GSK Reports Phase III Results In ErbB2-Positive Metastatic Breast Cancer Study

GlaxoSmithKline (GSK) has reported Phase III study results which showed that women with an aggressive form of breast cancer experienced a median survival of 14 months, when treated with an investigational combination of Tykerb (lapatinib) plus Herceptin (trastuzumab).

The results of the Phase III study in ErbB2-positive metastatic breast cancer were presented during the 32nd Annual CTRC-AACR San Antonio Breast Cancer Symposium, held in San Antonio, Texas.

Reportedly, the study included 296 women with a type of breast cancer known as ErbB2-positive disease, characterised by an overexpression of the ErbB2 protein in the cancer cells. Patients enrolled in the study experienced recurrence of breast cancer despite a median of three prior trastuzumab-based therapies. The data showed that patients overcame resistance to trastuzumab with the introduction of the lapatinib-trastuzumab combination.

In the study, the patients were randomised to receive single agent lapatinib (1500mg/daily) or a combination of lapatinib (1000mg po daily) plus trastuzumab (2mg/kg). For those patients treated with monotherapy lapatinib, cross-over to the combination was allowed if the disease progressed after at least four weeks of therapy.

Final analysis showed clinical activity for lapatinib in the control arm. Women treated with monotherapy lapatinib experienced a median overall survival of 9.5 months, compared to 14 months when treated with the combination.

Tykerb is currently indicated in combination with Xeloda (capecitabine) for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress ErbB2 and who have received prior therapy including an anthracycline, a taxane, and Herceptin (trastuzumab). Tykerb alone, or in combination with Herceptin, is not approved in this setting.

Kimberly Blackwell, primary investigator at Duke University Medical Center, said: “The clinical benefits brought forth by the lapatinib and trastuzumab combination are quite compelling and lead me to believe the agents may be acting together to form a sort of ‘dual blockade’ to obstruct the ErbB2 pathway necessary for the tumour to thrive.

“It’s possible that, by lapatinib working inside the cell and trastuzumab working outside the cell, the combination of agents is able to provide a more complete anti-tumour attack. To achieve a survival advantage of greater than one year for this aggressive form of breast cancer is very encouraging.”