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Enzon Presents New PEG-SN38 Preclinical Data at ASH

BRIDGEWATER, N.J.--(BUSINESS WIRE)--Dec 10, 2007 - Enzon Pharmaceuticals, Inc. (Nasdaq: ENZN) today announced new preclinical data showing that treatment with PEG-SN38, Enzon's PEGylated SN38 compound, resulted in excellent antitumor activity in xenograft models of non-Hodgkin's lymphoma (NHL). The data were presented at the ASH (American Society of Hematology) Conference in Atlanta, Georgia.

"The data further demonstrate the novel characteristics of our pegylated form of SN38, as this type of response by this class of drugs in NHL models is not expected," said Jeffrey H. Buchalter, Enzon's chairman and chief executive officer. "We continue to be encouraged by the positive preclinical results and await the completion of our Phase 1 clinical studies."

Marked Therapeutic efficacy of a novel polyethyleneglycol-SN38 conjugate, EZN 2208, in xenograft models of non-Hodgkin's Lymphoma (Publication #1387)

Data from this study demonstrated that EZN-2208 treatment given as a single dose or in multiple dose regimen can cure animals bearing human non-Hodgkin's lymphoma. EZN-2208 treatment cured animals and outperformed CPT-11, in very aggressive and advance disease preclinical models.

About PEG-SN38

SN38 is the active metabolite of the widely used cancer drug CPT-11, marketed as Camptosar(R) in the U.S. Although unmodified SN38 is 1,000 times more potent than Camptosar, it has not been converted into a viable drug candidate because it is insoluble. Using Enzon's new customized linker technology, the Company developed PEG-SN38 (EZN-2208), which results in a novel compound with excellent pharmaceutical properties as shown in animal models: increased solubility, higher exposure, and longer half-life than unmodified SN38. Previously reported preclinical data showed that these features led to greater efficacy over Camptosar in breast, colorectal and pancreatic cancer models.

About Enzon

Enzon Pharmaceuticals, Inc. is a biopharmaceutical company dedicated to the development, manufacturing, commercialization of important medicines for patients with cancer and other life-threatening conditions. Enzon has a portfolio of four marketed products, Oncaspar(R), DepoCyt(R), Abelcet(R) and Adagen(R). The Company's drug development programs utilize several cutting-edge approaches, including its industry-leading PEGylation technology platform used to create product candidates with benefits such as reduced dosing frequency and less toxicity. Enzon's PEGylation technology was used to develop two of its products, Oncaspar and Adagen, and has created a royalty revenue stream from licensing partnerships for other products developed using the technology. Enzon also engages in contract manufacturing for several pharmaceutical companies to broaden the Company's revenue base. Further information about Enzon and this press release can be found on the Company's web site at

Forward Looking Statements

There are forward-looking statements contained herein, which can be identified by the use of forward-looking terminology such as the words "believes," "expects," "may," "will," "should", "potential," "anticipates," "plans" or "intends" and similar expressions. Such forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause actual results, events or developments to be materially different from the future results, events or developments indicated in such forward-looking statements. Such factors include, but are not limited to the timing, success and cost of clinical studies; the ability to obtain regulatory approval of products, market acceptance of, and continuing demand for, Enzon's products and the impact of competitive products and pricing. A more detailed discussion of these and other factors that could affect results is contained in our filings with the U.S. Securities and Exchange Commission, including our transition report on Form 10-K for the year ended December 31, 2006 and our quarterly reports on Form 10-Q. These factors should be considered carefully and readers are cautioned not to place undue reliance on such forward-looking statements. No assurance can be given that the future results covered by the forward-looking statements will be achieved. All information in this press release is as of the date of this press release and Enzon does not intend to update this information.


Enzon Pharmaceuticals, Inc.
Craig Tooman, 908-541-8777
EVP, Finance and Chief Financial Officer

Posted: December 2007