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

Results from a 137-patient Phase II trial, which have been presented at the European Multidisciplinary Cancer Congress in Stockholm, show that patients with advanced HER2-positive breast cancer treated with T-DM1 (trastuzumab emtansine) benefited from an additional five months of life without their disease worsening when compared to the current best standard of care, Herceptin and chemotherapy. Median progression-free survival (PFS) showed an increase from 9.2 months with Herceptin and chemotherapy, to 14.2 months with T-DM1.

Also, patients who received T-DM1 experienced fewer side effects compared to those who received Herceptin plus chemotherapy, with the rate of side effects requiring hospitalisation reduced by nearly half (46.4%) with T-DM1 vsersus 89.4% with Herceptin and chemotherapy.

T-DM1 is an antibody drug conjugate (ADC) which contains a chemotherapy (maytansine) stably linked to Herceptin.  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.

There are three ongoing Phase III studies of T-DM1, including one that compares the 'armed antibody' with GlaxoSmithKline's Tykerb  (lapatinib) plus Roche's own chemotherapy Xeloda (capecitabine). The Swiss major expects the latter study, the results of which are due next year, to form the basis of regulatory submissions for T-DM1.

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