Novel nanoparticles mediate efficient siRNA/mRNA co-delivery to melanoma

Checkpoint immunotherapy has revolutionized treatment for patients with advanced or metastatic melanoma; however, many patients’ tumors either fail to respond or develop secondary resistance. As a result, there is an urgent need for an off-the-shelf local treatment that can improve therapeutic outcomes by increasing immune activation and reducing immunosuppressive factors. We developed a library of novel lipophilic poly(beta-amino ester) (PBAE)-based biodegradable nanoparticle (NP) formulations with different backbone, sidechain, and endcap monomers and various lipophilic/linear ratios to efficiently co-deliver mRNA and siRNA to melanoma cells in a single formulation. Optimized NPs formulated for co-delivery of mCherry mRNA and siRNA against GFP can engender 91.4% knockdown of GFP and 99.7% expression of mCherry in GFP expressing B16F10 melanoma cellsin vitro. We further confirmed that the NPs could deliver therapeutic constructs to melanoma cells; delivery of mRNA for IFNγ led to robust expression in vitro and delivery of siRNAs against PD-L1 and STAT3 led to efficient knockdown using the same NP formulation. Top formulations from in vitro screening were also tested in a B16F10 mouse melanoma model in vivo with optimized NPs delivering luciferase mRNA. Luminescent signal in melanoma tumors with the top four lipophilic formulations ranged from 5.7- to 16.7-fold over background 12h following intratumoral injection, demonstrating robust transfection in vivo. In conclusion, these novel lipophilic PBAE NPs mediate efficient mRNA/siRNA co-delivery to melanoma and represent a promising therapeutic platform for immune modulation and combination immunotherapy.