pH-Sensitive Nanodrug Carriers for Codelivery of ERK Inhibitor and Gemcitabine Enhance the Inhibition of Tumor Growth in Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC), a metabolic disorder, remains one of the leading cancer mortality sources worldwide. An initial response to treatments, such as gemcitabine (GEM), is often followed by emergent resistance reflecting an urgent need for alternate therapies. The PDAC resistance to GEM could be due to ERK1/2 activity. However, successful ERKi therapy is hindered due to low ligand efficiency, poor drug delivery, and toxicity. In this study, to overcome these limitations, we have designed pH-responsive nanoparticles (pHNPs) with a size range of 100-150 nm for the simultaneous delivery of ERKi (SCH 772984) and GEM with tolerable doses. These pHNPs are polyethylene glycol (PEG)-containing amphiphilic polycarbonate block copolymers with tertiary amine side chains. They are systemically stable and capable of improving in vitro and in vivo drug delivery at the cellular environment's acidic pH. The functional analysis indicates that the nanomolar doses of ERKi or GEM significantly decreased the 50% growth inhibition (IC50) of PDAC cells when encapsulated in pHNPs compared to free drugs. The combination of ERKi with GEM displayed a synergistic inhibitory effect. Unexpectedly, we uncover that the minimum effective dose of ERKi significantly promotes GEM activities on PDAC cells. Furthermore, we found that pHNP-encapsulated combination therapy of ERKi with GEM was superior to unencapsulated combination drug therapy. Our findings, thus, reveal a simple, yet efficient, drug delivery approach to overcome the limitations of ERKi for clinical applications and present a new model of sensitization of GEM by ERKi with no or minimal toxicity.