Tykerb and Herceptin developed by GlaxoSmithKline, are targeted therapies aimed at cancers that are HER2-positive, which means they make too much of the HER2/neu protein. While the Herceptin blocks the protein on the cancer cell's surface, Tykerb blocks the protein inside the cell. Because it uses a different mechanism to work, researchers do think Tykerb may be effective against HER2-positive cancers that have stopped responding to Herceptin.

Tykerb is an experimental drug, helps stall advanced breast cancer, said makers GlaxoSmithKline at the American Society of Clinical Oncology, Atlanta, USA. Glaxo said women who had not benefited from Herceptin, another breast cancer drug, benefited when receiving Tykerb, taken along with Xeloda was shown to be twice as effective in slowing down an aggressive type of breast cancer as Xeloda alone. Tykerb pill blocks proteins that encourage the development and spread of cancer.

Lapatinib (Tykerb) is an experimental drug that, like trastuzumab, blocks the activity of the HER2 protein, but it does so by a different mechanism. Lapatinib binds to the part of the protein that is found inside breast cancer cells.

GlaxoSmithKline (GSK) has announced the initiation of a global multicenter Phase II trial (known as EGF105084) to evaluate Tykerb (lapatinib) for the treatment of ErbB2-overexpressing (HER2+) breast cancer that has metastasized to the brain. Tykerb is an orally bioavailable small molecule which potently inhibits two the receptors ErbB2 and ErbB1, and is currently in development as a first-line treatment for ErbB2-overexpressing breast cancer. Several centers, first in the US and then throughout the world, will begin enrolling patients with breast cancer who have progressive brain metastases following cranial radiotherapy and prior trastuzumab (Herceptin)-based therapy. Tykerb at present does not have regulatory approval for therapeutic use in any market.