SOUTH SAN FRANCISCO ( TheStreet) --The Genentech unit of Roche ( RHHBY) announced positive top-line results from a phase III study of its experimental breast cancer drug T-DM1 that will allow the company to seek U.S. and European approval later this year. Patients with advanced metastatic breast cancer treated with T-DM1 lived significantly longer without their disease getting worse compared to patients treated with GlaxoSmithKline's ( GSK) Tykerb, Genentech said. Final results for overall survival are not yet mature. Detailed data from the phase III study, dubbed EMILIA, were withheld for presentation at a later medical meeting. Genentech said T-DM1's safety profile was "consistent" with previous studies of the drug. All patients in the study were on their second line of treatment for breast cancer, having already been treated with Genentech's Herceptin and chemotherapy. Based on these results, Genentech said it will submit T-DM1 for approval with the U.S. Food and Drug Administration later this year. Roche will seek European approval in the same time frame. T-DM1 is a second-generation version of Genentech's blockbuster breast cancer drug Herceptin. The drug consists of Herceptin (also known as trastuzumab) linked to a tumor-killing chemotherapy payload developed by ImmunoGen ( IMGN). If T-DM1 reaches the market, ImmunoGen will receive single-digit royalties pegged to the drug's sales by Genentech in the U.S. and Roche in the rest of the world. At Thursday's closing price of $13.74, ImmunoGen's market value of $1.05 billion more than accounts for T-DM1 sales. --Written by Adam Feuerstein in Boston. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: firstname.lastname@example.org. Follow TheStreet on Twitter and become a fan on Facebook.