Herein is described the development of a large-scale manufacturing process for molnupiravir, an orally dosed antiviral that was recently demonstrated to be efficacious for the treatment of patients with COVID-19. The yield, robustness, and efficiency of each of the five steps were improved, ultimately culminating in a 1.6-fold improvement in overall yield and a dramatic increase in the overall throughput compared to the baseline process.

The Pax6 gene has attracted intense research interest due to its apparently important role in the development of eyes and the central nervous system (CNS) in many animal groups. Pax6 is also of interest for comparative genomics since it has not been duplicated in tetrapods, making for a direct orthology between the Ciona intestinalis gene CiPax6 and Pax6 in mammals. CiPax6 has been shown to be expressed in the anterior brain, caudal nerve cord, and in parts of the brain associated with the photoreceptive ocellus. This information was extended here using in-situ hybridization, and shows that CiPax6 transcripts mark the lateral regions of the nerve cord, remarkably similar to Pax6 expression in the mouse. As a means of dissecting the cis-regulation of CiPax6 we tested 8 kb of sequence using transient reporter transgene assays. Three separate regions were found that work together to drive the overall CiPax6 expression pattern. A 211 bp sequence 2 kb upstream of the first exon was found to be a major enhancer driving expression in the sensory vesicle (the anterior portion of the ascidian brain). Other upstream sequences were shown to work with the sensory vesicle enhancer to drive expression in the remainder of the CNS. An "eye enhancer" was localized to the first intron, which controls specific expression in the central portion of the sensory vesicle, including photoreceptor cells. The fourth intron was found to repress ectopic expression of the reporter gene in middle portions of the embryonic brain. Aspects of this overall regulatory organization are similar to the organization of the Pax6 homologs in mice and Drosophila, particularly the presence of intronic elements driving expression in the eye, brain and nerve cord.

A robust, green, and sustainable manufacturing process has been developed for the synthesis of gefapixant citrate, a P2X3 receptor antagonist that is under investigation for the treatment of refractory and unexplained chronic cough. The newly developed commercial process features low process mass intensity (PMI), short synthetic sequence, high overall yield, minimal environmental impact, and significantly reduced API costs. The key innovations are the implementation of a highly efficient two-step methoxyphenol synthesis, an innovative pyrimidine synthesis in flow, a simplified sulfonamide synthesis, and a novel salt metathesis approach to consistently deliver the correct active pharmaceutical ingredient (API) salt form in high purity.

The manufacturing route toward gefapixant citrate generates a trace amount of cyanide as a byproduct of a reaction employing the reagent chloroacetonitrile. In the development of a cyanide control strategy, conventional process and analytical approaches fell short because of challenges and incompatibilities with the matrices of the process and waste streams. To overcome these, we identified and adapted specific procedures for cyanide control. Our strategy ensured safety for patients, operators, and waste management.

The development of a safe, robust, and efficient manufacturing route for the synthesis of diaminopyrimidine 1, a key intermediate to gefapixant citrate (MK-7264), is described. A full mechanistic understanding of the cyclization step in the presence of guanidine was established by performing isotopic labeling experiments and identification of impurities. Guided by the mechanistic understanding, further attempts to modify the cyclization reaction by employing additives to reduce the triazine (9) formation and guanidine loading will also be presented. This newly developed method delivered compound 1 in 88−94% yield on a commercial scale and addressed the shortcomings of the early synthetic route including high PMI, low atom economy, long cycle-time, and multiple purifications to achieve the desired quality.