LBA2002 Background: LGG is the most common pediatric brain cancer, and BRAF V600 mutation has been detected in ≈17% of cases. Most patients (pts) with pLGG have disease progression and require post-surgical therapy. The standard of care is chemotherapy, such as carboplatin + vincristine (C+V), which may be less effective in BRAF V600–mutant disease; thus, alternative treatment options are needed. Dab + tram showed encouraging efficacy in a Phase I/II study (NCT02124772) in pts with previously treated BRAF V600–mutant pLGG. We describe the results of a randomized Phase II study (NCT02684058) of first-line dab + tram vs C+V in BRAF V600–mutant pLGG. Methods: Pts aged 1 to <18 y with BRAF V600 mutation–positive gliomas and Karnofsky/Lansky performance status ≥50% were enrolled. In the pLGG cohort, pts with progressive disease after surgery or nonsurgical pts requiring systemic treatment were randomized (2:1) to receive either dab twice daily (<12 y, 5.25 mg/kg/d; ≥12 y, 4.5 mg/kg/d) + tram once daily (<6 y, 0.032 mg/kg/d; ≥6 y, 0.025 mg/kg/d) or C+V (standard dosing). The primary endpoint was overall response rate (ORR; independent review, RANO criteria). Secondary endpoints included investigator-assessed ORR, clinical benefit rate (CBR), duration of response, time to response, progression-free survival (PFS), overall survival, and safety. Results: A total of 110 pts were randomized to receive dab + tram (n=73) or C+V (n=37); 4 pts in the C+V arm withdrew before treatment. Baseline characteristics were well balanced between treatment arms. At data cutoff (August 23, 2021; median follow-up, 18.9 mo), 61 pts (84%) in the dab + tram arm and 8 (22%) in the C+V arm remained on treatment; in the C+V arm, 9 completed planned treatment and 16 discontinued before completion. The primary endpoint was met: the independently assessed ORR (CR+PR) was 47% (95% CI, 35%-59%) with dab + tram vs 11% (95% CI, 3%-25%) with C+V ( P<.001; odds ratio, 7.2 [95% CI, 2.3-22.4]), and the clinical benefit rate (CR+PR+SD ≥24 wk) was 86% (95% CI, 76%-93%) vs 46% (95% CI, 30%-63%). Median PFS was 20.1 mo (95% CI, 12.8 mo-not estimable) with dab + tram vs 7.4 mo (95% CI, 3.6-11.8 mo) with C+V ( P<.001; HR, 0.31 [95% CI, 0.17-0.55]); 12-mo Kaplan-Meier PFS rates were 67% vs 26%. There were no deaths in the dab + tram arm and 1 in the C+V arm due to LGG. Pts in the dab + tram arm had fewer grade ≥3 adverse events (AEs; 47% vs 94%) and fewer discontinuations due to AEs (4% vs 18%) than pts in the C+V arm. The most frequent AEs in the dab + tram vs chemotherapy arms were pyrexia (68% vs 18%), headache (47% vs 27%), and vomiting (34% vs 48%). Conclusions: Dab + tram significantly increased ORR and CBR and prolonged PFS compared with C+V in pts with BRAF V600 mutation–positive pLGG. These encouraging results and the tolerable safety profile suggest that dab + tram may be a promising first-line systemic treatment option for this pt population. Clinical trial information: NCT02684058.

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Ubiquitin proteasome-mediated protein degradation has been implicated in posttranslational oncogenesis in medulloblastoma. Current research is evaluating the clinical implications of proteasome inhibition as a therapeutic target. In medulloblastoma cell lines, proteasome inhibitors induce apoptosis and inhibit cell proliferation via multiple pathways involving activation of caspase pathways, NFκB (nuclear factor kappalightchain-enhancer of activated B cells) pathway inhibition, reduced AKT/mTOR pathway activity, and proapoptotic protein expression. Second-generation proteasome inhibitors demonstrate blood-brain barrier penetration while maintaining antitumor effect. This review summarizes the ubiquitin-proteasome system in the pathogenesis of medulloblastoma and the potential clinical implications.

Atypical teratoid rhabdoid tumors (ATRT) are rare and aggressive embryonal tumors of central nervous system that typically affect children younger than 3 years of age. Given the generally poor outcomes of patients with ATRT and the significant toxicities associated with conventional multi-modal therapies, there is an urgent need for more novel approaches to treat ATRT, one such approach being immunotherapy. The recent rise of large-scale, multicenter interdisciplinary studies has delineated several molecular and genetic characteristics unique to ATRT. This review aims to describe currently available data on the tumor immune microenvironment of ATRT and its specific subtypes and to summarize the emerging clinical and preclinical results of immunotherapy-based approaches. It will also highlight the evolving knowledge of epigenetics on immunomodulation in this epigenetically influenced tumor, which may help guide the development of effective immunotherapeutic approaches in the future.