* T-DM1 drug reaches both primary endpoints in trial
* Drug seen as successor to Herceptin blockbuster
* Potential peak sales seen at 1.7 bln Sfr
* Genentech to seek EU approval, already applied with FDA
By Emma Thomasson
ZURICH, Aug 27 (Reuters) - Swiss drugmaker Roche Holding AG said its "armed antibody" T-DM1 drug significantly extended the lives of women with an aggressive type of breast cancer compared with those receiving the standard drug cocktail.
Breast cancer is the most common cancer among women worldwide, with about 1.4 million new cases diagnosed each year and more than 450,000 women dying of the disease annually, according to the World Health Organisation's International Agency for Research on Cancer.
Roche said its Genentech unit will soon submit a marketing application to the European Medicines Agency for trastuzumab emtansine (T-DM1) and has already applied for a license with the U.S. Food and Drug Administration.
Roche said the study of the drug had now met both primary efficacy endpoints of significant improvements in overall survival and progression-free survival, adding it will present the data at an upcoming medical meeting.
Roche, the world's largest maker of cancer drugs, has been developing T-DM1 as a successor to its blockbuster Herceptin, its third-biggest seller, which could be exposed to so-called "biosimilar" generic competition in Europe from around 2015.
Vontobel analyst Andrew Weiss said the data could be presented at the San Antonio Breast Cancer Symposium in December, predicting possible peak sales for the drug of 1.7 billion Swiss francs ($1.8 billion).
"Roche is the dominant force in cancer and ... continues to drive innovation in this area," Weiss said as he confirmed his "buy" recommendation on Roche shares, which were up 0.3 percent by 0733 GMT.
The trial for women with breast cancer known as HER-2 positive - which makes up about a fifth of all breast cancers - compared T-DM1 to a combination of GlaxoSmithKline drug Tykerb, and Roche's Xeloda.
An advantage of T-DM1 over conventional treatment using Herceptin plus chemotherapy, is that it causes fewer adverse side-effects like hair loss and low white blood cell counts.
T-DM1 combines trastuzumab, an antibody and the active ingredient in Herceptin, with the agent DM1 - a derivative of a powerful type of chemotherapy called maytansine - which is carried directly into cells.
"We believe that antibody-drug conjugates have the potential to change the future treatment of cancer," Roche Chief Medical Officer Hal Barron said in a statement.
In June, U.S. health regulators approved Perjeta, another new breast cancer drug from Roche for HER2-positive women.
Genentech, which developed Perjeta, suffered a blow last year when the FDA revoked approval for its blockbuster drug Avastin as a treatment for breast cancer, saying the drug was not effective enough to justify its risks.