Sellas Life Sciences (NASDAQ:SLS) stock rose ~6% on Thursday after the company reported data from the final analysis of a phase 1/2 trial of its drug galinpepimut-S (GPS) in combination with Merck’s (NYSE:MRK) Keytruda (pembrolizumab) to treat patients with WT1(+) relapsed or refractory platinum-resistant advanced metastatic ovarian cancer.
Of the 17 patients, 16 received at least three doses of GPS and had follow-up cross-sectional imaging (CT/MRI) to determine tumor status.
The company said median Overall Survival (OS) was 18.4 months for GPS/Keytruda combo, compared to 13.8 months in a checkpoint inhibitor single agent study in a similar patient population treated with checkpoint inhibitor alone.
Median Progression-Free Survival ((PFS – length of time during/after treatment a patient lives with the disease without it getting worse) for GPS/Keytruda combo was 12 weeks compared to eight weeks in a checkpoint inhibitor single agent study in a similar patient population treated with checkpoint inhibitor alone, the company added.
Sellas noted that the overall response rate (ORR) of the trial is 6.3% with a disease control rate (DCR), which is the sum of overall response rate and rate of stable disease, of 50.1% at a median follow-up of 14.4 months.
In a checkpoint inhibitor single agent trial in a similar population treated with a checkpoint inhibitor alone, the DCR was 37.2%, consistent with a DCR rate increase of ~45% in the GPS/Keytruda combo over that seen for checkpoint inhibitors alone, according to the company.
Sellas said that survival and disease control benefits were seen in patients harboring tumors with any level of detectable PD-L1 expression.
The safety profile of GPS/Keytruda combination was similar to Keytruda alone, with the only addition of low-grade, rapidly resolving local reactions at the GPS injection site, which was consistent with other GPS studies.
“GPS has been primarily studied as maintenance therapy to provide an overall survival benefit after patients reach a state of minimal residual disease or complete remission. In contrast, in this very difficult to treat patient population with relapsed or refractory measurable advanced platinum-resistant ovarian cancer, who underwent intensive chemotherapy with no apparent enduring clinical benefit, the data suggests that the combination of GPS plus pembrolizumab may be effective in stabilizing active disease,” said Sellas President and CEO Angelos Stergiou.