Ch14.18 antibody produced in CHO cells in relapsed or refractory Stage 4 neuroblastoma patients: a SIOPEN Phase 1 study

Abstract

Purpose: This study aimed to assess the safety, pharmacokinetic and activity profiles of the human-mouse chimeric monoclonal anti-disialoganglioside GD2 antibody ch14.18 produced in Chinese hamster ovary (CHO) cells (ch14.18/CHO).

Methods: Sixteen children with recurrent/refractory neuroblastoma (median age 7.6 y) were enrolled in this Phase 1 dose-finding study. Patients received ch14.18/CHO courses of 10, 20 or 30 mg/m (2)/day as an eight-hour infusion over five consecutive days. Three courses at the same dose level were allowed unless disease progressed. Clearance and biodistribution of radiolabelled ch14.18/CHO in Balb/c and A/J mice were analyzed.

Results: A total of 41 ch14.18/CHO courses were given (10 × 3 courses, 5 × 2 courses, 1 × 1 course). Side effects were similar in expectedness, frequency and magnitude to those reported for ch14.18/SP2/0. The dose level of 20 mg/m(2)/day was confirmed. Toxicity was reversible and no treatment-related deaths occurred. In children, the peak plasma concentration was 16.51 µg/ml ± 5.9 µg/ml and the half-life was 76.91 h ± 52.5 h. A partial response following ch14.18/CHO was observed in 2/7 patients with residual disease. In mice, the half-lives were 22.7 h ± 1.9h for ch14.18/CHO and 25.0 h ± 1.9 h for ch14.18/SP2/0. The biodistribution of (125)I-ch14.18/CHO in mice with neuroblastoma was identical to (125)I-ch14.18/SP2/0, indicating GD 2 targeting activity in vivo. Ch14.18 produced in CHO cells showed an unchanged toxicity profile and pharmacokinetics in neuroblastoma patients compared with ch14.18 produced in SP2/0 cells, and evidence of clinical activity was observed. In mice, analysis of pharmacokinetics and biodistribution showed comparable results between ch14.18/CHO and ch14.18/SP2/0. Based on these results, ch14.18/CHO was accepted for prospective clinical evaluation.

Keywords: anti GD2; ch14.18/CHO; immunotherapy; monoclonal antibody; neuroblastoma.

Figure 1. Antibody ch14.18/CHO therapy associated clinical symptoms, laboratory parameters frequency of co-medication and pain management. All 16 patients were evaluated for ch14.18/CHO associated side effects including clinical symptoms and laboratory changes (A), the use of supportive care medication (B) and pain management including pain management related side effects (C). The data are given in percentage of patients separated for each course (course 1: white bar, course 2: gray bar, course 3: black bar). The absolute number of patients is additionally provided for each column.

Figure 2. Clearance and biodistribution of ch14.18/CHO in mice. ¹²⁵I-labeled ch14.18/CHO antibody (25 µg; 5 × 10E cpm) was injected into groups (n = 5) of Balb/c mice and neuroblastoma bearing A/J mice (average tumor weight 53 ± 12 mg) and clearance (A) as well as biodistribution (B) was analyzed and compared with indicated control antibodies. (A) The clearance of ¹²⁵I-ch14.18/CHO from the blood of Balb/c mice was analyzed at indicated time points and compared with ¹²⁵I-ch14.18/SP2/0. ¹²⁵I-ch14.18-IL2, ¹²⁵I-14G2a and ¹²⁵I-rituximab are shown as controls. Blood levels of antibodies investigated are given as percent injected dose per milliliter of blood. Each value represents mean and standard deviation (n = 5). The t ½ α and β values were 25.0 h ± 1.9 h and 134.6 h ± 29.9 h for ch14.18 SP2/0 and 22.7 h ± 1.8 h and 136.2 h ± 12.2 h for ch14.18/CHO (p > 0.05). The rapid clearance of ch14.18-IL2 (human-mouse chimeric antibody interleukin-2 fusion protein) and the long half-life of 14G2 (murine IgG2a) and rituximab compared with ch14.18 (human-mouse chimeric antibody) are shown as controls. The difference between mice treated with ch14.18/CHO compared with controls was statistically significant (* p < 0.01). (B) Organ specific activity was detected 8 h after injection of ¹²⁵I-ch14.18/CHO, ¹²⁵I-ch14.18/SP2/0 and ¹²⁵I-rituximab into neuroblastoma bearing A/J mice. Organ and tumor specific activity is given in percent of injected dose per gram of tissue. Each value represents the mean and standard deviation for five tumor bearing mice (* p < 0.01).