A Randomized Phase II Trial of Adjuvant Galinpepimut-S, WT-1 Analog Peptide Vaccine, after Multimodality Therapy for Patients with Malignant Pleural Mesothelioma

Purpose: Determine the 1-year progression-free survival (PFS) among patients with malignant pleural mesothelioma (MPM) receiving the WT1 peptide vaccine galinpepimut-S after multimodality therapy vs those receiving control adjuvants. Patients and Methods: This double-blind, controlled, two center phase II trial randomized MPM patients after surgery and another treatment modality to galinpepimut-S with GM-CSF and Montanide or GM-CSF and Montanide alone. An improvement in 1-year PFS from 50% to 70% was the predefined efficacy threshold, and 78 patients total were planned. The study was not powered for comparison between the two arms. Results: 41 patients were randomized. Treatment related adverse events were mild, self-limited, and not clinically significant. Based on a stringent prespecified futility analysis (futility = > 10 of 20 patients on one arm experiencing progression < 1 year), the control arm closed early. The treatment arm was subsequently closed because of the resultant unblinding. The PFS rate at 1 year from beginning study treatment was 33% and 45% in the control and vaccine arms, respectively. Median PFS was 7.4 months vs 10.1 months and median OS was 18.3 months vs 22.8 months in the control and vaccine arms, respectively. Conclusion: The favorable safety profile was confirmed. PFS and OS were greater in those who received vaccine but the trial was neither designed nor powered for comparison between the arms. Based on these promising results, the investigators are planning a larger randomized trial with greater statistical power to define the optimal use and benefit of galinpepimut-S in the treatment of MPM.

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