News Pressroom

September 14, 2005

MedImmune to Acquire Cellective Therapeutics, Inc.

- Cellective's Pipeline Provides MedImmune Additional Preclinical Cancer and Autoimmune Disease Product Candidates -

GAITHERSBURG, Md., Sept. 14 /PRNewswire-FirstCall/ -- MedImmune, Inc. (Nasdaq: MEDI) announced today that it has expanded its pipeline of potential drug candidates by signing a definitive agreement to acquire privately held Cellective Therapeutics, Inc. The transaction provides MedImmune with three preclinical stage programs developing monoclonal antibodies (MAbs) that target the B-cell antigens CD19, CD20 and CD22. These antigens are believed to play important roles in regulating the immune system.

"With our mutual focus on antibody research, the acquisition of Cellective is an excellent strategic fit for MedImmune," said James F. Young, Ph.D., president, research and development. "Cellective's lead product candidates, which are based on the extensive work on B cells by renowned immunologist Dr. Thomas F. Tedder of Duke University Medical Center, provide additional opportunities for MedImmune to expand its potential offering of treatments for patients battling cancer and autoimmune diseases."

"We are delighted that MedImmune recognizes the value of Cellective's promising portfolio of monoclonal antibodies and extensive knowledge in the field of B-cell biology," said Arthur M. Mandell, president and chief executive officer of Cellective Therapeutics. "With a proven track record of developing successful products and a strong commitment to developing antibody therapeutics, MedImmune is an ideal strategic partner for our company. Although Cellective has a relatively short history, it has multiple antibody product candidates with potential in both oncology and autoimmune diseases. MedImmune and Cellective look forward to taking these antibodies into the clinic and eventually to patients."

Under the terms of the agreement, MedImmune will acquire all outstanding equity interests of Cellective in a cash transaction, which is expected to close by the end of October 2005, subject to necessary government approval. MedImmune will also provide Cellective shareholders with future payments for the company's three preclinical antibody programs should certain product development and sales milestones be achieved.

CD19, CD20 and CD22 are B-cell lineage-specific molecules involved in immune regulation. Preclinical studies indicate that antibodies targeting these antigens may block B-cell activities that are associated with many tumors and autoimmune diseases, including multiple myeloma, B-cell lymphomas, rheumatoid arthritis, and lupus. Early research on the potential therapeutic benefits of blocking these molecules has been conducted by Thomas F. Tedder, Ph.D., chairman of the Department of Immunology at Duke University Medical Center and leading authority in B-cell biology.

Updated Financial Guidance

On August 31, 2005, MedImmune updated its financial guidance for 2005 as a result of concluding another major strategic business initiative by the company. Today's announcement also impacts MedImmune's financial guidance for 2005. MedImmune expects this transaction with Cellective, when consummated, will result in a one-time in-process research and development charge that will reduce its 2005 earnings by approximately $0.20 per diluted share. As such, MedImmune now anticipates that its 2005 diluted earnings per share will range from $0.04 to $0.10.

This transaction does not change any of MedImmune's financial guidance for 2006-2009 as announced on August 31, 2005. Guidance and targets provided by the company are projections and are based upon numerous assumptions, many of which MedImmune cannot control and that may not develop as MedImmune expects. For a discussion of the risks associated with these forward-looking statements, see the Disclosure Notice below.

About MedImmune

MedImmune strives to provide better medicines to patients, new medical options for physicians, rewarding careers to employees, and increased value to shareholders. Dedicated to advancing science and medicine to help people live better lives, the company is focused on the areas of infectious diseases, cancer and inflammatory diseases. With approximately 2,000 employees worldwide, MedImmune is headquartered in Maryland. For more information, visit http://www.medimmune.com.

About Cellective

Cellective Therapeutics, Inc. is a Maryland-based, early-stage biopharmaceutical company dedicated to the research, development, and eventual commercialization of a portfolio of therapeutic monoclonal antibodies targeting key receptors found on the surface of B-lymphocytes. B-lymphocytes play a critical role in the development of B-cell mediated cancers as well as a large assortment of autoimmune diseases. In a short time, Cellective acquired state-of-the-art technology and licenses and began developing multiple programs. It raised a strong Series A round of financing to fund its lead product candidates through early human clinical trials. The Series A financing, secured in late September, 2004 was led by Intersouth Partners with participation from five other leading venture capital firms: Alta Partners, BA Venture Partners, Forward Ventures, Latterell Venture Partners, and Sofinnova Ventures. Other participants included the investment arms of two renowned biotechnology companies: MedImmune, Inc. and Genentech. Cellective also has assembled a first-class management team with significant experience in the development, manufacturing, and commercialization of biotechnology drugs.

This announcement may contain, in addition to historical information, certain forward-looking statements that involve risks and uncertainties. Such statements reflect management's current views and are based on certain assumptions. Actual results could differ materially from those currently anticipated as a result of a number of factors, including risks and uncertainties discussed in MedImmune's filings with the SEC. MedImmune is developing products for potential future marketing. There can be no assurance that such development efforts will succeed, that such products will receive required regulatory clearance or that, even if such regulatory clearance were received, such products would ultimately achieve commercial success. There can also be no assurance that the proposed acquisition will close or that Cellective will be integrated successfully or without unanticipated costs.

This press release can be found on MedImmune's website at http://www.medimmune.com in the box marked "News" or with the archived press releases on the Investor Summary page.

SOURCE MedImmune, Inc.

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