Abstract
Aberrant mesenchymal epithelial transition receptor (MET) activation leads to neoplasia, promotes invasive tumor growth, angiogenesis, and metastasis. Deregulation of MET signaling pathway is frequently observed in pediatric CNS tumors making MET inhibition a potential therapeutic target in this patient population. A phase 1 first-in-children trial of the MET inhibitor savolitinib was performed in children with recurrent, progressive or refractory medulloblastoma, high-grade glioma (HGG), diffuse intrinsic pontine glioma (DIPG), and other CNS tumors harboring MET aberrations. The study sought to determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of savolitinib using a Rolling-6 design given orally once daily continuously, and to describe its toxicity profile and pharmacokinetics (PK). Once the MTD was established, a PK expansion cohort was opened to enrollment. This will be followed by an efficacy expansion cohort for patients whose tumors harbor activating genomic MET aberrations. Tumor tissue and blood were collected as part of correlative studies in consenting subjects. Twenty-eight patients enrolled (median age:12 years; range: 6-21); one patient was deemed ineligible, and 22 patients were evaluable for dose finding. The MTD/RP2D was 350 mg/m2 (dose level 3). Two dose limiting toxicities were reported in 2 subjects and consisted of grade 3 fatigue and grade 3 ALT elevation. The most common grade 3/4 toxicities were: neutropenia (7.7%) and lymphopenia (7.7%). One partial response was observed in a patient with recurrent HGG on dose level 1 (150 mg/m2). As of the most recent data freeze, the patient had completed 35 treatment courses. Sustained stable disease was experienced by 3 other patients with recurrent DIPG who remained on treatment for a median of 9 cycles (range: 4-24). Correlative studies are ongoing and will be presented. Savolitinib was well-tolerated in children with recurrent CNS tumors with an MTD/RP2D of 350 mg/m2. Antitumor activity was observed.