Cabozantinib for Plexiform Neurofibromas (PN) in Subjects With NF1 in Children and Adults

This is an open label Phase II clinical trial. For both cohorts, subjects will receive cabozantinib orally in continuous cycles. Each cycle is 28 days. In absence of progressive disease or dose limiting toxicity (DLT), subjects may continue therapy for a total of 24 cycles. Subjects with radiographic response (20% or greater reduction in tumor volume) at the end of 12 cycles can continue on therapy for up to an additional year. However, for Cohort A, subjects who do not achieve 15% reduction in tumor volume after 8 cycles will be considered treatment failure and taken off study. For Cohort B, the criteria that subjects who do not achieve 15% reduction by 8 cycles are considered treatment failure and taken off study was eliminated. Subjects will be carefully monitored for toxicities associated with cabozantinib.