A phase I/II study of TRC105 in combination with sorafenib in hepatocellular carcinoma (HCC)

291 Background: Endoglin (CD105) is an endothelial cell membrane receptor highly expressed on proliferating tumor vasculature, including HCC. CD105 is essential for angiogenesis and its expression is upregulated by hypoxia and VEGF inhibition. TRC105 is a chimeric IgG1 anti-CD105 monoclonal antibody that inhibits angiogenesis and causes ADCC and apoptosis of proliferating endothelium. Sorafenib is the only FDA-approved drug in HCC. Methods: Preclinical: Murine BNL HCC cells were grown subcutaneously in wildtype Balb/c mice and treated with antibody to murine CD105, (clone MJ7/18; 10-200ug) + sorafenib (10 mg/kg daily p.o.) or sorafenib alone with assessment for CD105 expression, tumor size. Clinical: Patients with HCC (Childs Pugh A/B7), ECOG 0/1, were enrolled in a phase I study of TRC105 at 3, 6, 10, 15mg/kg q 2wks plus sorafenib 400mg bid. Correlative biomarkers included DCE-MRI, color Doppler ultrasonography, circulating endothelial and endothelial progenitor cells, plasma levels of angiogenic factors, soluble CD105 and tumor IHC for CD105. Samples were also collected for immunogenicity and pharmacokinetics. Results: Preclinical studies: CD105 expression was increased in BNL HCC tumors by sorafenib. Anti-CD105 antibody + sorafenib reduced tumor volume compared to sorafenib alone. Clinical trial: 19 pts were enrolled; Hep B/C/NA: 2/10/7; M:F 13:6; Mean age of 60 (range 18-76); 1 DLT (increased AST) occurred at 10mg/kg. Three of 14 (21%) evaluable pts achieved PR by RECIST. Four patients had confirmed stable disease, one of whom was treated for 22 months. Median time on study was 4 months (range 2 to 22 months). Conclusions: TRC105 combined with sorafenib was well tolerated at the recommended single agent doses of both drugs. Encouraging evidence of activity was observed and the study is proceeding to the phase 2 stage. Full correlative and clinical data will be presented. Clinical trial information: NCT01306058.