Neurofibromatosis type 1 (NF1) is an autosomal dominant tumor predisposition syndrome that affects children and adults. Individuals with NF1 are at high risk for central nervous system neoplasms including gliomas. The purpose of this review is to discuss the spectrum of intracranial gliomas arising in individuals with NF1 with a focus on recent preclinical and clinical data. In this review, possible mechanisms of gliomagenesis are discussed, including the contribution of different signaling pathways and tumor microenvironment. Furthermore, we discuss the recent notable advances in the developing therapeutic landscape for NF1-associated gliomas including clinical trials and collaborative efforts.

1044 Background: Tucatinib is a potent and highly selective HER2-targeted tyrosine kinase inhibitor approved for use in combination with trastuzumab and capecitabine for patients with metastatic HER2+ breast cancer (MBC) who have received ≥1 prior HER2-based regimen in the metastatic setting, including patients with brain metastases (BM). TBCRC049 (NCT03501979) is an investigator-initiated phase 2 single-arm study currently enrolling to evaluate the safety and efficacy of tucatinib, trastuzumab and capecitabine in HER2+ BC with newly diagnosed LM. Here, we report the pre-specified pharmacokinetic (PK) analysis for the first 15 patients to determine bioavailability of tucatinib and its predominant metabolite, ONT-993, in the CSF. Methods: Eligible patients included adults with HER2+ MBC, KPS > 50, and newly diagnosed, untreated LM (defined as positive CSF cytology and/or radiographic evidence of LM, plus clinical signs/symptoms). Patients with treated or concurrent/new BM were allowed. The primary endpoint is overall survival with an accrual goal of 30 pts. Parallel PK samples were collected in plasma and CSF via Ommaya reservoir on day 1 of cycles 1 and 2 at 0h (baseline), 2-3h, 5-7h and 24h (optional) following initiation of tucatinib 300 mg BID. Tucatinib and ONT-993 were quantified in plasma (n=15) and CSF (n=13) using validated liquid chromatography-mass spectrometry methods. Results: Tucatinib and ONT-993 plasma concentrations were consistent with previous studies and exhibited high interindividual variability. Tucatinib and ONT-993 were detectable in the CSF within 2 hours post tucatinib administration; concentrations ranged from 0.57 to 25 ng/mL for tucatinib (IC50 for tucatinib against HER2 is 3.3 ng/mL) and 0.28 to 4.7 ng/mL for ONT-993. Tucatinib concentrations in the CSF per timepoint were in a similar range to unbound plasma (plasmaub) tucatinib. CSF to plasmaub ratios were generally consistent over time; the steady-state (cycle 2) median tucatinib CSF to plasmaub ratio was 0.83 (0.19 to 2.1). ONT-993 CSF to plasmaub ratios were similar to tucatinib CSF to plasmaub ratios. Conclusions: In patients with LM from HER2+MBC who were treated with tucatinib, trastuzumab, and capecitabine, tucatinib and ONT-993 were detectable in the CSF of all patients at median levels similar to plasmaub tucatinib. This is the first documented evidence of tucatinib distributing into the CSF in patients with HER2+MBC. Efficacy and safety of tucatinib, trastuzumab, and capecitabine in patients with HER2+ LM will be reported upon completion of TBCRC 049 accrual. Clinical trial information: NCT03501979 .

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Intraventricular melanoma is a very rare and highly malignant disease. Safe resection is the mainstay of treatment, but no standard guidelines exist for adjuvant therapy. Early histologic and molecular diagnosis is key for improved survival.

This study explores the repeated use of glucarpidase following HD-MTX in patients with CNSL. HD-MTX requires aggressive hydration and inpatient monitoring to prevent toxicity. Glucarpidase 50 units(u)/kg for delayed MTX clearance results in a reduction of systemic MTX levels without crossing the blood brain barrier. This study explores the use of 1000 or 2000 units of glucarpidase following repeated cycles of MTX 3–8 g/m2. Eligible adult patients had isolated CNSL, CrCl ≥ 60 mL/min, and KPS ≥ 50. Rituximab with MTX was administered for eight cycles. Glucarpidase was given 24 hours after each MTX infusion. MTX concentrations were monitored in serum and cerebrospinal fluid (CSF). Twelve patients enrolled to date and data are available for 50 doses of MTX (3 g/m2 (20), 6 g/m2 (21), 8 g/m2 (9)). Glucarpidase 1000u (14) or 2000u (36) resulted in at least a 95% reduction in serum MTX levels within 15 minutes following 49/50 doses. A 93% decrease was seen with the remaining dose. Glucarpidase was not detected in the CSF of 7 patients analyzed. Potentially cytotoxic MTX concentrations (10–6 M) were observed in CSF 1 hour (7/7) and 6 hours (4/7) after glucarpidase administration. Radiographic responses are evaluable in 9 patients: complete response (5), partial response (2), stable disease (1), and progressive disease (1). No grade 3 events were attributed to glucarpidase; one grade 4 event of anaphylaxis occurred. Anti-glucarpidase antibodies were detected in 2/5 patients analyzed. In summary, administration of low-dose glucarpidase 24 hours after MTX 3–8 g/m2 results in a reproducible rapid reduction in serum MTX levels in non-renally impaired patients. CSF MTX levels remain therapeutic and clinical response expected from MTX-based therapy does not appear compromised. Anti-glucarpidase antibodies may develop though significance remains unclear. Study is ongoing. Future directions will explore glucarpidase use for reduction of inpatient stay with HD-MTX.

Leptomeningeal metastasis is extremely rare in patients with ovarian cancer, but should be considered in patients presenting with neurologic deficits such as cauda equine syndrome. Given its poor prognosis and lack of data currently on management, additional studies are needed to optimize treatment regimens and improve outcomes.

2057 Background: Temozolomide (TMZ) transiently upregulates NKG2D ligands targeted by innate immune effector cells. Lymphodepletion impairs this immune response, however, genetic modification of ex vivo expanded γδ T cells with an MGMT-expressing lentivector confers resistance to TMZ, allowing concurrent chemotherapy and γδ T cell infusion, thereby targeting the tumor when NKG2DL are maximally expressed. This Drug Resistant Immunotherapy (DRI) is currently being evaluated in a Phase 1 first in human study (NCT04165941) and interim safety and biologic correlative analysis are detailed here for the first dosing cohort. Methods: Adults with newly diagnosed, untreated glioblastoma (GBM), adequate organ function, and a KPS≥70% will be enrolled. Subjects undergo subtotal resection and placement of a Rickham reservoir followed 3-4 weeks by apheresis from which γδ T cells are expanded, transduced with an MGMT-expressing lentivector, harvested, and cryopreserved. Standard of care induction TMZ/radiation therapy is initiated followed by 6 cycles of maintenance TMZ. Intravenous TMZ (150mg/m2) and intracranial dosing of 1 x 107 γδ T cells occur on day 1 of each maintenance cycle. Daily oral TMZ 150mg/m2 follows for Days 2-5. Dose level 1 (DL1) subjects receive 1 fixed dose of γδ T cells and DL2 receive 3 doses administered on Day 1 of each of first 3 cycles of TMZ dependent on absence of dose limiting toxicity. Primary endpoint is safety; secondary endpoints include progression free and overall survival. Immunologic and genomic correlative analyses are being conducted at specific time points from peripheral blood and cerebral spinal fluid collected from the Rickham. Results: Six subjects (4 females, 2 males) have been enrolled in DL1. All subjects were IDH1-WT with 5 subjects MGMT unmethylated and 1 methylated. Of these, 1 generated inadequate gd T cells and 2 withdrew consent prior to DRI treatment. For the 3 that received DRI, treatment-related adverse events with maximum CTCAE Grade 3 occurred in 1 subject; UTI, dehydration, and thrombocytopenia. The most common Grade 1/2 events included: fever, leukopenia, nausea, and vomiting which were attributable to TMZ or radiotherapy. Circulating T cells remained below normal range throughout maintenance phase in 2/3 subjects. NK and gd T cell numbers remained within low normal range for 3/3 and 2/3 subjects, respectively. Serum Th1 (IFNg, IL-2, TNFa) and Th2 (IL4, IL5, IL-10) cytokines were within clinical range although TNFa remained elevated from the gdT cell infusion through day +30 in 2 subjects. Conclusions: Administration of MGMT-gene modified gdT cells and TMZ as DRI is feasible in lymphodepleted subjects during TMZ maintenance phase and sufficiently safe to warrant further investigation at additional doses. Clinical trial information: NCT04165941.

Brain metastases are a significant source of morbidity and mortality in patients with non-small cell lung cancer. Historically, surgery and radiation therapy have been essential to maintaining disease control within the central nervous system due to poorly penetrant conventional chemotherapy. With the advent of targeted therapy against actionable driver mutations, there is potential to control limited and asymptomatic intracranial disease and delay local therapy until progression. In this review paper, intracranial response rates and clinical outcomes to biological and immune therapies are summarized from the literature and appraised to assist clinical decision making and identify areas for further research. Future clinical trials ought to prioritize patient-centered quality of life and neurocognitive measures as major outcomes and specifically stratify patients based on mutational marker status, disease burden, and symptom acuity.