Glaxo drug slows breast cancer in US study

ATLANTA, June 4 (Reuters) GlaxoSmithKline Plc's experimental pill Tykerb plus chemotherapy slowed aggressive breast cancers that had started growing despite treatment with the drug Herceptin, US researchers said.

A company-sponsored study of 321 women showed the disease did not progress for 37 weeks in patients treated with Tykerb and oral chemotherapy drug Xeloda, compared with 20 weeks for others who received only Xeloda.

Analysts say Tykerb, known generically as lapatinib, could become a multibillion dollar seller. Glaxo hopes to launch the drug next year.

The breast cancer trial was stopped ahead of schedule because women given Tykerb plus Xeloda did so much better than those on Xeloda alone.

Xeloda, known generically as capecitabine, is sold by Roche AG, which also sells Herceptin along with Genentech Inc.

If approved for sale, Tykerb could offer hope to women whose cancers return after they were successfully beaten back by Herceptin, said Dr Charles Geyer, director of breast medical oncology at Allegheny General Hospital in Pittsburgh and the study's lead author.

''The ability to control cancer growth a second time on this order of magnitude ... is really quite substantial for a patient,'' Geyer said.

The findings were released yesterday at an annual meeting of the American Society of Clinical Oncology.

Glaxo also is testing if Tykerb is useful earlier in breast cancer. As a pill it could prove to be a more convenient alternative to Herceptin, which must be injected. Herceptin's annual sales are about 1.8 billion dollars.

Herceptin, or trastuzumab, is given by injection to treat aggressive breast cancers that produce large amounts of the HER2 protein - about 20 per cent to 25 per cent of all cases.

Tykerb targets the HER2 protein as well as another known as EGFR. Both are believed to help tumors grow.

All of the patients studied by Glaxo had cancers that tested positive for the HER2 protein.

Geyer said no Tykerb patients developed symptoms of congestive heart failure, a serious potential side effect from Herceptin.

Side effects were similar between the Tykerb and Xeloda-only groups, although women who took Tykerb were more likely to experience diarrhea and rashes.

Fifty-eight percent of Tykerb patients reported mild to moderate diarrhea, compared with 39 per cent in the chemo-only group. The difference in rashes was 30 per cent for Tykerb patients versus 18 per cent.

REUTERS SY KOP0848