WT-1 Cancer Vaccine Could Benefit Myeloma Patients Undergoing Stem Cell Transplants

Multiple myeloma patients undergoing autologous stem cell transplants (ASCT) may strongly benefit from SELLAS‘ WT-1 cancer vaccine, galinpepimut-S, according to recent data from a Phase 2 study.

In a cohort of patients whose characteristics result in progression-free survival (PFS) rates of less than 12 months following ASCT, treatment with galinpepimut-S more than doubled this rate, inducing a PFS of 23.6 months.

Results will be revealed in an oral presentation at the 43rd Annual Meeting of the European Society for Blood and Marrow Transplantation March 26-29 in Marseille, France.

The breakthrough vaccine is composed of four modified peptide chains that stimulate specific immune cells, such as CD4-positive and CD8-positive T-cells, to respond against the WT1 antigen. This protein is usually not expressed in healthy adult cells, but appears in large quantities in many cancers, including myeloma. The WT1 antigen has been ranked by the National Cancer Institute (NCI) as the No. 1 target for cancer immunotherapy.

In June 2014, SELLAS Life Sciences Group started a Phase 2 study (NCT01827137) assessing galinpepimut-S in 20 myeloma patients undergoing ASCT. All patients had minimal residual disease (MRD+) after ASCT, meaning that patients had small numbers of cancer cells in the bone marrow at the time of treatment, and 15 had high-risk cytogenetics at diagnosis. Patients with such characteristics usually have PFS rates of less than 12 months following ASCT, even when receiving maintenance therapy.

Galinpepimut-S treatment, however, resulted in a median PFS of 23.6 months, and a 18-month overall survival of 88%.

Comparing these data with those from an unmatched cohort of myeloma patients with high-risk cytogenetics and MRD+ who received continuous thalidomide maintenance therapy, included in the Myeloma IX trial, galinpepimut-S therapy induced a 2.5-fold increase in median PFS, and a 2.6-fold increase in the 18-month PFS.

“This treatment has shown the ability to substantially extend the lifespan of patients with high-risk multiple myeloma, which remains a clinical challenge,” Guenther Koehne, MD, PhD, principal investigator on the trial, said in a news release.

“Based on these results, galinpepimut-S continues to provide strong indication of a meaningful clinical benefit following autotransplantation in high-risk multiple myeloma, particularly in the context of an adverse cytogenetic profile.

“The need for innovative, efficacious and tolerable therapies among multiple myeloma patients is undisputed, and we are excited about the possibility of applying a novel anti-WT1 active immunotherapy in myeloma. We are planning further studies to expand on and confirm our observations among this challenging patient group,” added Koehne, who is also an attending physician at Memorial Sloan Kettering Cancer Center and an associate professor of medicine at Weill Cornell Medical College.