A central goal of genetic therapies, including RNA-based medicines, is to develop vectors that enable clinical translation for the treatment of specific cell types. T cells provide a unique opportunity for genetic medicines, particularly in their relevance to CAR-T cell therapies, autoimmune diseases, and vaccines. However, T cells are notoriously difficult to transfect, and many RNA delivery vectors are designed with model systems that may not reflect true T cell morphology, compounding the difficulty in isolating trends in particle properties that promote efficacy. Here, we use primary human T cell populations and leverage design of experiment to optimize a lipid nanoparticle (LNP)-based delivery vector for genetic therapies in T cells. In doing so, we discern key trends in LNP composition that promote better efficacy in both the uptake and expression of mRNA, namely, that high cholesterol and low polyethylene glycol (PEG) compositions aid in the efficacy of the LNPs. Informed by these trends, our novelcell RNAxpression andctivity (TEA) LNP platform represents a strategy for transfection of primary human T cells. These TEA LNPs are investigated for their mechanism of efficacy, synergy with clinically relevant latency reversal agents, and T cell subtype affinity. Taken collectively, we not only highlight key trends in formulation design for T cells and provide a platform optimized for human T cells, but also more broadly highlight the value in leveraging genetic therapies for the treatment of disease. T E A
