Roche has presented more positive late-stage data on its eagerly-anticipated breast cancer drug T-DM1 which shows that the antibody drug conjugate met a co-primary endpoint of overall survival.

The Swiss major's Genentech unit announced updated results from the Phase III study known as Emilia, which showed that T-DM1, which combines the Swiss major's blockbuster Herceptin (trastuzumab) with partner ImmunoGen's chemotherapy DM1 (emtansine) significantly extended the lives of people with HER2-positive metastatic breast cancer compared to the combination of GlaxoSmithKline's Tykerb/Tyverb (lapatinib) and Roche's own chemotherapy Xeloda (capecitabine). This follows previous data from Emilia which showed that T-DM1 was significantly better than the current drug regimen (ie the Tykerb/Xeloda combo) at keeping HER2-positive mBC patients' advanced tumours from progressing (9.6 months versus 6.4 months).

Specific data regarding the OS endpoint will be presented at an upcoming medical meeting. Genentech has submitted a Biologics License Application for T-DM1 to the US Food and Drug Administration and Roche will shortly file the drug with the European Medicines Agency.

Based on the OS results, people in the Tykerb/Xeloda arm of Emilia will be offered the option to receive T-DM1 and Genentech is starting an expanded access programme in the USA to provide the drug to patients, under certain circumstances, while it seeks regulatory approval.

Roche's chief medical officer Hal Barron said "we believe that antibody-drug conjugates have the potential to change the future treatment of cancer, and we look forward to working with regulatory authorities in the hope of bringing another potential treatment option to people with HER2-positive mBC".

Analysts are impressed and Cowen & Co's Simos Simeonidis and Yatin Suneja issued a research note saying "the OS news is definitely an incremental positive, albeit expected, since it completes the data part of the story of T-DM1 being a very effective and safe drug". They added that "based on feedback from our breast cancer oncology consultants, we believe that once approved, T-DM1 will rapidly take over a significant portion of Herceptin's market share in the metastatic setting".

The brokers conclude that "since it will probably be priced at a meaningful premium to Herceptin, we think T-DM1 could end up as one of the biggest biotech drugs".