Biologics are highly complex molecules that are primarily derived from living species such as human, animal, and microorganisms or recombinantly produced using living cells. According to the US FDA, biologics include "a wide range of products such as vaccines, blood and blood components, allergens, somatic cells, gene therapy, tissues and recombinant therapeutic proteins." Biologics can be carbohydrates, proteins, lipids, nucleic acids or a complex mixture of these substances.
Biologics are being used as drugs to treat a variety of human and animal diseases including autoimmune diseases such as rheumatoid arthritis. In the case of autoimmune diseases, some biologics interrupt signals, and pathways in the immune system to reduce the damage inflicted by the autoimmune conditions. Biologics can be very micro-heterogenous mixtures of structural variants that are difficult to identify and characterize. Biological products are generally heat sensitive and susceptible to microbial contamination.