(555f) Synthesis of Poly(Aspartic Acid)-Doxorubicin Prodrug for Sequential Delivery of Afatinib and Doxorubicin

Combination therapy has a great potential for enhancing the efficacy of chemo drugs in treating cancer. Drug combinations that exploit the blockage of multiple survival pathways in cancerous cells hold great promise in achieving synergistic effects. Recent studies indicate that cancer cells can remarkably be sensitized to the effects of DNA-damaging drug, doxorubicin (Dox), after epidermal growth factor receptor (EGFR) signaling is suppressed. To achieve the maximum efficiency while minimizing the fast clearance and systemic toxicity, EGFR inhibitor needs to be released first while Dox is prevented from premature leakage via conjugation to a polymer to form a polymeric prodrug. In this study, we synthesized two poly(aspartic acid)-Dox prodrugs using different linkages: a stable amide bond (PAsp-Dox) and a pH-sensitive hydrazone bond (PAsp-pH-Dox). PAsp is an amino acid with a carboxylic group available at each side chain for the conjugation of many Dox molecules. Both PAsp-Dox and PAsp-pH-Dox prodrugs can be easily encapsulated in biocompatible and biodegradable poly(l-lactic acid)-polyethylene glycol (PLA-PEG) along with afatinib (Ai), which is complexed with dioleoyl phosphatidic acid (DOPA) via ion paring. By physically blending the two PAsp-Dox and PAsp-pH-Dox prodrugs at different ratios, we could get the desired programmed drug release profile. Both Dox and Ai were encapsulated inside the PLA-PEG with almost full encapsulation efficiency (EE >~90%) and high drug loadings (>~8%(wt)). The size of nanoparticles (NPs) encapsulating various different combination drugs ranges between ~70-80 nm, measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Our NP design has shown great promise for the sequential co-delivery with sustained release through results for release kinetics in phosphate-buffered saline (PBS) in pH 7.4 and 5 and In vitro cytotoxicity against three non-small cell lung carcinoma (NSCLC) cell lines, NCI-H358, NCI-H1650, and A549. This NP system can improve the therapeutic index by achieving sequential delivery with a desired time delay and reducing systemic exposure of drugs through decelerated blood clearance and high tumor accumulation.