(411f) Parallel Process Development and Enzyme Evolution for Drug Substance Manufacturing

Process development of a Dynamic Kinetic Resolution (DKR) step in the commercial synthesis of an API intermediate was undertaken in preparation for large-scale batch processing. By utilizing a Ketoreductase (KRED) enzyme in lieu of a Ru catalyst to catalyze the DKR reaction, the process could be streamlined to utilize a greener, safer, and more robust chemo-enzymatic through-process over the Ru-catalyzed route.

To support successful scale-up of this process, process development studies with cross-collaborative teams were performed at bench, kilo, and pilot plant scales in parallel with KRED evolution. The initial KRED variant limited process parameters to a narrow, stringent process. By understanding the process sensitivities of the enzyme such as organic solvent tolerance, pH, and temperature, a robust process was optimized that provided the necessary conversion of starting material while minimizing risk of enzyme degradation and generation of impurities. The DKR reaction was scaled up in the pilot plant at Merck & Co., Inc., Rahway, NJ, USA to understand scale-up behavior and risks. Key takeaways from the first batch provided valuable insight into important aspects of the process that required further investigation and improvement. The cross-functional team worked closely with internal and external partners to demonstrate a robust process that could be implemented in the pilot plant and eventually, the manufacturing production plant. Evolving the enzyme while developing a streamlined DKR through-process using common equipment was paramount to successful tech transfer of this reaction across sites and eventually, process characterization.