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A study of the process−property−performance relationship of a Bristol-Myers Squibb drug substance led to successful development of crystallization and drying processes that produce crystals with desired and consistent physical properties. A controlled crystallization technique was developed to obtain well-defined, large crystals with a narrow particle size distribution. This crystallization process provided a less compressible filter cake for effective cake washing and deliquoring and afforded an easily dried product with desired powder properties. To preserve the quality of the crystals during drying, a drying protocol using low shear agitation was developed. This protocol prevented crystal attrition during drying, which was shown to adversely affect the formulation process and, thus, drug product performance. API crystals prepared by this method consistently resulted in excellent formulation processing and drug product performance.

Allysine ethylene acetal [(S)-2-amino-5-(1,3-dioxolan-2-yl)-pentanoic acid (2)] was prepared from the corresponding keto acid by reductive amination using phenylalanine dehydrogenase (PDH) from Thermoactinomyces intermedius ATCC 33205. Glutamate, alanine, and leucine dehydrogenases, and PDH from Sporosarcina species (listed in order of increasing effectiveness) also gave the desired amino acid but were less effective. The reaction requires ammonia and NADH. NAD produced during the reaction was recyled to NADH by the oxidation of formate to CO(2) using formate dehydrogenase (FDH). PDH was produced by growth of T. intermedius ATCC 33205 or by growth of recombinant Escherichia coli or Pichia pastoris expressing the Thermoactinomyces enzyme. Using heat-dried T. intermedius as a source of PDH and heat-dried Candida boidinii SC13822 as a source of FDH,98%, but production of T. intermedius could not be scaled up. Using heat-dried recombinant E. coli as a source of PDH and heat-dried Candida boidinii 98%. In a third generation process, heat-dried methanol-grown P. pastoris expressing endogenous FDH and recombinant Thermoactinomyces98% ee.