A Study of Selumetinib in Chinese Paediatric and Adult Subjects With Neurofibromatosis Type 1 (NF1) and Inoperable Plexiform Neurofibromas (PN)

Inclusion Criteria: * Paediatric cohort: Chinese subjects ≥3 years and \<18 years of age * Adult cohort: Chinese subjects ≥18 years of age at the time of study enrollment * Subjects must be diagnosed with (i) NF1 as per NIH Consensus Development Conference Statement and（ii) PN is defined as a neurofibroma that has grown along the length of a nerve and may involve multiple fascicles and branches. (iii) inoperable PN * Subjects must have at least one measurable typical or nodular PN * Absolute neutrophil count ≥1.5×10\^9/L, haemoglobin ≥9g/dL, and platelet count ≥100×10\^9/L. Subject must be without growth factor support and platelet transfusion support 7 days before the screening assessment. * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2×upper limit of normal (ULN), total bilirubin ≤1.5×ULN except in the case of subjects with documented Gilbert's disease (≤2.5×ULN). Exclusion Criteria: * Evidence of malignant peripheral nerve sheath tumour. * Clinically significant cardiovascular disease * Prior malignancy (except for adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, or other cancer from which the subject had been disease free for ≥2 years or which would not have limited survival to \<2 years) or other cancer requiring treatment with chemotherapy or radiation therapy. * Subjects with the following ophthalmological findings/conditions: Current or past history of retinal pigment epithelial detachment/central serou…