Updated results from a phase III trial of Roche's antibody-drug conjugate (ADC) T-DM1 in breast cancer indicate the drug helps extend survival by nearly six months, a result which one investigator in the trial has described as "truly outstanding".
T-DM1, which combines Roche's anti-HER2 antibody Herceptin (trastuzumab) with a chemotherapy payload, is due to reach the market next year and has already been tipped as a major seller for Roche with some analysts predicting peak revenues of up to $3.5bn a year.
The new data from the EMILIA study were presented yesterday at the European Society for Medical Oncology (ESMO) annual meeting, and come from a study involving patients with HER2-positive breast cancer whose disease had progressed despite earlier treatment with Herceptin.
Those treated with T-DM1 (trastuzumab emtansine) lived for 30.9 months on average, compared to 25.1 months for patients treated with capecitabine and GlaxoSmithKline's Tykerb/Tyverb (lapatinib), which is currently the only approved regimen in this setting.
The ADC was also associated with significantly fewer chemotherapy-related side effects, with severe reactions occurring in 41 per cent of the T-DM1 group versus 57 per cent of patients treated with the comparator regimen.
"These results are truly outstanding and will positively alter the outlook and outcomes for patients with HER2-positive breast cancer," said Professor Paul Ellis of King's College London, which served as one of the investigating sites for the EMILIA trial.
"For T-DM1 to offer such a significant survival benefit, while also improving the quality of patients' lives by reducing the side effects of chemotherapy, is a remarkable achievement, particularly as HER2-positive breast cancer is so difficult to treat in its advanced stages," he added.
Aside from the patient benefits, T-DM1 is an important product commercially for Roche as it starts to consider life after Herceptin's patent protection starts to expire in 2014, placing the drug's $6bn annual revenues - and 15 per cent of Roche's total turnover - at risk of generic competition.
Roche is developing additional products intended to protect its Herceptin franchise, including a subcutaneous formulation of the drug partnered with Halozyme Therapeutics which is scheduled for filing later this year.