Abstract B003: A randomized controlled phase II clinical trial on mRNA electroporated autologous dendritic cells for stage III/IV melanoma patients who are disease-free following the local treatment of macrometastases

Autologous monocyte-derived synthetic mRNA electroporated dendritic cells (TriMixDC-MEL) are immunogenic and can induce anti-tumor activity in pretreated advanced melanoma patients when administered by the intradermal (id) and intravenous (iv) route. We investigated the safety and activity of TriMixDC-MEL in stage III/IV melanoma patients who are disease free following the local treatment of macrometastases. We performed a randomized, controlled, non-comparative phase II clinical trial where TriMixDC-MEL was administered iv (20.10 6 DCs) and id (4.10 6 DCs) at 2 separate sites of the body every 2 weeks for a total of 4 administrations and a fifth administration after 16 weeks in patients randomized to the treatment arm. Patients on the control arm did not receive treatment but were allowed to “cross-over” and be treated with TriMixDC-MEL at the time of non-salvageable recurrence. Tumor evaluations on both arms were performed by total-body 18-FDG-PET/CT every 12 weeks. The primary endpoint was the percentage of patients who were alive and free from melanoma macrometastases at 1 year following randomization. Patients were allowed to undergo local salvage treatments for loco-regional melanoma recurrences during the study (week 0-52). If local salvage treatment during the study resulted in a disease-free status that was confirmed at any of the planned assessment, but not earlier than 16 weeks after the salvage treatment, these patients were considered not to have reached the primary endpoint of the study. Between November 2012 and November 2014, 41 eligible patients were randomized between the TriMixDC-MEL treatment arm (n = 21) and control-arm (n = 20). Baseline characteristics (22M/19F; median age 57.5y (range 24-81); AJCC stage III/IV-M1a/-M1b/-M1c: 33/1/6/1 patients, ulcerated primary melanoma: 12 patients) were well balanced between both groups. After a median follow-up of 28 months (range 15 to 40 months) 21 patients experienced a non-salvageable melanoma recurrence (7 on the DC- and 14 on the control-arm). The rate of patients who were disease-free at 1 year (evaluable population = 41 patients) was higher in the TriMixDC-MEL treated group (68% [95%CI 46-86] vs. 35% [14-55]). The time-to-non-salvageable melanoma recurrence was significantly lower in the TriMixDC-MEL treated group (log-rank p = .021). Seven patients in the TriMixDC-MEL group and 3 patients in the control arm were offered local salvage therapy at first recurrence (surgery: 9 patients; RT: 1pt). TriMixDC-MEL was well tolerated (there were no grade ≥3 AE related to TriMixDC-MEL). AE were limited to: local skin injection reactions (grade 1-2; 17/21 patients), flu-like symptoms (grade 1-2; 4/21 patients), and post-infusion chills (grade 1-2; 4 [19%] patients). The results of this non-comparative randomized controlled phase II clinical trial of TriMixDC-MEL id/iv versus observation support the further evaluation of TriMixDC-MEL as a well-tolerated adjuvant therapy for melanoma patients following the resection of macrometastases. Citation Format: Bart Neyns, Yanina Jansen, Jurgen Corthals, Sofie Wilgenhof, Max Schreuer, Carlo Heirman, Kris Thielemans. A randomized controlled phase II clinical trial on mRNA electroporated autologous dendritic cells for stage III/IV melanoma patients who are disease-free following the local treatment of macrometastases [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B003.