Tetrazine-Mediated Bioorthogonally Activated Therapeutic (TBAT) Platforms.

Bioorthogonal chemistry has broadened the chemical repertoire accessible to biological systems by enabling selective transformations that operate orthogonally to endogenous biochemical processes. Among the diverse bioorthogonal reactions, tetrazine-mediated inverse-electron-demand Diels-Alder (IEDDA) chemistry has established it as a benchmark for kinetic efficiency, modularity, and biocompatibility. Beyond their classical roles in biomolecular labeling and bioimaging, tetrazine ligations have evolved into potent chemical actuators capable of governing biological functions through "click-to-function" activation as well as "click-to-release" payload deployment. Through deliberate modulation of tetrazine electronics, stereochemistry, photochemistry, and conditional masking, along with complementary dienophile engineering, this reaction manifold has been transformed into a programmable molecular switch capable of operating in complex physiological environments. Accordingly, these advances have catalyzed the emergence of tetrazine-mediated bioorthogonally activated therapeutic (TBAT) platforms to address long-standing challenges in drug delivery and precision oncology, including tumor hypoxia, "off-target" toxicity, therapeutic resistance, and insufficient subcellular targeting. Emerging applications now span organelle-specific phototherapy, sonodynamic therapy, immune receptor-guided cytotoxicity, and selective pretargeted nanomedicine, illustrating the breadth of biological contexts in which IEDDA reactivity can be precisely deployed. In this perspective, we provide a concise roadmap elucidating the evolution of tetrazine chemistry from a rapid bioconjugation reaction to a programmable molecular activation platform, emphasizing its potential toward targeted and precision-guided cancer therapies. We delineate the current state-of-the-art in TBAT platforms, highlighting pioneering advances across prodrug activation, photo and sonodynamic therapies, drug delivery, and pretargeted nanomedicine, and discuss how rational control over tetrazine-dienophile reactivity enables precision intervention in therapeutic pathways within complex biological environments.