London-based Glaxo said interim results from a mid-stage trial of the drug in 40 women with advanced breast cancer showed that 35 percent had their tumors shrink by at least 30 percent.
Lapatinib is an oral drug designed to block two biological switches involved in cancer growth.
The trial presented here at a meeting of the American Society of Clinical Oncology tests the drug as the first therapy for breast cancer patients whose tumors involve a protein called HER-2. Previously, the company had considered filing late this year on the basis of mid-stage trials in patients with advanced cancer who had failed other treatment options.
Paoletti said Glaxo has proven that lapatinib has activity, but the mid-stage trial data is not sufficient to support a regulatory filing. He said the company could seek approval of the drug in either the first-line or second-line breast cancer indications, depending on which trials are most successful.
