NFS-11. PHASE II STUDY OF AXITINIB IN PATIENTS WITH NEUROFIBROMATOSIS TYPE 2-RELATED SCHWANNOMATOSIS AND PROGRESSIVE VESTIBULAR SCHWANNOMAS

Abstract

Abstract BACKGROUND Axitinib is an oral multi-receptor tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR), platelet derived growth factor receptor (PDGFR), and c-KIT. These represent a clinically and/or preclinically validated molecular targets in vestibular schwannoma (VS). METHODS Eligible participants were age >5 years with a clinical diagnosis of neurofibromatosis type 2-related schwannomatosis (NF2-SWN) and at least one volumetrically measurable, progressive VS. Axitinib was given continuously in 28-day cycles for up to of 12 cycles. Primary endpoint was objective volumetric response rate to axitinib, hearing response was a secondary endpoint, along with validated quality of life assessments (NFTI-QOL). RESULTS Twelve participants were enrolled and eight completed 12 cycles, including two pediatric patients. Two patients were non-evaluable due to coming off study prior to the first scheduled response evaluation: one withdrew from the study for personal reasons and one for non-compliance. Due to slowing accrual, the study closed prior to meeting planned enrollment of 17 evaluable patients. Ten patients were evaluable for the primary endpoint, defined as ≥20% decrease in VS volume, with two volumetric responses observed; both were reached after three cycles and sustained during treatment. Best volumetric response was −53.9% after nine cycles. Hearing response was evaluable in nine participants, with three hearing responses observed, one of which was sustained during treatment. All participants experienced drug-related toxicities, the most common were diarrhea, hematuria and skin toxicity, not exceeding grade 2, as well as hypertension, not exceeding grade 3. NFTI-QOL scores remained stable or improved during treatment in all participants. CONCLUSIONS Axitinib therapy targeting VEGFR, PDGFR and c-KIT is feasible in this population and associated with volumetric and hearing responses in a subset of patients. The convenience of oral administration appears to be offset, however, by increased toxicity and lower response rates compared to VEGF-A targeted therapy with bevacizumab.