Galinpepimut-S is an investigational immunotherapy vaccine being developed by Sellas Life Sciences to potentially treat several types of cancer. The vaccine targets cancers that overproduce Wilm’s Tumor 1 (WT1), one of the most common cancer-associated proteins.

How Galinpepimut-S works

Galinpepimut-S consists of four peptide chains, or small proteins that are designed to elicit a strong immune response against WT1. The immune system responds to Ganpepimut-S by building an army of immune cells that can recognize and destroy cancer cells that produce WT1.

Galinpepimut-S also helps the immune system “remember” WT1, so that immune cells continue to destroy tumors that return and any cancer cells leftover after a treatment.

Galinpepimut-S in clinical trials

Several clinical trials to test galinpepimut-S for the treatment of a number of different cancers are either planned or underway.

Malignant pleural mesothelioma

A randomized Phase 2 trial (NCT01890980) in 41 patients with malignant pleural mesothelioma (MPM) compared the effect of treatment with galinpepimut-S combined with montanide and GM-CSF, both designed to increase the growth of white blood cells and increase immune response, to montanide + GM-CSF only. All included patients had been treated with surgery and chemotherapy — called combined modality therapy — prior to study start.

The results, published in a September 2017 issue of the scientific journal Clinical Cancer Research, showed that galinpepimut-S was safe and had possible clinical benefit; those who received galinpepimut -S had a longer progression-free survival (PFS) and overall survival (OS) than those who received montanide only. However, the authors acknowledged the trial was not designed to determine the statistical significance of this comparison.

A follow-up, Phase 3 trial in patients with mesothelioma is expected to start in late 2017.  Between 150 and 400 patients who previously have been treated with combined modality therapy will receive active treatment with galinpepimut-S for 13 to 18 months.

The treatment will be timed so that galinpepimut-S acts during the period when the risk of recurrence of the cancer is highest. The clinical benefit of the treatment will be measured by OS and PFS rates and the return of cancer.

Combination therapy for multiple cancers

A Phase 1/2 trial of galinpepimut-S combined with Keytruda (pembrolizumab) is planned to test the safety and clinical activity of the combination therapy in five cancer types: colorectal, ovarian, small cell lung, and triple negative breast cancers, as well as acute myeloid leukemia (AML). Participants will be randomized to receive either the combination therapy (galinpepimut-S plus Keytruda) or Keytruda alone, to compare clinical and immune responses. It is expected that the trial will begin in the first half of 2018.

Keytruda is an immunotherapy drug that targets programmed death ligand 1 (PD1), a protein many cancers produce to protect themselves from immune cells attacks. Blocking PD1 leaves the cancer cell more vulnerable to attacks, potentially making the immune response to the vaccine more effective.

Acute myeloid leukemia (AML)

A Phase 2 trial (NCT01266083) of serial vaccination with galinpepimut-S in patients with AML or acute lymphocytic leukemia (ALL) showed that the treatment was safe and well-tolerated, with evidence of clinical benefit, particularly in patients who mounted an immune response. Based on these positive results, presented at the annual meeting of the American Society of Clinical Oncology (ASCO) in June 2016, investigators are planning to proceed to a Phase 3 trial in AML patients.

Multiple myeloma (MM)

Sellas recently reported updated results from a Phase 2 trial (NCT01827137) in MM patients, showing that galinpepimut-S has a clinical benefit among high-risk patients. The study is ongoing at the Memorial Sloan Kettering Cancer Center in New York and has enrolled 20 patients, who are under long-term monitoring.

Ovarian cancer

An open-label, non-randomized Phase 1/2 clinical study (NCT02737787) is underway in New Jersey and New York to evaluate the safety and effectiveness of the combination of GS and Opdivo (nivolumab) in women with cancers of the ovaries, fallopian tubes, or the peritoneum (lining of the abdomen, which covers the outside of the uterus).The study is currently recruiting participants. To be included in the study, women must have cancers that have returned after previous treatments, but are currently in remission. Patients will be treated with the combination therapy for 14 weeks. Those who have not progressed at the end of the treatment period will receive a maintenance course of galinpepimut-S.

Additional information

Based on the positive results from the Phase 2 trials the U.S. Food and Drug Administration (FDA) granted orphan drug and fast track status to galinpepimut-S for the treatment of AML and MPM. These designations help speed up the approval process of the potential drug. The company also received a favorable opinion for European orphan drug designation for galinpepimut-S for the treatment of these cancers.


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