Reversal of malignant ADAR1 splice isoform switching with Rebecsinib
Leslie Crews, Wenxue Ma, Luisa Ladel, Jessica Pham, Larisa Balaian, Kathleen Steel, Phoebe Mondala, Raymond Diep, Christina Wu, Cayla Mason, Inge van der Werf, Isabelle Oliver, Eduardo Reynoso, Gabriel Pineda, Thomas Whisenant, Peggy Wentworth, James J. La Clair, Qingfei Jiang, Michael D. Burkart, Catriona Jamieson
Abstract
Adenosine deaminase acting on RNA1 (ADAR1) preserves genomic integrity by preventing retroviral integration and retrotransposition during stress responses. However, inflammatory-microenvironment-induced ADAR1p110 to p150 splice isoform switching drives cancer stem cell (CSC) generation and therapeutic resistance in 20 malignancies. Previously, predicting and preventing ADAR1p150-mediated malignant RNA editing represented a significant challenge. Thus, we developed lentiviral ADAR1 and splicing reporters for non-invasive detection of splicing-mediated ADAR1 adenosine-to-inosine (A-to-I) RNA editing activation; a quantitative ADAR1p150 intracellular flow cytometric assay; a selective small-molecule inhibitor of splicing-mediated ADAR1 activation, Rebecsinib, which inhibits leukemia stem cell (LSC) self-renewal and prolongs humanized LSC mouse model survival at doses that spare normal hematopoietic stem and progenitor cells (HSPCs); and pre-IND studies showing favorable Rebecsinib toxicokinetic and pharmacodynamic (TK/PD) properties. Together, these results lay the foundation for developing Rebecsinib as a clinical ADAR1p150 antagonist aimed at obviating malignant microenvironment-driven LSC generation.