Inclusion

1. Age >18 years of age with either sporadic or NF-2 associated VS
2. Growing VS defined as an increase in MRI volumetric growth (minimal 15%) on two successive scans within 18 months prior to registration
3. Patients may be either treatment naïve or have recurrent VS after previous surgery/ stereotactic radiosurgery
4. Essentially neurologically asymptomatic (with the exception of sensorineural hearing loss, mild tinnitus and facial numbness) as assessed by the investigator
5. Karnofsky performance score >70
6. Adequate renal, haematological, liver function within 7 days prior to registration
7. Willingness and ability to comply with scheduled visits, drug administration plan, laboratory tests, other study procedures, and study restrictions
8. Willingness and ability to provide informed consent

Exclusion

1. Brain stem compression with symptoms
2. Symptomatic hydrocephalus
3. T2/Flair signal changes with distortion of adjacent brain stem and IVth ventricle
4. Lower cranial nerve dysfunction
5. Concurrent or previous invasive malignancy, except adequately treated non-melanoma skin cancer or other solid tumours curatively treated with no evidence of disease for ≥ 3 years
6. Evidence of severe or uncontrolled systemic disease which in the opinion of the investigator makes it undesirable for the subject to participate in the study
7. Known hypersensitivity to the study drug or drug of similar chemical or biological composition

8. Impaired cardiac function including

   1. Congenital long QT syndrome or family history of long QT syndrome
   2. Clinically significant resting bradycardia (< 50 beats per minute)
   3. Myocardial infarction within 1 year prior to registration or other clinically significant heart disease (e.g. unstable angina, congestive heart failure, uncontrolled hypertension)
   4. History of or current clinically significant ventricular or atrial tachyarrhythmia
   5. QTcF > 450 msec on screening ECG. If QTcF > 450 msec and electrolytes are not within normal ranges then electrolytes should be corrected and the patient rescreened for QTcF.
   6. Unable to monitor the QT/QTc interval on ECG
9. Treatment with strong CYP3A4 inhibitors or CYP3A4 inducers and treatment cannot be either discontinued or switched to a different medication prior to starting study drug.
10. Treatment with any medications that have the potential to prolong the QT interval and cannot be either discontinued or switched to a different medication prior to starting study drug.
11. Impaired gastrointestinal (GI) function or GI disease that may significantly alter the absorption of study drug
12. History of acute or pancreatic disease within one year of study registration or past medical history of chronic pancreatitis.
13. Acute liver disease
14. History of significant congenital or acquired bleeding disorder
15. Use of any investigational agent within 28 days prior to enrollment in the study or foreseen use of an investigational agent during the study
16. Women who are pregnant or breastfeeding or of childbearing potential without a negative serum pregnancy test within 7 days prior to registration. Post menopausal women must be amenorrheic for at least 12 months to be considered of non-childbearing potential. Male or female patients of childbearing potential unwilling to use effective barrier contraceptives or medical contraceptive to avoid pregnancy throughout the trial and for 3 months following discontinuation.