Pleural Mesothelioma Vaccine, WT1, Named ‘Orphan Drug’ by FDA to Advance Its Development

Pleural Mesothelioma Vaccine, WT1, Named ‘Orphan Drug’ by FDA to Advance Its Development

SELLAS Life Sciences Group recently announced that the U.S. Food and Drug Administration (FDA) has granted the company’s WT1 cancer vaccine Orphan Drug Designation as a potential treatment for patients with malignant pleural mesothelioma (MPM).

The WT1 vaccine was originally developed by Memorial Sloan Kettering Cancer Center and later licensed to SELLAS. The vaccine targets the WT1 antigen, and is administered in combination with an adjuvant and an immune modulator to boost the immune response against WT1.

WT1 is a transcription factor not usually present in adult cells. Since it appears in a multitude of cancers, and in some cancer stem cells, the antigen is ranked as the No. 1 target for cancer immunotherapy by the National Cancer Institute.

The vaccine is intended to destroy residual tumor cells when a cancer is in remission, and to contribute to ongoing immune surveillance in case a tumor returns. MPM, as well as many of the more than 20 other cancers that the vaccine targets, have relapse rates of up to 80 percent.

SELLAS also announced positive results from a Phase 2 clinical trial of its WT1 vaccine in MPM patients. The vaccine was found to improve overall survival and double progression-free survival. Based on these results, the company intends to start a Phase 2b/3 trial of WT1 in patients with MPM by the end of 2016.

“We are thrilled with the progress of our WT1 vaccine program, which has received two orphan designations in the last two months and is advancing into pivotal studies in AML [acute myeloid leukemia] and in MPM patients in 2016, as well as further Phase 2 studies including in multiple myeloma, ovarian cancer, glioblastoma multiforme, and a series of genetically defined cancers in a basket-trial design,” Angelos M. Stergiou, SELLAS’ chairman and chief executive officer, said in a press release.

Miltiadis Sougioultzoglou, executive vice president of SELLAS, added, “MPM is a difficult-to-treat and aggressive cancer, and fewer than five percent of patients survive beyond five years. There is a significant need for new treatment options, and we look forward to the commencement of the pivotal Phase 2b/3 trial.”

The randomized, double-blind, placebo-controlled Phase 2 clinical trial of the WT1 vaccine in 40 MPM patients showed a median overall survival of 21.4 months for vaccinated patients, compared to 16.6 months in patients receiving placebo. The vaccine also increased median progression-free survival to 11.4 months, which is double the length observed in the placebo-treated group. The trial also showed that WT1 has a good safety and tolerability profile.

“Our WT1 cancer vaccine, also known as SLS-001, has demonstrated promising safety and efficacy data in clinical trials enrolling a total of 100 patients. We have been carefully proceeding with our development work in hematological malignancies (AML and Multiple Myeloma), as well as a solid tumor (MPM), and we will broaden the indications this year to advance our cancer vaccine in other unmet medical needs,” said SELLAS’ chief medical officer, Andres Gutierrez.

Orphan Drug Designation is a special FDA status given upon request to qualifying drugs or biological products designed to treat rare illnesses, and qualifies the drug’s sponsor for certain development incentives, including tax credits for approved clinical testing.

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