 2. Diagnosis: Phase I Dose escalation: Patients with NF1 and inoperable PNs defined as PNs that cannot be surgically completely removed without risk for substantial morbidity due to: encasement of or close proximity to vital structures, invasiveness, or high vascularity of the PN. The PN has to cause morbidity or have the potential to cause significant morbidity, such as but not limited to head and neck lesions that could compromise the airway or great vessels, brachial or lumbar plexus lesions that could cause nerve compression and loss of function, lesions that could result in major deformity e.g., orbital lesions or are significantly disfiguring, lesions of the extremity that cause limb hypertrophy or loss of function, and painful lesions. 