Roche has been boosted by more promising data on T-DM1, which combines its blockbuster Herceptin with partner ImmunoGen's chemotherapy drug DM1.

The Swiss major announced topline results from the 991-patient Emilia study, the first randomised Phase III trial of T-DM1 (trastuzumab emtansine). It showed that patients with HER2-positive metastatic breast cancer who received the combo lived significantly longer without their disease getting worse (ie progression-free survival) compared to those who received GlaxoSmithKline's Tykerb (lapatinib) plus Roche's own Xeloda (capecitabine).

The company noted that final results for overall survival (OS), a co-primary efficacy endpoint of Emilia, are not yet mature, adding that the safety profile of T-DM1 was consistent with that seen in previous studies.  Roche noted that the advantage of the combo is that it targets and inhibits HER2 signalling and at the same time delivers the chemotherapy directly inside HER2-positive cancer cells.

Saying that T-DM1 "represents a new approach for the treatment of patients with HER2-positive breast cancer that comes from our decades of research", Roche chief medical officer Hal Barron noted that the combo "is our first antibody drug conjugate and it may help people who still need more treatment options for this aggressive disease".

Based on these findings, Roche plans to submit the drug in Europe and the USA later this year. In addition to Emilia, there are two ongoing Phase III studies: the first, Marianne, compares three different regimens (T-DM1, T-DM1 plus Roche's investigational breast cancer drug pertuzumab and Herceptin plus a taxane chemotherapy), while Th3resa is comparing trastuzumab emtansine with physician's choice of treatment in people with HER2-positive metastatic breast cancer who have already received both Herceptin and Tykerb.

Herceptin goes off-patent in Europe in 2015 and Roche hopes T-DM1 will replace. Analysts are predicting another oncology blockbuster for the Basel-headquartered company.