Antisoma has started a Phase II study evaluating the addition of its investigational drug AS1402 to Novartis’ hormone therapy Femara for post-menopausal women receiving first-line treatment for advanced breast cancer.

The London-headquartered firm says that approximately 110 patients will be randomly assigned to receive either Femara (letrozole) plus AS1402 or standard treatment with letrozole alone. The Phase II trial builds on a Phase I study in patients with heavily pre-treated breast cancer, which showed that AS1402 monotherapy was well-tolerated and was associated with prolonged stable disease in a number of patients. Final results of the new study are due in 2010.

AS1402 targets a cancer-associated form of the cell-surface protein MUC1, which is found in 90% of breast cancers and in a wide range of other tumours. Antisoma says recent studies have shown that MUC1 up-regulates the oestrogen signalling pathway targeted by endocrine therapies, such as Femara, which is a big earner for Novartis. Second-quarter sales for the oral treatment for women with hormone-sensitive breast cancer were up 26% to $291 million.

Hospitals in the USA, Russia, Ukraine, Poland and France are taking part in the Phase II study. Principal investigator Nuhad Ibrahim, of the University of Texas, said that "there is a clear rationale for testing AS1402 in this group of breast cancer patients, and we are pleased to be participating in this well-designed study”.

Antisoma's chief operating officer Ursula Ney noted that worldwide, “over 90,000 women each year receive endocrine treatment for advanced breast cancer, so many patients could benefit from any add-on therapy that improved outcomes in this setting”.