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Endosomolytic polymersomes increase the activity of cyclic dinucleotide STING agonists to enhance cancer immunotherapy


Cyclic dinucleotide (CDN) agonists of stimulator of interferon genes (STING) are a promising class of immunotherapeutics that activate innate immunity to increase tumour immunogenicity. However, the efficacy of CDNs is limited by drug delivery barriers, including poor cellular targeting, rapid clearance and inefficient transport to the cytosol where STING is localized. Here, we describe STING-activating nanoparticles (STING-NPs)—rationally designed polymersomes for enhanced cytosolic delivery of the endogenous CDN ligand for STING, 2′3′ cyclic guanosine monophosphate–adenosine monophosphate (cGAMP). STING-NPs increase the biological potency of cGAMP, enhance STING signalling in the tumour microenvironment and sentinel lymph node, and convert immunosuppressive tumours to immunogenic, tumoricidal microenvironments. This leads to enhanced therapeutic efficacy of cGAMP, inhibition of tumour growth, increased rates of long-term survival, improved response to immune checkpoint blockade and induction of immunological memory that protects against tumour rechallenge. We validate STING-NPs in freshly isolated human melanoma tissue, highlighting their potential to improve clinical outcomes of immunotherapy.

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The data that support the findings of this study are available from the corresponding author upon reasonable request.

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We thank K. Rock for providing the DC2.4 cells, C. Duvall for use of the gel permeation chromatography equipment and in vivo imaging system, A. Richmond and A. Vilgelm for consultation on flow cytometry protocols, and J. Rhoades and A. Merkel for technical advice on tumour models. We thank the Koch Institute Swanson Biotechnology Center (specifically the Nanotechnology Materials Core Facility) for technical support on the cryogenic electron microscopy, the core facilities of the Vanderbilt Institute of Nanoscale Science and Engineering for use of dynamic light scattering and transmission electron microscope instruments, the VUMC Flow Cytometry Shared Resource (supported by the Vanderbilt-Ingram Cancer Center (VICC) (P30 CA68485) and Vanderbilt Digestive Disease Research Center (DK058404)) for the use of BD three-laser LSRII and BD five-laser LSRFortessa flow cytometers, the Vanderbilt Translational Pathology Shared Resource (supported in part by NCI/NIH Cancer Center Support Grant 5P30 CA684850-19) and the Vanderbilt Technologies for Advanced Genomics. 2′3′-cGAMP was provided by the Vanderbilt Institute of Chemical Biology Chemical Synthesis Core. This research was supported by grants from the National Science Foundation (1554623 to J.T.W.), Alex’s Lemonade Stand Foundation (SID924 to J.T.W.), the National Institutes of Health (K23 CA204726/CA/NCI to D.B.J., R00CA181491 to J.M.B. and 5R35GM119569-03 to M.A.), the VICC (Support Grant P30 CA68485 and VICC Ambassador Discovery Grant to M.A., and VICC-Vanderbilt Center for Immunobiology Pilot Grant to J.T.W.), the Melanoma Research Alliance (503565 to J.T.W.) and Stand Up To Cancer (SU2C) (Innovative Research Grant, grant no. SU2C-AACR-IRG 20-17 to J.T.W.). SU2C is a division of the Entertainment Industry Foundation. Research grants are administered by the American Association for Cancer Research, the scientific partner of SU2C.

Author information

D.S. and J.T.W. conceived of and designed the experiments. D.S. performed the majority of the experiments and data analysis. K.W.B. created the ISRE luciferase reporter B16.F10 cells used for longitudinal in vivo experimentation and assisted with tumour therapy studies. P.C. synthesized and characterized 2′3′-cGAMP. D.S.Y. and A.K.R.L.-J. obtained cryogenic transmission electron micrographs of nanoparticles. S.S. synthesized and characterized the PDSMA monomer. M.A. assisted with experimental design and cGAMP characterization. M.K. and D.B.J. provided resected tumour samples from melanoma patients. J.M.B. provided guidance on, and assisted with, the NanoString experiments and analysis of multiplexed gene expression data. D.S. and J.T.W. wrote the manuscript.

Competing interests

J.T.W. and D.S. are inventors on a pending patent related to the technology described in this manuscript. D.B.J. serves on the advisory board for Bristol-Myers Squibb and Merck, and receives research support from Bristol-Myers Squibb that is unrelated to this manuscript. J.M.B. receives research funding from Bristol-Myers Squibb, Genentech and Incyte, receives consulting and expertise testimony compensation from Novartis, and has patents pending concerning the use of HLA-DR as a predictive marker in immunotherapy responses.

Correspondence to John T. Wilson.

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Further reading

Fig. 1: Design, optimization and characterization of STING-NPs.
Fig. 2: STING-NPs enhance the delivery and immunostimulatory activity of cGAMP in the TME.
Fig. 3: STING-NPs shift the immunocellular composition of the tumour microenvironment.
Fig. 4: STING-NPs enhance the immunotherapeutic efficacy of cGAMP and synergize with ICB.
Fig. 5: STING-NPs enhance cGAMP activity in human metastatic melanoma.