D-2 is a novel, custom-synthesized ionizable cationic lipid that serves as the core functional component of the targeted lipid nanoparticle (LNP) delivery system. Its key function is to enable the efficient in vivo delivery of therapeutic mRNAs. Under acidic conditions, it ionizes to a positive charge, allowing it to complex with and encapsulate the negatively charged mRNAs encoding the anti-FAP CAR and Lgmn protease. At physiological pH, it returns to a neutral state, which helps reduce systemic toxicity and is crucial for promoting the release of the mRNA payload inside the target macrophages within the infarcted heart. As part of the optimized LNP formulation, D-2 is fundamental for achieving high transfection efficiency, thereby enabling the in situ generation of efferocytosis-boosted CAR-Ms to treat cardiac fibrosis.
