Human epidermal growth factor receptor 3 (HER3) expression is seen across a wide variety of solid malignancies and is associated with poor prognosis. Up-regulation of HER3 expression and activity is also associated with resistance to multiple pathway inhibitors. GSK2849330, a monoclonal antibody (mAb) targeting HER3, is a new agent for subjects whose tumors express HER3. This study aims to characterise the biodistribution and dose-receptor occupancy relationship of GSK2849330 in patients with advanced HER3 expressing solid tumours via the use of PET imaging. This study will be conducted in two parts. Part 1 will be the imaging phase where each subject will receive two doses of GSK2849330 containing both Zirconium-89 (89Zr) labelled GSK2849330 and unlabeled GSK2849330. The amount of unlabeled GSK2849330 present in each dose will be varied to explore the effect on target mediated uptake of 89Zr into HER3 expressing tissues and tumors. Subjects will then proceed to the continuation phase (Part 2) for continued treatment with unlabelled GSK2849330. The study is planned to enroll approximately 12-15 subjects.