A Study of Trastuzumab Emtansine Versus Taxane in Participants With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Advanced Gastric Cancer

Study Summary

This multicenter, randomized, adaptive Phase II/III study will evaluate the efficacy and safety of trastuzumab emtansine (T-DM1) compared to standard taxane (docetaxel or paclitaxel) treatment in participants with human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer. At the start of the trial (stage 1), participants will be randomized with a ratio 2:2:1 to one of three treatment arms: Arm A: trastuzumab emtansine 3.6 milligram per kilogram (mg/kg) per intravenous injection (IV) every 3 weeks; Arm B: trastuzumab emtansine 2.4 mg/kg IV every week; Arm C: standard taxane therapy (docetaxel 75 milligram per meter square \[mg/m\^2\] IV every 3 weeks or paclitaxel 80 mg/m\^2 kg IV every week per investigator choice). At the end of the first stage of the study, the dose and schedule of trastuzumab emtansine that will be used in the second stage of the study will be selected by an Independent Data Monitoring Committee (IDMC). The regimen selection analysis will be made after approximately 100 participants across all three study arms have been treated for at least 12 weeks. Once a trastuzumab emtansine regimen has been selected, Stage I participants who were assigned to the treatment arm which was selected for Stage II of the study and participants who were in the standard taxane group will continue to receive their assigned treatment regimen. Stage I participants who were assigned to the regimen that was not selected for further evaluation will continue to receive their assigned regimen and will continue to be followed for efficacy and safety. In Stage II of the study, additional participants will be recruited and randomized with a ratio 2:1 to either the selected regimen of trastuzumab emtansine or to the standard taxane therapy. Participants will receive study treatment until disease progression, unacceptable toxicity, initiation of another cancer therapy or withdrawal.

Primary Outcome

Overall survival was defined as the time between the date of randomization and date of death due to any cause. Kaplan-Meier estimates were used for analysis. Participants for whom no death was reported prior to an analysis cutoff (30 June 2015) was censored at the latest date before the cutoff in which they were known to be alive. All data from the standard taxane therapy and trastuzumab emtansine 2.4 mg (selected treatment arm) from phase 2 and phase 3 (Stage 2) are combined into phase 3 data,

Interventions

• DRUG Taxane
• DRUG trastuzumab emtansine