Japan’s Eisai Co Ltd said on Friday that its experimental treatment for advanced breast cancer had shown tumour fighting activity in mid-stage trials.

The drug candidate, called E7389, is one of Eisai’s most promising in-house cancer drugs, although it suffered a setback this year when the drug maker learned it could not seek early approval in the United States.

The median progression-free survival rate was 2.6 months, and the median overall survival rate was 10.3 months, according to the 299-patient Phase II study.

“The anti-tumour activity of E7389, as observed in this study, is encouraging, given the line of limited treatment options for women with advanced breast cancer who have previously received multiple lines of therapy,” lead investigator Linda Vahdat, of Weill Cornell Medical College in New York, said in a statement.

Patients in the trial had received a median of four prior chemotherapy regimens.

Results of the study will be presented at the American Society of Clinical Oncology meeting on June 2.

Eisai is best known for its Alzheimer’s drug Aricept but has thrown its lot behind cancer drugs, recently acquiring cancer specialist MGI Pharma Inc for $3.9 billion.

Japan’s fourth-largest drug maker has yet to bring any of its own cancer drug candidates to market, and an early approval of E7389 for advanced breast cancer would have been a significant milestone for the company.

It had been hoping to make a submission under special U.S. Food and Drug Administration rules that allow accelerated approval for serious or life-threatening diseases, but could not do so as FDA had approved another drug, ixabepilone, made by Bristol-Myers Squibb, for this specific indication.

TOKYO (Reuters)