Genentech announced that the phase 3 study of atezolizumab in combination with paclitaxel for the first-line treatment of patients with metastatic triple-negative breast cancer (TNBC) did not meet its primary end point in the PD-L1-positive population.

The multicenter, double-blind, placebo-controlled IMpassion131 study assessed the efficacy and safety of atezolizumab, a programmed death-ligand 1 (PD-L1) blocking antibody, plus paclitaxel in 651 adult patients with previously untreated, inoperable locally advanced or metastatic, centrally confirmed TNBC. Patients were randomized 2:1 to receive atezolizumab or placebo plus paclitaxel until disease progression or unacceptable toxicity. The primary end point was progression-free survival (PFS), as per RECIST 1.1.

Findings showed that the study did not meet statistical significance for PFS and also demonstrated a negative trend in overall survival (secondary end point) for patients in the atezolizumab plus paclitaxel arm. The study, however, was not powered for overall survival and data was immature at the time of analysis. The safety profile of atezolizumab was consistent with that seen in previous studies and no new safety signals were reported.

Full study results from IMpassion131 will be presented at a future medical meeting.

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“While we are disappointed by the results from the IMpassion131 study, we are grateful for all the patients, families and physicians who were involved in the study,” said Levi Garraway, MD, PhD, chief medical officer and head of Global Product Development. “Today’s results underscore the need to better understand the cancer and immune system interactions, including the chemotherapy backbone and associated regimens.”

Atezolizumab is marketed under the brand name Tecentriq and is currently approved in combination with Abraxane (paclitaxel [protein-bound]; Celgene) for the treatment of unresectable locally advanced or metastatic TNBC in patients whose tumors express PD-L1. In June 2020, Genentech announced results from the IMpassion031 study evaluating Tecentriq plus Abraxane in patients with previously untreated, early TNBC. Results showed the combination therapy demonstrated a statistically significant and clinically meaningful improvement in pathological complete response, regardless of PD-L1 expression (primary end point).

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Reference

1. Genentech provides update on phase III study of Tecentriq in combination with paclitaxel for people with metastatic triple-negative breast cancer. https://www.businesswire.com/news/home/20200806005915/en/Genentech-Update-Phase-III-Study-Tecentriq-Combination. Accessed August 7, 2020.