The FDA granted orphan drug designation to the WT1 cancer vaccine for the treatment of malignant pleural mesothelioma.
The FDA based the designation on results from a randomized, double blind, placebo-controlled phase 2 trial of the WT1 vaccine (SLS-001, SELLAS Life Sciences) in 40 patients with malignant pleural mesothelioma treated at Memorial Sloan Kettering Cancer Center and The University of Texas MD Anderson Cancer Center.
Results showed patients assigned the vaccine experienced longer median OS (21.4 months vs. 16.6 months) and median PFS (11.4 months vs. 5.7 months) than those assigned placebo. The vaccine also demonstrated a favorable safety profile, according to researchers.
A phase 2b/3 trial in malignant pleural mesothelioma is expected to begin by the third quarter of this year.
The FDA previously granted orphan drug status to WT1 for treatment of patients with acute myeloid leukemia.
Additional phase 2 studies are planned for patients with multiple myeloma, ovarian cancer and glioblastoma multiforme.
The WT1 antigen is a transcription factor that is expressed in several cancers, as well as in certain cancer stem cells, according to a SELLAS-issued press release. WT1 is not druggable by traditional approaches, but it can be targeted by the immune system.
“Our WT1 cancer vaccine … has demonstrated promising safety and efficacy data in clinical trials enrolling a total of 100 patients,” Andres Gutierrez, MD, PhD, chief medical officer of SELLAS, said in the press release. “We have been carefully proceeding with our development work in hematological malignancies [and malignant pleural mesothelioma] and we will broaden the indications this year to advance our cancer vaccine in other unmet medical needs.”
The FDA Office of Orphan Products Development grants orphan drug designation to novel drugs and biologics that are intended for the safe and effective treatment, diagnosis or prevention of rare diseases or disorders that affect fewer than 200,000 people in the United States. The designation allows manufacturers to qualify for various incentives, including tax credits for qualified clinical trials and — upon regulatory approval — seven years of market exclusivity.