Biotest AG engages in the development, manufacture, and marketing of plasma proteins and biotherapeutic drugs. It operates through the following segments: Therapy, Plasma and Services, and Other. The Therapy segment develops and produces blood plasma-based immunoglobulins, clotting factors, and albumins which are used to treat diseases of the immune system, haematological diseases, and in intensive care medicine. The Plasma and Services segment includes the areas of plasma sales and contract manufacturing. The Other segment refers to the merchandise business. The company was founded by Carl Adolf Schleussner and Hans Schleussner in 1946 and is headquartered in Dreieich, Germany.