Background: The combination of ipilimumab (IPI) and nivolumab (NIVO) remains a standard of care for patients with advanced melanoma, especially those with poor prognostic factors, albeit with a significant risk of toxicity. Therapeutic cancer vaccines are ideally positioned to improve outcomes without significantly increasing toxicity. UV1 is a therapeutic cancer vaccine generating T-cell responses against the universal cancer antigen telomerase. In a Phase I trial in melanoma (N = 30), UV1 plus pembrolizumab demonstrated a tolerable safety profile, a complete response rate of 33%, median PFS of 18.9 months, and 2-year OS rate of 73.3%. Recently, results from a randomized Phase II trial indicated a longer overall survival and a higher response rate for previously treated patients with advanced mesothelioma receiving UV1 in combination with IPI-NIVO (1). Methods: In this Phase II, open-label, multicenter study, we randomly assigned treatment-naïve patients with unresectable or metastatic melanoma (stage IIIb-IIId or IV) to IPI 3mg/kg + NIVO 1mg/kg for 4 cycles, followed by NIVO 480 mg as maintenance, with or without 8 intradermal injections of 300 µg UV1 (+GM-CSF). The primary endpoint was progression-free survival (PFS) assessed by blinded independent central review (BICR) according to RECIST 1.1. Secondary endpoints included overall survival (OS), objective response rate (ORR), duration of response, and safety. Results: A total of 156 patients underwent randomization; 78 patients were assigned to the IPI-NIVO-UV1 arm and 78 patients to the IPI-NIVO arm. The median age was 60, 48% had M1C or D disease, 38% had LDH >upper limit of normal, and 42% had a positive BRAF mutation status. With a minimum follow-up of 18 months, the 12-month PFS rate was 57% in both arms (HR 0.95, 95% CI 0.59-1.55, p value 0.845). The ORR was similar with IPI-NIVO-UV1 compared to IPI-NIVO, at 60% vs 59%, respectively (Odds ratio 1.12, 95% CI 0.58-2.16, p value 0.867). The 12-month OS rate was 87% and 88%, respectively (HR 1.15, 95% CI 0.60-2.20, p value 0.674). The occurrence of grade >3 adverse events was similar in both treatment arms. Conclusion: UV1 did not improve on outcomes of IPI-NIVO, in terms of PFS. Longer follow-up is required for the accurate assessment of OS. No significant toxicity increases were observed with the addition of UV1. Data from a biomarker driven cohort are awaited. 1. Helland et al, Eur J Cancer 2024. Clinical trial information: NCT04382664.