MedImmune Announces Positive Clinical Results at PAS Annual Meeting From Large Prospective Trial in Prevention of Serious RSV Disease

- Numax Achieves Primary Endpoint Among High-Risk Infants Versus Current Standard of Care and Shows Reduction of Medically Attended Outpatient RSV- Related Lower Respiratory Infections -

TORONTO, May 08, 2007 /PRNewswire-FirstCall/ -- MedImmune, Inc. today announced positive results from a large prospective trial conducted for prevention of respiratory syncytial virus (RSV). The trial compared motavizumab, the investigational monoclonal antibody (MAb) also known as Numax(R), with Synagis(R) (palivizumab), the standard of care for preventing RSV hospitalization in high-risk infants. In the Phase 3 study involving 6,635 pre-term infants at high risk for RSV, with a primary endpoint of non- inferiority, motavizumab demonstrated overall 26-percent fewer RSV hospitalizations compared with Synagis (p<0.01 for non-inferiority). Additionally, motavizumab demonstrated a statistically significant 50 percent reduction in the incidence of RSV-specific medically attended outpatient lower respiratory infections (LRIs) (p<0.01) compared with Synagis. These findings were presented today in a poster entitled, Phase 3 Trial of Motavizumab, an Enhanced Potency RSV-Specific MAb for the Prevention of Serious RSV Disease in High-Risk Infants, at the Pediatric Academic Societies' Annual Meeting in Toronto, Canada.

"As RSV continues to be the leading cause of lower respiratory tract infections in infants in the United States, we are very encouraged by the results of this Phase 3 trial, which suggest that motavizumab may help to reduce the chance that our most vulnerable babies will have serious RSV disease," said Edward M. Connor, M.D., chief medical officer and executive vice president. "Data from the study showed that motavizumab was statistically superior to Synagis for the secondary endpoint of outpatient medically attended LRI caused by RSV, and thus may reduce the overall burden of RSV disease compared to the current standard of care."

The Phase 3 study was designed to compare the safety and efficacy of motavizumab with that of Synagis, which was first launched by MedImmune in 1998, in reducing serious RSV disease in high-risk infants in the inpatient and outpatient settings. As defined in the study, infants who are at high risk for RSV include those who were born at 35 weeks gestation or less as well as those who have chronic lung disease (CLD) due to being born prematurely. The primary endpoint was to assess the incidence of RSV hospitalizations with motavizumab compared to Synagis. Motavizumab met the primary endpoint, demonstrating non-inferiority to Synagis with 26 percent fewer RSV hospitalizations in motavizumab-treated infants. The overall RSV attack rate was low in both treatment groups: 1.4 percent for infants who received motavizumab, compared with 1.9 percent for those who received Synagis [RR: 0.740, 95 percent CI: (0.503, 1.083)]. The p-value for non-inferiority was p<0.01, demonstrating a significant finding.

Analysis of the data also showed that motavizumab reduced the incidence of RSV-specific medically attended outpatient LRIs (the study's RSV-related secondary endpoint) by approximately 50 percent compared with Synagis. The overall RSV-specific medically attended LRI rate was 2.0 percent for infants who received motavizumab compared with 3.9 percent for those who received Synagis (p<0.01). There were no significant differences in other non-RSV- specific endpoints.

"I am very pleased with the study results for motavizumab," said Xavier Carbonell, M.D., Ph.D., lead study author, chairman of neonatology, Barcelona Hospital Clinic, and vice president, Spanish Neonatal Society. "As a practicing neonatologist, I look forward to the potential to use this next- generation antibody to help reduce RSV-related hospitalizations and LRIs in the outpatient setting."

Data from this trial demonstrate that both study drugs were well tolerated. The incidence and severity of adverse events (AEs) were comparable for both treatment groups and were consistent with prior experience with Synagis. There were comparable rates of related AEs and drug discontinuations between treatment groups [related AEs: motavizumab (N=298, 9.0 percent) vs. Synagis (N=258, 7.8 percent) p=not significant (NS); discontinuations: motavizumab (N=13, 0.4 percent) vs. Synagis (N=10, 0.3 percent) p=NS]. AEs related to skin hypersensitivity reactions resulted in discontinuation of dosing in motavizumab-treated patients at low frequency (N=9, 0.3 percent). In Synagis-treated patients, there were no AEs consistent with skin hypersensitivity reactions that resulted in dosing discontinuation. The overall mortality rates were not statistically different between the two groups (N=8, 0.2 percent motavizumab and N=4, 0.1 percent Synagis); no death was considered to be related to the study drugs and there were no RSV-related deaths. Immunogenicity in the motavizumab arm was less than 1 percent and comparable to the historical Synagis rate.

The trial was a randomized, double-blind study involving 6,635 high-risk infants at 347 centers in 24 countries through three RSV seasons. Study participants comprised premature infants born at 35 weeks gestational age or less who were six months of age or younger at randomization, as well as children with CLD related to prematurity requiring medical management within the six months prior to study entry, who were 24 months of age or less at randomization.

About RSV

Each year, an estimated 125,000 infants in the U.S. are hospitalized with severe RSV infections, the leading cause of lower respiratory tract infections in infants in the United States. RSV is the most common respiratory infection in infancy or childhood. Approximately one-half of all infants are infected with RSV during the first year of life, and nearly all children have been infected at least once by the time they reach their second birthday. Children born prematurely as well as those with CLD or congenital heart disease (CHD) are at highest risk for severe disease and hospitalization due to RSV. The virus may also cause severe illness in other high-risk groups such as the elderly, those with underlying respiratory or cardiac disease, and those with compromised immune systems (e.g., bone marrow transplant patients).

About Motavizumab

Motavizumab is an investigational humanized MAb being evaluated for its potential to prevent serious lower respiratory tract disease caused by RSV in pediatric patients at high risk of RSV disease. Phase 1 and Phase 2 study data have been reported showing that motavizumab appears to have a similar safety and pharmacokinetic profile to Synagis in infants. Additionally, in early phase studies children treated with motavizumab had reduced RSV replication in the upper respiratory tract.

About Synagis

Synagis is the only MAb approved by the U.S. Food and Drug Administration (FDA) to help prevent an infectious disease. Since its licensure in 1998, Synagis has been administered to more than 1,000,000 infants in the U.S. and has become the standard of care for infants at high risk for RSV. Synagis is indicated for the prevention of serious lower respiratory tract disease caused by RSV in pediatric patients at high risk of RSV disease, which is prominent in the Northern Hemisphere during the winter months. Synagis is a humanized MAb given by an intramuscular injection once a month during the RSV season. Synagis was approved in 1998 by the FDA; in 1999, by the European Medicines Evaluation Agency; and in 2002, by the Japanese Ministry of Health, Labor and Welfare. In 2003, the FDA expanded the U.S. label for Synagis for use in young children with hemodynamically significant CHD at risk of RSV disease. To date, Synagis has been approved in 62 countries, including the United States. Synagis is indicated for the prevention of serious lower respiratory tract disease caused by respiratory syncytial virus (RSV) in pediatric patients at high risk of RSV disease and is administered by intramuscular injection. Safety and efficacy were established in infants with bronchopulmonary dysplasia (BPD), infants with a history of premature birth (less than or equal to 35 weeks gestation age), and children with hemodynamically significant CHD. Synagis has been used in more than one million children in the U.S. since its introduction in 1998. The first dose of Synagis should be administered prior to commencement of the RSV season. Patients, including those who develop an RSV infection, should continue to receive monthly doses throughout the season.

Very rare cases (<1 per 100,000 patients) of anaphylaxis and rare (<1 per 1,000 patients) hypersensitivity reactions have been reported with Synagis. Cases of anaphylaxis were reported following re-exposure to Synagis and rare severe hypersensitivity reactions occurred on initial exposure or re-exposure. If a severe hypersensitivity reaction occurs, therapy with Synagis should be permanently discontinued. If milder hypersensitivity reaction occurs, caution should be used on re-administration of Synagis.

In clinical trials, the most common adverse events occurring at least 1 percent more frequently in Synagis-treated patients than controls were upper respiratory infection, otitis media, fever and rhinitis. Cyanosis and arrhythmia were seen in children with CHD.

For full prescribing information for Synagis, see the company's website at: www.medimmune.com/products/synagis/index.asp.

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 pediatric infectious diseases, cancer and inflammatory diseases. With more than 2,500 employees worldwide, MedImmune is headquartered in Maryland. For more information, visit the company's website at www.medimmune.com.

Forward Looking Statements

This announcement may contain, in addition to historical information, certain forward-looking statements regarding motavizumab, an investigational MAb, which 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 U.S. Securities and Exchange Commission. The company is developing motavizumab for potential future marketing. There can be no assurance that such development efforts will succeed, that motavizumab will receive required regulatory approval or that, even if such regulatory approval is received, that motavizumab would ultimately achieve commercial success.

Notice to Investors and Stockholders of MedImmune

This release is neither an offer to purchase nor a solicitation of an offer to sell shares of MedImmune. MedImmune stockholders are urged to read the relevant tender offer documents from AstraZeneca PLC which have been filed on May 3, 2007 because they will contain important information that stockholders should consider before making any decision regarding tendering their shares. AstraZeneca has filed tender offer materials with the U.S. Securities and Exchange Commission, and MedImmune has also filed a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the offer. The tender offer materials (including an Offer to Purchase, a related Letter of Transmittal and certain other offer documents) and the Solicitation/Recommendation Statement contain important information, which should be read carefully before any decision is made with respect to the tender offer. The Offer to Purchase, the related Letter of Transmittal and certain other offer documents, as well as the Solicitation/Recommendation Statement, are available for free at the U.S. Securities and Exchange Commission's web site at www.sec.gov, at AstraZeneca's website at www.astrazeneca.com or at MedImmune's website at www.medimmune.com.

CONTACT: Media, Kate Barrett, +1-301-398-4320, or Karen Lancaster (on-site at PAS Annual Meeting), +1-240-832-9720, or Investors, Peter Vozzo,+1-301-398-4358, all of MedImmune

Web site: http://www.medimmune.com/http://www.medimmune.com/products/synagis/index.asp/http://www.astrazeneca.com/

Ticker Symbol: (NASDAQ-NMS:MEDI)

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Posted: May 2007

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