Using antibiotics during treatment with immune checkpoint inhibitors may limit the therapy’s effect, according to study results published in the American Journal of Clinical Oncology.

In a retrospective analysis of electronic health records from 414 patients treated at a single institution from January 2011–December 2018, researchers looked at antibiotic use within the 12 weeks before or after patients began treatment with immune checkpoint inhibitor drugs (i.e., nivolumab, pembrolizumab, and atezolizumab). They found that antibiotic use after starting immune checkpoint inhibitor therapy, especially within the first six weeks, was significantly linked to poorer response to the medication. However, antibiotic use prior to beginning therapy did not have a significant impact on checkpoint inhibitor efficacy.

“This study demonstrates that the use of antibiotics during immune checkpoint inhibitor therapy significantly negatively impacts the efficacy of immunotherapy,” the researchers concluded. “The maximal negative impact occurs if the antibiotics are used in the first six weeks after initiating immune checkpoint inhibitors.”

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