PROJECT SUMMARY/ABSTRACT
This research will utilize spherical nucleic acid (SNA) nanostructures to develop effective, structure-informed
vaccines for advanced melanoma. Traditional treatments (i.e. chemotherapy or radiation) are less successful for
melanoma because of difficulties in discerning melanoma cells phenotypically. Immunotherapeutics must ensure
that melanoma—with a high mutational burden—cannot easily evade the immune system. SNAs can function
as robust cancer vaccines through the precise control over the presentation of multiple melanoma-associated
targets to immune cells which lowers its potential for immune evasion. SNAs are composed of a nanoparticle
core with a dense radial shell of nucleic acids. When synthesized using immunostimulatory “adjuvant”
oligonucleotides, SNAs induce immune responses. Indeed, this adjuvant only structure demonstrates the
enhanced responses generated from a 3D structure compared to linear adjuvant and forms the basis of an
ongoing Phase 1b/2 clinical trial. We have exploited the ease of chemical synthesis and modular architecture of
SNAs, and synthesized them to include both adjuvant and a single tumor-associated peptide (“antigen”). These
structures enhance antitumor responses and provide long-term protective immunity in model systems, and in
particular, there is a strong relationship between vaccine structure and efficacy. In our proposed work, we aim
to develop SNA vaccines against melanoma by precisely incorporating and presenting multiple
immunostimulatory cues to the immune system. SNAs will be synthesized with multiple clinically-relevant
melanoma antigens (MHC-I and -II restricted, tumor-associated, neoantigens), with structural variations in how
the adjuvant and antigen are presented. Control over structure, combined with in vitro and in vivo evaluations of
immunostimulation, will elucidate structure-activity relationships that will inform the future of cancer vaccine
design. Using structure to control the presentation of multiple immune system cues has the power to elevate
immune responses to melanoma and improve clinical outcomes. In Aim 1, we will synthesize SNAs containing
multiple antigens and varied stabilities to enhance antigen-specific T cell responses. We will analyze their uptake
by immune cells, subcellular trafficking of the SNA components, and kinetics of activation of multiple pathways
(e.g. antigen presentation, co-stimulatory marker expression). In Aim 2, we will compare different administration
routes and analyze in vivo biodistribution and uptake kinetics, as well as the antigen-specific immune responses
raised by SNAs in immunocompetent mice. We will assess raised responses after delivery of SNAs containing
human antigens to humanized mice and patient specimens. In Aim 3, we will evaluate SNA antitumor efficacy in
vivo alone and in combination with immune checkpoint blockade, and identify SNAs as candidates for further
preclinical studies and clinical translation. Significantly, this approach will generate a structure-based
understanding of SNA performance as vaccines, and improve immunotherapy by generating a breadth of T cell
responses with superior efficacies.
