Phase 1/2 Trial Shows Positive Data for Galinpepimut-S and Pembrolizumab Combination in WT1+ Ovarian Cancer

Galinpepimut-S (GPS) in combination with pembrolizumab (Keytruda) shows promising antitumor activity and initial immunobiological activity for Wilms Tumor–1 (WT1)–positive ovarian cancer as part of a phase 1/2 clinical trial, according to a press release from SELLAS Life Sciences Group, Inc.¹

Recent data from the study show 100% of patients in this group (n = 11) are still alive and 5 patients (45.5%) are continuing investigational treatment.

The open-label, multicenter, multi-arm study has a target enrollment goal of 20 patients with relapsed or refractory, platinum-resistant, advanced ovarian cancer. The primary end points are safety and overall response rate, with secondary end points of progression-free survival (PFS) and overall survival (OS).

Patients in this study who had previously failed second- or third-line therapy comprised 66.7% and 33.3%, respectively. Although OS data are not mature, all patients remained alive at 9 months which compares favorably with historical OS of 9 to 12 months with the standard of care.

At a median follow up of 15.4 weeks, the disease control rate (DCR) was 63.6% and median PFS was 11.8 weeks. Tumor WT1 positivity in the population remained high at 63.6%.

Three patients were evaluated for immune response at baseline and at 18 weeks with assessment of CD8- and CD4-positive T-lymphocytes isolated from peripheral and mononuclear cells. At 18 weeks, CD8-positive cells increased by 242% on average and CD4-positive cells increased 174%. In 2 out of the 3 patients, there was evidence of polyfunctional T-cell activation.

“Considering the overall poor prognosis in this particular clinical setting and based on the observed median PFS, overall survival, and DCR in this study, combining GPS with the PD-1 inhibitor pembrolizumab appears to be clinically promising as compared to bevacizumab [Avastin]–free salvage chemotherapy regimens and without the toxicity burden associated with the latter,” Angelos Stergiou, MD, ScDhc, president and chief executive officer of SELLAS Life Sciences Group, Inc, said in a press release.

In an announcement from December 2020, SELLAS reported positive activity of GPS in combination with pembrolizumab for patients with relapsed/refractory WT1-positive metastatic ovarian cancer (n = 8). The DCR in this group was 87.5% with a median follow-up of 9.4 weeks. At a 6-week post-therapy assessment, all patients were free of disease progression.²

Notably, the safety profile of the combination was similar to pembrolizumab alone with few additional low-grade local reactions at the site of GPS injection.

References:

1. SELLAS Reports Promising Updated Clinical Data and Initial Immune Response Profiles from Ongoing Phase 1/2 Study of Galinpepimut-S (GPS) Combined with Keytruda for Treating WT1+ Advanced Ovarian Cancer. News Release. SELLAS Life Sciences Group, Inc. June 30, 2021. Accessed July 1, 2021. https://bit.ly/2UlFSOw

2. SELLAS Announces Promising Initial Clinical Data for Galinpepimut-S (GPS) in Combination with Checkpoint Inhibitors in Two Solid Tumor Indications. News Release. SELLAS Life Sciences Group, Inc. December 21, 2020. Accessed July 1, 2021. https://bit.ly/2Tv2UCB