Key methods to manipulate DNA to create monoclonal antibodies are covered by a thicket of patents, including the "Winter patent" was invented by Gregory P. Winter of the Medical Research Council which covers methods to make chimeric, humanized antibodies and has been licensed to about fifty companies. Abgenix owned a patent on methods of making transgenic mice lacking endogenous heavy chains. The "Boss patent" was owned by Celltech and covered methods of making recombinant antibodies and antibody fragments, together with vectors and host cells useful in these processes. Genentech owned the "Old Cabilly" patent that covered altered and native immunoglobulins prepared in recombinant cell culture, as well as the "New Cabilly" patent that covers artificial synthesis of antibody molecules. Medarex owned a patent that covered high affinity human antibodies from transgenic mice. These patents have been broadly licensed and have been the subject of litigation among patent holders and companies that have brought monoclonal antibody drugs to market.