GlaxoSmithKline followed up the filing of its candidate breast cancer drug Tykerb in the USA last month with a similar application on the other side of the Atlantic.

The UK-headquartered drugmaker applied to the European Medicines Agency (EMEA) to market Tykerb (lapatinib) in combination with Roche Holding's chemotherapy treatment Xeloda (capecitabine), for advanced breast cancer in women who have already received other treatments.

The filing is based on a Phase III study - which was terminated early in March because it met its primary endpoint of extending the time to disease progression - and provided clear evidence that Tykerb was effective as part of a combination regimen in advanced HER2-positive breast cancer.

Tykerb is a potential rival to Roche’s blockbuster breast cancer drug Herceptin (trastuzumab), with the advantage of being an orally-active drug while Herceptin is dosed by injection. Both block the HER-2 receptor, while Tykerb also has activity against the epidermal growth factor receptor (EGFr).

GSK has suggested that Tykerb may lack the potential for cardiotoxicity seen with Herceptin, and because it is a small molecule can cross into the central nervous system to tackle brain metastases, something that Herceptin – an antibody - cannot do.

The initial filings for Tykerb in both the USA and Europe are in patients who have failed to respond to or cannot tolerate Herceptin, and GSK is planning to extend the indications for its drug into earlier-stage treatment.

If successful in this endeavour, Tykerb could become a blockbuster with multibillion dollar sales potential, according to analysts.