Lapatinib (trade name Tykerb) is an inhibitor of 4-anilinoquinazolina kinase with a unique mechanism of action, as it is a potent, reversible and selective inhibitor of the intracellular tyrosine- kinase of both receptor EGFR (ErbB1) and HER2 l (ErbB2). In particular, Lapatinib targets the intracellular domains of these two receptor tyrosine-kinases and it induces apoptosis and growth inhibition of tumor cells.
The drug is registered in combination with capecitabine for the treatment of advanced or metastatic breast cancer, whose tumors overexpress ErbB2, which have progressed after treatment including with anthracyclines, taxanes and therapy with trastuzumab for metastatic disease.
Compared to Trastuzumab, a monoclonal antibody that targets the HER2 protein on the outside of the cell, Tykerb is a small molecule that enters the cell and blocks the function.
For this reason, Tykerb is active in some HER2 positive tumors that were treated with Trastuzumab and can no longer benefit from treatment with the monoclonal antibody.
The approval of Tykerb is based on a randomized clinical trial in approximately 400 women with metastatic breast cancer or advanced HER+.
In the study, half of the patients received Tykerb with Capecitabine and half another was treated only with Capecitabine.
Compared with patients treated with Capecitabine alone, the group of patients treated with Tykerb and Capecitabine presented a statistically significant improvement in time to tumor progression.
In addition, the percentage of tumor response was higher in patients who received Tykerb and capecitabine (24% vs. 14%). The most common adverse events reported with the use of lapatinib were diarrhea, nausea, vomiting, rash and hand-foot syndrome. Reversible reductions were observed in cardiac function.