Abstract
RNA interference (RNAi)-based medicines offer precise targeting of virtually any transcript, making them an appealing new drug class for immuno-oncology. While RNAi therapies are highly effective in non-dividing cells, their efficacy in rapidly dividing cells, crucial for immuno-oncology, remains largely unexplored. Previous data suggest that full chemical modification of short interfering RNAs (siRNAs) in dividing cells has not consistently extended silencing duration, unlike in non-dividing cells. The present study explores key factors influencing the duration of effect of RNAi-based therapeutics (siRNAs) in dividing cancer and immune cells. Saturation of intracellular depots, a strategy to prolong silencing duration in non-dividing hepatocytes, had minimal impact on siRNA effect duration in dividing cells. However, modifying the guide strand with a 5'-(E)-vinylphosphonate significantly extended siRNA silencing duration to over 30 days both in vitro and in vivo. Our findings enable the rational design of the chemical architecture and administration regimens of RNAi-based therapies in immuno-oncology.