{
  "abstract": "Background Adenosine deaminase acting on RNA 1 (ADAR1) facilitates the conversion of adenosine (A) to inosine (I) in double-stranded RNAs (dsRNAs) through hydrolytic deamination. ADAR1 exists in two isoforms: nuclear p110 and p150, which shuttles between the nucleus and cytoplasm. The p150 isoform, driven by an interferon (IFN)-responsive promoter, features a Z-DNA/Z-RNA binding domain at its N-terminus. ADAR1 p150 contributes to immunotherapy resistance by suppressing immunogenic dsRNAs, including those from endogenous retroviral elements, and preventing the accumulation of Z-RNA elements. Depletion of ADAR1 leads to activation of ZBP1 by the Z-RNA and triggers necroptosis. As ADAR1 promotes tumor cell survival and immune evasion in various cancers, inhibiting ADAR1 p150 offers potential as a standalone or combination therapy for enhancing anti-tumor effects. Here, we describe the identification of a novel first-in-class Zα-targeted ADAR1 p150 inhibitor for cancer immunotherapy.Methods A series of ADAR1 p150 inhibitors (AVA-ADR) were identified using a high-throughput binding assay. Binding against Zα domain was confirm against in-house developed FRET based binding assay. Their ability to induce interferon responses was validated across multiple cell lines, with on-target effects confirmed via downstream PKR activation. The anti-tumor efficacy of AVA-ADR-001 was assessed in a B16F10 syngeneic melanoma mouse model, both as a monotherapy and in combination with anti-PD-1 therapy.Results We identified novel series of small-molecule inhibitor of ADAR1 p150 that elicits a robust interferon response in an MDA5-dependent manner. Binding studies revealed that the AVA-ADR compound series exhibits submicromolar affinity for the Zα-domain, surpassing the binding strength of earlier inhibitors. ADME and pharmacokinetic analyses confirmed favorable PK profiles and oral bioavailability. AVA-ADR inhibitors displayed micromolar EC50 values and significant anti-tumor activity in the B16F10 melanoma model. In vivo studies demonstrated 48% tumor growth inhibition (TGI) with AVA-ADR-001 monotherapy, compared to 35% TGI with anti-PD-1 alone. Combination therapy with AVA-ADR-001 and anti-PD-1 achieved a synergistic 60% TGI. Tumor samples from the combination group showed significantly elevated expression of interferon-stimulated genes and T-cell activation markers. Selective degradation of ADAR1 p150 was confirmed using a PROTAC derivative of the inhibitor, validating cellular target engagement.Conclusions To our knowledge, AVA-ADR series represent the first reported small-molecule inhibitors targeting the Zα domain of ADAR1 p150. Second-generation AVA-ADR compounds are stable, orally bioavailable, first-in-class ADAR1 inhibitors that induce robust interferon responses both in vitro and in vivo. These inhibitors achieve substantial tumor growth inhibition as a monotherapy and demonstrate synergistic efficacy when combined with anti-PD-1 therapy.",
  "authors": [
    {
      "affiliations": [
        "Avammune Lifesciences Pvt. Ltd, Bangalore, Karnataka, India"
      ],
      "name": "Avijit Goswami"
    },
    {
      "affiliations": [
        "Aten Porus Lifesciences, Levittown, PA, USA"
      ],
      "name": "Sandeep Goyal"
    },
    {
      "affiliations": [
        "Avammune Therapeutics Inc., Levittown, PA, USA"
      ],
      "name": "Princy Khurana"
    },
    {
      "affiliations": [
        "Avammune Therapeutics Inc., Levittown, PA, USA"
      ],
      "name": "Kawaljit Singh"
    },
    {
      "affiliations": [
        "Avammune Therapeutics Inc., Levittown, PA, USA"
      ],
      "name": "Aditya Kulkarni"
    }
  ],
  "title": "1179 Discovery of a first-in-class ADAR1 p150 inhibitor targeting the Zα-domain with potent anti-tumor efficacy in syngeneic mouse models",
  "uid": "bd69e0b7-b42d-566c-8631-d3bee287adf4"
}