{
  "abstract": "Background Human trophoblast cell surface antigen 2 (hTROP2), a transmembrane glycoprotein encoded by the Tumor Associated Calcium Signal Transducer 2 (TACSTD2) gene, is primarily expressed in trophoblasts and minimally in a few adult tissues. In various cancers, hTROP2 is overexpressed, making it a promising target for cancer immunotherapy. Here, we developed hTROP2 protein and circular mRNA-lipid nanoparticle (circRNA-LNP) vaccines and evaluated their efficacy in activating cellular immunity and suppressing hTROP2+ tumors in mice.Methods Recombinant protein antigens, consisting of hTROP2 fragments with or without immune enhancers, were produced in E. coli and 293T cells. The circRNA-LNP vaccine was prepared using standard in vitro transcription, circularization, and LNP-packaging methods. Mice were vaccinated with either protein antigen adjuvanted with a mixture of Poly(I:C) and Complete/Incomplete Freund’s Adjuvant by subcutaneous injection once a week for seven weeks or circRNA-LNP by one or two intramuscular injections. Cellular immunity was assessed by the INFγ ELISpot assay using splenocytes. Anti-cancer efficacy was evaluated by monitoring tumor growth of TROP2-humanized mouse cancer cells, MC38-hTROP2 or 4T1-hTROP2, inoculated subcutaneously in mice that received vaccine or control.Results hTROP2 vaccines demonstrated robust activity in activating cellular immunity in both wildtype and several HLA-I allele-humanized transgenic mice. Two highly immunogenic fragments, T1 and T2, were identified in these mice. hTROP2 protein vaccine inhibited the growth of MC38-hTROP2 tumors in C57BL6 mice by 80% and completely suppressed the growth of 4T1-hTROP2 tumors in BABL/c mice. In MC38-hTROP2 tumors collected from the vaccinated mice, the percentage of CD8α+/IFNγ+ T-cells was increased significantly albeit the cell number of CD8α+ T-cells remained unchanged, indicating that anti-tumor cytotoxicity was activated. hTROP2 circRNA-LNP vaccine achieved complete tumor inhibition in both MC38-hTROP2 and 4T1-hTROP2 tumor models.Conclusions hTROP2 vaccines effectively produce and present mouse and human MHC-I peptides, to activate cellular immunity in mouse models, leading to complete or near-complete hTROP2+ tumor suppression. hTROP2 vaccines, consisting of multiple epitopes for broad applicability across HLA variants, are promising for further development to treat TROP2+ cancers in humans.Ethics Approval All animal studies mentioned in this abstract were approved by Institutional Animal Care and Use Committee of CK Life Sciences Limited. The protocols of immunization and anti-cancer study were approved with the protocol number of 2023-01 and 2023-02, respectively. The period of these two protocols is from 5th Jan, 2024 to 4th Jan, 2027.",
  "authors": [
    {
      "affiliations": [
        "CK Life Sciences Development Limited, Hong Kong, Hong Kong"
      ],
      "name": "Zirong He"
    },
    {
      "affiliations": [
        "CK Life Sciences Development Limited, Hong Kong, Hong Kong"
      ],
      "name": "Fanyan Meng"
    },
    {
      "affiliations": [
        "CK Life Sciences Development Limited, Hong Kong, Hong Kong"
      ],
      "name": "Chi Han Samson Li"
    },
    {
      "affiliations": [
        "CK Life Sciences Development Limited, Hong Kong, Hong Kong"
      ],
      "name": "Nansheng Kenneth Lin"
    },
    {
      "affiliations": [
        "CK Life Sciences Development Limited, Hong Kong, Hong Kong"
      ],
      "name": "Melvin Toh"
    },
    {
      "affiliations": [
        "CK Life Sciences Development Limited, Hong Kong, Hong Kong"
      ],
      "name": "Hong Wang"
    }
  ],
  "title": "1172 Human TROP2 protein and circRNA vaccines inhibit tumor growth in TROP2-humanized mouse models",
  "uid": "a8371430-b7a4-5f73-b15c-36a3a7c9b5ab"
}