Some pharmaceutical substances, such as proteins, monoclonal antibodies, enzymes, and vaccines, are unstable in solution. They can degrade, for example by enzymatic or hydrolytic reactions. Lyophilization (also called freeze-drying) is the most common approach to address this.* Lyophilization is the process of dehydrating a material at low temperature and reduced pressure. Absent water, the rates of degradative enzymatic/hydrolytic processes are reduced substantially, and thus drug product stability is improved.