Chugai Pharmaceutical Co. Ltd. announced that it has filed a new drug application to the Ministry of Health, Labour and Welfare (MHLW), for antibody-drug conjugate ‘trastuzumab emtansine (T-DM1)' for the treatment of 'HER2-positive metastatic or recurrent breast cancer'. Chugai filed the application with the MHLW based on the results from an overseas phase III clinical trial (the EMILIA trial) and a domestic phase II clinical trial.

The EMILIA trial is an international phase III study comparing T-DM1 alone to lapatinib in combination with capecitabine in people with HER2-positive metastatic or unresectable locally advanced breast cancer who had previously been treated with trastuzumab and a taxane chemotherapy. Japanese patients were not included in the EMILIA trial. The EMILIA trial had progression free survival (PFS) as one of its primary endpoints, and patients who received T-DM1 experienced a 35% reduction in the risk of their disease worsening or death compared to those who received lapatinib plus capecitabine.

The median PFS improved by 3.2 months from 6.4 months of lapatinib and capecitabine to 9.6 months of T-DM1 (hazard ratio=0.65; p<0.0001). As for overall survival (OS), another primary endpoint, the results showed the risk of death was reduced by 32% for patients who received T-DM1 compared to those who received lapatinib plus capecitabine. Patients in the study treated with T-DM1 survived a median time of 5.8 months longer than those who received lapatinib and capecitabine (median OS: 30.9 months vs.

25.1 months) (hazard ratio=0.68; p=0.0006). Regarding safety, fewer patients who received T-DM1 experienced Grade 3 or higher AEs than those who received lapatinib plus capecitabine. The most common Grade 3 or higher AEs reported in patients receiving T-DM1, compared to those receiving lapatinib plus capecitabine, included low platelet count and increase of AST and ALT levels.

The phase II trial conducted in Japan confirmed the efficacy and the tolerability of T-DM1 in Japanese patients. The number of patients newly diagnosed with breast cancer in Japan continues to rise each year and is estimated at approximately 60,000 annual average in 2015-2019. And HER2 expression has been observed in approximately 20% of breast cancer patients.