Integration of the PD-L1 Inhibitor Atezolizumab and WT1/DC Vaccination Into Platinum/Pemetrexed-based First-line Treatment for Epithelioid Malignant Pleural Mesothelioma

In this multicenter phase I/II trial, the programmed death-ligand 1 (PD-L1) inhibitor atezolizumab and dendritic cells (DCs) loaded with the mesothelioma-associated tumor antigen WT1 will be integrated into platinum/pemetrexed-based first-line chemotherapy for the treatment of epitheloid malignant pleural mesothelioma (MPM). The general objective is to provide the first-in-human experimental demonstration that the combination of platinum/pemetrexed-based chemotherapy with atezolizumab and WT1/DC vaccination is feasible and safe, has clinical activity and enables the induction of mesothelioma-specific immune responses in patients with MPM.

Malignant pleural mesothelioma (MPM) is a highly aggressive and in virtually all cases fatal cancer that is tightly associated with prior asbestos exposure. Despite some improvement over time, the prognosis of patients diagnosed with MPM remains dismal with a median overall survival from diagnosis of only 9-16 months. In this single arm phase I/II trial the investigators want to demonstrate the feasibility and safety of integrating the programmed death-ligand 1 (PD-L1) inhibitor atezolizumab and WT1-targeted dendritic cell vaccination in epitheloid MPM patients in conjunction with first line platinum/pemetrexed-based chemotherapy. In addition, chemo-immunotherapy-induced immunogenicity will be studied and patient's clinical outcome will be documented for comparison with current patient's outcome allowing indication of the added value. Fifteen patients diagnosed with histologically proven epithelial MPM (stage I-IV) will be included. Patients should be able to undergo leukapheresis, chemotherapy and immunotherapy. Patients who underwent prior treatment for MPM or with a history of another malignancy within the last three years will be excluded. The intention of this study is to administer four 3-weekly (±3 days) platinum/pemetrexed-based chemotherapy cycles (CT1-4) combined with atezolizumab treatments (A1-4) and autologous WT1 messenger (m)RNA-loaded dendritic cells (V1-4) at day 0 and day 14 (±3 days) of each chemotherapy cycle, respectively. Additional atezolizumab doses and/or WT1/DC vaccines after the chemo-immunotherapy study scheme can be administered to the patient if consent for continuation of atezolizumab treatment and/or WT1/DC vaccination was obtained and residual WT1/DC vaccine aliquots are available. In that case, atezolizumab and/or WT1/DC vaccines will be administered on a 4-weekly basis (±1 week). The WT1/DC vaccines will be administered within 1 week after atezolizumab administration. After the final WT1/DC vaccination and/or atezolizumab administration, patients will enter a follow-up phase that lasts for up to 90 days after final WT1/DC vaccination and/or atezolizumab administration or 24 months after diagnosis, whichever occurs later.