ALC‑0159（Cat No.:I021737）is a PEGylated lipid excipient—specifically a methoxy‑PEG‑2000 conjugated to N,N‑ditetradecylacetamide—used in lipid nanoparticles (LNPs) for mRNA delivery . Present in Pfizer‑BioNTech’s Comirnaty COVID‑19 vaccine (~0.05 mg per dose, <2 mol %), it stabilizes LNPs by forming a hydrophilic “stealth” shield, extending circulation time and minimizing aggregation and immune recognition. This non‑ionic surfactant enhances nanoparticle shelf‑life, systemic persistence, and efficient cellular uptake of RNA. ALC‑0159 is widely utilized in research and drug delivery platforms for mRNA, siRNA, and oligonucleotide therapeutics.