Fastigium is a biotechnolgy involving the assembly of a stealth lipid nanoparticle (LNP) characterized by a long circulating blood half-life to deliver messenger RNA to a target tissue. This is achieved through the presence of a high density of polyethylene glycol (PEG) molecules on the surface of the LNP.

A small number of PEG molecules are conjugated to a ligand targeting one or more receptors located on the surface of target cells. The mRNA will make the transfected cells to produce a protein of interest in the targeted tissue for a few days.