Lymphodepletion chemotherapy followed by infusion of CD19-targeted chimeric antigen receptor–modified T (CAR-T) cells can be complicated by neurologic adverse events (AE) in patients with refractory B-cell malignancies. In 133 adults treated with CD19 CAR-T cells, we found that acute lymphoblastic leukemia, high CD19⁺ cells in bone marrow, high CAR-T cell dose, cytokine release syndrome, and preexisting neurologic comorbidities were associated with increased risk of neurologic AEs. Patients with severe neurotoxicity demonstrated evidence of endothelial activation, including disseminated intravascular coagulation, capillary leak, and increased blood–brain barrier (BBB) permeability. The permeable BBB failed to protect the cerebrospinal fluid from high concentrations of systemic cytokines, including IFNγ, which induced brain vascular pericyte stress and their secretion of endothelium-activating cytokines. Endothelial activation and multifocal vascular disruption were found in the brain of a patient with fatal neurotoxicity. Biomarkers of endothelial activation were higher before treatment in patients who subsequently developed grade ≥4 neurotoxicity. Significance: We provide a detailed clinical, radiologic, and pathologic characterization of neurotoxicity after CD19 CAR-T cells, and identify risk factors for neurotoxicity. We show endothelial dysfunction and increased BBB permeability in neurotoxicity and find that patients with evidence of endothelial activation before lymphodepletion may be at increased risk of neurotoxicity. Cancer Discov; 7(12); 1404–19. ©2017 AACR. See related commentary by Mackall and Miklos, p. 1371. This article is highlighted in the In This Issue feature, p. 1355

Objective: The purpose of this study was to determine whether gadolinium (Gd) is deposited in brain and bone tissues in patients receiving only non–Group 1 agents, either macrocyclic or linear protein interacting Gd-based contrast agents, with normal renal function. Group 1 agents are linear agents most associated with nephrogenic systemic fibrosis that the US Federal Drug Administration has defined as contraindicated in patients at risk for this disease. Materials and Methods: This study was institutional review board approved and Health Insurance Portability and Accountability Act compliant for retrospective review of records and also had signed autopsy consent authorizing use of decedent's tissue in research studies. Tissue samples were collected from 9 decedents undergoing autopsy who had contrast-enhanced magnetic resonance imaging (MRI) with only single agent exposure to a non–Group 1 Gd-based contrast agent. Decedents with only noncontrast MRI or no MRI served as controls. Multiple brain areas, including globus pallidus and dentate nucleus, as well as bone and skin, were sampled and analyzed for Gd using inductively coupled plasma mass spectrometry. Gadolinium levels were compared between groups of decedents using the Mann-Whitney test and between brain and bone tissues of the same cases using the Wilcoxon signed-rank test. Results: Of the 9 decedents, 5 received gadoteridol (ProHance; Bracco Diagnostics, Princeton, NJ), 2 received gadobutrol (Gadovist; Bayer Healthcare, Whippany, NJ), and 1 each had gadobenate (MultiHance; Bracco Diagnostics) and gadoxetate (Eovist; Bayer Healthcare). Gadolinium was found with all agents in all brain areas sampled with highest levels in globus pallidus and dentate. Bone levels measured 23 times higher (median) than brain levels (P = 0.008 for bone vs globus pallidus) and showed a significant correlation (r = 0.81, P = 0.022). In controls, Gd levels in the brain were at or below limits of measurement and were significantly lower compared with study cases (P = 0.005 for globus pallidus). Conclusion: Gadolinium deposition in normal brain and bone tissue occurs with macrocyclic and linear protein interacting agents in patients with normal renal function. Deposition of Gd in cortical bone occurs at much higher levels compared with brain tissue and shows a notable correlation between the two. Thus, the bone may serve as a surrogate to estimate brain deposition if brain Gd were to become a useful clinical or research marker.

Chimeric antigen receptor (CAR) T-cell immunotherapy has revolutionized the treatment of refractory leukemias and lymphomas, but is associated with significant toxicities, namely cytokine release syndrome (CRS) and neurotoxicity. A major barrier to developing therapeutics to prevent CAR T cell–mediated neurotoxicity is the lack of clinically relevant models. Accordingly, we developed a rhesus macaque (RM) model of neurotoxicity via adoptive transfer of autologous CD20-specific CAR T cells. Following cyclophosphamide lymphodepletion, CD20 CAR T cells expand to 272 to 4,450 cells/μL after 7 to 8 days and elicit CRS and neurotoxicity. Toxicities are associated with elevated serum IL6, IL8, IL1RA, MIG, and I-TAC levels, and disproportionately high cerebrospinal fluid (CSF) IL6, IL2, GM-CSF, and VEGF levels. During neurotoxicity, both CD20 CAR and non-CAR T cells accumulate in the CSF and in the brain parenchyma. This RM model demonstrates that CAR T cell–mediated neurotoxicity is associated with proinflammatory CSF cytokines and a pan–T cell encephalitis. Significance: We provide the first immunologically relevant, nonhuman primate model of B cell–directed CAR T-cell therapy–mediated CRS and neurotoxicity. We demonstrate CAR and non-CAR T-cell infiltration in the CSF and in the brain during neurotoxicity resulting in pan-encephalitis, accompanied by increased levels of proinflammatory cytokines in the CSF. Cancer Discov; 8(6); 750–63. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 663

Phosphorylation of tau protein is a critical event in the pathogenesis of Alzheimer's disease (AD). Increased phosphorylated tau and total tau levels, combined with reduced concentrations of amyloid-β 1–42 (Aβ42 ) in cerebrospinal fluid (CSF), but no

BACKGROUND. Temozolomide (TMZ) is one of the most potent chemotherapy agents for the treatment of glioblastoma. Unfortunately, almost half of glioblastoma tumors are TMZ resistant due to overexpression of methylguanine methyltransferase (MGMT^hi). Coadministration of O⁶-benzylguanine (O⁶BG) can restore TMZ sensitivity, but causes off-target myelosuppression. Here, we conducted a prospective clinical trial to test whether gene therapy to confer O⁶BG resistance in hematopoietic stem cells (HSCs) improves chemotherapy tolerance and outcome. METHODS. We enrolled 7 newly diagnosed glioblastoma patients with MGMT^hi tumors. Patients received autologous gene-modified HSCs following single-agent carmustine administration. After hematopoietic recovery, patients underwent O⁶BG/TMZ chemotherapy in 28-day cycles. Serial blood samples and tumor images were collected throughout the study. Chemotherapy tolerance was determined by the observed myelosuppression and recovery following each cycle. Patient-specific biomathematical modeling of tumor growth was performed. Progression-free survival (PFS) and overall survival (OS) were also evaluated. RESULTS. Gene therapy permitted a significant increase in the mean number of tolerated O⁶BG/TMZ cycles (4.4 cycles per patient, P < 0.05) compared with historical controls without gene therapy (n = 7 patients, 1.7 cycles per patient). One patient tolerated an unprecedented 9 cycles and demonstrated long-term PFS without additional therapy. Overall, we observed a median PFS of 9 (range 3.5–57⁺) months and OS of 20 (range 13–57⁺) months. Furthermore, biomathematical modeling revealed markedly delayed tumor growth at lower cumulative TMZ doses in study patients compared with patients that received standard TMZ regimens without O⁶BG. CONCLUSION. These data support further development of chemoprotective gene therapy in combination with O⁶BG and TMZ for the treatment of glioblastoma and potentially other tumors with overexpression of MGMT. TRIAL REGISTRATION. Clinicaltrials.gov NCT00669669. FUNDING. R01CA114218, R01AI080326, R01HL098489, P30DK056465, K01DK076973, R01HL074162, R01CA164371, R01NS060752, U54CA143970.