Engineering nanocarriers for PROTAC delivery: liposomes, cyclodextrin aggregates, and albumin-based nanoparticles for ACBI2 and ACBI3

PROteolysis-TArgeting Chimeras (PROTACs) are promising therapeutic modalities with the potential to expand the druggable space. However, their unfavorable physicochemical properties present a hurdle for their therapeutic application. Hence, efficient, transferable delivery strategies are needed. In this study, four nanocarrier formulations were developed and evaluated for the PROTACs ACBI2 and ACBI3 including non-PEGylated liposomes, PEGylated liposomes, cyclodextrin aggregates, and albumin-based nanoparticles (ANPs). The liposomal and cyclodextrin-based systems showed successful transferability between ACBI2 and ACBI3, while ACBI3-ANPs had unfavorable characteristics and were discarded. All other formulations yielded uniform (PDI < 0.2) nanocarriers with PROTAC concentrations > 1.28 mg/mL which were stable for at least 6 months at 5 °C. Electrostatic interactions between excipients and active pharmaceutical ingredients (APIs) were important for efficient API incorporation across all nanocarriers. In vitro evaluation showed antiproliferative activity of all formulations comparable to DMSO controls in A549 monolayers but not in tumor spheroids. There, PEGylated liposomes containing either ACBI2 or ACBI3 were less effective. These findings indicate that PROTACs sharing structural similarities, such as the same E3 ligase ligand, may be amenable to the same liposomal and cyclodextrin-based formulation strategies.