Abstract Details

G2 - Immune Targeting and Approaches with Genetically-Modified Cells and Cell Therapies (Including CAR-T, CAR-NK, TCR editing)

824: Sensitizing Solid Tumors to CAR-Mediated Immunity by Lipid Nanoparticle Delivery of Synthetic Antigens

Type: Poster Session

Poster Board Number: 824

Presentation Details

Session Title: Wednesday Posters: Immune Targeting and Approaches with Genetically-Modified Cells and Cell Therapies






Despite the therapeutic efficacy of chimeric antigen receptor (CAR) T cells to treat certain hematological malignancies, their clinical success against solid tumors remains limited. Technical challenges associated with the identification of neoantigens characteristic of individual tumors - along with the need to engineer and validate CARs or TCRs against new targets - are significant bottlenecks to achieving therapeutic efficacy across tumor types. Additionally, identifying targetable tumor-associated antigens (TAA) remains challenging as heterogenous antigen expression, low antigen density, and antigen loss reduce CAR T cell efficacy and raise concerns with antigen escape. Expression of CAR antigens at low-levels in healthy tissue also pose safety concerns arising from on-target off-tumor toxicities. T cells targeting solid TAAs (e.g., HER2), for example, show cross-reactivity with healthy cells in vital organs that limit safe and effective clinical translation. Collectively, these limitations underscore the need to develop strategies that reduce the bottleneck of antigen selection and enable CAR T cell recognition of tumors otherwise lacking targetable antigens.
Here, we developed synthetic antigens to sensitize solid tumors to CAR T cell mediated immunity agnostic to a tumor’s endogenous antigen expression profile. We repurposed a xenogeneic protein, the antigen binding fragment of the heavy-chain-only camelid antibodies (VHH), as a synthetic antigen. We deliver VHH as an mRNA-encoded synthetic antigen using lipid nanoparticles (LNPs) and demonstrate stable expression on the surface of various tumor types - including breast, colon, lung, prostate, and brain cancer - which subsequently led to recognition and killing by αVHH CAR T cells (Fig. 1A-B). Moreover, we show that αVHH CARs are well tolerated based on the measurement of cytokine release in a coculture of human αVHH CARs T cells with PBMCs as well as serum chemistry analysis in naïve C57BL/6J mice up to 100 days following adoptive transfer of murine αVHH CARs T cells. Adoptive transfer of αVHH CAR T cells to mice bearing VHH-treated tumors reduced tumor burden in multiple syngeneic and xenograft models of cancer, improved survival, induced epitope spread, prevented tumor growth after rechallenge, and mitigated antigen escape in heterogenous tumors (Fig. 1C-D). Our data show that sensitizing tumors to CAR-mediated cytotoxicity using synthetic antigens can potentiate antitumor immunity and improve responses against solid tumors.
Caption: Fig. 1 | (A) Following LNP-mediated synthetic antigen delivery, tumor cells express VHH and become sensitized to killing by αVHH CAR T cells. (B) Cytotoxicity of MDA-MB-468 tumor cells following coincubation with untransduced (UTD) or αVHH CAR T cells at various VHH-LNP doses. 2-way ANOVA, mean ± s.e.m., n=4. (C) Mice bearing a heterogenous tumor mixture comprised of 85% HER2- and 15% HER2+ tumor cells were treated with i.t. with either saline or VHH-LNP followed by transfer of αVHH or αHER2 CAR T cells (D) Tumor growth curves of following i.t. treatment with with saline or VHH-LNP and systemically with indicated T cells. 2-way ANOVA, mean ± s.e.m. n= 4-5.

Lena Gamboa¹, Ali Zamat¹, Chloé Thiveaud¹, Hee Jun Lee¹, Zizhen Zha¹, Elif Kulaksizoglu¹, Noah Campbell¹, Ching Shen Chan¹, Sydney Fábrega¹, Abbey Oliver¹, Fang-Yi Su¹, Hathaichanok Phuengkham¹, Daryll Vanover¹, Hannah Peck¹, Anirudh Sivakumar¹, Shreyas Dahotre¹, Adrian M. Harris¹, Philip Santangelo², Gabriel A. Kwong<sup>1

1</sup>Georgia Institute of Technology, Atlanta, GA,²Georgia Tech, Atlanta, GA"