Targeting ADAR1 in Cancer: Biology, Therapeutic Strategies, Challenges, and Limitations.

Adenosine deaminase acting on RNA 1 (ADAR1) is a critical regulator of innate immune signaling and a pan-cancer therapeutic target. Through catalyzing adenosine-to-inosine (A-to-I) editing and editing-independent mechanisms, ADAR1 suppresses activation of dsRNA sensing pathways, including protein kinase R (PKR), melanoma differentiation-associated protein 5 (MDA5), and oligodenylate-synthetase (OAS) signaling, that are critical for maintaining cellular tolerance to endogenous RNAs. In a subset of tumors characterized by elevated interferon-stimulated gene (ISG) expression and dsRNA stress, this function creates a dependency on ADAR1 for survival, establishing a therapeutic vulnerability that can be exploited to induce viral mimicry in cancer cells and enhance anti-tumor immune responses. Here, we review the emerging landscape of ADAR1 modulators, organizing reported compounds into mechanistic classes including nucleoside analogs, catalytic inhibitors, Zα domain modulators, RNA substrate engagement inhibitors, indirect pathway regulators, and PROTACs. We evaluate molecules within these classes with a focus on their mechanisms of action and experimental validation. We further discuss the challenges associated with distinguishing direct inhibition of ADAR1 activity from broader effects on RNA metabolism and innate immune activation. Finally, we highlight the therapeutic potential of ADAR1 targeting defined cancer subsets and examine combination strategies that leverage ADAR1 inhibition for improved sensitivity to current cancer therapeutics. Overall, this review outlines key considerations for the development of selective therapies targeting ADAR1.