LONDON - A experimental drug being developed by Roche blocks a common biological pathway linked to the spread of many cancers and has proved highly effective in mice, scientists said on Wednesday.

The compound GDC-0941 was originally pioneered by British biotechnology company Piramed, which was acquired by the Swiss drugmaker for $160 million in April.

It is currently in Phase I clinical studies, the first round of testing in humans, in Britain and the United States.

A study published in the journal Molecular Cancer Therapeutics showed the drug reduced the growth of glioblastoma -- the most common form of brain tumour -- in mice by up to 98 percent and decreased the growth of ovarian tumours 80 percent.

Scientists also found the drug worked against a number of cell lines derived from other human cancers.

GDC-0941 works by blocking the phosphatidylinositide 3-kinase (PI3) pathway which is often hijacked by cancer cells, enabling them to grow and spread.

Our hope is that that we have created a potent anti-cancer weapon that directly targets the processes which feed the cancer cells while sparing most of the healthy cells, said Paul Workman of Britain's Institute of Cancer Research.

But it's early days and we still have a lot to learn about the potential of this drug. (Reporting by Ben Hirschler; Editing by David Cowell)