Regulatable In Vivo Gene Expression via Adaptamers.

Precise, reversible control of transgene expression is essential for safe and durable gene therapy, yet current inducible systems remain difficult to translate in vivo due to large size, limited induction duration, and dependence on immunogenic regulators. Here we present the adaptamer (ADAR modulatable aptamer), a compact (<120 bp) RNA switch that couples an FDA-approved small-molecule-responsive aptamer with endogenous ADAR-mediated RNA editing to regulate expression. Ligand binding stabilizes a double-stranded RNA structure that recruits ADAR to convert a stop codon into a sense codon, restoring downstream protein translation. This cleavage-free, post-transcriptional mechanism enables precise, small-molecule-dependent modulation without exogenous protein machinery. We demonstrate that adaptamers are highly functional across multiple cell lines, including human T-cells. In mice, AAV-delivered adaptamer-controlled FGF21 expression induced metabolic remodeling, significantly increasing energy expenditure and reversing obesity. This minimal, programmable system offers a clinically compatible approach for tunable genetic medicines and safe deployment of pleiotropic and dose-limited proteins.