Trials of lapatinib ditosylate, a new drug for herceptin-resistant breast cancer, have proved so beneficial that GlaxoSmithKline (GSK) has ended the study early and is proceeding to obtain regulatory approval.

Only one in five breast tumours respond to herceptin, so there is an urgent need for alternative therapies. In this phase III study, 321 women with advanced herceptin-resistant breast cancer were given lapatinib ditosylate in combination with capecitabine, an existing chemotherapeutic agent. GSK say that they have observed a 50% delay in cancer growth in the treated women and have therefore, in consultation with the Independent Data Monitoring Committee, halted patient recruitment. “We are extremely encouraged by these data, which suggest that Tykerb [lapatinib ditosylate] may offer significant benefit as an oral medication in combination with chemotherapy” said Paolo Paoletti of GSK ( http://www.timesonline.co.uk, 4 April 2006).

This means that the drug might become available much sooner than expected. “On the basis of this and other data we now plan to file [for regulatory approval] in the US and Europe during the second half of 2006” said Paoletti (http://www.washingtonpost.com, 10 April 2006).

Lapatinab ditosylate is a small-molecule dual-kinase inhibitor that targets both EGFR and ERBB2. For this reason, it could also be used in lung cancer, and GSK are actively pursuing this possibility. Another advantage is that, unlike traditional chemotherapy, it is orally active.

Sarah Rawlings, of the UK's Breakthrough Breast Cancer, expressed cautious optimism from those outside the pharmaceutical industry: “This could be another option in the increasing armoury of breast [cancer] drugs available. We look forward to hearing in more detail the possible benefits and side-effects” (http://www.eveningnews.co.uk, 4 April 2006).