Pieter Cullis made significant contributions to the development of lipid nanoparticles (LNPs) for the delivery of nucleic acids in gene therapy. In 2005 he developed LNP technology for RNA-based drugs, leading to the siRNA drug patisiran. In 2009 he cofounded Acuitas Therapeutics, collaborating on mRNA vaccine development, which included working with BioNTech and Pfizer on the generation of a COVID-19 vaccine.