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Objectives Human epidermal growth factor receptor 3 (HER3) is a key dimerization partner for HER family members and is associated with resistance to other HER family receptor-targeted therapeutics. This study evaluated the safety, tolerability, pharmacokinetics and efficacy of patritumab (U3-1287), a fully human anti-HER3 monoclonal antibody, in combination with erlotinib, an epidermal growth factor receptor-tyrosine kinase inhibitor in patients with previously treated advanced non-small cell lung cancer (NSCLC). Patients and methods This study enrolled patients with stage IIIB/IV NSCLC with Eastern Cooperative Oncology Group performance status 0–1, life expectancy >3 months and who had progressed after at least one prior course of chemotherapy (excluding erlotinib). This open-label study included two parts: dose escalation (Part 1) and dose expansion (Part 2). In Part 1, patients received intravenous patritumab 9 or 18 mg/kg every 3 weeks in addition to per-oral erlotinib 150 mg/day daily. In Part 2, patients received the recommended dose of patritumab as determined in Part 1. Adverse event rates, pharmacokinetics and tumor responses were determined. Results Twenty-four Japanese patients received patritumab at 9 mg/kg (n = 3) or 18 mg/kg (n = 21), and erlotinib. No dose-limiting toxicities were reported, indicating the maximum-tolerated dose was not reached. The most frequent adverse events were gastrointestinal or skin toxicities, which were generally mild and manageable. Patritumab pharmacokinetics were similar to those reported in previous studies. The median progression-free survival (95% confidence interval) was 44.0 (22.0–133.0) days for the EGFR wild-type group (n = 9) and 107.0 (74.0–224.0) days for the EGFR-activating mutation group (n = 13). Evaluation of biomarkers by immunohistochemical analysis did not indicate a relationship between efficacy and HER3 expression in tumor tissues. Conclusion Patritumab in combination with erlotinib was well tolerated and the efficacy of the combination was encouraging, especially in patients where prior gefitinib treatment failed.

Stromal-epithelial interactions play a critical role in promoting tumorigenesis and invasion. To obtain detailed information on cancer cell behaviors on the stroma and kinetics of cell migration, which cannot be observed by conventionally-used Boyden chamber assays, this study was aimed at analyzing the cell invasion process in vitro using time-lapse microscopic observation. Serum-free conditions and reconstituted type I collagen gels which provided a basal membrane-stroma-like microenvironment were used to first establish a basal condition. Time-lapse microscopic observation for 30 h of cell invasion into the collagen gel revealed kinetic parameters and individualistic behavior of cancer cells. Of breast cancer MDA-MB-231 or MCF-7 cells and colon cancer LS180 or HT29 cells examined, MDA-MB-231 cells most rapidly disappeared from the collagen gel surface under basal conditions. Estrogen-dependent MCF-7 cells disappeared at a rate approximately two times slower than that of MDA-MB-231 cells under serum- and phenol red-free conditions. By the addition of 10 nM β-estradiol to the basal medium, MCF-7 cell invasion was facilitated to a rate similar to that of MDA-MB-231 cells. Microscopic analyses of collagen gel-sections demonstrated that most of the MDA-MB-231 and MCF-7 cells remained within 60 μm from the gel top under basal conditions, which is consistent with the observation obtained using Boyden chambers that no cells could cross the collagen I gel barrier unless 1% fetal calf serum was added to basal conditions. In summary, this study demonstrated future applicability of this method to understand the initial phase of cancer cell invasion processes.