What are the side effects of Tykerb?

Tykerb (Lapatinib)
March 2007

Because ErbB2 positive breast cancer may eventually progress during or
following treatment with trastuzumab, there has been a need for an
effective alternative treatment. - Charles Geyer M.D. Director of Breast
Medical Oncology at Allegheny General Hspital, Pittsburgh, Pennsylvania. [3]

On March 13, 2007, FDA approved Tykerb as a new targeted anti-cancer
treatment to be used in combination with Xeloda or patients with advanced,
metastatic breast cancer that is HER2 positive. [5]

Does Tykerb work better than Herceptin on Breast
Cancer?

Mechanism Comparison
Herceptin blocks the HER2 activities by binding to it on the outside of the
cell. While, tykerb blocks the HER2 breast cancer factor and EGFR (the same
molecular target of cancer medications such as Iressa).

Usage Comparison
Tykerb is a once-a-day pill, while Herceptin is a monthly infusion.

Complication Comparison
Herceptin may cause heart failure

ABOUT TYKERB
Tykerb is a small molecule that can be administered orally. It inhibits the
tyrosine kinase components of ErbB1 and ErbB2 receptors. Stimulation of
ErbB1 and ErbB2 is associated with cell proliferation and with multiple
processes involved in tumor progression, invasion, and metastasis.
Overexpression of these receptors has been reported in a variety of human
tumors. Glaxo is using pharmacogenetics and other advanced technologies
to better define patient populations that may respond to Tykerb.

GSK plans to submit Tykerb regulatory filings in the U.S. and Europe in the
2nd second of 2006. The compound has already been granted Fast Track
status by the FDA for the treatment of refractory advanced or metastatic
breast cancer in women (with ErbB2 overexpression and failure with
previous therapy).
Tykerb is also designed as GW572016.

ABOUT HERCEPTIN AND BREAST CANCER
Herceptin (Trastuzumab) was approved for use alone for certain patients
who have tried chemotherapy with little success or as a first-line treatment
for metastatic disease when used in combination with paclitaxel
(trade-name Taxol) on September 25, 1998. It was described as a new
biologic approach for the treatment of metastatic breast cancer, or cancer
that has spread beyond the breast and lymph nodes under the arm.

Breast Cancer
According to the American Cancer Society, an estimated 211,240 women will
be diagnosed with breast cancer and approximately 40,000 women will die
of the disease in the United States in 2005. Breast cancer is the most
common cause of cancer among women in the United States

Herceptin (Trastuzumab)
Herceptin (Trastuzumab) is actually a monoclonal antibody bioengineered
from a mouse antibody. Herceptin (Trastuzumab) binds to HER2 on the
surface of some normal cells and plays a role in regulating cell growth. In
the experimental studies, Herceptin (Trastuzumab) demonstrated its ability
to inhibit tumor cell growth by this binding action. In metastatic breast
cancer cells, about 30% of tumors produce excess amounts of HER2. Studies
show that cancer may be more aggressive when breast cancer tumors
produce excess amounts of the HER2 protein. In studies, patients suffered
from breast cancers showed better responses when they had higher levels
of HER2 protein.

Tykerb® (lapatinib) plus Xeloda® (capecitabine) was superior to
capecitabine alone, study shows.
Dr. Charles E. Geyer at Allegheny General Hospital, Pittsburg, concluded that
Tykerb® (lapatinib) plus Xeloda® (capecitabine) was superior to
capecitabine alone in women with HER2 (ErbB2) positive advanced breast
cancer who had progressed following prior therapy, including Herceptin®
(trastuzumab) in a Phase III study of women with HER2-positive, locally
advanced or metastatic breast cancer.

The study also showed that the combination-therapy was not associated
with higher incidence in either serious toxicity or rates of discontinuation
related to adverse side effects, compared to capecitabine treatment alone.
The most common side effects were diarrhea, hand-foot syndrome and rash
distinct from hand-foot syndrome. [4]

Potential Side Effects of Tykerb
The most commonly reported Tykerb-related side effects included diarrhea,
nausea, vomiting, rash and hand-foot syndrome which may include
numbness, tingling, redness, swelling and discomfort of hands and feet.
Generally reversible decreases in heart function (that can lead to shortness
of breath) have also been reported in a small percentage of patients.
Patients should talk to their doctor about potential side effects, potential
drug interactions, and other medical conditions including heart and liver
problems. [5]

Tykerb will be distributed by GlaxoSmithKline, of Research Triangle Park,
North Carolina.

SOURCES Glaxo's Tykerb Pill Shows the Advance of Breast Cancer in Study Bloomberg
June 3 2006. GlaxoSmithKline Initiates Trial of Tykerb (Lapatinib) in Patients With
ErbB2-Overexpressing Breast Cancer Brain Metastasis Following Herceptin and Cranial
Radiotherapy. PRNewswire Dec 9 2005 [3] GlaxoSmithKline Reports Positive New Data
on Tykerb (R) (Lapatinib Ditosylate) PR Newswire June 3 2006 [4] Lapatinib plus
Capecitabine for HER2-Positive Advanced Breast Cancer New England Journal of
Medicine (NEJM) Volume 355:2733-2743 December 28, 2006 Number 26. [5] FDA
Approves Tykerb for Advanced Breast Cancer Patients, FDA News, March 13, 2007.

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