{
  "abstract": "Background Antibody-drug conjugates (ADCs) and immune checkpoint inhibitors (ICPi), such as anti-PD-1 antibodies, represent significant advancements in cancer therapy. Their combination holds substantial promise to enhance anti-tumor efficacy, but traditional immunodeficient xenograft models often fall short in adequately evaluating ADC-mediated immune responses and assessing target-related toxicity. To address these limitations, Crown Bioscience has developed a series of humanized engineered syngeneic mouse models expressing various human tumor-associated antigens (hTAAs) offering an ideal setting for assessing ADC drugs and IO drug combinations.In this study, anti-PD1 combinations were assessed with T-Dxd (trastuzumab deruxtecan) and enfortumab vedotin ADCs across wild-type (WT) and humanized engineered syngeneic mice, with parallel evaluation of human tumor antigen retention and immune cell profiles.Methods Surface expression of human Her2 or Nectin-4 on MC-38 engineered cells was validated via flow cytometry pre-/post-inoculation. For In vivo, 5×106 cells were subcutaneously inoculated into C57BL/6-hHer2, C57BL/6-hNectin4, or WT mice. Tumor-bearing mice received T-Dxd or enfortumab vedotin monotherapy, or combination therapy with anti-PD1.Results The low human HER2-expressing MC38-hHER2 clone #18 (~8×10 4 molecules/cell) grew well in both C57BL/6 WT and C57BL/6-hHER2 mice but exhibited higher antigen retention in hHER2 mice (~3×104 vs. ~1×104 molecules/cell).The high-expressing MC38-hHER2 clone #2 (~5×105 molecules/cell) only grew in hHER2 mice, retaining ~2×105 molecules/cell. Combination therapy of T-DXd (10 mg/kg) with anti-PD-1 (3 mg/kg) demonstrated marked synergy in WT mice bearing MC38-hHER2 #18 tumors, achieving complete responses in 7/8 mice. Immunoprofiling revealed anti-PD-1 monotherapy substantially increased T-cell tumor infiltration, whereas the combination group showed elevated central memory CD8 + T cells (TCM) and naïve CD8+T cells (TN) alongside reduced exhausted CD8+T cells, with re-challenge studies confirming long-term immune memory. In the hHER2 mice bearing MC38-hHer2 #2 cells, synergistic efficacy with T-Dxd (2.5 mg/kg + 1 mg/kg, QW) and anti-PD1 (1.5 mg/kg, BIW) occurred in both small (~100 mm³) and large (~500 mm³) tumors, accompanied by significantly increased TILs and CD8+ naive T cells (TN). Robust synergy was also observed when combining enfortumab vedotin with anti-PD1 in hNectin-4- engineered syngeneic models.Conclusions hTAA humanized syngeneic mouse models, retaining an intact immune system, serve as effective preclinical platforms for evaluating ADC and immune checkpoint inhibitor combinations. Compared to wild-type mice, humanized engineered mice demonstrate superior antigen retention capacity. Furthermore, syngeneic models engineered to express human tumor-associated antigens (hTAA) can exhibit biodistribution and pharmacodynamic properties different from their wild-type counterparts, potentially leading to differences in toxicity and therapeutic response.",
  "authors": [
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Sylvia Xiaoze Wang"
    },
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Lily Rong Wang"
    },
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Kaixia Lian"
    },
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Rongfei Lu"
    },
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Jun Zhou"
    },
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Ludovic Bourre"
    },
    {
      "affiliations": [
        "Crown Bioscience Inc. San Diego, CA, USA"
      ],
      "name": "Jessie Wang"
    }
  ],
  "title": "714 Humanized engineered syngeneic mouse models for ADC/IO combination evaluation",
  "uid": "579c32e9-29b7-5261-94d5-d12529a263bc"
}