A potent cytidine deaminase biodegrader as pan-cancer cells sensitiser to deoxycytidine analogue-based chemotherapies

Deoxycytidine analogues (dC) are chemotherapy agents used to treat a range of solid tumours and blood cancers. However, their clinical efficacy is often limited by resistance mechanisms. Cytidine deaminase (CDA) plays a key role in this resistance by deaminating dC analogues into inactive metabolites. Although pharmacological inhibitors targeting the CDA catalytic site have been developed, they exhibit limited efficacy and/or off-target effects. To overcome these limitations, alternative strategies to target CDA are needed. Here, we develop a CDA biodegrader using a cell-based screening approach. This biodegrader consists of an intracellular anti-CDA VHH fused to the SPOP E3 ubiquitin ligase. We demonstrate that the CDA biodegrader is highly specific and effectively depletes CDA across various pancreatic, lung, and acute myeloid leukaemia cancer cell lines. Importantly, it sensitises these cancer cells to dC analogue treatment in vitro and CDA biodegrader combined with the dC analogue gemcitabine leads to pancreatic and lung tumours inhibition in vivo. For translational applications, we deliver mRNA encoding CDA biodegrader via virus-like particles and demonstrate efficient sensitisation of cancer cells to gemcitabine in vitro and in vivo. These findings highlight the CDA biodegrader as a promising therapeutic strategy to enhance the efficacy of dC analogues in cancer treatment.