Utility of Routine Preoperative Urinalysis in the Prevention of Surgical Site Infections

OBJECTIVE

Preoperative assessment is important for neurosurgical risk stratification, but the level of evidence for individual screening tests is low. In preoperative urinalysis (UA), testing may significantly increase costs and lead to inappropriate antibiotic treatment. We prospectively evaluated whether eliminating preoperative UA was noninferior to routine preoperative UA as measured by 30-day readmission for surgical site infection in adult elective neurosurgical procedures.

METHODS

A single-institution prospective, pragmatic study of patients receiving elective neurosurgical procedures from 2018 to 2020 was conducted. Patients were allocated based on same-day versus preoperative admission status. Rates of preoperative UA and subsequent wound infection were measured along with detailed demographic, surgical, and laboratory data.

RESULTS

The study included 879 patients. The most common types of surgery were cranial (54.7%), spine (17.4%), and stereotactic/functional (19.5%). No preoperative UA was performed in 315 patients, while 564 underwent UA. Of tested patients, 103 (18.3%) met criteria for suspected urinary tract infection, and 69 (12.2%) received subsequent antibiotic treatment. There were 14 patients readmitted within 30 days (7 without UA [2.2%] vs. 7 with UA [1.2%]) for subsequent wound infection with a risk difference of 0.98% (95% confidence interval -0.89% to 2.85%). The upper limit of the confidence interval exceeded the preselected noninferiority margin of 1%.

CONCLUSIONS

In this prospective study of preoperative UA for elective neurosurgical procedures using a pragmatic, real-world design, risk of readmission due to surgical site infection was very low across the study cohort, suggesting a limited role of preoperative UA for elective neurosurgical procedures.

CD8+ T cells maintain killing of MHC-I-negative tumor cells through the NKG2D-NKG2DL axis

The accepted paradigm for both cellular and anti-tumor immunity relies upon tumor cell killing by CD8+ T cells recognizing cognate antigens presented in the context of target cell major histocompatibility complex (MHC) class I (MHC-I) molecules. Likewise, a classically described mechanism of tumor immune escape is tumor MHC-I downregulation. Here, we report that CD8+ T cells maintain the capacity to kill tumor cells that are entirely devoid of MHC-I expression. This capacity proves to be dependent instead on interactions between T cell natural killer group 2D (NKG2D) and tumor NKG2D ligands (NKG2DLs), the latter of which are highly expressed on MHC-loss variants. Necessarily, tumor cell killing in these instances is antigen independent, although prior T cell antigen-specific activation is required and can be furnished by myeloid cells or even neighboring MHC-replete tumor cells. In this manner, adaptive priming can beget innate killing. These mechanisms are active in vivo in mice as well as in vitro in human tumor systems and are obviated by NKG2D knockout or blockade. These studies challenge the long-advanced notion that downregulation of MHC-I is a viable means of tumor immune escape and instead identify the NKG2D-NKG2DL axis as a therapeutic target for enhancing T cell-dependent anti-tumor immunity against MHC-loss variants.

Targeting the IL4 receptor with MDNA55 in patients with recurrent glioblastoma: Results of a phase IIb trial

BACKGROUND

MDNA55 is an interleukin 4 receptor (IL4R)-targeting toxin in development for recurrent GBM, a universally fatal disease. IL4R is overexpressed in GBM as well as cells of the tumor microenvironment. High expression of IL4R is associated with poor clinical outcomes.

METHODS

MDNA55-05 is an open-label, single-arm phase IIb study of MDNA55 in recurrent GBM (rGBM) patients with an aggressive form of GBM (de novo GBM, IDH wild-type, and nonresectable at recurrence) on their 1st or 2nd recurrence. MDNA55 was administered intratumorally as a single dose treatment (dose range of 18 to 240 ug) using convection-enhanced delivery (CED) with up to 4 stereo-tactically placed catheters. It was co-infused with a contrast agent (Gd-DTPA, Magnevist®) to assess distribution in and around the tumor margins. The flow rate of each catheter did not exceed 10μL/min to ensure that the infusion duration did not exceed 48 h. The primary endpoint was mOS, with secondary endpoints determining the effects of IL4R status on mOS and PFS.

RESULTS

MDNA55 showed an acceptable safety profile at doses up to 240 μg. In all evaluable patients (n = 44) mOS was 11.64 months (80% one-sided CI 8.62, 15.02) and OS-12 was 46%. A subgroup (n = 32) consisting of IL4R High and IL4R Low patients treated with high-dose MDNA55 (>180 ug) showed the best benefit with mOS of 15 months, OS-12 of 55%. Based on mRANO criteria, tumor control was observed in 81% (26/32), including those patients who exhibited pseudo-progression (15/26).

CONCLUSIONS

MDNA55 demonstrated tumor control and promising survival and may benefit rGBM patients when treated at high-dose irrespective of IL4R expression level.Trial Registration: Clinicaltrials.gov NCT02858895.

Abstract 4061: Systemic autologous lymphocyte transfer can enhance tumor-infiltrating lymphocyte infiltration in glioblastoma and license co-stimulatory immunotherapy

Glioblastoma is an immunologically ‘cold’ malignancy where few tumor infiltrating lymphocytes (TILs) are present. We sought to overcome this by ‘seeding’ the tumor with TILs via administration of autologous lymphocytes (ALT). We hypothesized that prior administration of ALT will enhance subsequent immunomodulatory therapies (e.g. immune checkpoint blockade (ICB) or co-stimulation). To evaluate this, we initially generated a pro-infiltrative TIL phenotype. CD45.1 splenocytes (C57/Bl6 background) were co-cultured with either IL2 and Concanavalin A (Con A) or IL7 and Con A for 5 days. Flow cytometric analysis found that both conditions resulted in similar CD4:CD8 ratios (20:80%) but IL7 co-culture upregulated expression of VLA-4, a pro migratory integrin. We then compared the entry of TILs into tumor bearing CNS when co-cultured with either IL2 or IL7. 8–10-week-old C57/Bl6 mice (n=5-6 per group) were implanted orthotopically with 30,000 CT2AvIII cells (syngeneic glioma) which established for 14 days. Mice received (1) CD45.1 lymphocytes activated with IL-7 and Con A (single intravenous (IV) injection, 1 × 107 cells) or (2) CD45.1 lymphocytes activated with IL2 and serial Con-A stimulation. Mice were sacrificed 3- and 48-hours following ALT and brains analysed for CD45.1+CD3+ populations. Groups were compared using a Mann-Whitney U test. Mice in Group 1 demonstrated significantly enhanced entry of CD8+ effector and memory T cells into tumor bearing hemispheres at both time points following administration compared to Group 2 (p = 0.005, p = 0.0159 respectively). By 48 hours post ALT, IL7 co-culture resulted in an average 810.1% expansion of CD8 T cell numbers in tumor bearing CNS compared to counts at Day 0. We then evaluated if mice with a TIL enriched CNS might be more responsive to ICB or co-stimulatory therapy. 8–10-week-old C57/Bl6 mice (n=5-7 per group) were implanted with 30,000 CT2AvIII cells that established over 10 days. On day 10, mice received IV ALT of either IL7 T cells only, or IL-7 and treatment courses of IP ICB (anti-PD1, anti-CTLA 4 or anti-41BB). Mice given ICB following IL7 ALT demonstrated a median survival (aPD1: 27 days, aCTLA-4: 25 days) similar to mice given IL7 ALT alone (25 days). However, 4/7 mice who received IL7 ALT and anti-41BB were still alive 45 days post tumor implantation (p=0.0004). Taken together, we demonstrated that certain ex vivo autologous lymphocyte co-culture conditions can generate a T cell population which infiltrates tumor bearing CNS in significant numbers. Further, we found that seeding a tumor with TILs prior to stimulatory therapy yields long term survival in vivo. Future work will focus on optimizing ex vivo culturing approaches for ALT and determine whether therapeutic efficacy is due to expansion of resident TILs at the tumor site, or ongoing recruitment of endogenous T cells from the periphery.

Citation Format: Kirit Singh, Kelly M. Hotchkiss, Eliese Moelker, Gary E. Archer, John H. Sampson, Mustafa Khasraw. Systemic autologous lymphocyte transfer can enhance tumor-infiltrating lymphocyte infiltration in glioblastoma and license co-stimulatory immunotherapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4061.

IL7 and IL7 Flt3L co-expressing CAR T cells improve therapeutic efficacy in mouse EGFRvIII heterogeneous glioblastoma

Chimeric antigen receptor (CAR) T cell therapy in glioblastoma faces many challenges including insufficient CAR T cell abundance and antigen-negative tumor cells evading targeting. Unfortunately, preclinical studies evaluating CAR T cells in glioblastoma focus on tumor models that express a single antigen, use immunocompromised animals, and/or pre-treat with lymphodepleting agents. While lymphodepletion enhances CAR T cell efficacy, it diminishes the endogenous immune system that has the potential for tumor eradication. Here, we engineered CAR T cells to express IL7 and/or Flt3L in 50% EGFRvIII-positive and -negative orthotopic tumors pre-conditioned with non-lymphodepleting irradiation. IL7 and IL7 Flt3L CAR T cells increased intratumoral CAR T cell abundance seven days after treatment. IL7 co-expression with Flt3L modestly increased conventional dendritic cells as well as the CD103+XCR1+ population known to have migratory and antigen cross-presenting capabilities. Treatment with IL7 or IL7 Flt3L CAR T cells improved overall survival to 67% and 50%, respectively, compared to 9% survival with conventional or Flt3L CAR T cells. We concluded that CAR T cells modified to express IL7 enhanced CAR T cell abundance and improved overall survival in EGFRvIII heterogeneous tumors pre-conditioned with non-lymphodepleting irradiation. Potentially IL7 or IL7 Flt3L CAR T cells can provide new opportunities to combine CAR T cells with other immunotherapies for the treatment of glioblastoma.

Outcomes in Patients with Intact and Resected Brain Metastasis Treated with 5-Fraction Stereotactic Radiosurgery

Purpose

Hypofractionated stereotactic radiosurgery (HF-SRS) with or without surgical resection is potentially a preferred treatment for larger or symptomatic brain metastases (BMs). Herein, we report clinical outcomes and predictive factors following HF-SRS.

Methods and Materials

Patients undergoing HF-SRS for intact (iHF-SRS) or resected (rHF-SRS) BMs from 2008 to 2018 were retrospectively identified. Linear accelerator-based image-guided HF-SRS consisted of 5 fractions at 5, 5.5, or 6 Gy per fraction. Time to local progression (LP), time to distant brain progression (DBP), and overall survival (OS) were calculated. Cox models assessed effect of clinical factors on OS. Fine and Gray's cumulative incidence model for competing events examined effect of factors on LP and DBP. The occurrence of leptomeningeal disease (LMD) was determined. Logistic regression examined predictors of LMD.

Results

Among 445 patients, median age was 63.5 years; 87% had Karnofsky performance status ≥70. Fifty-three % of patients underwent surgical resection, and 75% received 5 Gy per fraction. Patients with resected BMs had higher Karnofsky performance status (90-100, 41 vs 30%), less extracranial disease (absent, 25 vs 13%), and fewer BMs (multiple, 32 vs 67%). Median diameter of the dominant BM was 3.0 cm (interquartile range, 1.8-3.6 cm) for intact BMs and 4.6 cm (interquartile range, 3.9-5.5 cm) for resected BMs. Median OS was 5.1 months (95% confidence interval [CI], 4.3-6.0) following iHF-SRS and 12.8 months (95% CI, 10.8-16.2) following rHF-SRS (P < .01). Cumulative LP incidence was 14.5% at 18 months (95% CI, 11.4-18.0%), significantly associated with greater total GTV (hazard ratio, 1.12; 95% CI, 1.05-1.20) following iFR-SRS, and with recurrent versus newly diagnosed BMs across all patients (hazard ratio, 2.28; 95% CI, 1.01-5.15). Cumulative DBP incidence was significantly greater following rHF-SRS than iHF-SRS (P = .01), with respective 24-month rates of 50.0 (95% CI, 43.3-56.3) and 35.7% (95% CI, 29.2-42.2). LMD (57 events total; 33% nodular, 67% diffuse) was observed in 17.1% of rHF-SRS and 8.1% of iHF-SRS cases (odds ratio, 2.46; 95% CI, 1.34-4.53). Any radionecrosis and grade 2+ radionecrosis events were observed in 14 and 8% of cases, respectively.

Conclusions

HF-SRS demonstrated favorable rates of LC and radionecrosis in postoperative and intact settings. Corresponding LMD and RN rates were comparable to those of other studies.

Early Vasopressor Utilization Strategies and Outcomes in Critically Ill Patients With Severe Traumatic Brain Injury

BACKGROUND

Early hypotension after severe traumatic brain injury (sTBI) is associated with increased mortality and poor long-term outcomes. Current guidelines suggest the use of intravenous vasopressors, commonly norepinephrine and phenylephrine, to support blood pressure after TBI. However, guidelines do not specify vasopressor type, resulting in variation in clinical practice. We describe early vasopressor utilization patterns in critically ill patients with TBI and examine the association between utilization of norepinephrine, compared to phenylephrine, with hospital mortality after sTBI.

METHODS

We conducted a retrospective cohort study of US hospitals participating in the Premier Healthcare Database between 2009 and 2018. We examined adult patients (>17 years of age) with a primary diagnosis of sTBI who were treated in an intensive care unit (ICU) after injury. The primary exposure was vasopressor choice (phenylephrine versus norepinephrine) within the first 2 days of hospital admission. The primary outcome was in-hospital mortality. Secondary outcomes examined included hospital length of stay (LOS) and ICU LOS. We conducted a post hoc subgroup analysis in all patients with intracranial pressure (ICP) monitor placement. Regression analysis was used to assess differences in outcomes between patients exposed to phenylephrine versus norepinephrine, with propensity matching to address selection bias due to the nonrandom allocation of treatment groups.

RESULTS

From 2009 to 2018, 24,718 (37.1%) of 66,610 sTBI patients received vasopressors within the first 2 days of hospitalization. Among these patients, 60.6% (n = 14,991) received only phenylephrine, 10.8% (n = 2668) received only norepinephrine, 3.5% (n = 877) received other vasopressors, and 25.0% (n = 6182) received multiple vasopressors. In that time period, the use of all vasopressors after sTBI increased. A moderate degree of variation in vasopressor choice was explained at the individual hospital level (23.1%). In propensity-matched analysis, the use of norepinephrine compared to phenylephrine was associated with an increased risk of in-hospital mortality (OR, 1.65; CI, 1.46-1.86; P < .0001).

CONCLUSIONS

Early vasopressor utilization among critically ill patients with sTBI is common, increasing over the last decade, and varies across hospitals caring for TBI patients. Compared to phenylephrine, norepinephrine was associated with increased risk of in-hospital mortality in propensity-matched analysis. Given the wide variation in vasopressor utilization and possible differences in efficacy, our analysis suggests the need for randomized controlled trials to better inform vasopressor choice for patients with sTBI.

Multiepitope supramolecular peptide nanofibers eliciting coordinated humoral and cellular antitumor immune responses

Subunit vaccines inducing antibodies against tumor-specific antigens have yet to be clinically successful. Here, we use a supramolecular α-helical peptide nanofiber approach to design epitope-specific vaccines raising simultaneous B cell, CD8⁺ T cell, and CD4⁺ T cell responses against combinations of selected epitopes and show that the concurrent induction of these responses generates strong antitumor effects in mice, with significant improvements over antibody or CD8⁺ T cell-based vaccines alone, in both prophylactic and therapeutic subcutaneous melanoma models. Nanofiber vaccine-induced antibodies mediated in vitro tumoricidal antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). The addition of immune checkpoint and phagocytosis checkpoint blockade antibodies further improved the therapeutic effect of the nanofiber vaccines against murine melanoma. These findings highlight the potential clinical benefit of vaccine-induced antibody responses for tumor treatments, provided that they are accompanied by simultaneous CD8⁺ and CD4⁺ responses, and they illustrate a multiepitope cancer vaccine design approach using supramolecular nanomaterials.

A phase 0/surgical window-of-opportunity study in progress, evaluating evolocumab in patients with high-grade glioma or glioblastoma

TPS2076

Background: High-grade gliomas (HGGs) are immunologically ‘cold’ tumors. This phenomenon is partly due to reduced expression of major histocompatibility class (MHC) I on the surface of tumor cells, which prevents CD8+ cytotoxic T lymphocyte activity (CTLs). Blockade of proprotein convertase subtilisin/kexin type 9 (PCSK9) increases MHC class I expression, enhances CTL tumoral infiltration, and potentiates checkpoint inhibition in vivo. Evolocumab is an FDA-approved fully human IgG2 monoclonal antibody PCSK9 inhibitor which is clinically indicated for hyperlipidemia. This study seeks to determine whether evolocumab can cross the blood-brain barrier (BBB) and enhance MHC I expression on resected tumor cells, serving as a potential future adjunct for immunotherapy. Methods: This study will enroll ten patients over 18 years who have newly diagnosed or recurrent HGG. These patients will also need to be undergoing resection of their tumor as part of their planned treatment pathway. Following informed consent, patients will receive evolocumab (420mg, subcutaneously) 7-14 days before surgical debulking of the tumor. We will collect tissue which is not required for histological tumor analysis and compare it with a contemporaneous matched control cohort. This will consist of resected tumor specimens from patients not treated with evolocumab. Quantification of the drug will be performed using mass spectroscopy, flow cytometry, and single-cell sequencing. The primary objective of this study is to evaluate whether evolocumab can cross the BBB and be measured in resected tumor specimens taken from patients with HGG. Secondary objectives include an analysis of lipid metabolism and MHC-I expression on the tumor via flow cytometry and CITEseq. Wilcoxon rank-sum test or a two-sample t-test, will compare groups for these endpoints. Exploratory analyses will determine if evolocumab leads to changes in tumorigenic pathways and the immune profile of tumor infiltrating lymphocytes (TILs). Bioinformatic analyses will be performed using protein set enrichment, gene ontology (GO) annotations, and search tools from the retrieval of interactive genes/proteins (STRING). Progress: The study was activated on 10/04/2021 (NCT04937413) and at the time of submission has enrolled 5 participants (4 to control arm, 1 to intervention arm). Clinical trial information: NCT04937413.

Reproducibility of outcomes in sequential trials using CMV-targeted dendritic cell vaccination for glioblastoma

2005

Background: Vaccination with dendritic cells (DCs) fares poorly in primary and recurrent glioblastoma (GBM). Moreover, GBM vaccine trials are often underpowered due to limited sample size. Methods: To address these limitations, we conducted three sequential clinical trials utilizing Cytomegalovirus (CMV)-specific DC vaccines in patients with newly diagnosed GBM eligible to receive standard of care resection and adjuvant radiation therapy and temozolomide chemotherapy. Autologous DCs were generated and electroporated with mRNA encoding for the CMV protein pp65. Serial vaccination was given throughout adjuvant temozolomide cycles, and 111Indium radiolabeling was implemented to assess migration efficiency of DC vaccines. Patients were followed for median overall survival (mOS) and OS. Results: Our initial study was the phase II ATTAC study (NCT00639639; total n = 12) with 6 patients randomized to vaccine site preconditioning with tetanus-diphtheria (Td) toxoid. This led to an expanded cohort trial (ATTAC-GM; NCT00639639) of 11 patients receiving CMV DC vaccines containing granulocyte-macrophage colony-stimulating factor (GM-CSF). Follow-up data from ATTAC and ATTAC-GM revealed 5-year OS rates of 33.3% (mOS 38.3 months; CI95 17.5-undefined) and 36.4% (mOS 37.7 months; CI95 18.2-109.1), respectively. ATTAC additionally revealed a significant increase in DC migration to draining lymph nodes following Td preconditioning ( P = 0.049). Increased DC migration was associated with OS (Cox proportional hazards model, HR = 0.820, P = 0.023). Td-mediated increased migration has been recapitulated in our larger confirmatory trial ELEVATE (NCT02366728) of 43 patients randomized to preconditioning (Wilcoxon rank sum, Td n = 24, unpulsed DC n = 19; 24h, P = 0.031 and 48h, P = 0.0195). In ELEVATE, median follow-up of 42.2 months revealed significantly longer OS in patients randomized to Td ( P = 0.026). The 3-year OS for Td-treated patients in ELEVATE was 34% (CI95 19-63%) compared to 6% given unpulsed DCs (CI95 1-42%). Conclusions: We report reproducibility of our findings across three sequential clinical trials using CMV pp65 DCs. Despite their small numbers, these successive trials demonstrate consistent survival outcomes, thus supporting the efficacy of CMV DC vaccine therapy in GBM. Clinical trial information: NCT00639639, NCT02366728.

A phase 1 trial of D2C7-it in combination with an Fc-engineered anti-CD40 monoclonal antibody (2141-V11) administered intratumorally via convection-enhanced delivery for adult patients with recurrent malignant glioma (MG)

e14015

Background: D2C7 immunotoxin (D2C7-IT) is a dual-specific recombinant immunotoxin comprising an EGFR wild-type and mutant-specific (EGFRvIII) monoclonal antibody (Ab) fragment and a genetically engineered form of the Pseudomonas exotoxin. When injected directly into the tumor by convection enhanced delivery (CED), immunotoxins induce both direct tumor killing and secondary immune responses by activation of CD4+ and CD8+ T-cells. Tumor-associated macrophages (TAMs) are the most prominent glioma-infiltrating immune cells and constitute up to 40% of the tumor mass. Upon binding of D2C7-IT to EGFR and cellular internalization, the Pseudomonas exotoxin moiety of the D2C7-IT kills residual GBM cells, upregulates proinflammatory CD40, and induces pattern recognition receptor pathway transcriptome expression. This potentially creates a proinflammatory glioma microenvironment where TAM activation may be further stimulated by sequential CED of 2141-V11, an Fc engineered anti-human CD40 agonist antibody developed at Rockefeller University. We are conducting a first in human trial of the combination of D2C7-IT + 2141-V11 administered via CED in recurrent MG patients. Methods: Eligibility includes adult patients with recurrence of a solitary supratentorial WHO grade 3 or 4 MG; ≥ 4 weeks after chemotherapy, bevacizumab or study drug; adequate organ function; and KPS ≥ 70%. Cohorts of 3 patients are treated with increasing levels of 2141-V11 to determine the maximum tolerated dose (MTD) of the compound administered intratumorally in conjunction with D2C7-IT. Dose escalation and de-escalation are managed using a modified Bayesian optimal interval (BOIN) design to identify the MTD. Intratumoral administration of D2C7-IT via CED (4612 ng/mL over 72 hours) is followed by a 7-hour infusion of 2141-V11, both infused at 0.5 mL/hr. 2141-V11 is dose-escalated to determine the MTD when combined with D2C7-IT. Four dose levels (DL) are planned: #1: 0.70 mg; #2: 2.0 mg; #3: 7.0 mg; #4: 21.0 mg. Results: As of February 7, 2022, three patients were treated at DL1 and DL2, and two patients at DL3. No DLTs have been observed, and all eight patients remain alive and in observation on study after 7.0, 6.5, 6.0, 4.4, 2.8, 2.4, 0.9 and 0.5 months. Early signs of tumor response have been observed, with one patient at DL1 and 2 patients at DL2 without radiographic evidence of active tumor. Grade 2 or higher AEs due to D2C7-IT and/or 2141-V11 include: headache (grade 3, n = 1; grade 2, n = 2); paresthesia (grade 3, n = 1; grade 2, n = 1); dysphasia (grade 3, n = 1); pyramidal tract disorder (grade 3, n = 1; grade 2, n = 1); and depressed level of consciousness (grade 2, n = 1). Enrollment is ongoing. Conclusions: Intratumoral administration of D2C7-IT + 2141-V11 via CED is safe, and encouraging efficacy results have been observed. Clinical trial information: NCT04547777.

Nivolumab plus radiotherapy with or without temozolomide in newly diagnosed glioblastoma: results from exploratory phase 1 cohorts of CheckMate 143

Background

The phase 1 cohorts (1c+1d) of CheckMate 143 (NCT02017717) evaluated the safety/tolerability and efficacy of nivolumab plus radiotherapy (RT) ± temozolomide (TMZ) in newly diagnosed glioblastoma.

Methods

In total, 136 patients were enrolled. In part A (safety lead-in), 31 patients (n=15, methylated/unknown MGMT promoter; n=16, unmethylated MGMT promoter) received nivolumab and RT+TMZ (NIVO+RT+TMZ) and 30 patients with unmethylated MGMT promoter received NIVO+RT. In part B (expansion), patients with unmethylated MGMT promoter were randomized to NIVO+RT+TMZ (n=29) or NIVO+RT (n=30). Primary endpoint was safety/tolerability; secondary endpoint was overall survival (OS).

Results

NIVO+RT±TMZ was tolerable; grade 3/4 treatment-related adverse events occurred in 51.6% (NIVO+RT+TMZ) and 30.0% (NIVO+RT) of patients in part A and 46.4% (NIVO+RT+TMZ) and 28.6% (NIVO+RT) in part B. No new safety signals were detected. In part A, median OS (mOS) with NIVO+RT+TMZ was 33.38 months (95% CI, 16.2 to not estimable) in patients with methylated MGMT promoter. In patients with unmethylated MGMT promoter, mOS was 16.49 months (12.94-22.08) with NIVO+RT+TMZ and 14.41 months (12.55-17.31) with NIVO+RT. In part B, mOS was 14.75 months (10.01-18.6) with NIVO+RT+TMZ and 13.96 months (10.81-18.14) with NIVO+RT in patients with unmethylated MGMT promoter.

Conclusions

CheckMate 143 was the first trial evaluating immune checkpoint inhibition with first-line treatment of glioblastoma. Results showed that NIVO can be safely combined with RT±TMZ, with no new safety signals. Toxicities, including lymphopenia, were more frequent with NIVO+RT+TMZ. OS was similar with or without TMZ in patients with unmethylated MGMT promoter, and differences by MGMT methylation status were observed.

Glioblastoma Clinical Trials: Current Landscape and Opportunities for Improvement

Therapeutic advances for glioblastoma have been minimal over the past 2 decades. In light of the multitude of recent phase III trials that have failed to meet their primary endpoints following promising preclinical and early-phase programs, a Society for Neuro-Oncology Think Tank was held in November 2020 to prioritize areas for improvement in the conduct of glioblastoma clinical trials. Here, we review the literature, identify challenges related to clinical trial eligibility criteria and trial design in glioblastoma, and provide recommendations from the Think Tank. In addition, we provide a data-driven context with which to frame this discussion by analyzing key study design features of adult glioblastoma clinical trials listed on ClinicalTrials.gov as "recruiting" or "not yet recruiting" as of February 2021.

Designing Clinical Trials for Combination Immunotherapy: A Framework for Glioblastoma

Immunotherapy has revolutionized treatment for many hard-to-treat cancers but has yet to produce significant improvement in outcomes for patients with glioblastoma. This reflects the multiple and unique mechanisms of immune evasion and escape in this highly heterogeneous tumor. Glioblastoma engenders profound local and systemic immunosuppression and is remarkably effective at inducing T-cell dysfunction, posing a challenge to any immunotherapy-based approach. To overcome these mechanisms, multiple disparate modes of immune-oriented therapy will be required. However, designing trials that can evaluate these combinatorial approaches requires careful consideration. In this review, we explore the immunotherapy resistance mechanisms that have been encountered to date and how combinatorial approaches may address these. We also describe the unique aspects of trial design in both preclinical and clinical settings and consider endpoints and markers of response best suited for an intervention involving multiple agents.

Generation of Tumor Targeted Dendritic Cell Vaccines with Improved Immunogenic and Migratory Phenotype

Our group has employed methodologies for effective ex vivo generation of dendritic cell (DC) vaccines for patients with primary malignant brain tumors. In order to reliably produce the most potent, most representational vaccinated DC that will engender an antitumor response requires the ability to orchestrate multiple methodologies that address antigen cross-presentation, T-cell costimulation and polarization, and migratory capacity. In this chapter, we describe a novel method for augmenting the immunogenicity and migratory potential of DCs for their use as vaccines. We have elucidated methodologies to avoid the phenomenon known as immunodominance in generating cancer vaccines. We have found that culturing DC progenitors in serum-free conditions for the duration of the differentiation protocol results in a more homogeneously mature population of DCs that exhibit enhanced immunogenicity compared to DCs generated in serum-containing culture conditions. Furthermore, we demonstrate our method for generating high mobility DCs that readily migrate toward lymphoid organ chemoattractants using CCL3 protein. The combination of these two approaches represents a facile and clinically tractable methodology for generating highly mature DCs with excellent migratory capacity.

For whom the T cells troll? Bispecific T-cell engagers in glioblastoma

Glioblastoma is the the most common primary brain tumor in adults. Onset of disease is followed by a uniformly lethal prognosis and dismal overall survival. While immunotherapies have revolutionized treatment in other difficult-to-treat cancers, these have failed to demonstrate significant clinical benefit in patients with glioblastoma. Obstacles to success include the heterogeneous tumor microenvironment (TME), the immune-privileged intracranial space, the blood-brain barrier (BBB) and local and systemic immunosuppressions. Monoclonal antibody-based therapies have failed at least in part due to their inability to access the intracranial compartment. Bispecific T-cell engagers are promising antibody fragment-based therapies which can bring T cells close to their target and capture them with a high binding affinity. They can redirect the entire repertoire of T cells against tumor, independent of T-cell receptor specificity. However, the multiple challenges posed by the TME, immune privilege and the BBB suggest that a single agent approach may be insufficient to yield durable, long-lasting antitumor efficacy. In this review, we discuss the mechanism of action of T-cell engagers, their preclinical and clinical developments to date. We also draw comparisons with other classes of multispecific antibodies and potential combinations using these antibody fragment therapies.

Enhancing T Cell Chemotaxis and Infiltration in Glioblastoma

Glioblastoma is an immunologically 'cold' tumor, which are characterized by absent or minimal numbers of tumor-infiltrating lymphocytes (TILs). For those tumors that have been invaded by lymphocytes, they are profoundly exhausted and ineffective. While many immunotherapy approaches seek to reinvigorate immune cells at the tumor, this requires TILs to be present. Therefore, to unleash the full potential of immunotherapy in glioblastoma, the trafficking of lymphocytes to the tumor is highly desirable. However, the process of T cell recruitment into the central nervous system (CNS) is tightly regulated. Naïve T cells may undergo an initial licensing process to enter the migratory phenotype necessary to enter the CNS. T cells then must express appropriate integrins and selectin ligands to interact with transmembrane proteins at the blood-brain barrier (BBB). Finally, they must interact with antigen-presenting cells and undergo further licensing to enter the parenchyma. These T cells must then navigate the tumor microenvironment, which is rich in immunosuppressive factors. Altered tumoral metabolism also interferes with T cell motility. In this review, we will describe these processes and their mediators, along with potential therapeutic approaches to enhance trafficking. We also discuss safety considerations for such approaches as well as potential counteragents.

Broad immunophenotyping of the murine brain tumor microenvironment

Here we present a 14-color flow cytometry panel for the evaluation of 13 myeloid and lymphoid populations within murine glioblastoma samples. Reagents, processing protocols, and downstream analyses were thoroughly validated and optimized to resolve the following populations: T cells (CD4, CD8, CD3), B cells (B220), NK cells (NK1.1), neutrophils (Ly6G), classical and non-classical monocytes (Ly6c, CD43), macrophages (F4/80, CD11b), microglia (CD45-lo, CD11b), and dendritic cells (DCs) (CD11c, MHC class II). In addition, this panel leaves Alexa Fluor 488/FITC open for the inclusion of fluorescent reporters or congenic marker staining.

Targeting Immunometabolism in Glioblastoma

We have only recently begun to understand how cancer metabolism affects antitumor responses and immunotherapy outcomes. Certain immunometabolic targets have been actively pursued in other tumor types, however, glioblastoma research has been slow to exploit the therapeutic vulnerabilities of immunometabolism. In this review, we highlight the pathways that are most relevant to glioblastoma and focus on how these immunometabolic pathways influence tumor growth and immune suppression. We discuss hypoxia, glycolysis, tryptophan metabolism, arginine metabolism, 2-Hydroxyglutarate (2HG) metabolism, adenosine metabolism, and altered phospholipid metabolism, in order to provide an analysis and overview of the field of glioblastoma immunometabolism.

CaMKK2 deletion causes increased accumulation of CD4+ TILs and an improved ratio of effector memory TILs to Tregs

Objective

Glioblastoma (GBM) is the most lethal primary brain tumor in adults. Although immunotherapy has been successful in some cancers, it has shown limited success in GBM. This is partially due to poor T cell infiltration, and because many T cells found in tumors are either exhausted or Tregs. Re-analysis of publicly available data has shown that CaMKK2 is more highly expressed in advanced brain tumors, and high CaMKK2 expression results in worse survival outcomes in GBM. Additionally, in survival studies that we performed, CaMKK2−/− mice showed an impressive survival phenotype that was dependent on the presence of CD8+ tumor infiltrating lymphocytes (TILs). The objective of our study was to investigate what is different about T cells found in the TME of CaMKK2−/− mice, and if this can explain the observed survival benefit.

Methods

We performed flow cytometry to determine the identities of T cells found in the tumors of CaMKK2−/− and WT mice.

Results/Conclusions

Our experiments show that there was a greater percentage of CD4+ TILs relative to CD8+ TILs in CaMKK2−/− mice, and this increase in percentage was due to increased accumulation of CD4+ TILs. Additionally, we found that there was greater accumulation of CD4+ and CD8+ effector memory TILs and a greater ratio of effector memory TILs to Tregs in CaMKK2−/− mice. The increased accumulation of the CD8+ effector memory TILs is particularly interesting because it is not simply explained by an increased accumulation of cells, as is the case with the CD4+ TILs. The increased accumulation of CD4+ TILs and greater ratio of effector memory TILs to Tregs is expected to have an anti-tumor effect. These findings make CaMKK2 a promising target to treat GBM.

CaMKK2 deletion increases antitumor potential through enhanced MHC-II expression in Macrophages

Objective:

Glioblastoma is the most common and aggressive primary brain tumor with a 5 year prognosis of less than 5% survival. Efforts to extend this survival through therapeutic advancement have only led to modest improvements. Immunotherapy has shown promise in other cancers but only has limited effect in GBM, partially due to the dense infiltration of pro-tumor myeloid cells. Calmodulin-dependent Kinase Kinase 2 (CaMKK2) is highly expressed in myeloid cells and high expression is associated with a more severe tumor grade and worse survival in GBM. Preliminary studies show that CaMKK2 KO mice display extended median survival and tumor clearance. We hypothesize that CaMKK2 may drive myeloid cells’ pro-tumor function.

Methods:

To investigate this, immune cells were isolated from tumor-bearing CaMKK2 KO, LysMcre x CaMKK2fl/fl and CaMKK2-eGFP reporter mice. Multi-parameter flow was used to detect CaMKK2 and phenotype the tumor microenvironment (TME). The presence of CaMKK2 expressing myeloid cells in the TME was confirmed by confocal microscopy.

Results/Conclusions:

CaMKK2 is preferentially expressed in myeloid cells in naïve and tumorous mice. CaMKK2 deletion upregulated MHC-II in macrophages which is expected to promote an antitumor response. Upregulation was not seen in naive CaMKK2 KO mice suggesting it is a product of tumor-exposure. Conditional deletion of CaMKK2 in bone-marrow derived macrophages (BMDM) did not lead to this MHC-II upregulation suggesting that it is not a BMDM-intrinsic phenotype but results from CaMKK2 deletion in another cell-type. In summary, CaMKK2 deletion induced macrophages to a more immunostimulatory phenotype with expected anti-tumor effect, making CaMKK2 a promising therapeutic target for GBM.

First in human dose calculation of a single-chain bispecific antibody targeting glioma using the MABEL approach

Background

First-in-human (FIH) clinical trials require careful selection of a safe yet biologically relevant starting dose. Typically, such starting doses are selected based on toxicity studies in a pharmacologically relevant animal model. However, with the advent of target-specific and highly active immunotherapeutics, both the Food and Drug Administration and the European Medicines Agency have provided guidance that recommend determining a safe starting dose based on a minimum anticipated biological effect level (MABEL) approach.

Methods

We recently developed a T cell activating bispecific antibody that effectively treats orthotopic patient-derived malignant glioma and syngeneic glioblastoma in mice (hEGFRvIII:CD3 bi-scFv). hEGFRvIII:CD3 bi-scFv is comprized of two single chain antibody fragments (bi-scFvs) that bind mutant epidermal growth factor receptor variant III (EGFRvIII), a mutation frequently seen in malignant glioma, and human CD3ε on T cells, respectively. In order to establish a FIH dose, we used a MABEL approach to select a safe starting dose for hEGFRvIII:CD3 bi-scFv, based on a combination of in vitro data, in vivo animal studies, and theoretical human receptor occupancy modeling.

Results

Using the most conservative approach to the MABEL assessment, a dose of 57.4 ng hEGFRvIII:CD3 bi-scFv/kg body weight was selected as a safe starting dose for a FIH clinical study.

Conclusions

The comparison of our MABEL-based starting dose to our in vivo efficacious dose and the theoretical human receptor occupancy strongly supports that our human starting dose of 57.4 ng hEGFRvIII:CD3 bi-scFv/patient kg will be safe.

Once, Twice, Three Times a Finding: Reproducibility of Dendritic Cell Vaccine Trials Targeting Cytomegalovirus in Glioblastoma

Despite standard of care for glioblastoma, including gross total resection, high-dose radiation, and dose-limited chemotherapy, this tumor remains one of the most aggressive and therapeutically challenging. The relatively small number of patients with this diagnosis compared with more common solid tumors in clinical trials commits new glioblastoma therapies to testing in small, underpowered, nonrandomized settings. Among approximately 200 registered glioblastoma trials identified between 2005 and 2015, nearly half were single-arm studies with sample sizes not exceeding 50 patients. These constraints have made demonstrating efficacy for novel therapies difficult in glioblastoma and other rare and aggressive cancers. Novel immunotherapies for glioblastoma such as vaccination with dendritic cells (DC) have yielded mixed results in clinical trials. To address limited numbers, we sequentially conducted three separate clinical trials utilizing cytomegalovirus (CMV)-specific DC vaccines in patients with newly diagnosed glioblastoma whereby each follow-up study had nearly doubled in sample size. Follow-up data from the first blinded, randomized phase II clinical trial (NCT00639639) revealed that nearly one third of this cohort is without tumor recurrence at 5 years from diagnosis. A second clinical trial (NCT00639639) resulted in a 36% survival rate at 5 years from diagnosis. Results of the first two-arm trial (NCT00639639) showed increased migration of the DC vaccine to draining lymph nodes, and this increased migration has been recapitulated in our larger confirmatory clinical study (NCT02366728). We have now observed that nearly one third of the glioblastoma study patient population receiving CMV-specific DC vaccines results in exceptional long-term survivors.

PD-1 Inhibitors: Do they have a Future in the Treatment of Glioblastoma?

Glioblastoma (WHO grade IV glioma) is the most common malignant primary brain tumor in adults. Survival has remained largely static for decades, despite significant efforts to develop new effective therapies. Immunotherapy and especially immune checkpoint inhibitors and programmed cell death (PD)-1/PD-L1 inhibitors have transformed the landscape of cancer treatment and improved patient survival in a number of different cancer types. With the exception of few select cases (e.g., patients with Lynch syndrome) the neuro-oncology community is still awaiting evidence that PD-1 blockade can lead to meaningful clinical benefit in glioblastoma. This lack of progress in the field is likely to be due to multiple reasons, including inherent challenges in brain tumor drug development, the blood-brain barrier, the unique immune environment in the brain, the impact of corticosteroids, as well as inter- and intratumoral heterogeneity. Here we critically review the clinical literature, address the unique aspects of glioma immunobiology and potential immunobiological barriers to progress, and contextualize new approaches to increase the efficacy of PD-1/PD-L1 inhibitors in glioblastoma that may identify gaps and testable relevant hypotheses for future basic and clinical research and to provide a novel perspective to further stimulate preclinical and clinical research to ultimately help patients with glioma, including glioblastoma, which is arguably one of the greatest areas of unmet need in cancer. Moving forward, we need to build on our existing knowledge by conducting further fundamental glioma immunobiology research in parallel with innovative and methodologically sound clinical trials.

Antigen-loaded monocyte administration induces potent therapeutic antitumor T cell responses

Efficacy of dendritic cell (DC) cancer vaccines is classically thought to depend on their antigen-presenting cell (APC) activity. Studies show, however, that DC vaccine priming of cytotoxic T lymphocytes (CTLs) requires the activity of endogenous DCs, suggesting that exogenous DCs stimulate antitumor immunity by transferring antigens (Ags) to endogenous DCs. Such Ag transfer functions are most commonly ascribed to monocytes, implying that undifferentiated monocytes would function equally well as a vaccine modality and need not be differentiated to DCs to be effective. Here, we used several murine cancer models to test the antitumor efficacy of undifferentiated monocytes loaded with protein or peptide Ag. Intravenously injected monocytes displayed antitumor activity superior to DC vaccines in several cancer models, including aggressive intracranial glioblastoma. Ag-loaded monocytes induced robust CTL responses via Ag transfer to splenic CD8+ DCs in a manner independent of monocyte APC activity. Ag transfer required cell-cell contact and the formation of connexin 43-containing gap junctions between monocytes and DCs. These findings demonstrate the existence of an efficient gap junction-mediated Ag transfer pathway between monocytes and CD8+ DCs and suggest that administration of tumor Ag-loaded undifferentiated monocytes may serve as a simple and efficacious immunotherapy for the treatment of human cancers.

Checkpoint inhibitor immunotherapy for glioblastoma: current progress, challenges and future outlook

INTRODUCTION

Despite maximal surgical resection and chemoradiation, glioblastoma (GBM) continues to be associated with significant morbidity and mortality. Novel therapeutic strategies are urgently needed. Given success in treating multiple other forms of cancer, checkpoint inhibitor immunotherapy remains foremost amongst novel therapeutic strategies that are currently under investigation.

AREAS COVERED

Through a systematic review of both published literature and the latest preliminary data available from ongoing clinical studies, we provide an up-to-date discussion on the immune system in the CNS, a detailed mechanistic evaluation of checkpoint biology in the CNS along with evidence for disruption of these pathways in GBM, and a summary of available preclinical and clinical data for checkpoint blockade in GBM. We also include a discussion of novel, emerging targets for checkpoint blockade which may play an important role in GBM immunotherapy.

EXPERT OPINION

Evidence indicates that while clinical success of checkpoint blockade for the treatment of GBM has been limited to date, through improved preclinical models, optimization in the context of standard of care therapies, assay standardization and harmonization, and combinatorial approaches which may include novel targets for checkpoint blockade, checkpoint inhibitor immunotherapy may yield a safe and effective therapeutic option for the treatment of GBM.

Abstract 2667: CaMKK2 knockout in mice challenged by orthotopic GBM leads to upregulation of MHC II on TAMs and an increase in accumulation of CD4+ TILs

Glioblastoma (GBM) is the most lethal primary brain tumor in adults, with the median survival time for GBM patients being only about 15 months. Although immunotherapy treatments have been successful in more immunogenic tumors, it has shown very limited success in GBM. This could be because it is difficult for T cells to infiltrate the tumor, and the tumors have a very immunosuppressive tumor microenvironment (TME) that can often consist of up to about 30 percent tumor associated macrophages (TAMs) by mass. Thus, two ways of possibly improving immunotherapy treatments on GBMs would be to increase the number of tumor infiltrating lymphocytes (TILs) present, and to target tumor-supportive cells such as TAMs. Calmodulin Dependent Protein Kinase Kinase 2 (CaMKK2) is a gene that has been shown to be highly expressed in myeloid cells and is known to alter their phenotype. Recent studies in breast cancer have shown that myeloid cells adopt a more immunostimulatory phenotype in murine knockout CaMKK2 models. However, it is not well understood how CaMKK2 causes this immunosuppressive effect and warrants further exploration. The data from our experiments help to answer this question. High-dimensional flow cytometry with 15 parameters was used in order to determine the identities of immune cells found in the tumor of wildtype and CaMKK2-/- mice. The results of our experiments show that there appear to be more CD4+ TILs present in the TME of knockout mice and that there is an increase in MHC II expression on TAMs found in knockout mice. Since CD4+ TILs recognize peptides presented on MHC II molecules, and there is an increase in the number of CD4+ TILs and expression of MHC II on TAMs in knockout mice, we hypothesize that a stronger immune response could be instigated against the tumor. Therefore, it can be concluded that a possible reason that knocking out CaMKK2 leads to a less immunosupressive TME is because MHC II expression on TAMs is upregulated, and the number of CD4+ TILs in the TME is increased. Whether or not the increase in MHC II expression causes the increase in the number CD4+ TILs requires further exploration. This makes CaMKK2 a promising therapeutic target to treat tumors with immunosuppressive TMEs such as GBM.

Citation Format: Molly A. Chakraborty, William H. Tomaszewski, Jessica Waibl Polania, Lauren S. Riley, Luigi Racioppi, Luis A. Sanchez-Perez, John H. Sampson. CaMKK2 knockout in mice challenged by orthotopic GBM leads to upregulation of MHC II on TAMs and an increase in accumulation of CD4+ TILs [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2667.

GLP toxicology study of a fully-human T cell redirecting CD3:EGFRvIII binding immunotherapeutic bispecific antibody

We recently reported the development of a fully-human, CD3-binding bispecific antibody for immunotherapy of malignant glioma. To translate this therapeutic (hEGFRvIII-CD3- bi-scFv) to clinical trials and to help further the translation of other similar CD3-binding therapeutics, some of which are associated with neurologic toxicities, we performed a good laboratory practice (GLP) toxicity study to assess for potential behavioral, chemical, hematologic, and pathologic toxicities including evaluation for experimental autoimmune encephalomyelitis (EAE). To perform this study, male and female C57/BL6 mice heterozygous for the human CD3 transgene (20/sex) were allocated to one of four designated groups. All animals were administered one dose level of hEGFRvIII-CD3 bi-scFv or vehicle control. Test groups were monitored for feed consumption, changes in body weight, and behavioral disturbances including signs of EAE. Urinalysis, hematologic, and clinical chemistry analysis were also performed. Vehicle and test chemical-treated groups were humanely euthanized 48 hours or 14 days following dose administration. Complete gross necropsy of all tissues was performed, and selected tissues plus all observed gross lesions were collected and evaluated for microscopic changes. This included hematoxylin-eosin histopathological evaluation and Fe-ECR staining for myelin sheath enumeration. There were no abnormal clinical observations or signs of EAE noted during the study. There were no statistical changes in food consumption, body weight gain, or final body weight among groups exposed to hEGFRvIII-CD3 bi-scFv compared to the control groups for the 2- and 14-day timepoints. There were statistical differences in some clinical chemistry, hematologic and urinalysis endpoints, primarily in the females at the 14-day timepoint (hematocrit, calcium, phosphorous, and total protein). No pathological findings related to hEGFRvIII-CD3 bi-scFv administration were observed. A number of gross and microscopic observations were noted but all were considered to be incidental background findings. The results of this study allow for further translation of this and other important CD3 modulating bispecific antibodies.

Comparative study of α-helical and β-sheet self-assembled peptide nanofiber vaccine platforms: influence of integrated T-cell epitopes

Several different self-assembling peptide systems that form nanofibers have been investigated as vaccine platforms, but design principles for adjusting the character of the immune responses they raise have yet to be well articulated. Here we compared the immune responses raised by two structurally dissimilar peptide nanofibers, one a β-sheet fibrillar system (Q11), and one an α-helical nanofiber system (Coil29), hypothesizing that integrated T-cell epitopes within the latter would promote T follicular helper (Tfh) cell engagement and lead to improved antibody titers and quality. Despite significantly different internal structures, nanofibers of the two peptides exhibited surprisingly similar nanoscale morphologies, and both were capable of raising strong antibody responses to conjugated peptide epitopes in mice without adjuvant. Both were minimally inflammatory, but as hypothesized Coil29 nanofibers elicited antibody responses with higher titers and avidities against a conjugated model epitope (OVA_323-339) and a candidate peptide epitope for vaccination against S. aureus. Subsequent investigation indicated that Coil29 nanofibers possessed internal CD4+ T cell epitopes: whereas Q11 nanofibers required co-assembly of additional CD4+ T cell epitopes to be immunogenic, Coil29 nanofibers did not. Coil29 nanofibers also raised stronger germinal center B cell responses and follicular helper T cell (Tfh) responses relative to Q11 nanofibers, likely facilitating the improvement of the antibody response. These findings illustrate design strategies for improving humoral responses raised by self-assembled peptide nanofibers.

MDNA55 survival in recurrent glioblastoma (rGBM) patients expressing the interleukin-4 receptor (IL4R) as compared to a matched synthetic control

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Background: MDNA55 is an engineered IL-4 fused to pseudomonas exotoxin A being developed for GBM, an aggressive, universally fatal disease. No curative therapy exists and 75% of patients are not eligible for resection at recurrence. MDNA55 targets IL4R overexpressed in GBM, the immunosuppressive tumor microenvironment, and high expression is associated with poor survival outcomes in GBM. A Ph 2b trial of MDNA55 was completed in rGBM using convection-enhanced delivery to bypass the BBB. Here we report results from the Ph 2b trial and comparison against a matched Synthetic Control Arm (SCA). Methods: MDNA55-05 is an open-label, single-arm study of intratumoral delivery of ≤ 240 μg MDNA55 as a single treatment via ≤ 4 catheters in de novo GBM without IDH1/2 mutation at 1st or 2nd recurrence not eligible for resection, tumors ≤ 4 cm, KPS ≥ 70. IL4R expression in GBM tissues was determined by H-Score using a validated IHC assay. 1o endpoint is median overall survival (mOS); 2o endpoint includes the impact of IL4R status on mOS. An eligibility-matched SCA was identified retrospectively from patient registries at major neurosurgery centers with access to GBM tumor tissue banks under IRB-approved protocols. Results: 44 subjects comprise the MDNA55 per protocol analysis population: median age 56 (35 - 77); median dose 177 mg (range 18 – 240 mg), 50% had KPS ≤ 80. No systemic toxicities observed, drug-related AEs were primarily neurological and characteristic of GBM, no deaths attributed to MDNA55. Median OS was 11.6 months (95% CI 7.9 – 15.2). When stratified by IL4R expression, mOS in IL4R High (n = 21) was 15 vs. 8.4 months in IL4R Low (n = 19); p = 0.2175. OS12 is 57% vs. 33%. When compared to the SCA (n = 81), MDNA55 subjects survived significantly longer: mOS 12.4 vs. 7.7 months; p = 0.0077. When comparing IL4R High groups, mOS in MDNA55 (n = 21) was 15.8 vs. 6.2 months in the SCA (n = 17); p = 0.0626. Subgroup analysis in unmethylated MGMT subjects also show better survival with MDNA55 (n = 23) than the SCA (n = 31); mOS 12.3 vs. 7.7 months (p = 0.0268), indicating that MDNA55 may be beneficial in patients resistant to temozolomide. Conclusions: MDNA55 subjects represent a difficult to treat population ( de novo GBM, IDH wild-type, not eligible for surgery at recurrence). Single treatment with MDNA55 prolongs survival by nearly 10 months in a subset of rGBM expressing high levels of IL4R when compared to a matched SCA, providing an unprecedented outcome for this highly lethal disease. Clinical trial information: NCT02858895 .

Phase I trial of D2C7 immunotoxin (D2C7-IT) administered intratumorally via convection-enhanced delivery (CED) for recurrent malignant glioma (MG)

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Background: D2C7-IT is a recombinant immunotoxin comprised of a dual-specific antibody fragment targeting EGFRwt and EGFRvIII and a genetically engineered form of the Pseudomonas exotoxin, PE38-KDEL. We report the results of a phase I trial evaluating D2C7-IT delivered intratumorally by CED. Methods: Eligible patients were adults with recurrent supratentorial WHO grade III or IV MG; solitary tumor; ≥4 weeks after chemotherapy, bevacizumab or study drug; adequate organ function; and KPS>70%. Two patients per dose level (DL) were to enroll in the dose escalation portion (dose range: 40ng/mL to 23,354ng/mL). Results: From May 2015 to May 2018, 43 patients enrolled on study. Observed dose limiting toxicities include: grade 4 seizure (n=1) on DL3, grade 3 confusion and pyramidal tract syndrome (n=1) on DL13, and grade 4 cerebral edema (n=1) and grade 3 dysphasia (n=1) on DL17. Grade 3 or higher adverse events possibly related to D2C7-IT include: seizure (grade 4, n=2; grade 3, n=3), cerebral edema (grade 4, n=1), hydrocephalus (grade 3, n=5), headache (grade 3, n=4), hemiparesis (grade 3, n=4), dysphasia (grade 3, n=3), lymphopenia (grade 3, n=4), thromboembolic event (grade 3, n=3); and one each of grade 3 elevated ALT, urinary tract infection, fall, wound complication, generalized muscle weakness, confusion, encephalopathy, and somnolence. As of February 2020, four patients remain alive, with three patients demonstrating persistent radiographic partial response more than 54, 34 and 28 months after a single infusion of D2C7-IT. Conclusions: Dose level 13 (6,920ng/mL) was selected as the optimal phase II dose. Accrual in a dose expansion phase II trial is ongoing, and we are initiating a combination trial of D2C7-IT with checkpoint inhibitior. Clinical trial information: NCT02303678 .

Synthetic long peptide vaccines possessing a universal helper epitope can unmask the therapeutic effects of MHC I-restricted neoepitopes

Synthetic long peptide (SLP) vaccines targeting neoantigens arising from patient-specific missense mutations may offer a means to address the antigenic heterogeneity of glioblastoma (GBM) tumors by simultaneously targeting a multitude of tumor-specific antigens expressed throughout these heterogenous tumors. This approach is challenged by uncertainties pertaining to vaccine design, including peptide composition required for immunogenicity and efficacy. To this end, we investigated the mechanism of an efficacious SLP vaccine targeting the neoantigen Odc1, expressed within the mouse astrocytoma SMA560. This led to the identification of three generalizable principles governing the effectiveness of neoantigen-targeting SLPs: (1) SLPs containing an MHC I-restricted neoepitope may activate neoantigen-reactive CD8+ T cells, which drive direct antitumor effects; (2) to induce robust neoantigen-reactive CD8+ T-cell responses, CD40L-mediated T cell "help" is required; and, (3) CD40L interactions are conferred by an SLP only when a “helper” epitope is physically conjoined to an MHC I-restricted neoepitope. To leverage these findings for clinical translation, we developed a rationally-designed vaccine comprised of an MHC I-restricted neoepitope linked to a universal “helper” epitope. This design was capable of maintaining the effects of the Odc1 vaccine and, remarkably, unmasked the therapeutic effects of, otherwise, poorly immunogenic MHC I-restricted neoepitopes. Together, these findings are significant because they elucidate mechanisms required for efficacious SLP vaccines and demonstrate a clinically-tractable approach with the potential to expand the therapeutic breadth of neoantigen vaccines.

Abstract A80: The effects of CCL3 on dendritic cell migration and immune cell activation

Glioblastoma (GBM) remains uniformly lethal and current therapy is ineffective and incapacitating. Standard therapies are limited by nonspecific toxicity, and the median overall survival for patients with GBM remains &lt;15 months. Immunotherapy for GBM holds significant promise, as substantial evidence suggests that T cells can eradicate large, well-established tumors in mice and humans. Dendritic cell (DC) vaccines can, in some cases, effectively stimulate such T-cell responses as shown by several remarkable cases of individual patient responders. However, overall objective responses in early-phase clinical trials with tumor-targeted DC vaccination have remained under 15%. In a recent study in patients with newly diagnosed GBM published in Nature, we demonstrated that unilaterally preconditioning one vaccine site with the inflammatory recall antigens Tetanus/diphtheria toxoid (Td) resulted in increased bilateral DC migration to the draining lymph nodes and a significant increase in progression-free survival and overall survival—with half of the Td-treated patients living past 4.5 years. The benefit of vaccine site preconditioning could be recapitulated in a mouse model, as we found that Td increased DC migration to the draining lymph nodes and suppressed tumor growth in an antigen-dependent manner. In a search for potential mediators of these effects, we found that the only cytokine or chemokine significantly upregulated after Td preconditioning in both patients and mice was the chemokine (C-C motif) ligand 3 (CCL3). Furthermore, our data show that a source for CCL3 appears to be Td-specific CD4+ memory effector T cells (CD4Td-mem). In experiments where wild-type mice received either CCL3(-/-) or wild-type CD4Td-mem, DC migration was increased only in the wild-type CD4Td-mem setting, signifying that CCL3 from these cells is necessary for DC migration. Finally, we have found that exogenous CCL3 alone can enhance bilateral DC migration to the draining lymph nodes and reduce tumor growth similar to Td preconditioning, suggesting that exogenous CCL3 may be used to treat patients and increase objective responses associated with DC vaccines.

Citation Format: Teilo H. Schaller, Kristen A. Batich, Kelly Hotchkiss, Xiuyu Cui, Luis Sanchez-Perez, John H. Sampson. The effects of CCL3 on dendritic cell migration and immune cell activation [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A80.

CAR T cells and checkpoint inhibition for the treatment of glioblastoma

Introduction: Glioblastoma (GBM) is a highly aggressive brain tumor and is one of the most lethal human cancers. Chimeric antigen receptor (CAR) T cell therapy has markedly improved survival in previously incurable disease; however, this vanguard treatment still faces challenges in GBM. Likewise, checkpoint blockade therapies have not enjoyed the same victories against GBM. As it becomes increasingly evident that a mono-therapeutic approach is unlikely to provide anti-tumor efficacy, there evolves a critical need for combined treatment strategies.Areas covered: This review highlights the clinical successes observed with CAR T cell therapy as well the current efforts to overcome its perceived limitations. The review also explores employed combinations of CAR T cell approaches with immune checkpoint blockade strategies, which aim to potentiate immunotherapeutic benefits while restricting the impact of tumor heterogeneity and T cell exhaustion.Expert opinion: Barriers such as tumor heterogeneity and T cell exhaustion have exposed the weaknesses of various mono-immunotherapeutic approaches to GBM, including CAR T cell and checkpoint blockade strategies. Combining these potentially complementary strategies, however, may proffer a rational means of mitigating these barriers and advancing therapeutic successes against GBM and other solid tumors.

Current multidisciplinary management of brain metastases

Brain metastasis (BM), the most common adult brain tumor, develops in 20% to 40% of patients with late-stage cancer and traditionally are associated with a poor prognosis. The management of patients with BM has become increasingly complex because of new and emerging systemic therapies and advancements in radiation oncology and neurosurgery. Current therapies include stereotactic radiosurgery, whole-brain radiation therapy, surgical resection, laser-interstitial thermal therapy, systemic cytotoxic chemotherapy, targeted agents, and immune-checkpoint inhibitors. Determining the optimal treatment for a specific patient has become increasingly individualized, emphasizing the need for multidisciplinary discussions of patients with BM. Recognizing and addressing the sequelae of BMs and their treatment while maintaining quality of life and neurocognition is especially important because survival for patients with BMs has improved. The authors present current and emerging treatment options for patients with BM and suggest approaches for managing sequelae and disease recurrence.

Brain immunology and immunotherapy in brain tumours

Gliomas, the most common malignant primary brain tumours, remain universally lethal. Yet, seminal discoveries in the past 5 years have clarified the anatomy, genetics and function of the immune system within the central nervous system (CNS) and altered the paradigm for successful immunotherapy. The impact of standard therapies on the response to immunotherapy is now better understood, as well. This new knowledge has implications for a broad range of tumours that develop within the CNS. Nevertheless, the requirements for successful therapy remain effective delivery and target specificity, while the dramatic heterogeneity of malignant gliomas at the genetic and immunological levels remains a profound challenge.

The current state of immunotherapy for gliomas: an eye toward the future

The last decade has seen a crescendo of FDA approvals for immunotherapies against solid tumors, yet glioblastoma remains a prominent holdout. Despite more than 4 decades of work with a wide range of immunotherapeutic modalities targeting glioblastoma, efficacy has been challenging to obtain. Earlier forms of immune-based platforms have now given way to more current approaches, including chimeric antigen receptor T-cells, personalized neoantigen vaccines, oncolytic viruses, and checkpoint blockade. The recent experiences with each, as well as the latest developments and anticipated challenges, are reviewed.

Challenges to curing primary brain tumours

Despite decades of research, brain tumours remain among the deadliest of all forms of cancer. The ability of these tumours to resist almost all conventional and novel treatments relates, in part, to the unique cell-intrinsic and microenvironmental properties of neural tissues. In an attempt to encourage progress in our understanding and ability to successfully treat patients with brain tumours, Cancer Research UK convened an international panel of clinicians and laboratory-based scientists to identify challenges that must be overcome if we are to cure all patients with a brain tumour. The seven key challenges summarized in this Position Paper are intended to serve as foci for future research and investment.

Pharmacokinetic Analysis of a Novel Human EGFRvIII:CD3 Bispecific Antibody in Plasma and Whole Blood Using a High-Resolution Targeted Mass Spectrometry Approach

Bispecific single chain antibody fragments (bi-scFv) represent an emerging class of biotherapeutics. We recently developed a fully human bi-scFv (EGFRvIII:CD3 bi-scFv) with the goal of redirecting CD3-expressing T cells to recognize and destroy malignant, EGFRvIII-expressing glioma. In mice, we showed that EGFRvIII:CD3 bi-scFv effectively treats orthotopic patient-derived malignant glioma and syngeneic glioblastoma. Here, we developed a targeted assay for pharmacokinetic (PK) analysis of EGFRvIII:CD3 bi-scFv, a necessary step in the drug development process. Using microflow liquid chromatography coupled to a high resolution parallel reaction monitoring mass spectrometry, and data analysis in Skyline, we developed a bottom-up proteomic assay for quantification of EGFRvIII:CD3 bi-scFv in both plasma and whole blood. Importantly, a protein calibrator, along with stable isotope-labeled EGFRvIII:CD3 bi-scFv protein, were used for absolute quantification. A PK analysis in a CD3 humanized mouse revealed that EGFRvIII:CD3 bi-scFv in plasma and whole blood has an initial half-life of ∼8 min and a terminal half-life of ∼2.5 h. Our results establish a sensitive, high-throughput assay for direct quantification of EGFRvIII:CD3 bi-scFv without the need for immunoaffinity enrichment. Moreover, these pharmacokinetic parameters will guide drug optimization and dosing regimens in future IND-enabling and phase I studies of EGFRvIII:CD3 bi-scFv.

The Evolving Modern Management of Brain Metastasis

The incidence of brain metastases is increasing as cancer therapies improve and patients live longer, providing new challenges to the multidisciplinary teams that care for these patients. Brain metastatic cancer cells possess unique characteristics that allow them to penetrate the blood-brain barrier, colonize the brain parenchyma, and persist in the intracranial environment. In addition, brain metastases subvert the innate and adaptive immune system, permitting evasion of the antitumor immune response. Better understanding of the above mechanisms will allow for development and delivery of more effective therapies for brain metastases. In this review, we outline the molecular mechanisms underlying development, survival, and immunosuppression of brain metastases. We also discuss current and emerging treatment strategies, including surgery, radiation, disease-specific and mutation-targeted systemic therapy, and immunotherapy.

Oncolytic polio/rhinovirus recombinant (PVSRIPO) against WHO grade IV malignant glioma (MG): Experience with retreatment of survivors from the phase I trial

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Background: We completed a study evaluating a single intratumoral delivery of PVSRIPO in recurrent WHO grade IV MG patients (N Engl J Med. 2018 Jul 12;379(2):150-161). Some patients who originally benefitted from the infusion of PVSRIPO demonstrated tumor recurrence, and we hypothesized that retreatment could trigger an immune recall effect, further extending their survival. We now report the impact of second and third intratumoral reinfusion of PVSRIPO in patients treated in the original dose finding study. Methods: Eligible patients were adults with recurrent supratentorial WHO grade IV MG who were experiencing disease recurrence after having benefitted from the first infusion of PVSRIPO. Additional eligibility criteria included: solitary tumor 1-5.5cm in diameter; ≥4 weeks after chemotherapy, bevacizumab or study drug; adequate organ function; KPS≥70%; and positive anti-polio titer. One patient each was retreated at 1 x 107 TCID50 and 1 x 1010 TCID50, and three patients were retreated on the identified phase 2 dose of 5 x 107 TCID50. Results: As of 2/09/2019, five patients have received a second intratumoral dose of PVSRIPO on study, one of which received a total of 3 doses. The patients who received two infusions of PVSRIPO were retreated 72 months, 43 months, 34 months, and 6 months after the first infusion. One additional patient received a second infusion of PVSRIPO 60 months after the first infusion and a third infusion of PVSRIPO 78 months after the first infusion. All patients demonstrated soap bubble degeneration on imaging, and two patients demonstrated tumor contraction. No grade 3 or higher adverse events related to PVSRIPO were observed after retreatment. Three of these patients remain alive more than 81, 80 and 52 months following the first PVSRIPO infusion and more than 9, 20 and 18 months after the second infusion, respectively. Two patients died 63 months and 20 months after the first infusion of PVSRIPO and 19.6 and 14 months after the second, respectively. The patient treated 3 times received the third infusion more than 2 months ago. Conclusions: Intratumoral reinfusion of PVSRIPO via CED is safe, and encouraging efficacy results have been observed. Clinical trial information: NCT01491893.

MDNA55: A locally administered IL4 guided toxin as a targeted treatment for recurrent glioblastoma

2039

Background: IL4 receptor (IL4R) is frequently and intensely expressed on a variety of human cancers and is associated with poor survival outcomes. Determining the role of the IL4R biomarker in glioblastoma (GBM) will be important for treatment with targeted therapies such as the IL4 fusion toxin MDNA55. Methods: A classification for IL4Rα expression in GBM tissues by H-Score was developed using a validated immunohistochemistry-based approach. MDNA55-05 is an open-label study of MDNA55 administered intratumorally via convection enhanced delivery in recurrent GBM. Levels of IL4Rα expression were assessed retrospectively in 24 subjects in the clinical trial and were correlated with GBM history, imaging responses and survival outcomes following treatment with MDNA55 to explore clinical validation. Results: Range, linearity, specificity and sensitivity testing using a rabbit polyclonal antibody to IL4Rα were performed using normal cortex (negative control) and a panel of normal human tissues and GBM cases from tissue banks. A total of 41 GBM samples were screened and grouped by reactivity thresholds: H-Scores ≥50 were observed in 95% of cases (39/41), H-Scores ≥200 were observed in 51% of cases (21/41), and H-Scores ≥250 were observed in 24% of cases (10/41). GBM tissues obtained at initial diagnosis from subjects enrolled in the trial show that moderate/high IL4R expression (H-Score > 75) was associated with shorter time to first relapse when compared to subjects with low IL4R expression (H-Score ≤ 75) (10.3 mos vs. 16.7 mos, respectively) after upfront standard-of-care treatment, consistent with published findings that IL4R expression is associated with more aggressive disease. Remarkable decreases in tumor size seen in some subjects following MDNA55 treatment were associated only with moderate/high IL4R expression and survival rate at 12 months in this group was also improved (OS12 = 55%) compared to subjects with low IL4R expression (OS12 = 30%). Conclusions: Treatment options for patients with recurrent GBM are very limited and positive outcomes remain rare. Targeting therapies such as MDNA55 by IL4R status may improve patient outcomes and help guide patient selection strategies for future clinical studies. Clinical trial information: NCT02858895.

Safety of nivolumab in combination with dendritic cell vaccines in recurrent high-grade glioma

e13526

Background: Recurrence of high-grade glioma (HGG) (WHO grade III-IV) is a nearly universal phenomenon and necessitates the development of new therapeutic modalities. Two possible immunotherapeutic modalities are checkpoint blockade with agents such as nivolumab, a blocking antibody against the inhibitory checkpoint programmed cell death-1 (PD-1), and dendritic cell (DC) vaccination. We have shown in phase 1 and 2 trials that DC vaccination against the glioblastoma (GBM)-associated antigen human cytomegalovirus pp65-lysosomal-associated membrane protein (CMVpp65) is safe and possesses potential benefit. We hypothesized that nivolumab-induced immune checkpoint blockade could enhance efficacy of DC vaccination. Therefore, we undertook a phase 1 study to evaluate safety of nivolumab in combination with CMVpp65 mRNA pulsed DC vaccination in subjects with first or second recurrence of resectable HGG. Methods: We performed a phase 1, single-center, randomized study of nivolumab alone versus nivolumab + DC vaccination prior to planned surgical resection for both groups. We administered nivolumab 3 mg/kg IV q2weeks for 8 weeks followed by surgery and planned continuation of nivolumab. For the group receiving nivolumab + DC vaccination, we administered 3 vaccines before surgical resection with both groups receiving 5 planned post-resection DC vaccines. Primary endpoint was safety assessment using NCI-CTCAE 4.03. Results: We enrolled 6 subjects (4: GBM, 1: anaplastic astrocytoma, 1: anaplastic oligodendroglioma) with 3 receiving nivolumab alone and 3 receiving nivolumab + DC vaccination. Age range was 45-63 years subjects. We documented similar adverse events in both groups with most common grade 1-2 toxicities being fatigue (2 subjects, nivolumab alone) and thrombocytopenia (2 subjects, nivolumab + DC vaccine). Grade 4 toxicities included wound infection (2 subjects, nivolumab + DC vaccine) and meningitis (1 subject, nivolumab + DC vaccine). While we designed the study to enroll 66 subjects, we terminated the study early in light of CheckMate 143 phase III data showing nivolumab did not improve overall survival in recurrent GBM. Conclusions: Safety of nivolumab + DC vaccination in recurrent HGG is similar to nivolumab alone. Continued evaluation of new therapeutics including immunotherapy is underway for this patient population. Clinical trial information: NCT02529072.

Monocytes outperform ex vivo generated dendritic cells as cellular vaccines to trigger cytotoxic T lymphocyte responses against cancer in pre-clinical models

Conventional dendritic cell (DC) vaccines using ex vivo generated DC have been widely tested in clinical trials in the treatment of human cancers. These DC vaccines have often displayed limited efficacy despite a complex manufacturing process. Although the efficacy of DC vaccines is generally thought to depend on their antigen-presenting cell function, several lines of evidence suggest that, instead of directly presenting antigen (Ag) to naïve T cells, administered DC trigger cytotoxic T lymphocyte (CTL) responses in vivo mainly by transferring Ag to lymphoid-resident conventional DC (cDC). We tested here whether monocytes, known to transfer Ag to cDC in vivo, can be directly loaded with tumor Ag to trigger robust anti-tumor CTL responses. We found that IV administered monocytes loaded with protein or peptide Ag triggered stronger Ag-specific CTL responses than conventional adjuvant-based and DC vaccines. In several murine cancer models, including intra-cranial glioblastoma, we showed that monocyte vaccination suppressed tumor growth better than conventional adjuvant-based, GVAX and DC vaccines. Such anti-tumor activities could be further enhanced with immune checkpoint inhibition. Ag-loaded monocytes did not directly activate naïve CD8+T cells. Instead, they formed stable physical contacts with and transferred Ag to splenic CD8+cDC. This Ag transfer required the formation of connexin 43-containing gap junctions between monocytes and CD8+cDC. Our findings demonstrated that gap junctions are an efficient Ag transfer pathway in vivo between monocytes and splenic CD8+cDC and suggested that IV administered Ag-loaded monocytes may serve as a simple and efficacious cellular vaccine platform for the treatment of human cancers.

MTAP Loss Promotes Stemness in Glioblastoma and Confers Unique Susceptibility to Purine Starvation

Homozygous deletion of methylthioadenosine phosphorylase (MTAP) is one of the most frequent genetic alterations in glioblastoma (GBM), but its pathologic consequences remain unclear. In this study, we report that loss of MTAP results in profound epigenetic reprogramming characterized by hypomethylation of PROM1/CD133-associated stem cell regulatory pathways. MTAP deficiency promotes glioma stem-like cell (GSC) formation with increased expression of PROM1/CD133 and enhanced tumorigenicity of GBM cells and is associated with poor prognosis in patients with GBM. As a combined consequence of purine production deficiency in MTAP-null GBM and the critical dependence of GSCs on purines, the enriched subset of CD133⁺ cells in MTAP-null GBM can be effectively depleted by inhibition of de novo purine synthesis. These findings suggest that MTAP loss promotes the pathogenesis of GBM by shaping the epigenetic landscape and stemness of GBM cells while simultaneously providing a unique opportunity for GBM therapeutics. SIGNIFICANCE: This study links the frequently mutated metabolic enzyme MTAP to dysregulated epigenetics and cancer cell stemness and establishes MTAP status as a factor for consideration in characterizing GBM and developing therapeutic strategies.

Single-institution retrospective review of patients with recurrent glioblastoma treated with bevacizumab in clinical practice

BACKGROUND AND AIMS

This retrospective review of patients with recurrent glioblastoma treated at the Preston Robert Tisch Brain Tumor Center investigated treatment patterns, survival, and safety with bevacizumab in a real-world setting.

METHODS

Adult patients with glioblastoma who initiated bevacizumab at disease progression between January 1, 2009, and May 14, 2012, were included. A Kaplan-Meier estimator was used to describe overall survival (OS), progression-free survival (PFS), and time to greater than or equal to 20% reduction in Karnofsky Performance Status (KPS). The effect of baseline demographic and clinical factors on survival was examined using a Cox proportional hazards model. Adverse event (AE) data were collected.

RESULTS

Seventy-four patients, with a median age of 59 years, were included in this cohort. Between bevacizumab initiation and first failure, defined as the first disease progression after bevacizumab initiation, biweekly bevacizumab and bevacizumab/irinotecan were the most frequently prescribed regimens. Median duration of bevacizumab treatment until failure was 6.4 months (range, 0.5-58.7). Median OS and PFS from bevacizumab initiation were 11.1 months (95% confidence interval [CI], 7.3-13.4) and 6.4 months (95% CI, 3.9-8.5), respectively. Median time to greater than or equal to 20% reduction in KPS was 29.3 months (95% CI, 13.8-∞). Lack of corticosteroid usage at the start of bevacizumab therapy was associated with both longer OS and PFS, with a median OS of 13.2 months (95% CI, 8.6-16.6) in patients who did not initially require corticosteroids versus 7.2 months (95% CI, 4.8-12.5) in those who did (P = 0.0382, log-rank), while median PFS values were 8.6 months (95% CI, 4.6-9.7) and 3.7 months (95% CI, 2.7-6.6), respectively (P = 0.0243, log-rank). Treatment failure occurred in 70 patients; 47 of whom received salvage therapy, and most frequently bevacizumab/carboplatin (7/47; 14.9%). Thirteen patients (18%) experienced a grade 3 AE of special interest for bevacizumab.

CONCLUSIONS

Treatment patterns and outcomes for patients with recurrent glioblastoma receiving bevacizumab in a real-world setting were comparable with those reported in prospective clinical trials.

The effect of adoptive transfer of ex vivo activated T cells on the efficacy and tumor penetrance of intravenously-administered CD3-engaging bispecific antibody

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Background: Activated T cells are known to traffic throughout the body including past the blood-brain barrier where they perform routine immune surveillance. Whether activated T cells can be used to enhance the efficacy and delivery of intravenously-administered, immunotherapeutic antibodies has yet to be explored. Methods: To examine efficacy, T cell migration and antibody delivery in vivo, the invasive murine glioma, CT-2A-EGFRvIII, was implanted orthotopically in human CD3 transgenic mice. Cohorts of mice were given vehicle or 1x107 non-specifically activated, syngeneic T cells intravenously. Beginning the subsequent day, groups were treated with daily intravenous infusions of human-CD3-binding, tumor-lysis-inducing bispecific antibody (hEGFRvIII-CD3 bi-scFv) or control bispecific antibody. To block T cell extravasation, cohorts received natalizumab or isotype control via intraperitoneal injection every other day beginning on the day of adoptive cell transfer. T cell migration was assessed using whole body bioluminescence imaging of activated T cells transduced to express firefly luciferase. Bispecific antibody biodistribution was assessed using PET-CT imaging of iodine-124 labeled antibody. Results: Following intravenous administration, ex vivo activated T cells tracked to invasive, syngeneic, orthotopic glioma, reaching maximal levels on average four days following adoptive transfer. Administration of ex vivo activated T cells enhanced bispecific antibody efficacy causing a statistically significant increase in survival (p = 0.007) with 80% long-term survivors. Treatment with the T cell extravasation blocking molecule natalizumab abrogated the increase in efficacy to levels observed in cohorts that did not receive adoptive transfer of activated T cells (p = 0.922). Pre-administration with ex vivo activated T cells produced a statistically significant increase in tumor penetrance of radiolabeled bispecific antibody (p = 0.023). Conclusions: Adoptive transfer of non-specifically activated T cells enhances the efficacy and tumor penetrance of intravenously-administered CD3-binding bispecific antibody.

Brain Tumor Microenvironment and Host State: Implications for Immunotherapy

Glioblastoma (GBM) is a highly lethal brain tumor with poor responses to immunotherapies that have been successful in more immunogenic cancers with less immunosuppressive tumor microenvironments (TME). The GBM TME is uniquely challenging to treat due to tumor cell-extrinsic components that are native to the brain, as well as tumor-intrinsic mechanisms that aid in immune evasion. Lowering the barrier of immunosuppression by targeting the genetically stable tumor stroma presents opportunities to treat the tumor in a way that circumvents the complications of targeting a constantly mutating tumor with tumor antigen-directed therapies. Tumor-associated monocytes, macrophages, and microglia are a stromal element of particular interest. Macrophages and monocytes compose the bulk of infiltrating immune cells and are considered to have protumor and immunosuppressive effects. Targeting these cells or other stromal elements is expected to convert what is considered the "cold" TME of GBM to a more "hot" TME phenotype. This conversion could increase the effectiveness of what have become conventional frontline immunotherapies in GBM-creating opportunities for better treatment through combination therapy.