In this study, the application of Raman spectroscopy to quantitative in-line monitoring of the crystallization from solution of an enantiotropic polymorphic system, flufenamic acid, is explored. Separate feasibility studies were performed to evaluate the utility of Raman spectroscopy to quantitatively monitor changes in solution concentration and to measure polymorphic composition. The crystallization of flufenamic acid was then monitored as a function of temperature and time using an immersion probe coupled to a Raman spectrometer. The spectral data contained information about both the solution phase and the crystallized solids. Using standard data analysis techniques, solution and solids information could be deconvoluted. Changes in solute concentration as a function of time were quantified from the Raman data and showed good agreement with results from other techniques used for corroboration. The polymorphic forms initially crystallizing from solution, in the presence and absence of seeds, could be clearly identified. Furthermore, the kinetics of the conversion of the metastable form to the stable form could be readily followed. This study illustrates the complex nature of the crystallization process, the ability of Raman spectroscopy to monitor this process, and the potential for this technique to aid in process optimization and control.

The highly exothermic nature of Reformatsky reagent formation and the reported unpredictability of the induction time for its formation pose challenging problems for scaling up Reformatsky reactions. A zinc-activation procedure using DIBAL-H was developed and investigated using reaction calorimetry along with subsequent parts of the process. This procedure was shown to have important advantages for scale-up relative to previous zinc activation methods, including an immediate start of Reformatsky reagent formation with addition-controlled reaction. Calorimetric analysis was especially useful in specifying quickly a suitable temperature for Reformatsky reagent formation. The process was scaled up successfully.

LAB687 is an inhibitor of microsomal triglyceride transfer protein (MTP) designed to lower triglycerides and LDL cholesterol. The discovery of its polymorphic forms closely intertwines with the synthesis development of the molecule. At the early development stage, LAB687 was known to crystallize in two modifications, Forms A and B. Knowledge of the molecule’s polymorphic nature prompted extensive polymorphic screening using drug substance produced by the earlier synthesis routes. These studies revealed the existence of a third polymorph, Form C. Subsequently, Form C was selected for further development based on data from the additional formulation and polymorphic studies. Surprisingly, a new modification, Form D, appeared when the crystallization process known to routinely produce Form C was scaled up in the pilot plant. Once Form D was introduced to the laboratory, Forms A and C could no longer be made. We hypothesize that a change in drug substance impurity profile due to the changes in synthesis, led to the emergence of the most stable Form D.

DNA methyltransferase 3A (DNMT3A) is ade novocytosine methyltransferase responsible for establishing proper DNA methylation during mammalian development. Loss-of-function (LOF) mutations to DNMT3A, including the hotspot mutation R882H, frequently occur in developmental growth disorders and hematological diseases, including clonal hematopoiesis (CH) and acute myeloid leukemia (AML). Accordingly, identifying mechanisms that activate DNMT3A is of both fundamental and therapeutic interest. Here, we applied a base editor mutational scanning strategy with an improved DNA methylation reporter to systematically identify DNMT3A activating mutations in cells. By integrating an optimized cellular recruitment strategy with paired isogenic cell lines with or without the LOF hotspot R882H mutation, we identify and validate three distinct hyperactivating mutations within or interacting with the regulatory ADD domain of DNMT3A, nominating these regions as potential functional target sites for pharmacological intervention. Notably, these mutations are still activating in the context of a heterozygous R882H mutation. Altogether, we showcase the utility of base editor scanning for discovering functional regions of target proteins.SynopsisUsing base editor mutagenesis and a DNA methylation reporter optimized to find activating mutations, we identify novel hyperactivating mutations in DNMT3A that suggest new mechanisms of allosteric control.

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