Albumin-binding prodrugs via reversible iminoboronate forming nanoparticles for cancer drug delivery

Albumin-based nanomedicines are important nanoplatforms for cancer drug delivery. The drugs are either physically encapsulated or covalently conjugated to albumin or albumin-based nanosystems. Physical encapsulation is advantageous due to requiring no chemical modification of drug molecules, but many drugs, for instance, camptothecin (CPT) and curcumin (CCM), though very hydrophobic, can't be loaded in or form nanoformulations with albumin. Herein, we demonstrate prodrugs readily binding to proteins via iminoboronates and forming nanoparticles for cancer drug delivery. CPT and CCM were functionalized with 2-acetylphenylboronic acid (2-APBA) to produce prodrugs CPT-SS-APBA and CCM- APBA. The prodrugs bound to bovine serum albumin (BSA) via formation of iminoboronates and the produced BSA/prodrug readily self-assembled into well-defined nanoparticles with high loading efficiency, improved colloidal stability, and much-improved pharmacokinetics. The nanoparticles effectively released drugs in the intracellular acidic environment or the cytosol rich in glutathione (GSH). In vivo, the nanoparticles showed enhanced anticancer efficacy compared with clinically used irinotecan or sorafenib in subcutaneous 4 T1 or HepG2 tumor models. This work demonstrates a versatile protein-binding prodrug platform applicable to protein-based drug formulations and even antibody-drug conjugates.