This study is to evaluate the overall survival (OS) rate (determined from the time of randomization in the study) of subjects who receive dendritic cell immunotherapy with MesoPher plus best supportive care (BSC) compared to BSC alone.

This is an open-label, randomized Phase II/III study in adult subjects with mesothelioma to evaluate the efficacy and anti-tumor activity of dendritic cell immunotherapy with MesoPher plus best supportive care compared to best supportive care alone. The safety, tolerability, quality of life and immunogenicity of MesoPher will also be evaluated.

The study includes a screening phase, a 7 month open-label treatment phase during which subjects visit the study center for administration of study drug and follow-up evaluations. An end-of-study (EoS) visit will be performed after completion of the study, after which data on survival, subsequent therapies and response to these therapies will be collected.

A target of 230 subjects satisfying all study criteria, will be randomized to receive either dendritic cell therapy plus best supportive care (Arm A) or best supportive care alone (Arm B).

Subjects in Arm A will undergo leukapheresis to obtain monocytes from which dendritic cells will be generated. These dendritic cells will be loaded in vitro with an allogeneic tumor cell lysate (PheraLys). Treatment with autologous dendritic cells loaded with PheraLys is called MesoPher. The treatment with Mesopher will start within 9 to 13 weeks after the last dose of chemotherapy. Subjects will receive 3 bi-weekly injections with MesoPher in addition to BSC. In case of stable disease or partial/complete response, an additional 2 injections will be given at weeks 18 and 30. Subjects will be administered with a maximum of 5 doses of MesoPher.

Subjects in Arm B will be treated with best supportive care according to the discretion of the local investigator.

Subjects will only be included with a histologically confirmed diagnosis of pleural malignant mesothelioma, who are non-progressive after 4 to 6 cycles with first line chemotherapy with antifolate/platinum.