Genetic Engineering of Transfusable Platelets with mRNA-Lipid Nanoparticles is Compatible with Blood Banking Practices

• Donor platelets can be directly genetically modified in plasma and platelet additive solution using mRNA-lipid nanoparticles.

• mRNA-LNP transfection is scalable to physiological and supraphysiological platelet concentrations, and engineered platelets can be stored.

Platelets contribute to a variety of physiological processes including inflammation, sepsis and cancer. However, due to their primary role in hemostasis, platelet transfusions are largely restricted to managing thrombocytopenia and bleeding. One way to expand the utility of platelet transfusions would be to genetically engineer donor platelets with new or enhanced functions. We have previously shown that lipid nanoparticles containing mRNA (mRNA-LNP) can be used to genetically modify authentic platelets in a non-clinical crystalloid solution. Currently, platelets collected for transfusion are stored in plasma or in plasma supplemented with platelet additive solution (PAS) at supraphysiological concentrations at room temperature, or at 4 ºC if intended for use in acute hemorrhage. Here we describe a new plasma-optimized mRNA-LNP for transfecting platelets directly in plasma and plasma supplemented with PAS that is scalable to physiological and supraphysiological platelet concentrations. Transfecting platelets in clinical solutions with mRNA-LNP does not affect aspects of in vitro physiology, and transfected platelets are storable. The compatibility of this transfection system with current clinical practices could enable future mRNA-LNP based platelet products and cell therapies.