AAV manufacturers embark on a journey as they rapidly advance important therapies through the clinic, and the success of the journey depends on the quality, security of supply, and process economics of AAV production. Often, there is a tradeoff between process optimization and moving quickly into the clinic. The economics of a program’s first-generation process may not be suited to meet long term goals, and as a program moves to later stage clinical trials, the challenging task of scaling supply requires additional process improvements and creative implementation strategies., BridgeBio Gene Therapy has demonstrated significant process improvements with limited development time to achieve long term, sustainable manufacturing goals.<br/>To improve process economics and lower manufacturing risk, a novel strategy for impurity clearance was developed, including an acid precipitation step prior to harvest. This process improvement lowered manufacturing costs by allowing significant reduction of endonuclease and filtration consumables, while maintaining equivalent or better impurity clearance to the prior process. Additionally, implementations challenges were addressed in the transfection and harvest unit operations to allow bioreactor volume increase from 200L to 500L. In particular, risk mitigation strategies to address key incubation time limitations identified in process development and historical trending were implemented. These included bolus additions for pH adjustments, decoupling of filtration steps to de-risk delays from potential filter fouling, and hard coded controls in manufacturing batch records to reduce delays in transfection and pH adjustments. Successful at-scale transfection and low pH harvest operations depended on manufacturing training, careful batch record drafting, and confirmatory pilot scale runs.<br/>Both the first- and second-generation processes required pooling upstream lots to enable more favorable downstream processes, outlining the process bottleneck where months of cGMP activity were required prior to purification and drug product fill. As a more streamlined approach, we envision AAV production at 1000L scale and have developed proof of concept data for implementation of an intensified process strategy. With our current upstream productivity, we anticipate having a future process that can couple upstream and downstream without the need for intermediate freezing and lot pooling.

Journey of an AAV: Overcoming implementation challenges for manufacturing a second-generation production process for an adeno-associated virus

ACS Fall 2021

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