Sellas Life Sciences announced top-line data from the Phase 2 clinical study of its WT1 cancer vaccine in patients with malignant pleural mesothelioma (MPM).

The Phase 2 double-blind, randomized study compared WT-1 analog peptides vaccine in combination with Montanide-adjuvant plus granulocyte-macrophage colony-stimulating factor (GM-CSF) vs. Montanide-adjuvant plus GM-CSF in patients with MPM who had previously completed combined modality therapy. The study planned to enroll 39 patients in each arm, however, in May 2015, the trial’s independent Data Monitoring Committee requested discontinuation of the control arm due to futility while continuing the WT1 cancer vaccine arm. This change led to an earlier unblinding than planned, with total enrollment reaching 40 patients, 19 in the WT1 vaccine arm and 21 in the control arm.

The study showed clinically meaningful greater median overall survival (OS) in patients receiving the WT1 cancer vaccine: 39 months OS vs. 18 months OS for patients in the control arm. Typical median OS in patients with MPM receiving currently available treatment options ranges from 15-18 months. In addition, the WT1 cancer vaccine resulted in a median progression-free survival (PFS) of 11.5 months, more than double that of the control arm (5.5 months). The investigators continue to track patient outcomes. As the study was unblinded sooner than expected, there was a smaller patient cohort and shorter follow-up than originally planned.

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Results from this study and from other ongoing WT1 Phase 2 trials will be presented by the vaccine’s inventor, David A. Scheinberg, MD, PhD, at the upcoming 8th International WT1 Conference on November 19–20, 2015 in Kyoto, Japan. Earlier this month, he also presented results of recently completed Phase 2 study of the WT1 vaccine in 22 adults with Acute Myeloid Leukemia (AML) at the 17th Annual International Congress on Chronic Myeloid Leukemia in Lisbon, Portugal.

The WT1 vaccine, comprised of four modified peptide chains that induce a strong innate immune response (CD4+/CD8+ T-cells) against the WT1 antigen, is a late clinical-stage cancer immunotherapy administered in combination with an adjuvant and an immune modulator to improve the immune response to the target. It is being developed to target hematologic cancers and solid tumors, including AML, mesothelioma, multiple myeloma, ovarian cancer, and multiple other cancers.

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