Camptothecin is a monoterpene indole alkaloid (MIA) used to produce semisynthetic antitumor drugs. We investigated camptothecin synthesis in Camptotheca acuminata by combining transcriptome and expression data with reverse genetics, biochemistry, and metabolite profiling. RNAi silencing of enzymes required for the indole and seco-iridoid (monoterpene) components identified transcriptional crosstalk coordinating their synthesis in roots. Metabolite profiling and labeling studies of wild-type and RNAi lines identified plausible intermediates for missing pathway steps and demonstrated nearly all camptothecin pathway intermediates are present as multiple isomers. Unlike previously characterized MIA-producing plants, C. acuminata does not synthesize 3-a(S)-strictosidine as its central MIA intermediate and instead uses an alternative secoiridoid pathway that produces multiple isomers of strictosidinic acid. NMR analysis demonstrated that the two major strictosidinic acid isomers are (R) and (S) diastereomers at their glucosylated C21 positions. The presence of multiple diastereomers throughout the pathway is consistent with their use in synthesis before finally being resolved to a single camptothecin isomer after deglucosylation, much as a multilane highway allows parallel tracks to converge at a common destination. A model "diastereomer" pathway for camptothecin biosynthesis in C. acuminata is proposed that fundamentally differs from previously studied MIA pathways.

A primary function of the parenteral drug product manufacturing process is to ensure sterility of the final product. The two most common methods for sterilizing parenteral drug products are terminal sterilization (TS), whereby the drug product is sterilized in the final container following filling and finish, and membrane sterilization, whereby the product stream is sterilized by membrane filtration and filled into presterilized containers in an aseptic processing environment. Although TS provides greater sterility assurance than membrane sterilization and aseptic processing, not all drug products are amenable to TS processes, which typically involve heat treatment or exposure to ionizing radiation. Oligonucleotides represent an emerging class of therapeutics with great potential for treating a broad range of indications, including previously undruggable targets. Owing to their size, structural complexity, and relative lack of governing regulations, several challenges in drug development are unique to oligonucleotides. This exceptionality justifies a focused assessment of traditional chemistry, manufacturing, and control strategies before their adoption. In this article, we review the current state of sterile oligonucleotide drug product processing, highlight the key aspects to consider when assessing options for product sterilization, and provide recommendations to aid in the successful evaluation and development of TS processes. We also explore current regulatory expectations and provide our interpretation as it pertains to oligonucleotide drug products.