Combined low-dose ipilimumab and pembrolizumab after sequential ipilimumab and pembrolizumab failure in advanced melanoma.

With the wide use of anti-PD-1 therapy, an increasing number of patients progress under treatment. Combined immunotherapy with anti-CTLA-4 and anti-PD-1 antibodies induces higher response rates as first-line treatment in comparison to single-agent therapy, however, with substantial toxicity since the combination of ipilimumab (3 mg/kg) and nivolumab (1 mg/kg) induced 55% grade 3/4 treatment-related adverse events and treatment discontinuation rates of 39%. In this case series, we investigated the efficacy and toxicity of the combined immunotherapy with low-dose ipilimumab (1 mg/kg) plus pembrolizumab (2 mg/kg) in patients with metastatic melanoma with progressive disease under sequential monotherapy with both agents. All patients had received at least three lines of treatment, 78% of patients were M1c, and 67% had brain metastases. Stable disease was observed in 3 out of 9 patients with a median overall survival of 8 months after double checkpoint inhibition. No treatment-related grade 3/4 adverse events occurred, and none of the patients needed to discontinue the treatment due to toxicity. Further trials are needed to investigate combined immunotherapy as rescue treatment in heavily pretreated melanoma patients to find optimal dosage in regard to outcome and toxicity.