Proton pump inhibitors and antibiotics — two of the most commonly prescribed drug classes — may be sabotaging the effectiveness of durvalumab in patients with stage III non-small cell lung cancer. A post hoc analysis of the landmark PACIFIC trial found that patients on these medications before starting immunotherapy had significantly shorter survival. Researchers suspect gut microbiome disruption may be the culprit.
Two of the most widely used drug classes in medicine — proton pump inhibitors (PPIs) and antibiotics — may be undermining immunotherapy outcomes in lung cancer patients. A post hoc analysis of the phase 3 PACIFIC trial, published in Lancet Oncology, found that patients with unresectable stage III non-small cell lung cancer (NSCLC) who were exposed to either medication before starting durvalumab had meaningfully worse survival compared to those who weren't.
The analysis covered 660 patients who received durvalumab or placebo after chemoradiotherapy, with a median follow-up of over 62 months. Notably, the survival impact was specific to the durvalumab group — the medications showed no effect in placebo patients — pointing to a treatment-dependent pattern likely tied to gut microbiome disruption.
By the Numbers
Why it matters: This is the first study to flag this association in the curative-intent, earlier-stage NSCLC setting. While prospective validation is still needed, clinicians may want to carefully weigh the necessity of PPIs and antibiotics in patients about to start immune checkpoint inhibitor therapy.
