PRJNA379764
Baseline gut microbiota predicts clinical response and colitis in metastatic melanoma patients treated with ipilimumab
Ipilimumab, an immune checkpoint inhibitor targeting CTLA-4, prolongs survival in a subset of patients with metastatic melanoma but can induce immune-related adverse events, including enterocolitis. We hypothesized that baseline gut microbiota could predict ipilimumab anti-tumor response and/or intestinal toxicity.Patients and MethodsTwenty-six patients with metastatic melanoma treated with ipilimumab were prospectively enrolled. Fecal microbiota composition was assessed at baseline and before each ipilimumab infusion, using 16S rRNA gene sequencing. Patients were further clustered based on microbiota patterns. Peripheral blood lymphocytes immunophenotypes were studied in parallel.ResultsA distinct baseline gut microbiota composition was associated with both clinical response and colitis. As compared to patients whose baseline microbiota was driven by Bacteroides (Cluster B, n=10), patients whose baseline microbiota was enriched with Faecalibacterium genus and other Firmicutes (Cluster A, n=12) had longer progression-free survival (p=0.0039) and overall survival (p=0.051). Most of the baseline colitis-associated phylotypes were related to Firmicutes (eg, relatives of Faecalibacterium prausnitzii and Gemmiger formicilis), whereas no-colitis related phylotypes were assigned to Bacteroidetes. A low proportion of peripheral blood regulatory T cells was associated with Cluster A, long-term clinical benefit and colitis. Ipilimumab led to a higher Inducible T-cell COStimulator induction on CD4+ T cells and to a higher increase in serum CD25 in patients who belonged to Faecalibacterium-driven Cluster A.ConclusionBaseline gut microbiota enriched with Faecalibacterium and other Firmicutes is associated with beneficial clinical response to ipilimumab and more frequent occurrence of ipilimumab-induced colitis.