ROCKVILLE, MD, September 15, 2005—EntreMed, Inc. (Nasdaq: ENMD), a clinical-stage pharmaceutical company developing therapeutics primarily for the treatment of cancer and inflammatory diseases, today announced that it has entered into a Cooperative Research and Development Agreement (CRADA) with the National Cancer Institute to evaluate the role of HIF-1α inhibition in the treatment of cancer.

Under the terms of the three-year agreement, the NCI’s Developmental Therapeutics Program Screening Technologies Branch (DTP-STB) and EntreMed will combine expertise and resources to investigate the mechanism of action by which EntreMed’s lead compound, 2-methoxyestradiol (2ME2) and a second generation analog of 2ME2, ENMD-1198, inhibits tumor hypoxia factor-1 alpha (HIF-1α) in human cell lines. Additionally, animal tumor models will be used to establish the relationship between levels of 2ME2 in blood or tumor tissue and the inhibition of tumor growth.

The Tumor Hypoxia Laboratory within the NCI-DTP-STB has developed significant expertise in defining the role of HIF-1α inhibition in the development of novel anticancer and antiangiogenic agents. This expertise will help to further clarify and define the antiangiogenic and antitumor properties of 2ME2 and its analog, ENMD-1198.

It has been demonstrated in preclinical studies that 2ME2 is a potent inhibitor of HIF-1α, and its down-regulation is closely associated with 2ME2’s tubulin inhibitor properties. HIF-1α is over-expressed in more than 70% of human tumors and HIF-1α over-expression correlates with tumor aggressiveness, metastases and poor prognosis. 2ME2 attacks tumors on multiple fronts – directly by disrupting microtubules, an intracellular matrix necessary for the rapid division of cancer cells (mitosis), by inducing programmed cell death (apoptosis), and by blocking blood vessels that feed tumors (angiogenesis inhibition).

Carolyn F. Sidor, M.D., M.B.A, EntreMed Vice President and Chief Medical Officer, commented on the CRADA, “We are pleased to have the opportunity to work with the National Cancer Institute and their team of experts in the field of tumor hypoxia. We believe that 2ME2 has the potential to be a unique cancer therapy by attacking tumors that are dependent on the pro-angiogenic activity of HIF-1α. The NCI collaboration will provide EntreMed with access to well-established in vitro and in vivo models of HIF-1α inhibition.”

Dr. Sidor added that, “Studies performed under this CRADA will further enhance our understanding of the mechanism of action by which 2ME2 and ENMD-1198 inhibit HIF-1α in human tumors. EntreMed is currently evaluating several formulations of 2ME2 (Panzem® Capsules and Panzem® NCD) in Phase I and II clinical oncology studies. We expect that the results from these and other 2ME2 mechanism studies will help guide our ongoing Panzem® clinical development program. The Company is also conducting IND-directed studies with ENMD-1198 and plans to submit an IND to the FDA for this compound later this year.”

About EntreMed

EntreMed, Inc. (Nasdaq: ENMD) is a clinical-stage pharmaceutical company developing therapeutic candidates primarily for the treatment of cancer and inflammation. Panzem® (2-methoxyestradiol or 2ME2), the Company’s lead drug candidate, is currently in clinical trials for cancer, as well as in preclinical development for non-oncology indications. EntreMed’s goal is to develop and commercialize new compounds based on the Company’s expertise in angiogenesis, cell cycle regulation and inflammation—processes vital to the treatment of cancer and other diseases, such as rheumatoid arthritis. Additional information about EntreMed is available on the Company’s website at www.entremed.com and in various filings with the Securities and Exchange Commission.

Forward Looking Statements

This release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act with respect to the outlook for expectations for future financial or business performance, strategies, expectations and goals. Forward-looking statements are subject to numerous assumptions, risks and uncertainties, which change over time. Forward-looking statements speak only as of the date they are made, and no duty to update forward-looking statements is assumed. Actual results could differ materially from those currently anticipated due to a number of factors, including those set forth in Securities and Exchange Commission filings under “Risk Factors,” including risks relating to the need for additional capital and the uncertainty of additional funding; the early-stage products under development; uncertainties relating to preclinical and clinical trials; success in the clinical development of any products; dependence on third parties; future capital needs; and risks relating to the commercialization, if any, of the Company’s proposed products (such as marketing, safety, regulatory, patent, product liability, supply, competition and other risks).