The study compared trastuzumab emtansine to standard treatment with Herceptin (trastuzumab) plus docetaxel chemotherapy.
The results of the trial suggested that the patients who were given trastuzumab emtansine experienced 41% reduction in the risk of their disease worsening or death (progression-free survival, PFS) and lived a median of five months longer without their disease worsening.
In addition, people who received trastuzumab emtansine experienced fewer common and severe adverse events compared to those who received Herceptin plus chemotherapy.
Genentech Global Product Development chief medical officer and head Hal Barron said the improvement in progression-free survival with fewer side effects seen with trastuzumab emtansine.
"We believe this investigational antibody-drug conjugate approach, in which chemotherapy is attached to the antibody and selectively delivered to tumor cells, is an important potential weapon for fighting cancer and we look forward to the Phase III study results with trastuzumab emtansine," Barron said.