 The specific activity of recombinant Factor IX was 75 units/mg... compared to 150 units/mg measured for plasma-derived Factor IX...In 1992, the FDA approved Factor VIII produced using transgenic Chinese hamster ovary cells, the first such blood clotting factor produced using recombinant DNA technology to be approved.Recombinant DNA techniques have also been employed to create transgenic farm animals that can produce pharmaceutical products for use in humans.