Biologics are large, structurally complex proteins derived from living cells such as bacteria, yeasts or mammalian cells. In comparison to a small molecule or chemical drug, biologics may be 200 to 1,000 times bigger, with high molecular complexity. Biologics include therapeutic proteins and monoclonal antibodies. Biologics that are similar to each other in terms of safety, efficacy and quality to a reference biologic product are referred to as biosimilars.