GlaxoSmithKline seeks US approval for Tykerb® (lapatinib ditosylate) for the treatment of advanced breast cancer

Issued – Monday 18 September 2006, London

Application based on a phase III study showing that Tykerb, in combination with chemotherapy, significantly improves time to progression

GlaxoSmithKline plc today announced the submission of a New Drug Application (NDA) to the United States Food and Drug Administration (FDA) for approval to market Tykerb ® (lapatinib ditosylate), in combination with Xeloda® (capecitabine), for the treatment of advanced or metastatic HER2 (ErbB2) positive breast cancer in women who have received prior therapy, including Herceptin® (trastuzumab). The compound has been granted Fast Track status by the FDA in this patient population. TYKERB is a small molecule dual kinase inhibitor developed by GSK as an oral therapy, and is currently being investigated in breast cancer and other solid tumors. TYKERB is an investigational drug and has not been approved for marketing by any regulatory body.

“This filing is the result of many years of tremendous research and development work by the scientists at GSK. It is truly an outstanding milestone, especially for the many thousands of women who are facing the devastating effects of advanced breast cancer,” said Paolo Paoletti, M.D., Senior Vice President of the Oncology Medicine Development Center at GSK. “Many of these women are desperately in need of alternative treatments, and this filing demonstrates that we have turned the corner toward a new era of targeted agents.”

GSK plans to submit the Marketing Authorization Application (MAA) for Tykerb in Europeduring the 4th quarter of this year.

About the data submitted1

A planned interim analysis of the Phase III international, multicenter, open-label trial randomized 324 women who had advanced or metastatic breast cancer with documented HER2 overexpression and whose disease progressed following treatment with Herceptin and other cancer therapies, to TYKERB and Xeloda or Xeloda alone. In this pivotal trial, the combination of TYKERB and Xeloda versus Xeloda alone nearly doubled median time to progression (36.7 weeks [8.5 months] in the combination arm versus 19.1 weeks [4.4 months] with Xeloda alone, p=0.00008).

The most common adverse events (>25%) during therapy with TYKERB plus Xeloda were gastrointestinal (diarrhea, nausea, and vomiting) or dermatologic (palmer-plantar erythrodysesthesia and rash). The majority of adverse events and laboratory abnormalities were mild to moderate in severity.

The study was originally presented by trial principal investigator Charles Geyer, M.D., Director of Breast Medical Oncology at Allegheny General Hospital (Pittsburgh, Pennsylvania) at the 2006 American Society of Clinical Oncology (ASCO) annual meeting in Atlanta, Georgia, in June.

In March 2006, an Independent Data Monitoring Committee (IDMC) made a unanimous recommendation to stop enrollment of the study based on the early success of the trial. The study met its primary endpoint of time to disease progression, and exceeded the predetermined stopping criteria outlined in the committee charter. GSK stopped enrollment to the study in April 2006.

About Tykerb

Tykerb, a small molecule that is administered orally, inhibits the tyrosine kinase components of EGFR (ErbB1) and HER2 receptors. Stimulation of EGFR and HER2 is associated with cell proliferation and with multiple processes involved in tumor progression, invasion, and metastases. Overexpression of these receptors has been reported in a variety of human tumors and is associated with poor prognosis and reduced overall survival.

GSK is using advanced technologies, including pharmacogenetics, to better define patient populations that may respond to Tykerb.

About GlaxoSmithKline

GlaxoSmithKline – one of the world’s leading research-based pharmaceutical and healthcare companies – is committed to improving the quality of human life by enabling people to do more, feel better, and live longer. For company information, visit GlaxoSmithKline at http://www.gsk.com.

Cautionary statement regarding forward-looking statements

Under the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995, the company cautions investors that any forward-looking statements or projections made by the company, including those made in this announcement, are subject to risks and uncertainties that may cause actual results to differ materially from those projected. Factors that may affect the Group’s operations are described under ’Risk Factors’ in the Operating and Financial Review and Prospects in the company’s Annual Report on Form 20-F for 2005.

Notes to editors

Tykerb® is a registered trademark of the GlaxoSmithKline group of companies in the United States and Europe.

Herceptin®is a registered trademark of Genentech, Inc. in the US and Roche Pharmaceuticals in Europe.

Xeloda®is a registered trademark of Roche Pharmaceuticals.

To access the latest GSK Oncology media materials, visit http://www.gskcancermedia.com

References

1. Data on file, GlaxoSmithKline, King of Prussia.

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