sentences:  The clinical value of PEGylation is now well established.ADAGEN (pegademase bovine) manufactured by Enzon Pharmaceuticals, Inc., US was the first PEGylated protein approved by the U.S. Food and Drug Administration (FDA) in March 1990, to enter the market.It is used to treat a form of severe combined immunogenicity syndrome (ADA-SCID), as an alternative to bone marrow transplantation and enzyme replacement by gene therapy.