{
  "abstract": "Background Interleukin-18 (IL-18) is a potent proinflammatory cytokine that drives IFN-γ-mediated anti-tumor immunity but is sequestered in many cancers by its high-affinity decoy, IL-18 binding protein (IL-18BP). IL-18BP localizes at the invasive tumor-stromal interface, forming a spatially restricted immunosuppressive barrier, particularly in immune-excluded or checkpoint-resistant tumors. We hypothesized that direct blockade of IL-18BP with a compact heavy-chain antibody would restore endogenous IL-18 signaling, trigger adaptive checkpoint upregulation, and thereby create a microenvironment primed for novel checkpoint inhibitor combinations and rationale for bi-specific designs.Methods Colon cancer samples were examined for IL-18, IL-18BP, and IL-18R expression by immunohistochemistry. We engineered a panel of high-affinity single-domain (VHH) antibodies targeting IL-18BP and validated their neutralization in vitro. Lead candidate CFX-887, a fully humanized candidate was evaluated across multiple syngeneic models (MC38, B16F10, and LLC1) measuring tumor growth inhibition, IFN-γ cytokine levels, single-cell RNA sequencing, and FACS-based immune profiling of tumors, tumor-draining lymph nodes, and the spleen.Results In human colon adenocarcinomas (mismatch repair-proficient, KRAS/NRAS/BRAF wild-type), IL-18BP was heterogeneously expressed, peaking at the invasive tumor-stromal interface, and inversely correlating with IL-18 levels. In vitro, CNFX887-Fc neutralized IL-18BP to restore IL-18 signaling, driving CD8+, CD4+, and NKT cell proliferation, enhancing NK- and T-cell cytotoxicity via IFN-γ, and upregulating PD-L1 expression ~3-fold. In syngeneic models (MC38, B16F10, LLC1), CNFX887-Fc monotherapy slowed tumor growth by 2.0-2.5x, remodeling the TME and boosting IFN-γ, promoting M1 macrophage polarization, enhancing DC co-stimulation, and reducing T-cell exhaustion. When combined with anti-PD-L1 or recombinant IL-18, we saw further amplification of cytotoxic T and NK cell proliferation, CXCR3-dependent lymph node trafficking, and a coordinated surge in adaptive checkpoint molecules. Single-cell RNA-seq confirmed upregulation of inflammatory chemokines and interferon-stimulated genes alongside depletion of suppressive myeloid subsets. Unlike recombinant IL-18 alone, IL-18BP blockade selectively reactivated endogenous cytokine pools with improved safety.Conclusions Our findings establish that IL-18BP forms a strategic immunosuppressive barrier, precisely at the tumor-immune boundary. Targeting IL-18BP in combination therapy (or bi-specific design) results in sustained and durable IL-18-driven IFN-γ converting an immunologically cold microenvironment into an inflamed one. These findings justify further development of our optimized IL-18BP-targeted biologics with favorable tumor penetration and safety profiles and bispecific formats as a novel strategy to broaden the efficacy of cancer immunotherapy.",
  "authors": [
    {
      "affiliations": [
        "Pledge Therapeutics, Canton, MA, USA"
      ],
      "name": "Xue Yao"
    },
    {
      "affiliations": [
        "Pledge Therapeutics, Leuven, Flanders, Belgium"
      ],
      "name": "Onno Akkermans"
    },
    {
      "affiliations": [
        "Massachusetts Institute of Technology, Cambridge, MA, USA"
      ],
      "name": "Vipul Chitalia"
    },
    {
      "affiliations": [
        "Pledge Therapeutics, Leuven, Flanders, Belgium"
      ],
      "name": "Stephen D Weeks"
    },
    {
      "affiliations": [
        "Pledge Therapeutics, Canton, MA, USA"
      ],
      "name": "Ali H Munawar"
    }
  ],
  "title": "1274 IL-18BP inhibition elicits adaptive checkpoint expression and enables novel immune-checkpoint inhibitor (ICI) combinations in colon cancer",
  "uid": "1ca87dc9-51b8-5e5e-ba4b-ba01a3a1daf5"
}