A DNA plasmid melanoma cancer vaccine, SCIB1, combined with nivolumab + ipilimumab in patients with advanced unresectable melanoma: Efficacy and safety results from the open-label phase 2 SCOPE trial.

Abstract

9535 Background: Targeting melanoma by T cells drives anti-tumor responses. We previously showed that SCIB1, a DNA vaccine incorporating T cell epitopes from TRP-2/gp100 into an antibody framework to allow Fc targeting of activated dendritic cells, was successful as monotherapy in a Phase 1/2 trial in Stage III/IV melanoma patients. Disease control was achieved in 60% of cases of unresectable melanoma. In addition, 88% of 20 Stage III/IV patients treated with SCIB1 who had had a previous successful tumor resection, were disease free for 5 years. 1st line combination treatment with nivolumab and ipilimumab in advanced melanoma has a reported ORR of 50%. The current SCOPE trial tests the hypothesis that patients with unresectable melanoma may improve response rate when SCIB1 is given with checkpoint inhibitors (CPI). Methods: Previously untreated patients with unresectable Stage III/IV melanoma were treated with nivolumab with ipilimumab and SCIB1 (8 mg) i.m. using needle-free injections at a fixed dosing schedule for a total of 10 doses over 24 months. The CPI therapy was administered in accordance with respective SmPC. ORR, as measured by RECIST 1.1 in the intention-to-treat population, is the primary endpoint. The study is designed using Simon's two stage methodology with 80% power when the ORR of no interest is 50% and the true ORR is 70% with an overall type I error of 5%. In the 1st stage, 15 patients have been enrolled and as there were more than 8 clinical responses (ORR [CR or PR]) within 25 weeks of the 1st SCIB1 dose. Having passed Simon Stage 1, further recruitment continues. The null hypothesis will be rejected if 27 or more responses are observed in 43 patients. Results: To date, 23 patients have received the combination of SCIB1 with nivolumab and ipilimumab. At study entry, all patients were Stage IV. 13 patients have reached the first imaging timepoint at 13 weeks, the objective response rate is 11/13 (85%). 11/11 responses were confirmed in a subsequent scan (1 CR and 10 PRs); DCR 12/13 (92%) and 1 PD. Patients showed a 40-100% reduction in tumor volume at 13 and/or 25 weeks. Most of the SCIB1 adverse reactions were Grade 1/2 injection site related or headaches. 3 patients reported Grade 3 events (rash, neutropenia and raised GGT) all related to the CPIs. Observed toxicity frequency and intensity was in line with reported figures from ipilimumab/nivolumab therapy. Serious adverse reactions to date have all been related only to the CPIs. Conclusions: SCIB1 given with nivolumab and ipilimumab, as 1st line treatment in unresectable melanoma, improved the ORR to 85% without an increase in clinically meaningful adverse events. These results, if confirmed in the larger ongoing patient cohort, provide confidence in initiating a randomized registration program in unresectable melanoma patients with this novel DNA plasmid technology. Clinical trial information: NCT04079166 .