Enzon and Micromet End Research Collaboration

Since April 2002, the two companies combined their complementaryexpertise in single-chain antibody (SCA) technology and shared equallyin the costs related to the identification of several antibody-basedcompounds. Under the termination agreement, Enzon will make a finalpayment to Micromet in satisfaction of its obligations under thecollaboration. In addition, Micromet receives rights to the leadcompound (MT203) generated within the scope of the collaboration andEnzon will receive royalties on any future product sales.

The termination of the research and development collaboration doesnot affect the companies' other agreements, including a cross-licenseagreement between the parties and a marketing agreement under whichMicromet is the exclusive marketer of the two companies' combinedintellectual property estate in the field of single-chain antibodytechnology (SCA). Under the marketing agreement, the two companiesshare equally in any revenues resulting from Micromet's licensingactivities.

About Single-Chain Antibodies

Antibodies are proteins produced by the body's immune system inresponse to the presence of antigens, such as bacteria, viruses orother disease causing agents. Antibodies of identical molecularstructure that bind to a specific target are called monoclonalantibodies. Single-chain antibodies are genetically engineeredantibodies that incorporate only the antigen binding domains of anantibody. Thus, SCAs have the binding specificity and affinity ofmonoclonal antibodies; however, in their native form they are onlyone-fifth to one-sixth the size of a monoclonal. The small size ofSCAs typically gives them shorter half-lives than monoclonalantibodies, making them better suited for use in acute indications orin other indications where the large size of a monoclonal antibodywould inhibit the compound from reaching the area of potentialtherapeutic activity. In addition, SCAs are a well-establisheddiscovery format-of-choice in generating antibodies from phage oryeast display libraries.

About Micromet

Micromet AG, a private Munich-based biotechnology company, putsnovel concepts in immunotherapy to work. Using proprietarytechnologies, the Company is building a strong pipeline of innovativedrug candidates for the treatment of cancer, inflammation andautoimmune disease. Two candidates are currently in clinical trials.The Company has established a powerful drug development platform basedon its BiTE(TM) technology, a unique drug format that leverages thecytotoxic potential of T cells, the most powerful 'killer cells' ofthe human immune system. Micromet has integrated infrastructure andexpertise in all disciplines of drug design and development. TheCompany has attracted both top-tier life science investors andcorporate partners, such as MedImmune, Inc., Enzon PharmaceuticalsInc, and Serono. For further information, please visit the Company'swebsite at www.micromet.de.

About Enzon

Enzon Pharmaceuticals, Inc. is a biopharmaceutical companydedicated to the development and commercialization of therapeutics totreat patients with cancer and other life-threatening diseases.Enzon's specialized sales force markets ABELCET(R), ONCASPAR(R),ADAGEN(R), and DEPOCYT(R) in North America. In addition, Enzon alsoreceives royalties on sales of PEG-INTRON(R), marketed bySchering-Plough Corporation, and MACUGEN(R), marketed by OSIPharmaceuticals, Inc. and Pfizer Inc. Enzon's product-driven strategyincludes an extensive drug development program that leverages itsproprietary technologies, including a next-generation PEGylationplatform that utilizes linkers designed to release compounds at acontrolled rate. Enzon complements its internal research anddevelopment efforts with strategic initiatives, such as partnershipsdesigned to broaden its revenue base or provide access to promisingnew technologies or product development opportunities. Furtherinformation about Enzon and this press release can be found on theCompany's web site at www.enzon.com.

All information in this press release is as of November 28, 2005and Enzon and Micromet undertake no duty to update this information.

This release is also available at www.enzon.com andwww.micromet.de