Sellas Life Sciences announces results from trastuzumab +/- NPS trial at ASCO
Sellas Life Sciences announced results from a preplanned analysis of immunologic responses in the cohort of patients with triple negative breast cancer, or TNBC, from the prospective, randomized, single-blinded, controlled Phase 2b independent investigator-sponsored clinical trial of nelipepimut-S, or NPS, +/- trastuzumab targeting HER2 low-expressing breast cancer patients. This analysis was presented at the American Society of Clinical Oncology, or ASCO. The Phase 2b study enrolled patients with HER2-low expressing breast cancer who remained clinically disease-free after completion of frontline standard of care therapy. Patients were selected to harbor node-positive disease and/or TNBC, as well as expressing human leukocyte antigen, or HLA, types indicated for NPS administration. Patients were randomized to placebo with granulocyte-macrophage colony-stimulating factor or NPS with GM-CSF, while they all received trastuzumab every 3 weeks for one year. The company previously reported results of the final analysis of efficacy and safety outcomes in the cohort of patients whose tumors did not express hormone receptors. DFS of patients treated with NPS plus trastuzumab was 92.6% compared to 70.2% for those treated with trastuzumab alone and represented a clinically meaningful and a statistically significant improvement with the combination therapy. This was associated with a statistically significant reduction by 71.9% in the frequency of clinically detected recurrences in favor of the combination in the TNBC cohort. Ninety-one of the 97 TNBC patients in this clinical study were analyzed for immune responses, or IR, at five timepoints, 51 of whom received the combination therapy. IR were evaluated ex vivo by clonal expansion of antigen NPS-specific cytotoxic T-lymphocytes, or CTL, by dextramer-staining/flow cytometry at predefined time points over three years. In vivo IR were assessed by cutaneous delayed type hypersensitivity, or DTH, reactions periodically, by measuring the diameter of skin induration post intradermal NPS treatment. NPS plus trastuzumab-treated TNBC patients exhibited increases in CTL frequencies compared with baseline. The mean CTL frequencies in these patients increased at baseline at a 2.86-fold difference that was clinically indicative, as compared with patients receiving trastuzumab only. Three patients in the combination arm recurred as compared with 12 in the trastuzumab-alone arm. TNBC patients treated with NPS plus trastuzumab whose disease recurred did not mount an IR by ex vivo assessment or by in vivo DTH, while non-recurrent patients mounted both vigorous NPS-specific clonal CTL expansion and enhanced in vivo DTH.