By way of background, Hemophilia A patients lack sufficient factor VIII, often requiring periodic infusions of "replacement" human factor VIII to halt the spontaneous bleeding associated with that condition. Replacement human factor VIII may be derived from the pooled plasma of thousands of donors or, as is the case with newer products, may be of recombinant form manufactured using the techniques of genetic engineering. Approximately twenty-five percent of those treated with replacement human factor VIII eventually develop neutralizing antibodies to that product, since their immune systems recognizes the replacement human factor VIII as foreign protein to be attacked and inactivated. Those hemophiliacs, known as inhibitor or "alloantibody" patients, can no longer be treated with human factor VIII. In the past, these patients have often been treated with a variation of factor VIII known as porcine factor VIII, a product until recently sold commercially under the name Hyate:C and derived from the plasma of pigs. While Hyate:C had often proven to be effective in the treatment of both alloantibody and autoantibody patients, its availability had been severely and chronically limited due to its difficulty of manufacture. The long time marketer of Hyate:C, French drug maker Ipsen, has teamed with Octagen in an effort to develop and commercialize a genetically engineered, recombinant form of porcine factor VIII, known internally as "OBI-1."