ALC-0159 is a polyethylene glycolated lipid that can be used as a vaccine excipient and has been used in the pharmaceutical field to form lipid nanoparticles (LNPs) for the delivery of RNA. It is also a component of the lipid matrix for the prophylactic SARS-CoV-2 mRNA vaccine manufactured by Pfizer/BioNTech in low levels (<2 mol %). ALC-0159 promotes the stabilisation of nanoparticles through the three-dimensional mechanism of its poly((ethylene glycol)) (PEG) molecules. ethylene glycol (PEG) molecule, ALC-0159 promotes nanoparticle stabilisation through its steric mechanism. Studies have shown that ALC-0159 (PEGylated lipid) may induce anaphylaxis.