Safety and preliminary activity results of the GATTO study, a phase Ib study combining the anti-TA-MUC1 antibody gatipotuzumab with the anti-EGFR tomuzotuximab in patients with refractory solid tumors.

BACKGROUND: The phase I GATTO study (NCT03360734) explored the feasibility, tolerability and preliminary activity of combining gatipotuzumab, a novel humanized monoclonal antibody binding to the tumor-associated epitope of mucin 1 (TA-MUC1) and an anti-epidermal growth factor receptor (anti-EGFR) antibody in refractory solid tumors. PATIENTS AND METHODS: Initially the study enrolled primary phase (PP) patients with EGFR-positive metastatic solid tumors, for whom no standard treatment was available. Patients received gatipotuzumab administered at 1400 mg every 2 weeks, 6 weeks after the start of the glyco-optimized anti-EGFR antibody tomuzotuximab at 1200 mg every 2 weeks. As this regimen was proven safe, enrollment continued in an expansion phase (EP) of patients with refractory metastatic colorectal cancer, non-small-cell lung cancer, head and neck cancer and breast cancer. Tomuzotuximab and gatipotuzumab were given at the same doses and gatipotuzumab treatment started 1 week after the first dose of the anti-EGFR antibody. Additionally, investigators could use a commercial anti-EGFR antibody in place of tomuzotuximab. RESULTS: A total of 52 patients were enrolled, 20 in the PP and 32 in the EP. The combined treatment was well tolerated and no dose-limiting toxicity was observed in the whole study, nor related serious adverse event or death. Preliminary activity of the combination was observed, with one and four RECIST partial responses in the PP and EP, all in colorectal cancer patients. The trial was accompanied by a comprehensive translational research program for identification of biomarkers, including soluble TA-MUC1 (sTA-MUC1) in serum. In the EP, patients with baseline sTA-MUC1 levels above the median appeared to have improved progression-free survival and overall survival. CONCLUSIONS: Combination of a TA-MUC1-targeting antibody and an EGFR-targeting antibody is safe and feasible. Interesting antitumor activity was observed in heavily pretreated patients. Future studies should test this combination together with chemotherapy and explore the potential of sTA-MUC1 as a companion biomarker for further development of the combination.

Maintenance therapy of patients with recurrent epithelial ovarian carcinoma with the anti-tumor-associated-mucin-1 antibody gatipotuzumab: results from a double-blind, placebo-controlled, randomized, phase II study.

BACKGROUND: Gatipotuzumab is a humanized monoclonal antibody recognizing the carbohydrate-induced epitope of the tumor-associated mucin-1 (TA-MUC1). This study aimed to evaluate the efficacy and safety of switch maintenance therapy with gatipotuzumab in patients with TA-MUC1-positive recurrent ovarian, fallopian tube, or primary high-grade serous peritoneal cancer. PATIENTS AND METHODS: In this double-blind, randomized, placebo-controlled, phase II trial, patients with at least stable disease (SD) following chemotherapy were randomized 2:1 to receive intravenous gatipotuzumab (500 mg followed by 1700 mg 1 week later) or placebo every 3 weeks until tumor progression or unacceptable toxicity occurred. Stratification factors were the number of prior chemotherapy lines (2 versus 3-5), response versus SD after the most recent chemotherapy, and progression-free survival (PFS) <6 versus 6-12 months following the prior therapy. Primary endpoint was PFS according to modified immune-related RECIST 1.1 response criteria. Secondary endpoints were PFS at 6 months, safety, overall response rate, CA-125 progression, overall survival, quality of life, and pharmacokinetics. RESULTS: Overall, 216 patients were randomized to gatipotuzumab (n  = 151) or placebo (n  = 65). Median PFS with gatipotuzumab was 3.5 months as compared with 3.5 months with placebo (hazard ratio 0.96, 95% confidence interval 0.69-1.33, P  = 0.80). No advantage for gatipotuzumab over placebo was seen in the secondary efficacy endpoints or in any stratified subgroups. Gatipotuzumab was well tolerated, with mild to moderate infusion-related reactions being the most common adverse events. CONCLUSIONS: Gatipotuzumab switch maintenance therapy does not improve outcome in TA-MUC1-positive ovarian cancer patients. TRIAL REGISTRATION: ClinicalTrials.govNCT01899599; https://clinicaltrials.gov/ct2/show/NCT01899599.

A randomized phase II study comparing the efficacy and safety of the glyco-optimized anti-EGFR antibody tomuzotuximab against cetuximab in patients with recurrent and/or metastatic squamous cell cancer of the head and neck - the RESGEX study.

BACKGROUND: The aim of the RESGEX study was to compare the efficacy and safety of the anti-epidermal growth factor receptor (anti-EGFR) antibody tomuzotuximab against cetuximab both in combination with chemotherapy in patients with recurrent and/or metastatic squamous cell cancer of the head and neck in the first-line treatment. PATIENTS AND METHODS: In this phase II trial 240 patients were equally randomized for six cycles to receive either tomuzotuximab (initial dose 990 mg then 720 mg) weekly and cisplatin 100 mg/m2 and fluorouracil (5-FU; 1000 mg/m2/day, days 1-4) every 3 weeks or cetuximab (400 mg/m2 subsequent 250 mg/m2) weekly with the same chemotherapeutic backbone followed by antibody maintenance treatment. The primary endpoint was progression-free survival. RESULTS: Median progression-free survival was 6.5 months [95% confidence interval (CI) 5.9-7.9 months] in the tomuzotuximab group and 6.2 months (95% CI 5.8-7.3 months) in the cetuximab group (P = 0.86). The median overall survival (OS) estimate was 11.6 months (95% CI 9.5-17.2 months) in the tomuzotuximab group and 13.8 months (95% CI 12.3-16.4 months) in the cetuximab group (P = 0.96). In an exploratory analysis a small subgroup of p16-positive patients had a significantly longer OS compared with p16-negative patients (hazard ratio 1.860, 95% CI 1.09-3.16, P = 0.02). CONCLUSIONS: The glyco-engineered antibody tomuzotuximab failed to demonstrate improved efficacy with a chemotherapeutic backbone in the first-line treatment of recurrent or metastatic head and neck squamous cell carcinoma. It remains a so far unanswered question whether such antibody would partner better with different drugs such as checkpoint inhibitors.