Phase 3 IMpassion131 Study Fails to Improve Progression-Free Survival in Metastatic Triple-Negative Breast Cancer

The phase 3 Impassion131 study — designed to evaluate the immunotherapy Tecentriq (atezolizumab) in combination with the chemotherapy paclitaxel in patients with PD-L1-positive metastatic triple-negative breast cancer (TNBC) — failed to meet its primary endpoint of improving progression-free survival, compared with placebo plus paclitaxel.

“(These) results underscore the need to better understand the cancer and immune system interactions, including the chemotherapy backbone and associated regimens,” said Dr. Levi Garraway, Genentech’s chief medical officer and head of global product development, in a company-issued press release. “We remain committed to finding optimal treatments for all people living with this aggressive disease.”

Genentech noted in the release that full data from the study will be presented at a future scientific meeting.

PD-L1 is a protein some cancers express to avoid detection by the immune system, and Tecentriq disables it with the aim of helping the body to recognize and fight the disease. Breast cancer characterized as triple-negative when it is not fueled by hormones or the protein HER2.

In the multi-center, randomized, double-blind phase 3 study, the researchers evaluated Tecentriq or placebo, in combination with chemotherapy, as a first-line treatment for patients with previously untreated, inoperable, locally advanced or metastatic TNBC.

Measuring progression-free survival, which is the time from treatment to disease worsening, was the main goal of the study. Additional secondary goals included measuring overall survival, objective response rate and duration of response.

Although the data for overall survival shows a negative trend, according to the release, the data were immature at the time of analysis. Further analysis of overall survival data is planned. No new side effects were identified in the analysis and the Tecentriq combination demonstrated similar side effects to what is already associated with each treatment.