IL-5 Targeted Therapies for Nervous System Tumors – Progress, Pitfalls, and Prospects

The molecular genetic understanding of nervous system tumors has expanded rapidly offering insight into potentially targetable oncogenic driver alterations. In monogenic tumor susceptibility syndromes such as tuberous sclerosis, neurofibromatosis type 1, and von Hippel Lindau syndrome targeted drugs have demonstrated efficacy and are now approved in the United States for the treatment of subependymal giant cell astrocytoma, plexiform neurofibroma, and hemangioblastoma, respectively. Some genetic alterations like BRAF V600E mutations or neurotrophic receptor tyrosine kinase (NTRK) fusions, occur across multiple cancers, including certain types of gliomas. Dabrafenib in combination with trametinib is approved for use in gliomas that harbor BRAF V600E mutations and larotrectinib is approved in gliomas that harbor certain NTRK fusions. In pediatric low-grade astrocytoma, one of the most common solid tumors of childhood, BRAF truncation-fusion events may render these tumors susceptible to tovorafenib, a type 2 RAF inhibitor, which is under study in clinical trials. Mutations in the isocitrate dehydrogenase (IDH) gene occur in the majority of low-grade and anaplastic gliomas, create specific metabolic vulnerabilities, and several IDH-mutant targeting strategies are under investigation. Glioblastoma is characterized by intratumoral molecular heterogeneity so strategies that target single genetic alterations may not be as effective as in other types of gliomas although a number of novel targeted strategies have been advanced to clinical trials. Other types of nervous system tumors such as medulloblastoma, meningioma, primary central nervous system diffuse large B-cell lymphoma, and craniopharyngioma harbor targetable genetic alterations and clinical trials are ongoing. Finally, metastatic brain tumors may harbor targetable genetic alterations that may differ from the primary site of cancer highlighting the importance of biopsy and molecular analysis of the brain metastases in order to enroll patients in clinical trials of targeted therapies.