RT Journal Article SR Electronic T1 Dose escalation phase 1 study of radiotherapy in combination with anti-cytotoxic-T-lymphocyte-associated antigen 4 monoclonal antibody ipilimumab in patients with metastatic melanoma JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP e000627 DO 10.1136/jitc-2020-000627 VO 8 IS 2 A1 Celine Boutros A1 Nathalie Chaput-Gras A1 Emilie Lanoy A1 Alicia Larive A1 Christine Mateus A1 Emilie Routier A1 Roger Sun A1 Yun Gan Tao A1 Christophe Massard A1 Rastilav Bahleda A1 Dominique Schwob A1 Nathalie Ibrahim A1 Rita Maria Khoury Abboud A1 Caroline Caramella A1 Andrea Lancia A1 Lydie Cassard A1 Severine Roy A1 J -C Soria A1 Caroline Robert A1 Eric Deutsch YR 2020 UL http://jitc.bmj.com/content/8/2/e000627.abstract AB Background A synergy between radiotherapy and anti-cytotoxic-T-lymphocyte-associated antigen 4 (anti-CTLA-4) monoclonal antibody has been demonstrated preclinically. The Mel-Ipi-Rx phase 1 study aimed to determine the maximum tolerated dose (MTD) and safety profile of radiotherapy combined with ipilimumab in patients with metastatic melanoma.Patients and methods A 3+3 dose escalation design was used with 9, 15, 18 and 24 Gy dose of radiotherapy at week 4 combined with 10 mg/kg ipilimumab every 3 weeks for four doses. Patients with evidence of clinical benefit at week 12 were eligible for maintenance with ipilimumab 10 mg/kg every 12 weeks starting at week 24 until severe toxicity or disease progression. The database lock occurred on April 30, 2019. Tumor growth rate of irradiated lesions and non-irradiated lesions were analyzed to assess the systemic immunologic antitumor response. Blood immune monitoring was performed before and during treatment to determine if radiotherapy could modify ipilimumab pharmacodynamics.Results 19 patients received ipilimumab between August 2011 and July 2015. Nine patients received the four doses of ipilimumab. All patients received the combined radiotherapy. Grade 3 adverse events occurred in nine patients, the most common being colitis and hepatitis. No drug-related death occurred. Dose limiting toxicity occurred in two of six patients in the cohort receiving 15 Gy. The MTD was 9 Gy. Two patients had complete response, three had partial response response and seven had stable disease, giving an objective response rate of 31% and a clinical benefit rate of 75% at week 24. The median duration of follow-up was 5.8 years (Q1=4.5; Q3=6.8). The median overall survival (95% CI) was estimated at 0.9 years (0.5–2). The median progression-free survival (PFS) (95% CI) was 0.4 (0.2–1.4). Radiotherapy combined with ipilimumab was associated with increased CD4+ and CD8+ICOS+ T cells. Increased CD8+ was significantly associated with PFS.Conclusion When combined with ipilimumab at 10 mg/kg, the MTD of radiotherapy was 9 Gy. This combination of ipilimumab and radiotherapy appears to be associated with antitumor activity. Increased CD8+ was significantly associated with PFS. Thus, immune biomarkers may be useful for early response evaluation.Trial registration number NCT01557114.