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Given in combination with capecitabine (Xeloda, Roche), lapatinib (Tykerb, GlaxoSmithKline) has been approved for treating advanced or metastatic breast cancer.
"Lapatinib is a dual kinase inhibitor, targeting two receptor proteins on breast cancer cells, HER2 and EGFR [epidermal growth factor receptor]," said Laura Boehnke Michaud, Pharm.D., BCOP, clinical pharmacy specialist in breast oncology at the University of Texas M. D. Anderson Cancer Center. Michaud explained that these receptors are very important for breast cancer growth and division and allow for targeted therapy. "We know from previous work with trastuzumab that giving drugs that block HER2 also appears to make chemotherapy, and probably hormone therapy, more effective against the cancer cells. We don't exactly understand the mechanism behind this increased activity, but it is clear that this occurs with lapatinib as well."
Lapatinib is likely to increase exposure to concomitantly administered drugs that are metabolized by CYP3A4 or CYP2C8. Strong inhibitors of CYP3A4 should be avoided. If impossible, a dose reduction to 500 mg per day of lapatinib should be considered. Patients taking lapatinib should also avoid strong inducers of CYP3A4; however, a gradual dosage increase from 1250 mg up to 4500 mg per day of lapatinib should be considered if coadministration is unavoidable, and should be based on tolerability. When severe hepatic impairment exists, a reduction to 750 mg per day is predicted to adjust the area under the curve (AUC) into the normal range.
"This is the future of cancer therapy," Michaud said of the newer, more targeted therapies such as trastuzu-mab and lapatinib. "Over the past 10 years, we have been able to improve the rates of survival and duration of life for women with metastatic breast cancer through the development and availability of new drugs."
Lapatinib will be available through specialty pharmacy ivpcare, a division of OTN Specialty Services. Prescriptions can be called in directly to ivpcare at 1-(800) 424-9002 or faxed to 1-(800) 874-9179. In addition, GSK will launch Tykerb CARES, a program for patients and healthcare professionals that will address product inquiries, offer assistance obtaining the product, and help with reimbursement issues. Tykerb CARES can be reached at 1-(866) 4-TYKERB.
TIPS TO REMEMBER Tykerb