TRC105 for the treatment of hepatocellular carcinoma: Preclinical data and preliminary results from two clinical trials evaluating monotherapy and combination with sorafenib.

Abstract

211 Background: Endoglin (CD105), is an endothelial cell membrane receptor highly expressed on proliferating tumor vasculature, including in 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 acts by endothelial cell growth inhibition, ADCC and apoptosis. 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. 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; or (if sorafenib-refractory) a phase II study of TRC105 at 10 or 15mg/kg q 2wks. Correlative biomarkers: DCE-MRI; FDG-PET; color Doppler ultrasonography; circulating endothelial and endothelial progenitor cells, plasma levels of angiogenic factors; soluble CD105 and tumor IHC for CD105. Results: Preclinical studies: CD105 expression was increased in BNL HCC tumors of mice treated with sorafenib. Anti-CD105 + sorafenib was more effective than sorafenib alone. Clinical trials (N=16): M:F 13:3; Median age = 55 (range 24-67); Phase I with sorafenib (N=8): 1 DLT (increased AST) occurred at 10mg/kg. The most frequent toxicity has been epistaxis. One patient with coronary stenosis developed a fatal MI and one patient with thrombocytopenia developed G3 cerebral tumor hemorrhage. Phase II (N=8): No grade 3/4 treatment-related toxicities . Most frequent toxicities headache (G2; N=3) and epistaxis (G1; N=4). No patient was progression free at 4 months. Median time on study: Phase I- 4 months; Phase II - 2 months. Preliminary evidence of biologic response seen on DCE-MRI in 1pt (of 3 evaluable) with a reduction in Ktrans and kep and 3pts (of 3 evaluable) with reduction in intra-tumoral color flow on Doppler. Conclusions: TRC105 is well tolerated both as single agent and combined with sorafenib. Evidence of biological activity was observed. Full preclinical, clinical and correlative data will be presented. Clinical trial information: NCT01306058, NCT01375569.