Abstract 1607: Durable efficacy and anti-cancer immunity following intratumoral administration of messenger RNAs encoding IL-36γ, IL-23 and OX40L
Authors: Frederick Josh P. , Bai Ailin , Hewitt Susannah , Karp Russ , Zielinski John , Ichikawa Kana , Apte Ameya , Bailey Dyane , Arnold Kristen , Farlow Sam , Potz Darren , Ying Bo , MacLean Graham , Benenato Kerry , Sedic Maja , Kelsey Steve M. 
Published: July 2017

Abstract
Immunologic responses to cancer involve complex interactions of cells within the tumor microenvironment (TME). These interactions are mediated in part through co-stimulatory and inhibitory transmembrane proteins, cytokines and chemokines. Direct intratumoral (ITu) administration of messenger RNA results in synthesis of proteins that can prime and enhance an anti-cancer immune response. Priming, expansion and migration of anti-cancer T-cell clones may also result in a systemic or ‘abscopal’ response in distal lesions. There is mounting preclinical evidence that OX40-OX40L signaling boosts anti-cancer immunity via co-stimulatory activity on T-cells. We generated mRNA constructs encoding OX40L with miR-122 binding sites that have been shown to suppress protein translation in hepatocytes yet not within tumor cells. A single ITu injection of OX40L mRNA, formulated in a lipid nanoparticle, resulted in transfection of up to 25% of live tumor cells, predominantly cancer and myeloid cells. OX40L protein persisted for 7 days after mRNA injection, and a resulting increase in tumor T-cells was observed. Repeat dosing of OX40L mRNA induced complete responses in a model that is sensitive to immune-meditated therapies, such as anti-PD1/PD-L1 blockade, yet was ineffective in a related model that might better represent an immunologically barren or immunosuppressive TME. The OX40L-resistant tumor model was also resistant to anti-PD1 treatment and was shown to contain fewer infiltrating immune cells. As this model may represent a subset of human cancers that do not respond well to checkpoint inhibitors, it was used to test various mRNA constructs designed to cooperatively harness components of both the innate and adaptive immune systems in igniting a productive anti-cancer response. Both IL-36γ and IL-23 have established roles in mediating immune responses in humans and have been implicated in driving various inflammatory diseases. IL-36γ activates innate immune cells and promotes Th1 responses, whereas IL-23 has been implicated in Th1/Th17 immunity as well as in the modulation of antigen presenting cells. Repeated weekly intratumoral co-administration of mRNAs encoding IL-23 and IL-36γ resulted in durable complete responses in both anti-PD1-sensitive and -resistant tumors in a synergistic fashion. A further modest improvement in outcomes was observed when the IL-23/36γ mRNA doublet was co-administered with OX40L mRNA. Further pharmacodynamic and mechanism of action studies with this combination are underway. ITu injection of mRNA encoding combinations of co-stimulatory proteins and cytokines represents a novel platform for cancer immunotherapy, and may be able to induce responses in patient tumors that are resistant to checkpoint inhibition. The co-formulated combination of mRNAs encoding human OX40L, IL-23 and IL-36γ is planned to enter clinical trials in 2017.
Citation Format: Josh P. Frederick, Ailin Bai, Susannah Hewitt, Russ Karp, John Zielinski, Kana Ichikawa, Ameya Apte, Dyane Bailey, Kristen Arnold, Sam Farlow, Darren Potz, Bo Ying, Graham MacLean, Kerry Benenato, Maja Sedic, Steve M. Kelsey. Durable efficacy and anti-cancer immunity following intratumoral administration of messenger RNAs encoding IL-36γ, IL-23 and OX40L [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1607. doi:10.1158/1538-7445.AM2017-1607