Phase II Study of FCN-159 in NF2 Nerve Sheath Tumors

Inclusion Criteria: 1. ≥16 years of age, regardless of gender. 2. meet the revised 2022 diagnostic criteria for NF2-associated nerve sheath tumors or pathologically confirmed NF2-associated nerve sheath tumors. 3. should meet one of the following criteria: 1) Incomplete surgical resection, or postoperative recurrence. 2) Systemic therapy is required as determined by the Investigator. 4. the presence of a measurable lesion, as defined by REiNS or RECIST V1.1 criteria. 5. Karnofsky physical status score of ≥70. 6. the patient has adequate organ and bone marrow function. 7. International Normalized Ratio (INR) and activated partial thromboplastin time (APTT) ≤ 1.5 x ULN. 8. For patients of childbearing potential: During treatment and for at least 90 days after the last dose, patients should agree to use a highly effective method of contraception. 9. avoid excessive sun exposure and be willing to use an adequate amount of sunscreen in anticipation of sun exposure. 10. be able to understand and voluntarily sign a written informed consent form. Exclusion Criteria: * Previously received one of the following treatments: 1. Pharmaceutical or biological therapy within 3 weeks or 5 half-lives prior to enrollment, whichever is longer. 2. Use of growth factors that promote platelet, red blood cell, or white blood cell count or function within 7 days prior to enrollment. 3. Patients who have received major surgery or anti-tumor immunotherapy within 4 weeks prior to enrollment. 4. Radiation therapy for nerve sheath tumors within 4 weeks prior to enrollment. 5. Dose adjustment for patients treated with dexamethasone or other corticosteroids within 1 week prior to enrollment. 6. Patients who have participated in another interventional clinical trial within 4 weeks prior to enrollment. 7. Prior treatment with Selumetinib or any other MEK 1/2 inhibitor. 2. history of or concurrent with other malignancies. 3. inability to undergo MRI and/or contraindications to MRI. 4. uncontrolled hypertension. 5. the presence of dysphagia, active gastrointestinal disease, malabsorption syndrome, or other condition that interferes with the absorption of the study medication. 6\. previous or current retinal vascular disease. 7. interstitial pneumonitis 8. cardiac function or co-morbidities 9. Immediate family history of sudden cardiac death before age 50. 10.History of any acute neurological condition 11. with active bacterial, fungal or viral infections 12. known hypersensitivity to the study drug, other MEK1/2 inhibitors, or their excipients.