The FDA said the phase 3trial showed that atezolizumab plus paclitaxel did not significantly reduce the risk of cancer progression and death, when compared with paclitaxel plus placebo, in programmed death-ligand 1 (PD-L1)–positive patients.
“Additionally, interim overall survival results favored paclitaxel plus placebo over paclitaxel plus atezolizumab in both the PD-L1-positive population and total population,” the FDA noted.
As a result, “health care professionals should not replace paclitaxel protein-bound (Abraxane) with paclitaxel in clinical practice,” the FDA advised.
Atezolizumab is approved for use in combination with protein-bound paclitaxel, also known as nanoparticle albumin–bound paclitaxel (nab-paclitaxel), to treat patients with unresectable, locally advanced, or metastatic TNBC whose tumors express PD-L1, as detected by an FDA-approved test. The combination was granted accelerated approval for this indication last year.
Atezolizumab plus nab-paclitaxel is the combination most often used in PD-L1-positive TNBC, as opposed to atezolizumab and unbound paclitaxel, said, an associate professor of medicine and director of the Stanford Cancer Institute Breast Cancer Program at Stanford (Calif.) University.
However, as the FDA noted, “continued approval of atezolizumab in combination with [nab-paclitaxel] may be contingent on proven benefit of the treatment in additional trials.”
Dr. Telli explained that atezolizumab was granted accelerated approval for the treatment of PD-L1-positive TNBC based on results of the phase 3 trial, which compared nab-paclitaxel plus atezolizumab with nab-paclitaxel plus placebo.
“Additional data from IMpassion131 was hoped to be used to support the conversion of the accelerated approval to a full approval. Since IMpassion131 was negative, it unfortunately places the status of atezolizumab in [TNBC] in jeopardy as the benefits were not corroborated. The FDA may move to revoke the approval of atezolizumab for [TNBC],” Dr. Telli said.
In its alert, the FDA stated that it “will review the findings of IMpassion131 and will communicate new information regarding the IMpassion131 results and any potential changes to prescribing information.”
“We need to wait for full presentation and publication of the study results, but, in my assessment, the negative results in IMpassion131 are most likely due to differences in patient selection [from IMpassion130],” Dr. Telli said.
Results from IMpassion131 are scheduled to be presented at the.
The IMpassion trials were funded by Roche, maker of atezolizumab. Dr. Telli disclosed relationships with AbbVie, AstraZeneca, Merck, PharmaMar, Pfizer, and Tesaro.