Abstract
Immune checkpoint blockade involves targeting immune regulatory molecules with antibodies. Preclinically, complex multi-antibody regimes of both inhibitory and stimulatory targets are a promising candidate for the next generation of immunotherapy. However, in this setting, the antibody platform may be limited due to excessive toxicity caused by off target effects as a result of systemic administration. RNA can be used as an alternate to antibodies as it can both downregulate immunosuppressive (siRNA) or induce expression of immunostimulatory (mRNA) checkpoints. In this study we demonstrate that the combination of both siRNA and mRNA in a single formulation can simultaneously knock down and induce expression of immune checkpoint targets thereby reprogramming the tumour microenvironment from immunosuppressive to immunostimulatory phenotype. To achieve this, RNA constructs were synthesized and formulated into stable nucleic acid lipid nanoparticles (SNALPs); the SNALPs produced were 140-150 nm in size with >80% loading efficiency. SNALPs could transfect macrophages and B16F10 cells in vitro resulting in 75% knockdown of inhibitory checkpoint (PDL1) expression and simultaneous express high levels of stimulatory checkpoint (OX40L) with minimal toxicity. Intratumoural treatment with the proposed formulation resulted in statistically reduced tumour growth, a greater density of CD4+ and CD8+ infiltrates in the tumour and immune activation within tumour draining lymph nodes. These data suggest that a single RNA based formulation can successfully reprogram multiple immune checkpoint interactions on a cellular level. Such a candidate may be able to replace future immune checkpoint therapeutic regimes composed of both stimulatory and inhibitory receptor targeting antibodies.
| Original language | English |
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| Journal | ACS Nano |
| Publication status | Accepted/In press - 2 Sept 2021 |
