Inverted V-shaped albumin binding and CES1/CES2 cascade conversion in aliphatic alcohol-modified CPT prodrug albumin nanoparticles

Albumin-based drug-delivery systems garner attention due to their inherent biocompatibility and tumor-targeting potential. However, they are limited by weak human serum albumin (HSA) affinity for drugs like camptothecin (CPT). To address this, we synthesize five CPT prodrug derivatives (CPT-SA-C6–C14) with tunable aliphatic alcohol chains as HSA-binding motifs and a succinic acid linker for carboxylesterase (CES1/CES2)-mediated cascade activation. CPT-SA-C10, C12, and C14 achieve ultrahigh drug loading (>30%) in albumin nanoparticles (ANPs) via enhanced HSA affinity. Aliphatic chain length shows an inverted V-shaped correlation with both HSA-binding affinity and CES1-catalyzed hydrolysis. The resulting intermediate is hydrolyzed by CES2 to release CPT. CPT-SA-C12 ANPs exhibit the highest albumin affinity and fastest enzymatic conversion, yielding superior therapeutic efficacy and favorable tolerability. This work elucidates the structure-activity relationship of albumin-bound prodrugs and advances the design of CES-responsive nanomedicines.