Dual Antiangiogenesis Agents Bevacizumab Plus Trebananib, without Chemotherapy, in First-line Treatment of Metastatic Colorectal Cancer: Results of a Phase II Study

Purpose: To assess the efficacy and safety of dual antiangiogenesis agents, bevacizumab plus trebananib, without chemotherapy, in first-line treatment of metastatic colorectal cancer (mCRC).

Patients and Methods: This open-label phase II study enrolled patients with unresectable mCRC with no prior systemic treatment. All patients received bevacizumab 7.5 mg/kg 3-weekly and trebananib 15 mg/kg weekly. The primary endpoint was disease control [stable disease, partial response (PR), or complete response (CR)] at 6 months (DC6m). Secondary endpoints included toxicity, overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). Exploratory biomarkers in plasma angiogenesis–related proteins, tumor gene expression, and plasma antibodies to tumor antigens were examined.

Results: Forty-five patients were enrolled from four Australian sites. DC6m was 63% [95% confidence interval (CI), 47–77]. ORR was 17% (95% CI, 7–32), comprising of seven PRs. Median duration of response was 20 months (range, 10–48 months). Median PFS was 8.4 months and median OS 31.4 months. Grade 1–2 peripheral edema and joint-related symptoms were common. Overall incidence of grade 3–4 adverse events (AE) of any type was 33% (n = 15). Expected AEs of bevacizumab treatment did not appear to be increased by the addition of trebananib.

Conclusions: In a first-line mCRC population, the dual antiangiogenic combination, bevacizumab plus trebananib, without chemotherapy, was efficacious with durable responses. The toxicity profile of the combination was manageable and did not exceed that expected with bevacizumab +/− chemotherapy. Exploratory biomarker results raise the hypothesis that the antiangiogenic combination may enable the antitumor immune response in immunotolerant colorectal cancer.