The safety and accuracy of intratumoral catheter placement to infuse viral immunotherapies in children with malignant brain tumors: a multi-institutional study

OBJECTIVE

Relatively little is known about the safety and accuracy of catheter placement for oncolytic viral therapy in children with malignant brain tumors. Accordingly, this study combines data from two phase I clinical trials that employed viral immunotherapy across two institutions to describe the adverse event profile, safety, and accuracy associated with the stereotactic placement and subsequent removal of intratumoral catheters.

METHODS

Children with progressive/recurrent supratentorial malignant tumors were enrolled in two clinical trials (NCT03043391 and NCT02457845) and treated with either the recombinant polio:rhinovirus (lerapolturev) or the genetically modified oncolytic herpesvirus (G207). Age, sex, race, tumor diagnosis, and tumor location were analyzed. Events related to the catheter placement or removal were categorized. A catheter that was either pulled back or could not be used was defined as "misplaced." Neuronavigation software was used to analyze the accuracy of catheter placement for NCT03043391. Descriptive statistics were performed.

RESULTS

Nineteen patients were treated across the two completed trials with a total of 49 catheters. The mean ± SD (range) age was 14.1 ± 3.6 (7-19) years. All tumors were grade 3 or 4 gliomas. Nonlobar catheter tip placement included the corpus callosum, thalamus, insula, and cingulate gyrus. Six of 19 patients (31.6%) had minor hemorrhage noted on CT; however, no patients were symptomatic and/or required intervention related to these findings. One of 19 patients had a delayed CSF leak after catheter removal that required oversewing of the surgical site. No patients developed infection or a neurological deficit. In 7 patients with accuracy data, the mean ± SD distance of the planned trajectory (PT) to the catheter tip was 1.57 ± 1.6 mm, the mean angle of the PT to the catheter was 2.43° ± 2.1°, and the greatest distance of PT to the catheter in the parallel plane was 1.54 ± 1.5 mm. Three of 49 (6.1%) catheters were considered misplaced.

CONCLUSIONS

Although instances of minor hemorrhage were encountered, they were clinically asymptomatic. One of 49 catheters required intervention for a CSF leak. Congruent with previous studies in the literature, the stereotactic placement of catheters in these pediatric tumor patients was accurate with approximately 95% of catheters having been adequately placed.

Maternal Prenatal Use of Alcohol, Tobacco, and Illicit Drugs and Associations with Childhood Cancer Subtypes

BACKGROUND

The association between childhood cancer risk and maternal prenatal substance use/abuse remains uncertain due to modest sample sizes and heterogeneous study designs.

METHODS

We surveyed parents of children with cancer regarding maternal gestational use of tobacco, alcohol, and illicit drugs, using a Likert-type scale, and demographic, perinatal, and clinical variables. Multivariable log-Poisson regression assessed differences in frequency of prenatal substance use across fifteen childhood cancer subtypes, adjusting for birthweight, gestational age, and demographic factors.

RESULTS

Respondents from 3,145 unique families completed the survey (92% biological mothers). A minority reported gestational use of tobacco products (14%), illicit drugs including marijuana or cocaine (4%), or more than a moderate amount of alcohol (2%). Prenatal illicit drug use was associated with increased prevalence of intracranial embryonal tumors [prevalence ratio (PR) = 1.94; confidence interval [CI], 1.05-3.58], including medulloblastoma (PR = 1.82) and supratentorial primitive neuroectodermal tumors (PNET; PR = 2.66), and was also associated with retinoblastoma (PR = 3.11; CI, 1.20-8.08). Moderate to heavy alcohol consumption was strongly associated with elevated prevalence of non-Hodgkin lymphoma (PR = 5.94; CI, 1.84-19.21). Prenatal smoking was not associated with elevated prevalence of any childhood cancer subtype.

CONCLUSIONS

We identify novel associations between illicit drug use during pregnancy and increased prevalence of nonglioma central nervous system tumors, including medulloblastoma, supratentorial PNETs, and retinoblastoma. Gestational exposure to alcohol was positively associated with non-Hodgkin lymphoma.

IMPACT

Although alcohol and tobacco use during pregnancy has declined, gestational cannabis use has risen. Investigating its impact on neurodevelopment and brain tumorigenesis is vital, with important implications for childhood cancer research and public health education.

The type II RAF inhibitor tovorafenib in relapsed/refractory pediatric low-grade glioma: the phase 2 FIREFLY-1 trial

BRAF genomic alterations are the most common oncogenic drivers in pediatric low-grade glioma (pLGG). Arm 1 (n = 77) of the ongoing phase 2 FIREFLY-1 (PNOC026) trial investigated the efficacy of the oral, selective, central nervous system-penetrant, type II RAF inhibitor tovorafenib (420 mg m-2 once weekly; 600 mg maximum) in patients with BRAF-altered, relapsed/refractory pLGG. Arm 2 (n = 60) is an extension cohort, which provided treatment access for patients with RAF-altered pLGG after arm 1 closure. Based on independent review, according to Response Assessment in Neuro-Oncology High-Grade Glioma (RANO-HGG) criteria, the overall response rate (ORR) of 67% met the arm 1 prespecified primary endpoint; median duration of response (DOR) was 16.6 months; and median time to response (TTR) was 3.0 months (secondary endpoints). Other select arm 1 secondary endpoints included ORR, DOR and TTR as assessed by Response Assessment in Pediatric Neuro-Oncology Low-Grade Glioma (RAPNO) criteria and safety (assessed in all treated patients and the primary endpoint for arm 2, n = 137). The ORR according to RAPNO criteria (including minor responses) was 51%; median DOR was 13.8 months; and median TTR was 5.3 months. The most common treatment-related adverse events (TRAEs) were hair color changes (76%), elevated creatine phosphokinase (56%) and anemia (49%). Grade ≥3 TRAEs occurred in 42% of patients. Nine (7%) patients had TRAEs leading to discontinuation of tovorafenib. These data indicate that tovorafenib could be an effective therapy for BRAF-altered, relapsed/refractory pLGG. ClinicalTrials.gov registration: NCT04775485 .

A Pilot Study Omitting Radiation in the Treatment of Children with Newly Diagnosed Wnt-Activated Medulloblastoma

PURPOSE

Treatment of wingless (WNT)-activated medulloblastoma (WNT+MB) with surgery, irradiation (XRT), and chemotherapy results in excellent outcomes. We studied the efficacy of therapy de-intensification by omitting XRT entirely in children with WNT+MB.

PATIENTS AND METHODS

Tumors were molecularly screened to confirm the diagnosis of WNT+MB. Eligible children were treated within 31 days following surgery with nine cycles of adjuvant chemotherapy per ACNS0331. No XRT was planned. The primary endpoint was the occurrence of relapse, progression, or death in the absence of XRT within the first two years after study enrollment. Four events in the first 10 evaluable patients would result in early study closure.

RESULTS

Fourteen children were prescreened, and nine met the protocol definition of WNT+MB. Six of the nine eligible patients consented to protocol therapy, and five completed planned protocol therapy. The first two children enrolled relapsed shortly after therapy completion with local and leptomeningeal recurrences. The study was closed early due to safety concerns. Both children are surviving after XRT and additional chemotherapy. A third child relapsed at completion of therapy but died of progressive disease 35 months from diagnosis. Two children finished treatment but immediately received post-treatment XRT to guard against early relapse. The final child's treatment was aborted in favor of a high-dose therapy/stem cell rescue approach. Although OS at 5 years is 83%, no child received only planned protocol therapy, with all receiving eventual XRT and/or alternative therapy.

CONCLUSIONS

Radiotherapy is required to effectively treat children with WNT-altered medulloblastoma. See related commentary by Gottardo and Gajjar, p. 4996.

Recombinant polio-rhinovirus immunotherapy for recurrent paediatric high-grade glioma: a phase 1b trial

BACKGROUND

Outcomes of recurrent paediatric high-grade glioma are poor, with a median overall survival of less than 6 months. Viral immunotherapy, such as the polio-rhinovirus chimera lerapolturev, is a novel approach for treatment of recurrent paediatric high-grade glioma and has shown promise in adults with recurrent glioblastoma. The poliovirus receptor CD155 is ubiquitously expressed in malignant paediatric brain tumours and is a treatment target in paediatric high-grade glioma. We aimed to assess the safety of lerapolturev when administered as a single dose intracerebrally by convection enhanced delivery in children and young people with recurrent WHO grade 3 or grade 4 glioma, and to assess overall survival in these patients.

METHODS

This phase 1b trial was done at the Duke University Medical Center (Durham, NC, USA). Patients aged 4-21 years with recurrent high-grade malignant glioma (anaplastic astrocytoma, glioblastoma, anaplastic oligoastrocytoma, anaplastic oligodendroglioma, or anaplastic pleomorphic xanthoastrocytoma) or anaplastic ependymoma, atypical teratoid rhabdoid tumour, or medulloblastoma with infusible disease were eligible for this study. A catheter was tunnelled beneath the scalp for a distance of at least 5 cm to aid in prevention of infection. The next day, lerapolturev at a dose of 5 × 107 median tissue culture infectious dose in 3 mL infusate loaded in a syringe was administered via a pump at a rate of 0·5 mL per h as a one-time dose. The infusion time was approximately 6·5 h to compensate for volume of the tubing. The primary endpoint was the proportion of patients with unacceptable toxic effects during the 14-day period after lerapolturev treatment. The study is registered with ClinicalTrials.gov, NCT03043391.

FINDINGS

Between Dec 5, 2017, and May 12, 2021, 12 patients (11 unique patients) were enrolled in the trial. Eight patients were treated with lerapolturev. The median patient age was 16·5 years (IQR 11·0-18·0), five (63%) of eight patients were male and three (38%) were female, and six (75%) of eight patients were White and two (25%) were Black or African American. The median number of previous chemotherapeutic regimens was 3·50 (IQR 1·25-5·00). Six of eight patients had 26 treatment-related adverse events attributable to lerapolturev. There were no irreversible (ie, persisted longer than 2 weeks) treatment-related grade 4 adverse events or deaths. Treatment-related grade 3 adverse events included headaches in two patients and seizure in one patient. Four patients received low-dose bevacizumab on-study for treatment-related peritumoural inflammation or oedema, diagnosed by both clinical symptoms plus fluid-attenuated inversion recovery MRI. The median overall survival was 4·1 months (95% CI 1·2-10·1). One patient remains alive after 22 months.

INTERPRETATION

Convection enhanced delivery of lerapolturev is safe enough in the treatment of recurrent paediatric high-grade glioma to proceed to the next phase of trial.

FUNDING

Solving Kids Cancer, B+ Foundation, Musella Foundation, and National Institutes of Health.

Intratumor childhood vaccine-specific CD4+ T-cell recall coordinates antitumor CD8+ T cells and eosinophils

BACKGROUND

Antitumor mechanisms of CD4⁺ T cells remain crudely defined, and means to effectively harness CD4⁺ T-cell help for cancer immunotherapy are lacking. Pre-existing memory CD4⁺ T cells hold potential to be leveraged for this purpose. Moreover, the role of pre-existing immunity in virotherapy, particularly recombinant poliovirus immunotherapy where childhood polio vaccine specific immunity is ubiquitous, remains unclear. Here we tested the hypothesis that childhood vaccine-specific memory T cells mediate antitumor immunotherapy and contribute to the antitumor efficacy of polio virotherapy.

METHODS

The impact of polio immunization on polio virotherapy, and the antitumor effects of polio and tetanus recall were tested in syngeneic murine melanoma and breast cancer models. CD8⁺ T-cell and B-cell knockout, CD4⁺ T-cell depletion, CD4⁺ T-cell adoptive transfer, CD40L blockade, assessments of antitumor T-cell immunity, and eosinophil depletion defined antitumor mechanisms of recall antigens. Pan-cancer transcriptome data sets and polio virotherapy clinical trial correlates were used to assess the relevance of these findings in humans.

RESULTS

Prior vaccination against poliovirus substantially bolstered the antitumor efficacy of polio virotherapy in mice, and intratumor recall of poliovirus or tetanus immunity delayed tumor growth. Intratumor recall antigens augmented antitumor T-cell function, caused marked tumor infiltration of type 2 innate lymphoid cells and eosinophils, and decreased proportions of regulatory T cells (Tregs). Antitumor effects of recall antigens were mediated by CD4⁺ T cells, limited by B cells, independent of CD40L, and dependent on eosinophils and CD8⁺ T cells. An inverse relationship between eosinophil and Treg signatures was observed across The Cancer Genome Atlas (TCGA) cancer types, and eosinophil depletion prevented Treg reductions after polio recall. Pretreatment polio neutralizing antibody titers were higher in patients living longer, and eosinophil levels increased in the majority of patients, after polio virotherapy.

CONCLUSION

Pre-existing anti-polio immunity contributes to the antitumor efficacy of polio virotherapy. This work defines cancer immunotherapy potential of childhood vaccines, reveals their utility to engage CD4⁺ T-cell help for antitumor CD8⁺ T cells, and implicates eosinophils as antitumor effectors of CD4⁺ T cells.

Assisted reproductive technology and association with childhood cancer subtypes

OBJECTIVES

To investigate the association between assisted reproductive technology (ART) use and childhood cancer subtype.

STUDY DESIGN

We deployed a cross-sectional survey of 1701 parents of children with cancer about their ART use, demographics, and gestational and perinatal factors. Multivariable logistic regression modeled the association between ART use, birthweight and multiple gestation status with childhood cancer, by subtype.

RESULTS

ART use was highest among children with osteosarcoma relative to children with other cancer types, and this association was statistically significant in multivariable models (OR = 4.4; 95% CI = 1.7-11.3; p = 0.0020). ART use was also elevated among children with hepatoblastoma, but this relationship appeared to be due to the strong associations between ART use and lower birthweight in our sample. No specific ART modality appeared to drive these associations. In univariate models, multiple gestation was associated with a 2.7-fold increased odds of hepatoblastoma (OR = 2.71; 95% CI = 1.14-6.42; p = 0.02) and a 1.6-fold increased odds of neuroblastoma (OR = 1.62; 95% CI = 1.03-2.54; p = 0.03), but these associations were not retained in multivariable models.

CONCLUSIONS

Associations between ART use and hepatoblastoma risk may be attributable to birthweight, a known hepatoblastoma risk factor. ART use may also be associated with osteosarcoma, independent of birthweight, an association not previously observed in studies limited to cancers diagnosed before adolescence. Evaluating long-term health outcomes in children conceived by ART, throughout adolescence and potentially into adulthood, appears warranted.

Pediatric Central Nervous System Cancers, Version 2.2023, NCCN Clinical Practice Guidelines in Oncology

Central nervous system (CNS) cancers account for approximately one quarter of all pediatric tumors and are the leading cause of cancer-related death in children. More than 4,000 brain and CNS tumors are diagnosed each year in children and teens, and the incidence rate has remained stagnant in recent years. The most common malignant pediatric CNS tumors are gliomas, embryonal tumors consisting of predominately medulloblastomas, and germ cell tumors. The inaugural version of the NCCN Guidelines for Pediatric Central Nervous System Cancers focuses on the diagnosis and management of patients with pediatric diffuse high-grade gliomas. The information contained in the NCCN Guidelines is designed to help clinicians navigate the complex management of pediatric patients with diffuse high-grade gliomas. The prognosis for these highly aggressive tumors is generally poor, with 5-year survival rates of <20% despite the use of combined modality therapies of surgery, radiation therapy and systemic therapy. Recent advances in molecular profiling has expanded the use of targeted therapies in patients whose tumors harbor certain alterations. However, enrollment in a clinical trial is the preferred treatment for eligible patients.

CTIM-15. RESULTS OF A PHASE IB TRIAL OF RECOMBINANT POLIO:RHINOVIRUS IMMUNOTHERAPY FOR RECURRENT PEDIATRIC HIGH GRADE GLIOMA

BACKGROUND

Outcomes of recurrent pediatric high grade glioma (pHHG) are poor with a median overall survival (OS) of &lt; 6 months. Viral immunotherapy such as the polio:rhinovirus chimera, PVSRIPO, is a novel treatment approach for recurrent pHHG. PVSRIPO is genetically engineered to prevent neurovirulence. In adults with recurrent glioblastoma treated with PVSRIPO, 21% survived &gt; 36 months. The poliovirus receptor, CD155, is ubiquitously expressed in malignant pediatric brain tumors including pHHG.

METHODS

The primary objective of this Phase 1b clinical trial was to evaluate the safety and feasibility of PVSRIPO for recurrent pHGG. PVSRIPO was given at a single dose, 5x107 50% tissue-culture infectious dose (TCID50) administered by convection enhanced delivery (CED) to children with biopsy-confirmed recurrent pHHG between ≥ 1 and ≤ 5.5 in diameter. 3 mL of PVSRIPO was delivered at 0.5 mL/hr via a single catheter.

RESULTS

Eight patients were treated with PVSRIPO including 5 males and 3 females with a median age of 16.5 (range 9-19). Six patients had recurrent glioblastoma, 2 had recurrent anaplastic astrocytoma. The median number of previous recurrences prior to enrollment was 3.5 (range 1-5). Four patients received bevacizumab on-study for treatment-related peritumoral inflammation/edema. Six of 8 patients experienced 26 treatment related adverse events (AEs) possibly, probably, or definitely related to protocol treatment. There were no Grade 4 or 5 AEs. There were 3 Grade 3 AEs: 2 headaches and 1 seizure. There were no AEs related to biopsy or CED catheter insertion/removal. Median OS was 4.13 months (range 1.23-NA). One patient is currently alive at &gt; 21 months. Monocyte and T cell inflammatory phenotypes and total CD4+ T cells were increased in peripheral blood after treatment.

CONCLUSIONS

CED of PVSPRIO is both safe and feasible for the treatment of recurrent pHHG. Histologic correlative results will also be presented.

EPID-22. MATERNAL USE OF TOBACCO, ALCOHOL, AND ILLICIT DRUGS DURING PREGNANCY AND ASSOCIATION WITH CHILDHOOD CANCER SUBTYPES

OBJECTIVE

To investigate the association between maternal prenatal substance use/abuse and diagnosis of childhood cancer subtypes, including childhood brain tumors. To minimize recall bias, we employed a case-only study design in which all respondents had a child diagnosed with cancer. STUDY DESIGN: We deployed a cross-sectional, case-only survey of parents of children diagnosed with cancer regarding prenatal smoking, drinking, and illicit drug use behaviors (scored on 1-7 Likert scale), demographic, gestational, and perinatal factors. Multivariable logistic regression assessed associations of gestational smoking, alcohol, and illicit drug use with childhood cancer subtypes, adjusting for child sex, race/ethnicity, birthweight, and household income.

RESULTS

3145 families completed the survey, including 232 with astrocytoma (grades I-IV, including DIPG) and 210 with an embryonal CNS tumor (medulloblastoma, AT/RT, PNET). A minority reported ever smoking tobacco products during pregnancy (Likert score ≥ 2; 14%), ever consuming illicit drugs during pregnancy (Likert score ≥ 2; 4%), or drinking more than a moderate amount of alcohol during pregnancy (Likert score ≥ 5; 2%). Prenatal smoking was associated with lower odds of rhabdomyosarcoma (OR=0.48, P=0.023) and moderately elevated odds of non-Hodgkin lymphoma (OR = 1.52, P=0.098) and AML (OR = 1.52, P = 0.083). Moderate to heavy alcohol consumption was unassociated with cancer subtypes. Prenatal illicit drug use was associated with increased odds of retinoblastoma (OR = 5.03, 95% CI = 1.73-14.7, P = 0.003) and CNS embryonal tumors (OR = 2.56, 95% CI = 1.32-4.99, P = 0.006), with similar effects across subgroups of medulloblastoma, AT/RT, and supratentorial PNETs.

CONCLUSIONS

Associations between self-reported use of alcohol, tobacco, and illicit drugs during pregnancy and risk of childhood cancer is often biased by differential misreporting among parents of affected children. Consistent with prior reports, we observe elevated odds of hematologic malignancies in association with gestational tobacco smoke exposure and novel association between maternal illicit drug use during pregnancy and elevated odds of retinoblastoma and CNS embryonal tumors.

CTNI-68. FIREFLY-1 (PNOC026): PHASE 2 STUDY OF PAN-RAF INHIBITOR TOVORAFENIB IN PEDIATRIC AND YOUNG ADULT PATIENTS WITH RAF-ALTERED RECURRENT OR PROGRESSIVE LOW-GRADE GLIOMA OR ADVANCED SOLID TUMORS

BACKGROUND

RAF alterations are oncogenic drivers found in most pediatric low-grade gliomas (LGGs). Tovorafenib is an investigational, oral, selective, CNS-penetrant, small molecule, type II pan‑RAF inhibitor.

METHODS

FIREFLY-1 (NCT04775485) is a multicenter phase 2 study evaluating the safety and efficacy of tovorafenib monotherapy. Registrational arm 1 enrolled patients with recurrent/progressive LGG harboring an activating BRAF alteration. Patients aged 6 months–25 years who progressed following ≥ 1 prior line of systemic therapy were eligible. Tovorafenib 420 mg/m2 (≤ 600 mg) was administered weekly (tablet or liquid suspension formulation) until progression or for ≥ 26, 28-day cycles. The primary endpoint (arm 1) was overall response rate, as defined by RANO criteria, per independent review.

RESULTS

As of April 14, 2022, 25 patients were enrolled to arm 1 and had ≥ 6 months of follow-up. Median age at enrollment was 8 years (range 3–18). Most patients had astrocytomas (92%), 48% with optic pathway involvement. Patients were heavily pretreated (56% with ≥ 3 prior lines of therapy), and 72% previously received MAPK pathway-targeted agents. Tumors harbored BRAF fusions (84%) or BRAF V600E mutations (16%). Per independent assessment, partial responses (1 unconfirmed) were seen in 14 (64%) of 22 evaluable patients, with 6 additional patients having stable disease, and a clinical benefit rate of 91%. Responses were achieved in tumors with BRAF fusions and V600E mutations. Most treatment-emergent adverse events (AEs) were grade 1 or 2 (96%). The most common grade ≥ 3 AEs were anemia (12%), vomiting, increased blood creatinine phosphokinase and maculopapular rash (8% each). Seven patients (28%) required dose modification for treatment-related AEs; no patients discontinued tovorafenib due to AEs. Updated results, including efficacy per RAPNO assessments will be presented.

CONCLUSIONS

Tovorafenib was generally well tolerated and showed encouraging evidence of antitumor activity in children with pretreated BRAF-altered LGG.

CTIM-23. DOSE ESCALATION TRIAL OF FC-ENGINEERED ANTI-CD40 MONOCLONAL ANTIBODY (2141-V11) ADMINISTERED INTRATUMORALLY WITH D2C7-IT VIA CONVECTION-ENHANCED DELIVERY (CED) FOR RECURRENT MALIGNANT GLIOMAS (RMGS)

BACKGROUND

D2C7-IT, a novel immunotoxin-based cytotoxic therapy, targets epidermal growth factor receptor (EGFR) and mutant EGFR variant III. In preclinical studies, D2C7-IT kills tumor cells and prolongs survival, but is unable to generate cures in all animals. We hypothesized that immunosuppression in glioblastoma limits D2C7-IT efficacy. Eliminating glioblastoma immunosuppression via CD40 co-stimulation is anticipated to enhance D2C7-IT-induced antitumor responses. In murine glioma models, CED of D2C7-IT+αCD40 generated cures and long-term tumor-specific adaptive immunity. Hence, we are conducting a phase 1 trial of D2C7-IT+2141-V11 (αhuman-CD40) administered via CED in rMG patients.

METHODS

Eligibility includes adult patients with solitary supratentorial rMG (WHO grade 3/4); ≥ 4 weeks after chemotherapy, bevacizumab, or study drug; adequate organ function; and KPS ≥ 70%. Cohorts of 3 patients are treated with increasing doses of 2141-V11 to determine the maximum tolerated dose when administered sequentially following D2C7-IT (166,075 ng) via CED at 0.5 mL/hr. Five dose levels (DLs) are evaluated (2141-V11 at: #1: 0.70 mg; #2: 2.0 mg; #2**: 3.0 mg #2*: 4.0 mg; #3: 7.0 mg).

RESULTS

As of May 29, 2022, 13 patients were treated (3 patients on DL1, DL2, and DL2**; 2 patients on DL3 and DL2*). No dose-limiting toxicities were observed; however, lower DLs were added due to higher frequency of adverse events (AEs) expected with D2C7-IT+2141-V11 with DL3 and DL2* (fever, neurologic symptoms). All patients remain alive 0.7-10.6 months after therapy. Grade ≥ 2 AEs due to D2C7-IT+2141-V11 include: headache (grade 3, n = 1; grade 2, n = 4); pyramidal tract disorder (grade 3, n = 1; grade 2, n = 2); paresthesia (grade 3, n = 1); dysphasia (grade 3, n = 1); seizures (grade 2; n = 2); fever (grade 2; n = 2); and one each of grade 2 depressed level of consciousness, fatigue, and concentration impairment. Enrollment is ongoing.

CONCLUSIONS

Intratumoral administration of D2C7-IT+2141-V11 via CED is safe, encouraging efficacy results are observed.

Incidence and survival of choroid plexus tumors in the United States

Background

There are limited data available on incidence and survival of patients with choroid plexus tumors (CPT). This study provides the most current epidemiological analysis of choroid plexus tumors from 2004 to 2017 in the United States.

Methods

Data on 2013 patients with CPT were acquired from the Central Brain Tumor Registry of the United States in collaboration with the Centers for Disease Control and Prevention (CDC) and the National Cancer Institute, from 2004 to 2017. CPT cases were classified by the following pathological subtypes: choroid plexus papilloma (CPP), atypical choroid plexus papilloma (aCPP), and choroid plexus carcinoma (CPC). Frequencies and age-adjusted incidence rates (AAIR) per 100 000 and rate ratios per 100 000 (IRR) were reported for age, sex, race, and ethnicity for each pathological subtype with 95% confidence intervals (95% CI). Using CDC's National Program of Cancer Registries survival database, survival curves and hazard ratios (HRs) evaluated overall survival from 2001 to 2016.

Results

CPP had the highest overall incidence (AAIR: 0.034, 95% CI: 0.033-0.036), followed by CPC (AAIR: 0.008, 95% CI: 0.008-0.009) and aCPP (AAIR: 0.005, 95% CI: 0.005-0.006). Incidence was highest among children less than one year old among all subtypes (CPP AAIR: 0.278; aCPP AAIR: 0.140; CPC AAIR: 0.195), reducing as patients aged. Overall survival was worse among patients with CPC, being five times more likely to die compared to patients with CPP (HR: 5.23, 95% CI: 4.05-7.54, P < .001).

Conclusions

This analysis is the most current and comprehensive study in the US on the incidence and survival for CPT. Population based statistics provide critical information in understanding disease characteristics, which impact patient care and prognosis.

D2C7 CAR: A novel CAR T cell that simultaneously targets wildtype EGFR and its mutant isoform EGFRvIII for treatment of glioma

Brain tumors are the leading cause of cancer death in children and a significant cause of morbidity and mortality in adults. Conventional treatments are suboptimal, thus signifying the need for novel therapeutic strategies, such as immunotherapy. Chimeric antigen receptor (CAR) T cells represent a revolutionary class of immunotherapy, achieving considerable success in eliminating hematological cancers but generally failing to control solid tumors in part due to the lack of a suitably-expressed target antigen. Epidermal growth factor receptor (EGFR) is the most ubiquitous and homogeneous antigen on glial brain tumors, and EGFR-directed therapies have been hotly pursued. Moreover, the mutant EGFR variant, EGFRvIII, is present on a subset of pediatric and adult high grade gliomas, representing a targetable, tumor-specific antigen. Unfortunately, CAR T cells targeting EGFRvIII fail to treat tumors possessing as few as 5–10% EGFRvIII-negative cells due to antigen escape. Thus, a CAR T cell that can target both EGFR and EGFRvIII is expected to be superior to a CAR that targets EGFRvIII alone. In this study, we developed a novel third generation CAR T cell consisting of the D2C7scfv targeting moiety that binds a shared epitope between EGFR and EGFRvIII. This D2C7 CAR was able to specifically and potently kill tumor cells expressing wildtype EGFR or EGFRvIII. Importantly, D2C7 CAR significantly prolonged survival of mice bearing EGFR or EGFRvIII-expressing gliomas of both adult (U87) and pediatric (DAOY) origin. Toxicity experiments involving EGFR-expressing human skin grafts provided evidence that D2C7 CAR is safe and effective when administered intracranially to mice bearing intracranial tumors.

Epidemiology of pineoblastoma in the United States, 2000-2017

Background

Pineoblastoma (PB) is a rare malignant brain tumor originating in the pineal gland. Here, we provide a comprehensive epidemiological analysis of PB in the United States from 2000 to 2017.

Methods

Data on 1133 patients with PB were acquired from the Central Brain Tumor Registry of the United States, in collaboration with the Centers for Disease Control and Prevention and the National Cancer Institute, from 2000 to 2017. Age-adjusted incidence rates (AAIRs) per 100 000 and incidence rate ratios (IRRs) were reported for age, sex, race, and ethnicity. Using the National Program of Cancer Registries survival database, median survival and hazard ratios (HRs) were evaluated for overall survival from 2001 to 2016.

Results

Incidence was highest in ages 0-4 years (AAIR: 0.049, 95% CI: 0.042-0.056), decreasing as age increased. Incidence was higher among patients who are Black compared to patients who are White (IRR: 1.71, 95% CI: 1.48-1.98, P < .001), and was impacted by age at diagnosis, with Black-to-White incidence highest in children ages 5-9 years (IRR: 3.43, 95% CI: 2.36-4.94, P < .001). Overall survival was lower for males (HR: 1.39, 95% CI: 1.07-1.79, P = .013). All age groups, excluding those over 40, had improved survival compared to ages 0-4 years. Those who received surgical intervention had better survival compared to those who did not receive surgical treatment.

Conclusion

PB incidence is highest among children and patients who are Black, and there may be a potential interaction between these factors. Survival is worse among males, young children, and elderly adults, and those who received no surgery. Comprehensive, population-based statistics provide critical information on PB characteristics that could be useful in impacting patient care and prognosis.

CTIM-18. LUMINOS-101: INITIAL SAFETY AND TOLERABILITY OF PVSRIPO AND PEMBROLIZUMAB COMBINATION THERAPY IN RECURRENT GLIOBLASTOMA

BACKGROUND

Recurrent glioblastoma (rGBM) is rapidly fatal with current therapies. PVSRIPO is an intratumoral immunotherapy targeting CD155 on antigen-presenting and malignant cells of solid tumors. Preclinically, PVSRIPO treatment leads to systemic, tumor antigen-specific, polyfunctional T-cell–mediated anti-tumor response, predominately driven by type I/III interferons. This inflammatory signature generates anti-tumor immunity and upregulates the programmed death (PD)-1 immune checkpoint in the tumor microenvironment. Preclinical models (including GBM) have shown that PVSRIPO+anti-PD-1/L1 therapy was more efficacious than either agent alone, warranting further investigation.

METHODS

Adults with histologically confirmed rGBM (1-2 prior progressions), Karnofsky performance status (KPS) ≥70, and an active, supratentorial, contrast-enhancing lesion (1-5.5 cm), received PVSRIPO (5x107 TCID50) intratumorally via convection-enhanced delivery (Day 1), followed by 200 mg pembrolizumab IV at week 2, given every 3 weeks for up to 24 months, to evaluate the safety/efficacy of the combination. A safety lead-in period (n=3-6) with a minimum 21–28-day delay before treatment of subsequent patients was planned, with a data safety monitoring board (DSMB) evaluating safety/tolerability prior to expansion (up to N=30).

RESULTS

The first 3 patients enrolled (ages 55-60, KPS 90-100) all received PVSRIPO followed by pembrolizumab (1-5 cycles), as planned. At cutoff (26-106 days of follow-up), there were no dose-limiting toxicities, treatment-emergent (TE) serious adverse events (SAE), or TEAEs necessitating a delay in initial/subsequent pembrolizumab treatments. All patients experienced a related TEAE, all grade 1 or 2 in severity. One patient experienced an AE of special interest (peritumoral edema, resulting in headache and hemiparesis), successfully managed with low-dose bevacizumab and corticosteroids. The DSMB unanimously recommended the study proceed without modification.

CONCLUSIONS

Intratumoral PVSRIPO+pembrolizumab was reasonably well tolerated, warranting continued investigation of the safety and efficacy of this combination in patients with rGBM.

EXTH-59. GENERATION OF A THIRD GENERATION CAR T CELL THAT SIMULTANEOUSLY TARGETS WILDTYPE EGFR AND ITS MUTANT ISOFORM EGFRVIII FOR TREATMENT OF GLIOBLASTOMA

Glioblastoma (GBM) is the most aggressive primary brain cancer with a median survival of less than 16 months. This dire prognosis signifies the urgent need for improved treatment options, such as immunotherapy. Chimeric antigen receptor (CAR) T cells have helped revolutionize immunotherapy, achieving considerable success in eliminating hematological cancers but generally failing to control solid tumors. One major hindrance to CAR T cell success in solid tumors is tumor heterogeneity. Tumor-associated or tumor-specific antigens (TAA or TSA, respectively) are rarely expressed by all malignant cells within a tumor. As a specific example in GBM, the most prevalent TSA, EGFRvIII, is present in just 30% of tumors, and then on only 30-50% of cells. Our pre-clinical and clinical experiences with CAR T cells reveal that tumors possessing as few as 5-10% EGFRvIII-negative cells will easily escape EGFRvIII-targeted CARs. Tumor cells that lack EGFRvIII expression often overexpress the wildtype isoform of EGFR (EGFRwt). Notably, EGFR is absent on normal brain. Therefore, a superior approach would be to simultaneously target EGFRvIII and EGFRwt, an approach that would bypass EGFR heterogeneity in EGFRwt/EGFRvIII-expressing tumors. Here, we generated a third generation CAR using the D2C7 single-chain variable fragment (scFv) targeting moiety that recognizes an epitope present in EGFRwt and EGFRvIII. Initial in vitro characterization of D2C7 CAR validated the specificity and function of D2C7 CAR, as it potently killed murine cell lines engineered to express either EGFRwt or EGFRvIII, but not a cell line expressing neither. Concomitant IFN-γ release supported these conclusions. Additionally, D2C7 CAR killed the human-derived GBM cell line U87 and vIII-transfected U87, U87vIII. Importantly, intracranially-administered D2C7 CAR significantly prolonged survival of mice bearing orthotopic U87vIII or U87/U87vIII heterogeneous tumors compared to mock-treated controls. Altogether, these data provide evidence that D2C7 CAR T cells represent a viable therapeutic option for EGFRwt/EGFRvIII heterogeneous tumors.

INNV-31. NEURO-ONCOLOGY OUTPATIENT SATISFACTION IS MAINTAINED IN THE ERA OF COVID-19 TELEMEDICINE

INTRODUCTION

The use of telemedicine increased during the COVID-19 pandemic. However, the impact on patient satisfaction in the Neuro-oncology population is unknown. This quality improvement project compares outpatient satisfaction before and during the COVID-19 pandemic as well as in-person versus telemedicine platforms during the pandemic.

METHODS

We performed an IRB-exempt retrospective analysis of aggregate de-identified outpatient satisfaction scores among Neuro-oncology patients seen at The Preston Robert Tisch Brain Tumor Center (PRTBTC) at Duke University. The Clinician & Group Consumer Assessment of Healthcare Providers and Systems (CG-CAHPS) is a survey developed and distributed by Press Ganey Associates, and is the most widely used outpatient satisfaction survey in the United States. We compared pre-COVID-19 CG-CAHPS scores from patients who received in-person care at the PRBTC between April 2019 and March 2020 to COVID-19 pandemic CG-CAHPS scores (i.e. those who received either telemedicine or in-person care at the PRTBTC) from April 2020 to March 2021.

RESULTS

Approximately 1448 surveys were completed for both in-person and telemedicine visits. During the pandemic, 48.6% of surveys represented telemedicine, with monthly variations from 84.6% (April 2020) to 21.4% (March 2021). Patient satisfaction scores pre-COVID-19 were similar to those during the pandemic: overall provider rating from 0-10 (9.28 v 9.36), knowledge of medical history (96.9% v 95.4%), listens carefully (96.6% v 96.9%), shows respect (97.2% v 98.1%), and time spent (93.2% v 95.5%). During the COVID-19 pandemic, in-person and telemedicine demonstrate similar levels of satisfaction: overall provider rating from 0-10 (9.29 v 9.48), knowledge of medical history (94.9% v 96.1%), listens carefully (95.4% v 99.0%), shows respect (97.5% v 99.0%), and time spent (94.7% v 96.7%).

CONCLUSION

Outpatient satisfaction prior to and during the COVID-19 pandemic was similar. Patients reported similar satisfaction between in-person and telemedicine platforms. We support the ongoing use of telemedicine for outpatient Neuro-oncology.

CTIM-10. REPRODUCIBILITY OF CLINICAL TRIALS USING CMV-TARGETED DENDRITIC CELL VACCINES IN PATIENTS WITH GLIOBLASTOMA

INTRODUCTION

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 primary GBM. 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%).

CONCLUSION

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.

QOLP-28. COMPARING KNOWLEDGE OF AND BELIEFS ABOUT PALLIATIVE CARE AMONG NEURO-ONCOLOGY PATIENTS, CAREGIVERS, PROVIDERS AND A NATIONALLY-REPRESENTATIVE U.S. SAMPLE

INTRODUCTION

There is increasing recognition that palliative care (PC) can benefit patients with advanced cancers. However, early referral to PC is not yet a reality for patients diagnosed with a primary brain tumor. We hypothesize that lack of knowledge and/or misperceptions regarding PC by patients, caregivers, or their providers remain barriers.

METHODS

This is an IRB-exempt, one-time QR-accessible REDcap questionnaire administered to patients, caregivers, and providers at the Preston Robert Tisch Brain Tumor Center between September 2020 and May 2021. We administered 9 questions regarding knowledge and beliefs about PC from the Health Information National Trends Survey 5, Cycle 2: results of this nationally representative U.S. sample are publicly available and used for comparison.

RESULTS

We had 141 survey respondents: 25 providers, 59 patients, and 57 caregivers. The median patient and caregiver ages were 49 (21-74) and 50 years (24-73), respectively. Caregivers were more likely female (55.2 %) and identified as a spouse or domestic partner (58.2%). Providers, were equally distributed by years of experience. Compared to patients and caregivers, providers reported more baseline knowledge of PC (p&lt; 0.0001, p&lt; 0.0001) and better understood the role of PC in pain/symptom management (p=0.0038, p=0.0087) and social/emotional support (p=0.0044, p=0.0279). Interestingly, most providers (76.0%) disagreed with the statement “the goal of palliative care is to give patients more time at the end of life.” Compared to a general U.S. sample (n=1,162) our patients (n=39) were better informed in only 2 of 9 questions. Whereas, caregivers (n=48) were better informed in 6 of 9 questions.

CONCLUSION

Neuro-oncology providers were knowledgeable, but a minor gap in understanding the goal of PC was identified. Caregivers were overall more knowledgeable than patients. However, Neuro-oncology patients, had similar knowledge and beliefs compared to a nationally representative sample. PC interventions should prioritize filling knowledge gaps for Neuro-oncology patients.

QOLP-10. A LONGITUDINAL OBSERVATIONAL STUDY OF EXERCISE BEHAVIOR IN GLIOBLASTOMA PATIENTS TREATED WITH TUMOR-TREATING FIELDS

Glioblastoma (GBM) patients can use tumor-treating fields (TTFs) with adjuvant temozolomide (TMZ) to treat their disease. TTFs involve wearing transfixed transducers to the shaved scalp, and the transducers are wired to a battery pack that is either fixed or carried (weighing 2.7 pounds). EF-14 clinical trial did evaluate health-related quality of life with standardized patient-report outcome measures but did not measure exercise behavior. We sought to evaluate the exercise behavior of GBM patients using TTFs. We consented GBM patients who intended to use TTFs with adjuvant TMZ after completion of chemoradiation. After informed consent and before starting TTFs, patients completed a self-administered questionnaire, Godin Leisure-Time Exercise Questionnaire, to assess exercise behavior/physical function. To calculate our primary outcome of total exercise behavior, the frequency of exercise sessions per week within each intensity category was multiplied by the average reported duration, weighted by an estimate of the MET, summed across all intensities, and expressed as average MET-hr/wk. Prior work has defined that physical function can be compared as &lt; 9 MET-h/wk vs. ≥ 9 MET-h/wk. We evaluated at baseline and up to 24-week exercise behavior in patients with TTFs vs. historical controls not using TTFs. We enrolled 19 total GBM patients, with 14 proceeding to use TTFs. Of the 14 patients on TTFs, seven patients (50%) completed ≥ 9 MET-h/wk of exercise, and this level was maintained 8, 16, and 24 weeks after starting TTFs. Six months after the completion of chemoradiation, mean MET-h/wk was decreased in the TTFs group (n=6) (10.71 sd=7.06) vs. historical controls (n=38) (27.35 sd=46.94). TTFs did not interfere with exercise behavior in our GBM cohort, but when compared to GBM patients not utilizing TTFs, there could be a long-term impact on exercise behavior. More research is needed to evaluate exercise behavior in GBM patients using TTFs.

IMMU-06. TARGETING IDH1 MUTANT GRADE II RECURRENT GLIOMAS USING A PEPTIDE VACCINATION STRATEGY

INTRODUCTION

While primary GBM is largely heterogeneous and devoid of homogeneously expressed neoantigens, mutant IDH1 (R132H) is a uniformly expressed hallmark in &gt;70% of low grade gliomas. As such, IDH1 mutations represent a potentially valuable vaccination target.

METHODS

Here, we report an update on the immunogenicity results of the mutant IDH1 peptide vaccine alone and in combination with temozolomide (TMZ). In the phase I RESIST clinical trial (NCT02193347), patients with recurrent and resectable IDH1 R132H mutant grade 2 glioma received peptide vaccinations composed of 500 µg of mutant IDH1 peptide and 150 µg of GM-CSF mixed 1:1 with Montanide adjuvant prior to surgical resection. Vaccines 1, 2, and 3 were given 15 (+/-) 3 days apart. 7-12 days after vaccine 3, patients underwent standard of care tumor (SOC) resection. After resection, patients with grade 2 gliomas were given up to 15 doses of peptide vaccine in combination with TMZ regimens while patients with transformed grade 3 gliomas were given up to 15 doses of peptide vaccine in combination with SOC radiation therapy + TMZ regimens. T cell responses against the mutant peptide were measured after vaccine 3 using IFN-γ ELISPOT and intracellular flow cytometry for IL-2, TNFα,and IFNγ.

RESULTS

3/20 patients were taken off the study before completion of study related activities. 1/20 patients progressed before completion of all vaccines. Out of 134 total doses of vaccine delivered, only one dose generated a grade 2 or higher injection site reaction according to the CTCAE guidelines. Vaccination with the mutant peptide led to an overall increase in IFN-γ+ spot-forming splenocytes specific to the mutant peptide (p=0.0408).

CONCLUSION

Administering the mutant IDH1 peptide vaccine in patients with recurrent IDH-mutant gliomas was able to induce anti-IDH1 R132H immune responses in this initial phase I study.

LGG-08. TREATMENT OUTCOMES AND TOLERABILITY OF TRAMETINIB IN PROGRESSIVE CIRCUMSCRIBED LOW-GRADE GLIOMAS

Circumscribed low-grade gliomas comprise roughly one-third of pediatric CNS tumors. Most of these tumors are caused by activating mutations in the mitogen-activated protein kinase (MAPK) pathway. Drugs targeting the MAPK pathway are effective in other cancers and are being utilized in low-grade gliomas. We describe treatment outcomes and toxicities in a series of thirteen low-grade glioma patients treated with trametinib. We performed a retrospective chart review to evaluate response on T2/FLAIR MRI images per updated RANO criteria, visual outcomes, tolerability, and durability of response in progressive low-grade glioma patients treated with trametinib. Thirteen patients age 22 months to 34 years were included. Best radiographic response on therapy included 2/13 partial response, 3/13 minimal response, 5/13 stable disease, and 3/13 progressive disease. Diagnoses included pilocytic astrocytoma (n=6), desmoplastic infantile ganglioglioma (DIG; n=1), and low-grade glial neoplasms (n=2). Molecular drivers included BRAF:KIAA1549 fusion (n=3), V600E mutation (n=1), and somatic NF1 mutation (n=1). Three patients had germline NF1. In patients with partial or minimal response, best response was seen after longer durations of therapy; 4 of 5 best responses occurred after at least 12 months on therapy. Five patients completed prescribed therapy. Three patients remain stable off therapy at 6, 12, and 21 months; two patients recurred at 1 and 10 months off therapy. Skin manifestations were the predominant form of toxicity. This was more severe in older males, and symptoms improved with intermittent dosing. All patients with optic pathway tumors showed at least stable vision throughout treatment, with some patients having dramatic improvement. Trametinib is effective and well-tolerated in patients with low-grade glioma. Dermatologic toxicity can be mitigated by intermittent dosing. Best responses tended to occur later in therapy, sometimes after relatively stable MRIs. Patients with optic pathway lesions showed stable to improved vision even in the absence of significant radiographic response.

EPCT-01. A NOVEL PEPTIDE VACCINE DIRECTED TO CMV PP65 FOR TREATMENT OF RECURRENT MALIGNANT GLIOMA AND MEDULLOBLASTOMA IN CHILDREN AND YOUNG ADULTS: PRELIMINARY RESULTS OF A PHASE I TRIAL

Introduction

The cytomegalovirus (CMV) antigen, pp65, is ubiquitously expressed in malignant glioma and medulloblastoma but not in healthy brain. The objective of this Phase I trial (NCT03299309) was to assess the safety and feasibility of a novel pp65 peptide vaccine (PEP-CMV) in children and young adults with recurrent medulloblastoma and malignant glioma.

Methods

Vaccines contain a synthetic long peptide (SLP) of 26 amino acids encoding multiple potential class I, class II, and antibody epitopes of CMV pp65 across several haplotypes. This SLP is administered as an emulsion in Montanide ISA 51. Patients receive a single course of temozolomide to induce lymphopenia, tetanus/diphtheria toxoid site preconditioning, then vaccines administered intradermally every two weeks for 3 doses, then monthly.

Results

To date, 22 patients have been enrolled. Diagnoses include medulloblastoma (n=2), glioblastoma (n=12), anaplastic oligodendroglioma (n=2), anaplastic astrocytoma (n=3), and malignant glioma NOS (n=3). Mean number of prior treatment regimens is 4.9 (range 1–12). Mean age is 22yo (range 6–35) and 45% of patients are male. The median KPS is 80. The median number of vaccines given at time of analysis is 3.3 (range 1–12). There have been no ≥ 3 Grade toxicities related to the vaccine. One patient developed nausea, vomiting, palpitations, and tachycardia after vaccination and had elevated inflammatory cytokines consistent with cytokine release syndrome. Median PFS is 2.5 months (95% CI: 1.7,4.5) and median OS is 6.5 months (95% CI 3.3, 7.9). Immune response to pp65 as determined by ELISpot was found in 75% of patients. On MRI 6 of the 11 evaluable patients have had at least stable disease with three of those having a partial response.

Conclusions

Preliminary results demonstrate that PEP-CMV is well-tolerated and elicits an immune response in heavily pretreated, multiply recurrent patients. A multi-institutional Phase II trial is scheduled to open fall 2021.

FIREFLY-1: A phase 2 study of the pan-RAF inhibitor DAY101 in pediatric patients with low-grade glioma

TPS10056

Background: The mitogen-activated protein kinase (MAPK) signaling pathway is an essential pathway that regulates key cell functions such as growth, survival, and differentiation. Genomic alterations and dysregulation of the MAPK pathway including BRAF fusions, point mutations (e.g. BRAF V600) and in-frame deletions have been described in many different types of malignancies, including pediatric low-grade glioma (pLGG) and other pediatric cancers. The identification of the KIAA1549:BRAF fusion in 2008 led to deeper understanding of the genomic events driving growth of pLGG (Jones, Cancer Res 2008). Despite the low-grade histology and excellent long-term survival, pLGGs are often associated with tumor- and treatment-associated morbidity and significant late-effects that persist throughout the lifespan of the patient. DAY101 is an oral, highly selective, CNS-penetrant small-molecule, Type II pan-RAF kinase inhibitor that is being developed for patients with pLGG harboring an activating BRAF-alteration. DAY101 has demonstrated tumor inhibition in preclinical models and has achieved clinically meaningful and durable responses in 7/8 patients with RAF-altered LGG in a pediatric phase 1 trial, including 2 complete responses, 3 partial responses, 2 stable disease and 1 progressive disease with a median time to response of 10.5 weeks. Patients have been treated for up to two years with no discontinuations due to toxicity or disease progression (Wright, SNO 2020). Methods: FIREFLY-1 is an open-label, multi-center, international Phase 2 study with DAY101 in pediatric and young adult patients between the ages of 6 months and 25 years with LGG harboring a documented BRAF-alteration as determined by local laboratory testing. DAY101 is administered orally once a week on a continuous 28-day schedule. Patients who respond will be treated for a minimum of two years after which they may at any point, opt to enter a “drug holiday” discontinuation period. Dosing is based on body surface area. DAY101 is available in a pediatric-friendly oral liquid formulation and tablets. The primary endpoint is objective response rate based on Response Assessment for Neuro-Oncology (RANO) as determined by an independent review committee. Secondary endpoints include objective response rate based on Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group criteria, duration of response and safety. Exploratory endpoints include quality-of-life measurements as well as functional outcomes. Molecular abnormalities will be characterized through the analysis of archival tissue. Enrollment began in February 2021 and is ongoing. Clinical trial information: NCT03429804.

MBCL-25. PILOT STUDY OF A SURGERY AND CHEMOTHERAPY-ONLY APPROACH IN THE UPFRONT THERAPY OF CHILDREN WITH WNT-POSITIVE STANDARD RISK MEDULLOBLASTOMA: UPDATED OUTCOMES

BACKGROUND

Wnt+ medulloblastoma (WPM) is a favorable subtype with EFS > 90% when treating postoperatively with craniospinal irradiation and posterior fossa boost (CSI/XRT) followed by adjuvant chemotherapy. This pilot study explored the safety of omitting radiation in standard-risk WPM.

METHODS

Subjects had to meet standard-risk criteria (< 1.5 cm2 residual tumor, no metastatic spread, no anaplasia) and have a WPM. Subjects received chemotherapy following the COGACNS0331 AAB-AAB-AAB (A=cisplatin/CCNU/VCR; B=cyclophosphamide/vincristine) backbone.

RESULTS

Six children were enrolled on study treatment prior to early study closure. Subject #1 completed planned protocol therapy but relapsed 3 months following the completion of therapy. Subject #2 completed planned protocol therapy but relapsed 6 months following the completion of therapy. In both cases, relapse was local and disseminated. Further accrual was halted. Both subjects were salvaged with CSI/XRT followed by adjuvant chemotherapy. Of the remaining 4 subjects, two had recently completed planned protocol therapy at the time of study closure and received CSI/XRT while in remission and remain in remission approximately one year from the completion of treatment. One subject aborted protocol therapy and transitioned to a Head Start regimen and remains in remission 10 months from completion of therapy. The final subject had just completed protocol therapy and had new areas of restricted diffusion concerning for early relapse. Went on to receive CSI/XRT but subsequently relapsed and is now receiving salvage chemotherapy.

CONCLUSIONS

Chemotherapy following ACNS0331, omitting CSI/XRT, appears to be insufficient for the treatment of non-metastatic WPM.

THER-05. GENETICALLY STABLE POLIOVIRUS VECTOR CARRYING H3.3K27M ANTIGEN FOR TREATMENT OF DIFFUSE MIDLINE GLIOMA BY INTRAMUSCULAR INJECTION

BACKGROUND

H3 K27M-mutant diffuse midline glioma (DMG) is invariably lethal. Viruses naturally engage innate immunity, induce antigen presentation, and mediate CD8 T cell priming against foreign antigens. Polioviruses, in particular, are uniquely tropic for dendritic cells (DC) and potently activate DC, inducing Th1-dominant cytokine profiles, CD8 T cell immunity, and enhanced epitope presentation. Thus, poliovirus is ideally suited for vectored delivery of signature tumor neoantigens, e.g. the H3 K27M feature of DMG. However, poliovirus vector design is inherently limited by genetic instability and the underlying neuropathogenicity of poliovirus.

METHODS

We created a genetically stable, polio:rhinovirus chimera vector devoid of neuropathogenicity and modified for stable expression of the HLA-A2 restricted H3.3 K27M antigen (RIPO (H3.3)).

RESULTS

RIPO(H3.3) infects, activates, and induces H3.3K27M antigen presentation in DCs in vitro. Given intramuscularly in vivo, RIPO(H3.3) recruits and activates DCs with Th1-dominant cytokine profiles, efficiently primes H3.3K27M-specific CD8 T cells, induces antigen-specific CD8 T cell migration to the tumor site, delays tumor growth, and enhances survival in murine tumor models.

CONCLUSION

This novel approach leverages the unique ability of polioviruses to activate DCs while simultaneously introducing the H3.3 K27M antigen. In this way, DCs are activated optimally in situ, while being simultaneously infected to express/present tumor antigen. RIPO(H3.3), given by intramuscular injection, will be evaluated in a clinical trial for children with H3 K27M-mutant diffuse midline glioma.

EPID-16. INTEGRATION OF EHR AND CANCER REGISTRY DATA TO CONSTRUCT A PEDIATRIC NEURO-ONCOLOGY SURVIVORSHIP COHORT AND IMPROVE LONG-TERM FOLLOW-UP CARE

BACKGROUND

Pediatric neuro-oncology (PNO) survivors suffer long-term physical and neurocognitive morbidity. Comprehensive care addressing late effects of brain tumors and treatment in these patients is important. Clinical guidelines offer a framework for evaluating late effects, yet lack of extended follow-up is a significant barrier. The electronic health record (EHR) allows novel and impactful opportunities to construct, maintain, and leverage survivorship cohorts for health care delivery and as a platform for research.

METHODS

This survivorship cohort includes all PNO cases ≤18-years-old reported to the state-mandated cancer registry by our institution. Data mining of the EHR for exposures, demographic, and clinical data identified patients with lack of extended follow-up (>1000 days since last visit). Explanatory variables included age, race/ethnicity, and language. Primary outcome included date of last clinic visit.

RESULTS

Between January 1, 2013 and December 31, 2018, there were 324 PNO patients reported to our institutional registry with ongoing analysis to identify the specific survivorship cohort. Thirty patients died with an overall mortality of 9.3%. Two-hundred-and-sixteen patients were seen in PNO clinic, of which 18.5%% (n=40) did not receive extended follow-up. Patients without extended follow-up were an average of 3.5 years older up (p<0.01); however, there was no significant difference in preferred language (p=0.97) or race/ethnicity (p=0.57).

CONCLUSION

Integration of EHR and cancer registry data represents a feasible, timely, and novel approach to construct a PNO survivorship cohort to identify and re-engage patients without extended follow-up. Future applications include analysis of exposures and complications during therapy on late effects outcomes.

EPCT-13. CMV PP65 RNA-PULSED DENDRITIC CELL VACCINES FOR PEDIATRIC GLIOBLASTOMA AND MEDULLOBLASTOMA: PHASE I TRIAL RESULTS

BACKGROUND

Recurrent medulloblastoma and malignant glioma are lethal tumors that are virtually incurable. The cytomegalovirus (CMV) antigen pp65 is ubiquitously expressed on medulloblastoma and malignant glioma but not on healthy brain. We evaluated autologous CMV pp65 RNA-pulsed dendritic cell (DC) vaccines in children and young adults in a phase I trial.

METHODS

Circulating monocytes were harvested using leukapheresis, differentiated into DCs, matured, and pulsed with pp65 RNA using electroporation. DCs were packaged into vaccines (2x10⁷DC/vaccine) and administered intradermally following tetanus-diphtheria toxoid site preconditioning every 2 weeks x3, then monthly. The primary objectives of the study were to establish the feasibility of generating at least 3 vaccines and safety. An exploratory objective was to evaluate the ability of vaccination to create and enhance patient pp65-specific T cell responses.

RESULTS

Eleven patients were enrolled with medulloblastoma (n=3) or glioblastoma (n=8). Ages ranged from 9–30 years old (mean 15.5y). Ten of 11 patients (91%) generated at least 3 vaccines (mean 6.2). Eight patients received at least 3 vaccines. To date, 4 patients have received all generated vaccines without progression, 4 patients have progressed, and 2 patients are still receiving vaccines. There have not been any severe adverse events probably or definitely related to vaccines. More mature data will be presented at ISPNO.

CONCLUSIONS

Leukapheresis and monocyte differentiation is a feasible strategy for generating adequate DCs for active immunization in children with malignant brain tumors. CMV pp65 RNA-pulsed DCs are well-tolerated and immunogenic. Efficacy endpoints will be evaluated in a subsequent phase II trial.

DDRE-20. GENERATION OF A HIGH-AFFINITY EGFR/EGFRvIII-TARGETED D2C7 CAR-T CELL

BACKGROUND

The intent of this investigation is to validate a novel, high-affinity epidermal growth factor receptor (EGFR) chimeric antigen receptor (CAR) T-cell product for adoptive immunotherapy of EGFR-expressing malignancies of the central nervous system (CNS). Wild type EGFR is ubiquitously expressed on glial tumors in both children and adults, and the majority of solid tumors that metastasize to the CNS but is not expressed on healthy CNS tissues. EGFR and its isoform mutant, EGFRvIII, are hyperactivated or overexpressed receptor tyrosine kinases described in many human cancers. D2C7 is a recombinant monoclonal antibody short chain variable fragment (scFv) that binds to both wild type EGFR and EGFRvIII. We hypothesize that D2C7 adapted as a CAR on primary human T cells will generate potent, cytotoxic activity against EGFR-expressing tumors in vivo.

METHODS

In vitro interferon gamma release assays comparing the D2C7 CAR to the EGFRvIII CAR have proven that D2C7 CAR-T cells have high specificity and potent cytotoxicity against established murine glioblastoma (GBM) tumor cell lines, expressing both EGFR and EGFRvIII. Next steps include pre-clinical in vivo testing of the D2C7 CAR-T cells in murine models of CNS tumors expressing EGFR/EGFRvIII such as GBM, non-small cell lung carcinoma (NSCLC), breast carcinoma, and melanoma.

CONCLUSIONS

To improve and validate the effectiveness of CAR T-cell therapy for EGFR-expressing CNS tumors, our team has designed a high-affinity CAR-T cell that targets both EGFRvIII and wild-type EGFR, known as a D2C7 CAR-T cell. This investigation has established pre-clinical anti-tumor activity of D2C7-CAR T cells in vitro and we plan to present more mature data regarding efficacy in orthotopic murine models of GBM, NSCLC, breast carcinoma, and melanoma at the meeting this Fall.

CTIM-21. PEPTIDE VACCINE DIRECTED TO CMV pp65 FOR TREATMENT OF RECURRENT MALIGNANT GLIOMA AND MEDULLOBLASTOMA IN CHILDREN AND YOUNG ADULTS: PRELIMINARY RESULTS OF A PHASE I TRIAL

INTRODUCTION

The cytomegalovirus (CMV) antigen, pp65, is ubiquitously expressed in malignant glioma and medulloblastoma but not in healthy brain. The objective of this Phase I trial (NCT03299309) was to assess the safety and feasibility of a novel pp65 peptide vaccine (PEP-CMV) in children and young adults with recurrent medulloblastoma and malignant glioma.

METHODS

Vaccines contain a synthetic long peptide (SLP) of 26 amino acids encoding multiple potential class I, class II, and antibody epitopes of CMV pp65 across several haplotypes. This SLP is administered as an emulsion in Montanide ISA 51. Patients receive a single course of temozolomide to induce lymphopenia, tetanus/diphtheria toxoid site preconditioning, then vaccines administered intradermally every two weeks for 3 doses, then monthly.

RESULTS

To date, 17 patients have been enrolled. Diagnoses include medulloblastoma (n=1), glioblastoma (n=9), anaplastic oligodendroglioma (n=2), anaplastic astrocytoma (n=2), and malignant glioma NOS (n=3). Mean number of prior treatment regimens is 4.9 (range 1–12). Mean age is 22yo (range 6–35) and 41% of patients are male. The median KPS is 80. The median number of vaccines given at time of analysis is 3.3 (range 1–12). There have been no ≥ 3 Grade toxicities related to the vaccine. One patient developed nausea, vomiting, palpitations, and tachycardia after vaccination and had elevated inflammatory cytokines consistent with cytokine release syndrome. Median PFS is 2.5 months (95% CI: 0.8, not estimable) and median OS is 6.5 months (95% CI 1.8, not estimable). Interim analysis of immune monitoring bloodwork and perfusion MRI to quantify responses to PEP-CMV has been delayed due to COVID-19. However, adults with GBM who received PEP-CMV (NCT02864368) had significant (p≤0.05) increases in GCSF, GM-CSF, IFN-γ, IL-10, IL-2, IL-8, MIP1-α, and TNF-α levels.

CONCLUSIONS

Preliminary results demonstrate that PEP-CMV is feasible and well-tolerated in heavily pretreated, multiply recurrent patients.

BIOM-17. BRAF MUTATION IS AN EARLY EVENT IN THE EVOLUTION OF A SUBSET OF GLIOBLASTOMAS AND IS ASSOCIATED WITH INCREASED PD-L1 EXPRESSION

INTRODUCTION

BRAF is a RAF-family kinase that regulates MAPK/ERK signaling. Activating BRAF mutations, including V600E, are common in circumscribed low-grade gliomas of childhood and young adulthood, but are uncommon in infiltrative astrocytomas, including glioblastoma. Their role in glioblastoma initiation and progression requires analysis of large datasets given the low frequency (1.0%) in TCGA IDH-wild-type glioblastomas.

METHODS

Molecular profiling was done on 4679 FFPE gliomas by next-generation sequencing at Caris Life Sciences, of which 3170 underwent RNA-sequencing for gene fusion and 4603 DNA-sequencing for mutations. MGMT promoter methylation was tested by pyrosequencing and PD-L1 IHC was performed using the SP142 clone.

RESULTS

Excluding variants of uncertain significance, BRAF mutations/fusions were most common in pleomorphic xanthoastrocytoma (PXA; N=12/24, 50%), glioneuronal tumors (N=6/13, 46%), pilocytic astrocytoma (PA; N=15/48, 31%), and ganglioglioma (n=5/18, 28%). BRAF fusions were uncommon (N=17), most frequent in PA (N=8/31, 26%) where they were associated with older age at daignosis (P=0.043), and typically involved KIAA1549 as fusion partner (70%). BRAF-mutated/fused glioblastoma patients (N=59/3126, 2%) were younger than BRAF-wild-type glioblastoma patients (54 versus 59 years, P=3.5x10-3); more likely to be MGMT-unmethylated (75% versus 56%, P=5.0x10-3); and 3x more likely to express PD-L1 (55% versus 17%, P=2.1x10-10). In tumors harboring a V600E mutation, the variant allele frequency (VAF) was similar in glioblastoma as in PXA, PA, ganglioglioma, and glioneuronal tumors (median VAF=35%).

CONCLUSIONS

BRAF-mutated glioblastoma were 3x more likely to express PD-L1 than BRAF-wild-type glioblastoma. We observed no differences in BRAF V600E clonality in BRAF-mutated glioblastoma compared to BRAF-mutated PXA, PA, ganglioglioma, and glioneuronal tumors, suggesting BRAF mutation is an initiating event in the clonal evolution of a subset of glioblastoma. There is rationale to evaluate combined BRAF inhibition with checkpoint inhibition in BRAF-mutated glioblastoma, potentially synergizing the complete response profile of the former with the durable response profile of the latter.

CTIM-23. A PHASE 1 TRIAL OF D2C7-IT IN COMBINATION WITH ATEZOLIZUMAB IN RECURRENT WHO GRADE IV MALIGNANT GLIOMA (MG)

BACKGROUND

D2C7 immunotoxin (D2C7-IT) is a dual-specific recombinant immunotoxin comprising an EGFR-wt and mutant-specific (EGFRvIII) monoclonal antibody fragment and a genetically engineered form of the pseudomonas exotoxin. When injected directly into the tumor mass by convection enhanced delivery (CED), in addition to direct tumor cell killing, immunotoxins induce secondary immune responses by the activation of CD4+ and CD8+ T-cells. We completed a phase 1 dose escalation study of D2C7-IT injected by CED into recurrent WHO grade III-IV MG and identified the phase 2 dose (6,920 ng/mL). Three patients remain in partial response more than 58, 38, and 32 months after a single D2C7-IT intratumoral infusion. As optimal induction of anti-tumor immune responses by immunotoxins is impeded by potent MG-mediated immunosuppression, we are assessing the toxicity of the combination of D2C7-IT with atezolizumab in patients with recurrent WHO grade IV MG.

METHODS

Eligibility includes adult patients with recurrence of a solitary supratentorial WHO grade IV MG; ≥4 weeks after chemotherapy, bevacizumab or study drug; adequate organ function; and KPS &gt;70%. Patient receives an intratumoral infusion of D2C7-IT and initiates two weeks later atezolizumab at 1200mg, followed by atezolizumab every 3 weeks for up to 2 years. Two cohorts of 3 patients are initially accrued to assess the toxicity of the combination. Assuming accrual continues after the initial two cohorts of 3 patients, an additional 12 patients will be accrued to the study.

RESULT

The first enrolled patient experienced a grade 3 DLT (grade III ALT elevation) after the first infusion of atezolizumab, but showed a more extensive immunotherapeutic effect by imaging than observed with patients on the D2C7-IT monotherapy trial. Enrollment is ongoing.

CONCLUSION

D2C7-IT monotherapy has shown prolonged survival and disease control in some patients. We are now evaluating the combination of D2C7-IT with checkpoint inhibition.

Current medulloblastoma subgroup specific clinical trials

Medulloblastoma is a heterogeneous disease with at least four distinct molecular subgroups: wingless (WNT), sonic hedgehog (SHH), Group 3, and Group 4. Recently there has been considerable progress defining the molecular drivers and prognostic factors of each subgroup. However, this information has only rarely been used to stratify risk or impact treatment. The purpose of this work is to provide an update on current clinical trials that provide molecularly stratified treatment paradigms. A search was conducted on ClinicalTrials.gov using the following search terms: "medulloblastoma and subgroup", "medulloblastoma and SHH", "medulloblastoma and WNT", and "medulloblastoma and Non-WNT/Non-SHH". This search resulted in nine distinct clinical trials, five for newly diagnosed medulloblastoma and four for recurrent medulloblastoma. Four trials for newly diagnosed medulloblastoma had a component of craniospinal irradiation reduction for patients with WNT medulloblastoma. Molecularly stratified trials for recurrent medulloblastoma largely focus on SHH. As these trials are ongoing, there are limited data available. A trial in which newly-diagnosed WNT patients received modest chemotherapy without radiation has been closed to accrual due to several early failures. Phase II trials evaluating vismodegib for SHH medulloblastoma in children and adults have been disappointing. In conclusion, although there is an expanding array of clinical trials which incorporate molecular data in prescribing treatment for newly-diagnosed and recurrent medulloblastoma, treatments for these diseases are fairly uniform, with craniospinal radiation dose being the main variable. As the drivers of the distinct subgroups and their associated prognoses are better elucidated, future clinical trials and novel targeted agents are needed to improve outcomes and reduce toxicity where feasible.

QOLP-34. DOSE FREQUENCY MODIFICATION OF TRAMETINIB TO MITIGATE SEVERE RASH AND IMPROVE QUALITY OF LIFE IN PEDIATRIC LOW-GRADE GLIOMA PATIENTS

Circumscribed low-grade glioma is generally driven by MAP kinase pathway activation, and this discovery motivates use of the non-competitive MEK 1/2 inhibitor trametinib for children and adults with progressive disease. However, rash is a common dose-limiting toxicity with trametinib. Accordingly, we evaluated intermittent, 3-days-on, 1-day-off dosing in an effort to reduce the incidence and severity of rash. Seven patients with MAP-kinase activated low grade glioma were treated with trametinib (6 pilocytic astrocytoma (PA), one desmoplastic infantile ganglioglioma with V600E). Patients initiated treatment at 0.025mg/kg/day up to the maximum adult dosing of 2mg. Three teenage patients with PA were treated with the maximum daily adult dose of 2mg. All three developed a painful, grade 3 acneiform rash within 3 weeks, requiring trametinib hold and treated with topical cleansers and oral antibiotics. One patient discontinued treatment, and two restarted trametinib at a reduced dose (1.5mg) administered 3-days-on and 1-day-off. With this modified dosing, patients experienced no more than grade 1 rash. Two younger patients initiated trametinib with daily dosing, and both developed grade 1 eczematous rash within 3 weeks, progressing to grade 2 in one patient. The rash resolved without recurrence after dose frequency modification to 3-days-on, 1-day-off at the same overall dose. Two younger patients initiated trametinib with 3-days-on, 1-day-off dosing and have not developed a rash. All of the younger patients are currently continuing on therapy with no progression to date. However, both teenage patients developed progressive disease by 11 months into therapy. In conclusion, acneiform rash appears to preferentially impact teenage or young adult patients but can be mitigated with modified dose frequency 3 days on, 1 day off. However, continued assessment is needed to evaluate the effect of dosing frequency modification on treatment response.

QOLP-29. MINDFULNESS MEDITATION PRACTICE IN MALIGNANT GLIOMA PATIENTS THROUGHOUT CONCOMITANT RADIATION AND TEMOZOLOMIDE: A FEASIBILITY STUDY

With a bleak prognosis for malignant glioma, maintaining quality of life (QoL) and decreasing distress of the patient are important in the clinical care of the patient. Mindfulness meditation is a mind-body therapy that has been recently investigated in the oncology field as a non-pharmacological strategy to ameliorate cancer symptoms and to improve QoL. This practice has not been studied in the primary brain tumor population. We initiated a pilot study among newly diagnosed brain tumor patients with the hypothesis that mindfulness meditation practice may benefit the patient by decreasing stress and anxiety and provide a means to cope with their new diagnosis. The specific aim of this pilot study is to determine the feasibility of a mindfulness meditation program to this population during standard of care chemoradiation and to determine whether it merits additional research in a subsequent trial. The intervention consists of six weekly one hour telephone-based mindfulness sessions followed by one in- person mindfulness session consisting of: mindfulness and healing, understanding stress, abiding in kindness, working with difficult emotions, finding peace, going forward and living fully. Subjects are provided with downloadable guided meditations. We plan to enroll fifteen newly diagnosed WHO grade III or IV malignant glioma subjects prior to their 6 week chemoradiation course. We will determine the percentage of subjects approached vs enrolled, number of sessions that each subject attends, completion of study questionnaires and satisfaction of the subjects. QoL surveys include: Functional Assessment of Cancer Therapy- Brain, Functional Assessment of Cancer Therapy- Cognitive Function, Pittsburgh Sleep Quality Index, Functional Assessment of Chronic Illness Therapy-Fatigue and the Five Facet Mindfulness Questionnaire – short form. 13 subjects have been approached and 8 signed consent over a two-month period. We will provide final study results at time of presentation.

PDCT-10. FEASIBILITY OF LEUKAPHERESIS FOR HARVESTING MONOCYTES AND GENERATING AUTOLOGOUS DENDRITIC CELL VACCINES IN CHILDREN WITH MALIGNANT BRAIN TUMORS

BACKGROUND

Recurrent medulloblastoma and malignant glioma are virtually incurable. In children, these tumors are often disseminated or occur in deep midline structures that preclude surgery and are not amenable to highly inflammatory treatments. Active immunization is an attractive immunotherapeutic approach. We are conducting a phase I trial evaluating autologous CMV pp65 RNA-pulsed dendritic cell (DC) vaccines in children with recurrent malignant glioma or medulloblastoma. A primary objective is establishing the feasibility of using leukapheresis to harvest sufficient monocytes in order to generate at least 3 autologous DC vaccines.

METHODS

For children unable to receive two 16-guage IVs, a temporary pheresis catheter is placed in the jugular vein under anesthesia. Leukapheresis is performed with the goal of processing 3 total blood volumes. Circulating monocytes are collected and cultured for 7 days in media supplemented with GM-CSF and IL-4, then matured into dendritic cells and loaded with antigen. The target dose for a single vaccine is 2 x 107 dendritic cells.

RESULTS

To date, five patients (ages 9, 13, 16, 17, 30) have undergone leukapheresis. All patients tolerated leukapheresis without complications, with run times between 3 to 6 hours depending on achievable pheresis flow rate. Patients generated 2, 3, 7, 8, 8, and 8 vaccines. The medulloblastoma patient who generated 2 vaccines underwent a second leukapheresis that generated 8 vaccines. In this patient, although the initial leukapheresis collected a high number of monocytes, the conversion rate to mature DCs was low. Thusfar, there has not been a strong correlation between the number of monocytes collected and the eventual number of mature dendritic cells.

CONCLUSIONS

Leukapheresis is tolerable for younger children and appears to be a viable strategy for harvesting sufficient monocytes for creating DC vaccines. Conversion rates between harvested monocytes and the final number of mature dendritic cells vary.

TEM8/ANTXR1-Specific CAR T Cells as a Targeted Therapy for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive disease lacking targeted therapy. In this study, we developed a CAR T cell-based immunotherapeutic strategy to target TEM8, a marker initially defined on endothelial cells in colon tumors that was discovered recently to be upregulated in TNBC. CAR T cells were developed that upon specific recognition of TEM8 secreted immunostimulatory cytokines and killed tumor endothelial cells as well as TEM8-positive TNBC cells. Notably, the TEM8 CAR T cells targeted breast cancer stem-like cells, offsetting the formation of mammospheres relative to nontransduced T cells. Adoptive transfer of TEM8 CAR T cells induced regression of established, localized patient-derived xenograft tumors, as well as lung metastatic TNBC cell line-derived xenograft tumors, by both killing TEM8⁺ TNBC tumor cells and targeting the tumor endothelium to block tumor neovascularization. Our findings offer a preclinical proof of concept for immunotherapeutic targeting of TEM8 as a strategy to treat TNBC.Significance: These findings offer a preclinical proof of concept for immunotherapeutic targeting of an endothelial antigen that is overexpressed in triple-negative breast cancer and the associated tumor vasculature. Cancer Res; 78(2); 489-500. ©2017 AACR.

HER2-Specific Chimeric Antigen Receptor-Modified Virus-Specific T Cells for Progressive Glioblastoma: A Phase 1 Dose-Escalation Trial

Importance

Glioblastoma is an incurable tumor, and the therapeutic options for patients are limited.

Objective

To determine whether the systemic administration of HER2-specific chimeric antigen receptor (CAR)-modified virus-specific T cells (VSTs) is safe and whether these cells have antiglioblastoma activity.

Design, Setting, and Participants

In this open-label phase 1 dose-escalation study conducted at Baylor College of Medicine, Houston Methodist Hospital, and Texas Children's Hospital, patients with progressive HER2-positive glioblastoma were enrolled between July 25, 2011, and April 21, 2014. The duration of follow-up was 10 weeks to 29 months (median, 8 months).

Interventions

Monotherapy with autologous VSTs specific for cytomegalovirus, Epstein-Barr virus, or adenovirus and genetically modified to express HER2-CARs with a CD28.ζ-signaling endodomain (HER2-CAR VSTs).

Main Outcomes and Measures

Primary end points were feasibility and safety. The key secondary end points were T-cell persistence and their antiglioblastoma activity.

Results

A total of 17 patients (8 females and 9 males; 10 patients ≥18 years [median age, 60 years; range, 30-69 years] and 7 patients <18 years [median age, 14 years; range, 10-17 years]) with progressive HER2-positive glioblastoma received 1 or more infusions of autologous HER2-CAR VSTs (1 × 106/m2 to 1 × 108/m2) without prior lymphodepletion. Infusions were well tolerated, with no dose-limiting toxic effects. HER2-CAR VSTs were detected in the peripheral blood for up to 12 months after the infusion by quantitative real-time polymerase chain reaction. Of 16 evaluable patients (9 adults and 7 children), 1 had a partial response for more than 9 months, 7 had stable disease for 8 weeks to 29 months, and 8 progressed after T-cell infusion. Three patients with stable disease are alive without any evidence of progression during 24 to 29 months of follow-up. For the entire study cohort, median overall survival was 11.1 months (95% CI, 4.1-27.2 months) from the first T-cell infusion and 24.5 months (95% CI, 17.2-34.6 months) from diagnosis.

Conclusions and Relevance

Infusion of autologous HER2-CAR VSTs is safe and can be associated with clinical benefit for patients with progressive glioblastoma. Further evaluation of HER2-CAR VSTs in a phase 2b study is warranted as a single agent or in combination with other immunomodulatory approaches for glioblastoma.