News Pressroom

May 25, 2005

Preclinical Data Support Link Between IL-9 and Airway Hyperresponsiveness Associated With Asthma

- MedImmune Plans to Initiate Second Phase 1 Study With Lead Monoclonal Antibody Targeting IL-9 as Potential Asthma Therapy -

SAN DIEGO, May 25, 2005 /PRNewswire-FirstCall via COMTEX/ -- MedImmune, Inc. (Nasdaq: MEDI) today announced data from a preclinical study demonstrating a correlation between interleukin-9 (IL-9) and increased airway hyperreactivity (AHR), a key component of asthma. The data indicate that one aspect of IL-9's role in AHR is the regulation of mast cells, which release mediators that cause the bronchi or bronchial airway to constrict and thereby impair airflow into the lungs. Results from this preclinical study also demonstrated that using an anti-IL-9 monoclonal antibody (MAb) reduced AHR.

"Evidence of IL-9's direct role in the growth and proliferation of airway mast cells supports MedImmune's approach to developing therapies to treat or prevent asthma," said Anthony Coyle, Ph.D., senior director, research, and head, inflammation biology. "We look forward to advancing the development of antibody therapies to block IL-9, which may have the potential to reduce mast cell-derived respiratory factors associated with asthma and other illnesses."

The preclinical study presented at the 100th Annual International Conference of the American Thoracic Society showed that IL-9 regulated airway responsiveness. Data demonstrated that IL-9's effect on AHR depended on the proliferation and maturation of mast cells. In the study, the overexpression of mast cells was associated with high lung levels of two mediators, cysteinyl leukotrienes (CystLTs) and prostaglandin E2 (PGE2), which are known to have direct effects on smooth muscle and have been previously associated with changes in intrinsic airway tone, manifesting as AHR. These data were presented via a poster entitled, "Regulation of Airway Hyperresponsiveness by Interleukin-9: Potential Role of Mast Cells."

About MedImmune's Anti-IL-9 Program and Asthma

The data presented yesterday contribute to a growing body of scientific knowledge about IL-9's mechanism of action. IL-9 has been associated with symptoms of asthma including mucous production, lung infiltration of inflammatory cells, and IgE (an immune globulin associated with allergic disease) production. It is one of at least 29 naturally occurring interleukins in the human body.

MedImmune is conducting research to evaluate the potential to use MAbs targeting IL-9 to treat or prevent symptomatic, moderate-to-severe, persistent asthma. In early 2005, the company completed a Phase 1 dose-escalation, intravenously administered study in healthy adults with its lead anti-IL-9 MAb. The company plans to initiate a subcutaneously administered Phase 1 dose- escalation study in healthy adults with this MAb in mid-2005.

According to the U.S. Centers for Disease Control and Prevention (CDC), more than 20 million Americans reported having asthma in 2001, including more than six million children. The National Institutes of Health (NIH) have estimated that asthma-related healthcare costs in the U.S. exceed $14 billion annually.

About MedImmune, Inc.

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 the company's website at http://www.medimmune.com.

This announcement contains, in addition to historical information, certain "forward-looking statements" regarding the development of a monoclonal antibody product targeting IL-9. Such forward-looking statements are based on current expectations and involve inherent risks and uncertainties, including factors that could delay, divert or change and could cause actual outcomes and results to differ materially from current expectations. In addition to risks and uncertainties discussed in MedImmune's filings with the U.S. Securities and Exchange Commission, no assurance exists that development efforts for any such product will succeed, that any such product will receive required regulatory approval or that, even if regulatory approval is received, any such product will be commercially successful. MedImmune undertakes no obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise except as may be required by applicable law or regulation.

SOURCE MedImmune, Inc.

Media:
Jamie Lacey, +1-301-398-4035
Investors:
Pete Vozzo, +1-301-398-4358
both of MedImmune, Inc.