Randomized, phase II, placebo-controlled trial of onartuzumab and/or bevacizumab in combination with weekly paclitaxel in patients with metastatic triple-negative breast cancer

Background: Increased hepatocyte growth factor/MET signaling is associated with an aggressive phenotype and poor prognosis in triple-negative breast cancer (TNBC). We evaluated the benefit of adding onartuzumab, a monoclonal anti-MET antibody, to paclitaxel with/without bevacizumab in patients with TNBC. Patients and methods: Women with metastatic TNBC were randomized to receive onartuzumab plus placebo plus weekly paclitaxel (OP; n = 60) or onartuzumab plus bevacizumab plus paclitaxel (OBP; n = 63) or placebo plus bevacizumab plus paclitaxel (BP; n = 62). The primary end point was progression-free survival (PFS); additional end points included overall survival (OS), objective response rate (ORR), and safety. This trial was hypothesis generating and did not have power to detect minimum clinically meaningful differences between treatment arms. Results: There was no improvement in PFS with the addition of onartuzumab to BP [hazard ratio (HR), 1.08; 95% confidence interval (CI) 0.69-1.70]; the risk of a PFS event was higher with OP than with BP (HR, 1.74; 95% CI 1.13-2.68). Most patients had MET-negative tumors (88%); PAM50 subtype analysis showed basal-like tumors in 68% of samples. ORR was higher in the bevacizumab arms (OBP: 42.2%; 95% CI 28.6-57.1; BP: 54.7%; 95% CI 41.0-68.4) compared with OP (27.5%; 95% CI 15.9-40.6). Median OS was shorter with OBP (HR, 1.36; 95% CI 0.75-2.46) and OP (HR, 1.92; 95% CI 1.03-3.59), than with BP. Peripheral edema was more frequent in the onartuzumab arms (OBP, 51.8%; OP, 58.6%) versus BP (17.7%). Conclusion: This study did not show a clinical benefit of the addition of onartuzumab to paclitaxel with/without bevacizumab in patients with predominantly MET-negative TNBC. ClinicalTrials.gov: NCT01186991.