467P - Phase I study of U3-1287, a human monoclonal antibody targeting HER3, in Japanese patients with advanced solid tumors

Date 01 October 2012
Event ESMO Congress 2012
Session Poster presentation III
Topics Clinical research
Basic Scientific Principles
Presenter Hiroshi Wakui
Authors H. Wakui1, N. Yamamoto2, S. Nakamichi2, Y. Tamura2, H. Nokihara2, Y. Yamada3, T. Tamura2
  • 1Division Of Thoracic Oncology, National Cancer Center Hospital, 104-0045 - Tokyo/JP
  • 2Division Of Thoracic Oncology, National Cancer Center Hospital, Tokyo/JP
  • 3Medical Oncology, National Cancer Center Hospital, Tokyo/JP



HER3 is a key dimerization partner for HER-family members that activates oncogenic signaling pathways lead to cell survival and proliferation. Acquired-resistance to EGFR inhibitors may result from the activation of HER3 and/or HER2, which share overlapping the signaling pathways. U3-1287 is a fully human anti-HER3 monoclonal antibody that has demonstrated anticancer activity in preclinical models. In a preceding US phase I study, the tolerability of U3-1287 was evaluated up to the dose of 20 mg/kg without dose-limiting toxicities (DLTs). In this study, we evaluated the tolerability, pharmacokinetics (PK) and potential antitumor activities of U3-1287 in Japanese patients with solid tumors up to the dose of 18 mg/kg.


Patients received U3-1287 at a dose of 9 mg/kg or 18 mg/kg intravenously every 3 weeks (q3w). Tumor response, incidence of anti-U3-1287 antibodies (HAHA), and level of soluble HER3 (sHER3) were also evaluated.


Nine patients, 3 at 9 mg/kg and 6 at 18 mg/kg, were enrolled. Five patients were male and median (range) age of 67 (50-69) years. Tumor types were lung (2), colorectal (2), esophageal (2), breast (1), cervical (1), and sarcoma (1). No DLTs were reported. U3-1287-related AEs were ALT increase (3 patients), thrombocytopenia, diarrhea, stomatitis, cheilitis, rash, and AST increase (2 each). Plasma disappearance was bi-phasic and terminal half-life at the dose of 18 mg/kg was approximately 9 days. PK profiles were similar to those in the US phase I study. Four patients had best responses of stable disease. All patients tested were negative for HAHA formation. Level of sHER3 unexpectedly increased about four times in all patients. Mean sHER3 concentrations at baseline and day 15 were 3.8 ng/mL and 16.5 ng/mL, respectively. These changes did not correlate with clinical response (at day15 in SD and PD patients; 16.7 ng/mL and 16.9 ng/ml, respectively).


U3-1287 was well tolerated up to 18 mg/kg in Japanese patients with solid tumors. These data support a dosing regimen of 18 mg/kg q3w in future studies.


All authors have declared no conflicts of interest.