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.

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.
Competing Interests: Competing interests: CB has acted as a board advisor for BMS, has been a speaker for Merck and has received travel fees from Amgen and Pfizer. NC-G has received research grants from Cytune Pharma, GSK and Sanofi. She has acted as a board advisor for AstraZeneca and has been a speaker for Sanofi and AstraZeneca. CM has acted as consultant of BMS and Merck. ER has acted as a consultant for BMS, Novartis and Roche, and has received travel fees from BMS and Novartis. RS has received travel fees from AstraZeneca. CM has acted as a consultant from Amgen, Astellas, Astra Zeneca, Bayer, BeiGene, BMS, Celgene, Debiopharm, Genentech, Ipsen, Janssen, Lilly, MedImmune, MSD, Novartis, Pfizer, Roche, Sanofi and Orion. He is the principal or subinvestigator of clinical trials for Abbvie, Aduro, Agios, Amgen, Argen-x, Astex, AstraZeneca, Aveopharmaceuticals, Bayer, Beigene, Blueprint, BMS, BoeringerIngelheim, Celgene, Chugai, Clovis, DaiichiSankyo, Debiopharm, Eisai, Eos, Exelixis, Forma, Gamamabs, Genentech, Gortec, GSK, H3 biomedecine, Incyte, InnatePharma, Janssen, Kura Oncology, Kyowa, Lilly, Loxo, Lysarc, LytixBiopharma, Medimmune, Menarini, Merus, MSD, Nanobiotix, NektarTherapeutics, Novartis, Octimet, Oncoethix, OncopeptidesAB, Orion, Pfizer, Pharmamar, Pierre Fabre, Roche, Sanofi, Servier, Sierra Oncology, Taiho, Takeda, Tesaro and Xencor. J-CS has received consultancy fees from AstraZeneca, Astex, Clovis, GSK, GamaMabs, Lilly, MSD, Mission Therapeutics, Merus, Pfizer, PharmaMar, Pierre Fabre, Roche/Genentech, Sanofi, Servier, Symphogen and Takeda. He has been a full-time employee of MedImmune since September 2017. He is a shareholder of AstraZeneca and Gritstone. CR has acted as a consultant of Amgen, BMS, GSK, Merck, Novartis and Roche. ED has received research grants from Roche, Servier, AstraZeneca, Merck Serono, BMS, MSD, Amgen, Accuray and Boerhinger. He has received personal fees from Roche, AstraZeneca, Merck Serono, Amgen, Accuray and Boerhinger.
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