The current landscape of mRNA therapy and the strategies for mRNA purification and dsRNA removal

Messenger RNA (mRNA) technology has emerged as a cornerstone in vaccine development and therapeutic applications, offering key benefits such as high potency, rapid scalability, and cost-effectiveness. The success of COVID-19 mRNA vaccines has underscored their efficacy and safety. However, residual byproducts generated during mRNA synthesis, such as unincorporated caps, nucleoside triphosphates (NTPs), DNA templates, enzymes, abortive transcripts, and double-stranded RNA (dsRNA), pose significant challenges to the clinical application of the RNA therapy. Among these, dsRNA is particularly problematic as it can activate various innate immune responses, suppress mRNA translation and potentially compromise the therapeutic efficacy of mRNA. Therefore, effectively removing dsRNA from in vitro synthesized mRNA is essential before its used in preclinical or clinical settings. In this review article, we provide a comprehensive overview of current mRNA development pipelines and ongoing clinical trials, and recent advances in mRNA purification techniques. Specifically, we focus on strategies for dsRNA removal, which can be broadly categorized into two approaches: (1) separating or removing dsRNA from in vitro transcription (IVT) mRNA products using methods such as RP-HPLC chromatography and cellulose-based purification; and (2) minimizing dsRNA formation during IVT by employing engineered RNA polymerase mutants, chaotropic agents, and magnetic beads, as well as modifying/optimizing DNA templates or RNA molecules to reduce dsRNA generation. We also discuss the advantages and limitations of these purification methods, the factors influencing the selection of purification strategies, and explore potential future directions for improving dsRNA purification technologies and their applications in mRNA-based therapeutics.