Cryopreservation of siRNA-Treated Cells Is Feasible

Cryopreservation is a routine step in the manufacturing process of adoptive cell therapies (ACT), providing critical logistic flexibility. RNA interference (RNAi)-based therapies are increasingly being explored as enhancers or modulators of ACT. However, the impact of cryopreservation on cells treated with RNAi-based therapies has not been investigated before. In this study, we addressed this knowledge gap by examining silencing efficacy in small interfering RNA (siRNA)-treated cells that undergo cryopreservation. Our findings demonstrate that silencing in cryopreserved cells is comparable to that in cells maintained continuously in culture. Moreover, we found that the duration of siRNA exposure plays a significant role in cells that later undergo cryopreservation, with extended exposure improving silencing efficiency. However, this effect diminishes at higher siRNA concentrations. Additionally, we showed that siRNA treatment is feasible at low temperatures (2°C–8°C), and siRNA-treated cells can be cryopreserved for extended periods (at least 1 month) without loss of efficacy. Our work establishes the feasibility of integrating siRNA treatments into current manufacturing processes for ACT.