Influenza virus infection in pigs is both an animal health problem and a public health concern. As such, surveillance and characterization of influenza viruses in swine is important to the veterinary community and should be a part of human pandemic preparedness planning. Studies in 1976/1977 and 1988/1989 demonstrated that pigs in the U.S. were commonly infected with classical swine H1N1 viruses, whereas human H3 and avian influenza virus infections were very rare. In contrast, human H3 and avian H1 viruses have been isolated frequently from pigs in Europe and Asia over the last two decades. From September 1997 through August 1998, we isolated 26 influenza viruses from pigs in the north central United States at the point of slaughter. All 26 isolates were H1N1 viruses, and phylogenetic analyses of the hemagglutinin and nucleoprotein genes from 11 representative viruses demonstrated that these were classical swine H1 viruses. However, monoclonal antibody analyses revealed antigenic heterogeneity among the HA proteins of the 26 viruses. Serologically, 27.7% of 2,375 pigs tested had hemagglutination-inhibiting antibodies against classical swine H1 influenza virus. Of particular significance, however, the rates of seropositivity to avian H1 (7.6%) and human H3 (8.0%) viruses were substantially higher than in previous studies.

Background: Endoglin is an endothelial cell membrane receptor essential for angiogenesis and highly expressed on the vasculature of many tumor types, including hepatocellular carcinoma (HCC). TRC105 is a chimeric IgG1 anti-CD105 monoclonal antibody that inhibits angiogenesis and tumor growth by endothelial cell growth inhibition, ADCC and apoptosis, and complements VEGF inhibitors. Objective: The aim of this phase II study was to evaluate the efficacy of anti-endoglin therapy with TRC105 in patients with advanced HCC, post-sorafenib. Methods: Patients with HCC and compensated liver function (Childs-Pugh A/B7), ECOG 0/1, were enrolled to a single-arm, phase II study of TRC105 15 mg/kg IV every two weeks. Patients must have progressed on or been intolerant of prior sorafenib. A Simon optimal two-stage design was employed with a 50% four-month PFS target for progression to the second stage. Correlative biomarkers evaluated included DCE-MRI as well as plasma levels of angiogenic biomarkers and soluble CD105. Results: A total accrual of 27 patients was planned. However, because of lack of efficacy and in accordance with the Simon two-stage design, 11 patients were enrolled. There were no grade 3/4 treatment-related toxicities. Most frequent toxicities were headache (G2; N ¼ 3) and epistaxis (G1; N ¼ 4). One patient had a confirmed partial response by standard RECIST criteria and biologic response on DCE-MRI but the four-month PFS was insufficient to proceed to the second stage of the study. Conclusions: TRC105 was well tolerated in this HCC population following sorafenib. Although there was evidence of clinical activity, this did not meet prespecified criteria to proceed to the second stage. TRC105 development in HCC continues as combination therapy with sorafenib.

270 Background: Tremelimumab is a fully human monoclonal antibody that binds to CTLA-4 expressed on the surface of activated T lymphocytes and results in inhibition of B7-CTLA-4-mediated downregulation of T-cell activation. Transcatheter arterial chemoembolization (TACE), radiofrequency ablation (RFA) and cryoablation (CA) have been shown to induce a peripheral immune response which may enhance the effect of anti-CTLA4 treatment in patients with advanced HCC. Methods: Patients with HCC [Childs Pugh A/B7; BCLC B/C; ECOG 0/1; post-sorafenib (BCLC stage C only)] or refractory BTC were enrolled in a study of Tremelimumab combined with subtotal TACE, RFA or CA performed on week 6. All BTC patients received RFA as the immune-stimulant in combination with tremelimumab. Tumor biopsies were performed at baseline and at time of RF/TACE. Results: 34 pts enrolled (28 HCC, 6 BTC). Characteristics: M:F 26:8; Median age 54(range 42-76); In HCC pts cirrhosis present in 17pts, BCLC Stage B/C: 9/19; Hepatitis B/C/neg: 4/15/9. 13 pts received TACE, 16 underwent RFA (inc 6 BTC pts), 3 CA during week 6 of tremelimumab therapy. 2 pts did not receive an ablative procedure. No DLT encountered. Most common toxicity was pruritus. One patient developed pulmonitis and was taken off study but remained disease-free at 16m. Of N = 17 pts evaluable for response outside of TACE/RFA-treated lesion 4 (23.5%) achieved confirmed partial responses. 8 of 9 pts with quantifiable HCV experienced a marked reduction in viral load. 6-week tumor biopsies showed immune cell infiltration on all evaluable patients. Median PFS for the evaluable HCC population (N = 25) was 5.7m. Conclusions: Tremelimumab in combination with subtotal TACE, RFA or CA in patients with advanced HCC and BTC is safe and feasible. Obtaining tumor biopsies at baseline and at the time of RFA/TACE is safe. Evidence of immune cell infiltration was seen on evaluable patients. Encouraging clinical activity seen with objective confirmed responses, PFS 5.7m and possibly surrogate reductions in HCV viral load. Clinical trial information: NCT01853618.