TRLS-08. EXPERIENCE WITH THE SELECTIVE FIBROBLAST GROWTH FACTOR INHIBITOR ERDAFITINIB IN THREE PEDIATRIC PATIENTS WITH CNS TUMORS

Activation of FGF signaling has been described for at least 3% of pediatric solid tumors including pediatric gliomas. Therapeutic actionability of FGF signaling activations, however, remains challenging. Here, we report on three patients with FGFR activation treated with erdafitinib, originally approved for the treatment of FGFR3 or FGFR2 mutated urothelial carcinoma. Our patients were treated for posterior fossa group A ependymoma (patient (Pat) 1&2) and glioma NOS °II-III (Pat3). Dose of erdafitinib at initiation of therapy was 5,2mg/kg/d; 3,8mg/kg/d and 2,8mg/kg/d for Pat1-3 respectively. Rationale for treatment with erdafitinib was increased FGFR3 expression in tumor tissue (TT) of Pat1, increased FGFR1 expression in TT of Pat2, and in Pat3 an activating FGFR1 internal tandem duplication (ITD). Both ependymoma patients received erdafitinib as a fourth line treatment and progressed rapidly under therapy. Treatment was discontinued after 2 weeks (Pat2) and 3 months (Pat1) due to progressive disease. Pat3, with the FGFR1 ITD, responded very well to therapy with a decrease in tumor size and reduced contrast-enhancement after 3&6 months. Therapy was discontinued after six months due to dystrophic nail changes. During treatment, our patients reported on diarrhea, abdominal pain, pain in the lower extremities, dysgeusia, hypersensitivity of the oral mucosa, dry skin and dystrophic nail changes. Additionally, we observed a distinct increase in longitudinal growth (Pat1&3), increased serum phosphate levels, LFPs, alpha-amylase, cholinesterase, alkaline phosphatase and LDH. Summing up, treatment with erdafitinib has high potential for a selected cohort of pediatric CNS tumor patients, as demonstrated by the treatment response of Pat3 with the FGFR1 IDT. However, further defining the exact molecular alterations that predict the individual patient’s response as well as side effects in the pediatric population are imperative to elucidate the further role of erdafitinib in treatment of pediatric CNS tumors.