Enzon Names Dr. Ivan Horak Chief Scientific Officer

Dr. Horak brings an impressive background in drug development toEnzon and is a board certified medical oncologist. He has held anumber of senior medical and scientific positions in thepharmaceutical industry, as well as the National Cancer Institute(NCI).

"The addition of Dr. Horak to our executive management teamfurther strengthens the pharmaceutical expertise at Enzon. Dr Horakwill be instrumental in enhancing the productivity of our R&Dpipeline," said Jeffrey H. Buchalter, Enzon's chairman and chiefexecutive officer. "I have known Dr. Horak professionally for manyyears and have full confidence his continued leadership within theoncology community will contribute greatly to our long-term success inthis therapeutic area."

Dr. Horak joins Enzon from Immunomedics, Inc. (Nasdaq: IMMU),where he served as Chief Scientific Officer since July 2003 andExecutive Vice President of Research and Development since May 2002.Before joining Immunomedics, Dr. Horak was employed by Pharmacia as aVice President for Clinical Oncology, where he helped direct theglobal development of oncology compounds from 1999 to 2002, includingCamptosar(R) for metastatic colorectal cancer.

From 1996 to 1999, Dr. Horak held a variety of clinical researchpositions at Janssen Research Foundation, a subsidiary of the Johnson& Johnson Company, including International Director for ClinicalResearch and Development, Oncology.

Prior to joining Janssen, Dr. Horak spent nine years at the NCIwhere he most recently served as a cancer expert for the MetabolismBranch.

In addition to over 50 scientific publications, Dr. Horak is amember of several prominent medical societies and has served onvarious committees for the American Association for Cancer Researchand the International Union Against Cancer. He also serves on theeditorial board of the prestigious journal, Cancer Research.

About Enzon

Enzon Pharmaceuticals is a biopharmaceutical company dedicated tothe development and commercialization of therapeutics to treatlife-threatening diseases. The Company has developed or acquired anumber of marketed products, including PEG-INTRON(R), marketed bySchering-Plough, and ABELCET(R), ONCASPAR(R), ADAGEN(R), andDEPOCYT(R), marketed in North America by Enzon's specialized salesforce. Enzon's science-driven strategy includes an extensive drugdevelopment program that leverages the Company's macromolecularengineering technology platforms, including PEG modification andsingle-chain antibody (SCA(R)) technologies. Internal research anddevelopment efforts are complemented by strategic transactions thatprovide access to additional marketed products and promising clinicalcompounds. Further information about Enzon can be found on theCompany's web site at www.enzon.com.

All information in this press release is as of September 6, 2005and the Company undertakes no duty to update this information.