. The batches occur in semiannual 27-day production runs of five batches each, so various economic models were considered for operation: a standalone facility, renting space and equipment from a toll manufacturer, operating as a toll manufacturer, and operating as part of a larger company. The process is highly profitable in all four cases, with ROI values ranging from 92-94% based on bsAb prices of $30 million per kg, which includes a 25% reduction compared to list prices of comparable bsAbs on the market. For the toll manufacturing rental model, which offers the greatest flexibility and eliminates challenges associated with plant construction, there is a 93.51% IRR, 94.86% ROI, and $4.78 billion NPV. However, it should be noted that these values depend strongly on the mAb raw material price, which has a high degree of uncertainty. Overall, in addition to being an economically attractive process, the adaptability of the design offers the potential to facilitate efficient production of a variety of bsAbs for different treatment applications, expanding access to this innovative therapeutic platform to more patients.



Date Posted:25 May 2023