A Phase 1 Open Label Study to Assess the Safety, Tolerability, Pharmacokinetics and Clinical Efficacy of Selumetinib, a Selective Mitogen Activated Protein Kinase Kinase (MEK) 1 Inhibitor, in Chinese Paediatric and Adult Subjects with Neurofibromatosis Type 1 (NF1) and Inoperable Plexiform Neurofibromas (PN).

Paediatric and adult patients with Neurofibromatosis Type 1 (NF1) and Inoperable Plexiform Neurofibromas (PN) will be evaluated in the screening visit to confirm eligibility. Approximately 16 paediatric and 16 adult qualified patients will receive oral selumetinib 25 mg/m^2 twice a day (approximately every 12 hours) continuously until disease progression or unacceptable drug-related toxicity, whichever occurs first. Once a patient has discontinued the study treatment then the patient will be followed for specified period for safety assessment

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 serous retinopathy or retinal vein occlusion; Intraocular pressure >21 mmHg (or ULN adjusted by age) or uncontrolled glaucoma (irrespective of IOP); Subjects with known glaucoma and increased IOP who do not have meaningful vision (light perception only or no light perception) and are not experiencing pain related to the glaucoma, may be eligible after discussion with the study physician; Any other significant abnormality on ophthalmic examination that would make the subject unsuitable for enrolment into the study, as assessed by the investigator.

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal. All request will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA Pharma Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the de-identified individual patient-level data in an approved sponsored tool . Signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information. Additionally, all users will need to accept the terms and conditions of the SAS MSE to gain access. For additional details, please review the Disclosure Statements at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.