SELLAS Vaccine More Than Doubles Time to Myeloma Progression, Phase 2 Trial Shows

SELLAS Life Sciences’  Galinpepimut-S vaccine more than doubles the time it takes for high-risk multiple myeloma patients’ cancer to worsen, a Phase 2 clinical trial shows.

Myeloma expert Guenther Koehne presented the results at the Annual Meeting of the European Society for Blood and Marrow Transplantation in Lisbon, Portugal, March 18-21. Her poster presentation was titled “Clinical benefit after galinpepimut-S (GPS), a Wilms’ tumor 1 (WT1) immunotherapeutic, correlates with antigen-specific immune responses in high-risk multiple myeloma: Complete analysis of the Phase 2 GPS maintenance study.“

“High-risk multiple myeloma is a disease subset with high potential of short-term disease progression following autologous stem cell transplants, providing opportunities to improve on this limited clinical outcome,” he said in a press release.

Galinpepimut-S targets a faulty version of the Wilms’ tumor (WT1) protein. Normal WT1 helps kidneys and other organs develop properly. But an abnormal version can lead to cancer.

Abnormal WT1 is found in a number of tumor types, including myeloma. America’s National Cancer Institute lists it as the number one target for cancer immunotherapy.

Because cancer cells are produced by a person’s own body, the immune system has trouble recognizing and fighting them. This means they need to be trained, experts say.

SELLAS created Galinpepimut-S to trigger an immune response against WT1. In addition to destroying cancer cells containing the protein, it is designed to help the immune system remember the threat. This memory component is aimed at getting the system to fight tumors that return or residual cancer left after a tumor is removed.

The main objective of the trial (NCT01827137) was to see if Galinpepimut-S could be used as a maintenance therapy to prevent or delay the progression of myeloma in patients who had received an autologous stem cell transplant. 

SELLAS said the study involved 19 high-risk patients who had achieved at least a stable disease after a transplant, but still had cancer cells in their blood or bone marrow.

It typically takes less than a year for high-risk myeloma to return after a transplant. This is true even when patients are on a maintenance therapy of  immunomodulatory drugs or proteasome inhibitors.

The time it took for patients treated with Galinpepimut-S to have their myeloma return increased dramatically to a median of 23.6 months — a 2.5-fold increase.

Another finding was that 88 percent of the 18 patients whom researchers were able to evaluate were still alive at 18 months.

The results compared favorably with those in a study of high-risk multiple myeloma patients who received thalidomide as a maintenance therapy after a stem cell transplant.

An additional finding was that Galinpepimut-S generated an immune response to WT1 in 91% of the patients.

The results support further evaluation of the therapy’s effectiveness in more extensive clinical trials, SELLAS said.

“These results are encouraging, particularly given the patients’ poor prognosis due to their high-risk cytogenetic profile at disease presentation and their still harboring minimal residual disease prior to GPS [Galinpepimut-S] treatment,” said Angelos M. Stergiou, SELLAS’s president and chief executive officer.  

“The improved PFS [progression-free survival] at 23.6 months in this setting instills further confidence in our advancing GPS development as an important immunotherapeutic treatment option for aggressive multiple myeloma,” he added.