CTNI-46. WINDOW-OF-OPPORTUNITY TRIAL OF ULIXERTINIB FOR MAPK-ACTIVATED LOWER GRADE GLIOMAS IN ADULTS

Abstract Overexpression of MAPK (Ras-Raf-MEK-ERK) signaling is well known in NF1-associated tumors. MEK inhibition has shown promising results in pediatrics NF1-associated tumors. In addition, we have observed augmented MAPK signaling and anti-tumor activity with MAPK inhibition in preclinical models of CIC-mutated vs. wild-type oligodendroglioma. Ulixertinib is a small molecule inhibitor of ERK that is being developed as a novel anti-cancer drug. A phase I study of ulixertinib in advanced solid malignancies had shown two central nervous system responses. We hypothesized that ulixertinib crosses the blood-brain barrier (BBB) and it will result in improved responses in MAPK-activated lower-grade gliomas in adults (recurrent NF1-mutated gliomas grade 1,2,3 and oligodendrogliomas grade 2,3 which are enriched in CIC-mutation). This is a window-of-opportunity study of ulixertinib in patients ≥18 yo. Twenty patients who are candidates for non-emergent surgical resection will be enrolled (10 in each cohort). Patients will receive neoadjuvant ulixertinib at 600mg BID. Selected patients will undergo CSF collection 1-week after and all will undergo surgical intervention 2-weeks after initiation of ulixertinib. Patients will then continue treatment until disease progression or unacceptable toxicity. Primary endpoints are ulixertinib tumor concentration and tumor/plasma ratio in enhancing and non-enhancing disease. Secondary endpoints include median PFS, overall response rate (ORR) and disease control rate at 12mo, duration of response, time-to-next intervention and time-to-response, safety profile, and ulixertinib CSF and tumor/CSF ratio. Exploratory endpoint includes ORR of plexiform neurofibromas in NF1 patients. To date, 4 patients have been dosed; 3 CIC-mutated oligodendroglioma and 1 NF1-mutated glioma. A fifth patient with NF1-mutated glioma has been consented. Upon collection of tumor tissue on all 5 patients, initial assessment of tumor and CSF drug concentration will be conducted and presented at the conference. Ulixertinib’s ability to cross the BBB could influence what tumor types may be explored for further patient benefit.