Selumetinib for NF2-Related Schwannomatosis

The goal of this clinical trial is to evaluate the efficacy and safety of the MEK1/2 inhibitor selumetinib in treating patients with neurofibromatosis type 2-related schwannomatosis (NF2-SWN), including both adults and children with inoperable or progressive tumors.

Inclusion Criteria: 1. Patients must have a pathogenic variant in the NF2 gene (either in the germline or in two NF2-related tumors)OR a confirmed diagnosis of NF2 by fulfilling National Institute of Health (NIH)criteria or Manchester criteria: The genetic test report should be issued by companies or hospitals with corresponding qualifications. The NIH criteria includes presence of: * Bilateral vestibular schwannomas, OR * First-degree relative with NF2 and EITHER unilateral eighth nerve mass OR two of the following: neurofibroma, meningioma, glioma, schwannoma, juvenile posterior subcapsular lenticular opacity. The Manchester criteria includes presence of: * Bilateral vestibular schwannomas, OR * First-degree relative with NF2 and EITHER unilateral eighth nerve mass OR two of the following: neurofibroma, meningioma, glioma, schwannoma, juvenile posterior subcapsular lenticular opacity, OR * Unilateral vestibular schwannoma AND any two of: neurofibroma, meningioma, glioma, schwannoma, juvenile posterior subcapsular lenticular opacity,OR * Multiple meningiomas (two or more)AND unilateral vestibular schwannoma OR * any two of: schwannoma, glioma, neurofibroma, cataract. 2. Subjects must have ≥1 measurable target vestibular schwannoma meeting all of the following conditions: * Measurable on MRI with a minimum diameter ≥3 mm; * Evidence of radiographic progression within the past 36 months according to REiNS criteria, OR documented clinical progression attributable to the target tumor (e.g., hearing decline, cranial nerve dysfunction). * Subjects whose Word Recognition Score (WRS)ranging from 50%to 88%at the side of target vestibular schwannoma. 3. The target tumor must be considered not amenable to surgery due to: * High surgical risk (e.g., risk of neurological deficit), OR * Patient refusal of surgery after adequate medical counseling. 4. Male or female subjects aged ≥3 years at the time of informed consent. 5. Adequate functional status Subjects aged ≥16 years: * Karnofsky Performance Status ≥70,OR * ECOG Performance Status 0-1 Subjects aged \470 ms (adults)\[\>450 ms for pediatric thresholds as specified in protocol appendix\], or clinically significant baseline prolongation per investigator/medical monitor. * Clinically significant arrhythmia (symptomatic ventricular tachycardia, sustained ventricular tachycardia, uncontrolled atrial fibrillation). Subjects with well controlled atrial fibrillation may be considered after Medical Monitor review. * Acute coronary syndrome within 6 months, unstable angina, symptomatic congestive heart failure NYHA class II-IV, or LVEF below institutional lower limit of normal (LLN)or \5 ×ULN (or per protocol specified threshold for severe impairment), total bilirubin \>3 ×ULN (unless Gilbert's syndrome).(See inclusion for minimum acceptable labs;exclude those with more severe dysfunction.) 8. Ophthalmologic conditions:current or prior history of MEK-associated retinopathy / central serous retinopathy /retinal pigment epithelial detachment /retinal vein occlusion, or any active ocular condition judged by the investigator/ophthalmologist to increase the risk of serious ocular adverse events (e.g., uncontrolled glaucoma with elevated IOP and meaningful vision at risk). Subjects with stable, chronic ophthalmic findings that are not expected to worsen with MEK inhibition may be eligible after ophthalmology clearance. 9. Known hypersensitivity to selumetinib or any excipients. 10. Active, uncontrolled infection including: * Positive HIV test (known HIV infection with uncontrolled disease or on unstable antiretroviral therapy that interacts with study drug)-no evidence AIDS and no contraindicating ART may be considered after Medical Monitor review. * Active hepatitis B or C infection (HBsAg positive or HCV RNA positive). Subjects with resolved HBV (HBsAg negative, anti-HBc positive)may be eligible per local hepatology guidance and prophylaxis plan. 11. Concomitant medications that: * Are known to prolong QT interval and cannot be safely discontinued;OR * Are strong CYP3A4 or CYP2C19 inducers/inhibitors that cannot be stopped and would significantly alter selumetinib exposure (refer to protocol drug-interaction appendix for permitted/forbidden lists). 12. Gastrointestinal conditions that preclude reliable oral absorption (e.g., severe malabsorption, short bowel syndrome, recent (within 6 months)major intestinal resection)or inability to swallow intact capsules. 13. Conditions requiring urgent neurosurgical intervention (e.g., symptomatic hydrocephalus requiring immediate shunting, life-threatening brainstem compression)-subjects requiring emergent neurosurgery are not eligible until stabilized and reevaluated. 14. Prior organ transplantation (allogeneic)or ongoing immunosuppression that would confound safety assessment. 15. Concomitant vitamin E†or other agents judged to have potential interaction with the study drug if they cannot be discontinued per protocol (e.g., vitamin E to be stopped ≥7 days before first dose if required by protocol). 16. Pregnancy or breastfeeding at screening (positive pregnancy test). Female subjects of childbearing potential who are unwilling/unable to use acceptable contraception during the study and for the duration specified in the contraceptive guidance (see protocol)are excluded. 17. Any other clinically significant medical, psychiatric, or social condition that, in the opinion of the investigator or Medical Monitor, would compromise subject safety or protocol compliance (including inability to undergo MRI, when MRI is required for tumor assessment).