There is no recommended therapy for malignant pleural mesothelioma that has progressed after first-line pemetrexed and platinum-based chemotherapy. Disease control has been less than 30% in all previous studies of second-line drugs. Preliminary results have suggested that anti-programmed cell death 1 (PD-1) monoclonal antibody could be efficacious in these patients. We thus aimed to prospectively assess the anti-PD-1 monoclonal antibody alone or in combination with anti-cytotoxic T-lymphocyte protein 4 (CTLA-4) antibody in patients with malignant pleural mesothelioma.

This multicentre randomised, non-comparative, open-label, phase 2 trial was done at 21 hospitals in France. Eligible patients were aged 18 years or older with an Eastern Cooperative Oncology Group performance status of 0–1, histologically proven malignant pleural mesothelioma progressing after first-line or second-line pemetrexed and platinum-based treatments, measurable disease by CT, and life expectancy greater than 12 weeks. Patients were randomly allocated (1:1) to receive intravenous nivolumab (3 mg/kg bodyweight) every 2 weeks, or intravenous nivolumab (3 mg/kg every 2 weeks) plus intravenous ipilimumab (1 mg/kg every 6 weeks), given until progression or unacceptable toxicity. Central randomisation was stratified by histology (epithelioid vs non-epithelioid), treatment line (second line vs third line), and chemosensitivity to previous treatment (progression ≥3 months vs <3 months after pemetrexed treatment) and used a minimisation method with a 0·8 random factor. The primary outcome was the proportion of patients who achieved 12-week disease control, assessed by masked independent central review; the primary endpoint would be met if disease control was achieved in at least 40% of patients. The primary endpoint was assessed in the first 108 eligible patients. Efficacy analyses were also done in the intention-to-treat population and safety analyses were done in all patients who received at least one dose of their assigned treatment. This trial is registered at ClinicalTrials.gov, number NCT02716272.

Between March 24 and August 25, 2016, 125 eligible patients were recruited and assigned to either nivolumab (n=63) or nivolumab plus ipilimumab (n=62). In the first 108 eligible patients, 12-week disease control was achieved by 24 (44%; 95% CI 31–58) of 54 patients in the nivolumab group and 27 (50%; 37–63) of 54 patients in the nivolumab plus ipilimumab group. In the intention-to-treat population, 12-week disease control was achieved by 25 (40%; 28–52) of 63 patients in the nivolumab group and 32 (52%; 39–64) of 62 patients in the combination group. Nine (14%) of 63 patients in the nivolumab group and 16 (26%) of 61 patients in the combination group had grade 3–4 toxicities. The most frequent grade 3 adverse events were asthenia (one [2%] in the nivolumab group vs three [5%] in the combination group), asymptomatic increase in aspartate aminotransferase or alanine aminotransferase (none vs four [7%] of each), and asymptomatic lipase increase (two [3%] vs one [2%]). No patients had toxicities leading to death in the nivolumab group, whereas three (5%) of 62 in the combination group did (one fulminant hepatitis, one encephalitis, and one acute kidney failure).

Anti-PD-1 nivolumab monotherapy or nivolumab plus anti-CTLA-4 ipilimumab combination therapy both showed promising activity in relapsed patients with malignant pleural mesothelioma, without unexpected toxicity. These regimens require confirmation in larger clinical trials.

French Cooperative Thoracic Intergroup.