GPS, originally developed by MSKCC and licensed to SELLAS, incorporates a set of immunogenic peptides that have been shown to stimulate both CD4 and CD8 T-cells. In addition, key amino acids from some of these peptides have been modified to improve their immunogenicity. SELLAS is further optimizing the manufacturing process towards a lyophilized formulation with high stability features.
GPS is administered in combination with an adjuvant and an immune modulator (GM-CSF) to improve the immune response to the target. Initial pilot clinical studies were conducted in patients with AML and thoracic cancers, such as lung cancer and MPM. Based on encouraging results in these initial studies, additional Phase 2 trials were launched in hematopoietic cancers and solid tumors. Based on the results of these initial studies, SELLAS believes that GPS is capable of inducing a robust immune response to the antigen. Patients enrolled in the AML and MPM trials have shown prolonged survival following active immunization with GPS.
In patients with advanced cancers over-expressing WT1, GPS is designed to prevent relapses and potentially improve survival rates of patients, while maintaining their quality of life.
Acute Myeloid Leukemia (AML)
Initial clinical studies of GPS were conducted in AML due to the high levels of WT1 expression observed in this tumor type and the deep institutional experience of MSKCC with AML.
- Phase 1 and Phase 2 studies were conducted with 9 and 22 patients, respectively. These patients were treated with GPS in the maintenance setting, i.e. after having successfully achieved their first morphological complete remission (CR1) post-upfront standard antileukemic chemotherapy. The Phase 2 clinical trial met its primary endpoint of an actual overall survival (OS) rate of at least 34%, measured three years into the clinical study, with an actual OS rate of 47.4% being demonstrated at the 3-year timepoint. In the Phase 2 study, in older patients (>60 years), median overall survival reached 35.3 months, and reached 67.6 months in patients across all ages. Compelling CD4 and CD8 reactivity was observed.
- GPS was further independently validated at the Moffitt Cancer Center (MCC) in a more severe AML population – i.e., in patients who had reached their second complete remission (CR2, post 2nd line chemotherapy), where it showed statistically significant clinical benefit when compared with a cohort at the same institution contemporaneously treated with best standard therapy, leading to a median overall survival of 16.3 months vs. 5.4 months.
- A Phase 3 clinical trial for AML in the CR2 setting was commenced in January 2020 (ClinicalTrials.gov Identifier: NCT04229979).
Malignant Pleural Mesothelioma (MPM)
MPM was chosen as an indication to study due to the high levels of expression of WT1 in patients with this tumor type.
- A 41-patient Phase 2, double-blind, randomized study performed at MSKCC and MD Anderson Cancer Center and co-sponsored by the Department of Defense (DOD), demonstrated a well-tolerated safety profile.
- Median OS was 22.8 months in the GPS arm vs. 18.3 months in the control arm, (HR: 0.79), with a median follow-up of 17.2 months.
Multiple Myeloma (MM)
Phase 2 open-label study in high-risk patients after successful front-line therapy
20 patients enrolled; 18 evaluable.
- 88% actuarial OS at 18 months and median OS not reached.
- Median PFS of 23.6 months.
- All evaluable patients had evidence of minimal residual disease (MRD) after autologous stem cell transplantation (ASCT) and 15/18 patients also had high-risk cytogenetics as well as additional unfavorable clinical characteristics at diagnosis.
- Typically, patients with the above features exhibit PFS rates that do not exceed 12 months following ASCT, even while on maintenance therapy with immunomodulatory drugs (IMIDs) or proteasom inhibitors.
Galinpepimut-S data source: Koehne G, et al. 44th Ann. Meeting of the European Society for Blood and Marrow Transplantation (EBMT), 2018; Abstr. # O132.
IN COMBINATION WITH PD-1 INHIBITORS
Ovarian Cancer
Phase 1/2 study in the maintenance setting in combination with nivolumab (OPDIVO®), an inhibitor of Programmed cell Death protein 1 (PD1)
11 patients (10 evaluable) with recurrent ovarian cancer who are in second or greater clinical remission
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Combination therapy over 14-weeks with galinpepimut-S every 2 wks x 6 inoculations in combination with 7 infusions of nivolumab every 2 weeks
- No additional toxicity burden above and beyond what would be expected with nivolumab alone
- PFS rate at 1 year since initiation of salvage chemotherapy was 70% for patients who received >2 doses of the combination (n=10), which compared favorably with historical 1-yr PFS rates of 43-50% in this setting
- Median follow-up of 33 months shows 30% of patients being progression free at 2 years (historical controls are 3-10%); WT1-specific IgG observed in 86% of patients (wks -27) as well as CD4 and CD8 T cell responses
Galinpepimut-S data source: O’Cearbhaill RE, et al. J Clin Oncol. 2018;36[15; Suppl], 5553).
Various Advanced Malignancies
Phase 1/2 study (5-arm ‘basket’ trial) in combination with pembrolizumab (KEYTRUDA®), a PD1 inhibitor.
Currently enrolling patients in two indications, ovarian cancer (second or third line) and colorectal cancer (third or fourth line), to be followed by AML (patients unable to attain deeper morphological response than partial on hypomethylating agents and who are not eligible for allogeneic hematopoietic stem cell transplant), triple negative breast cancer (second line) and small cell lung cancer (second line). The study is planned to enroll approximately 90 patients at up to 20 centers in the United States.
This study will assess the efficacy and safety of the combination, comparing overall response rates (ORRs – by RECIST criteria) and immune response markers achieved with the combination versus prespecified rates based on those seen with pembrolizumab alone in comparable patient populations.
(ClinicalTrials.gov Identifier: NCT03761914).
Malignant Pleural Mesothelioma (MPM)
SELLAS has entered into an agreement with Memorial Sloan Kettering Cancer Center (MSK) for the conduct of an investigator-sponsored clinical trial (IST) of GPS in combination with Bristol-Myers Squibb’s anti-PD-1 therapy, nivolumab, in patients with malignant pleural mesothelioma (MPM). The Phase 1 open-label clinical study will enroll patients with MPM who harbor relapsed or refractory disease after having received frontline standard of care multimodality therapy. The study is expected to commence in the first quarter of 2020.
For more information on GPS, please see “Galinpepimut-S: Publications and Presentations” on this website.