Locoregional delivery of IL-13Rα2-targeting CAR-T cells in recurrent high-grade glioma: a phase 1 trial

Chimeric antigen receptor T cell (CAR-T) therapy is an emerging strategy to improve treatment outcomes for recurrent high-grade glioma, a cancer that responds poorly to current therapies. Here we report a completed phase I trial evaluating IL-13Rα2-targeted CAR-T cells in 65 patients with recurrent high-grade glioma, the majority being recurrent glioblastoma (rGBM). Primary objectives were safety and feasibility, maximum tolerated dose/maximum feasible dose and a recommended phase 2 dose plan. Secondary objectives included overall survival, disease response, cytokine dynamics and tumor immune contexture biomarkers. This trial evolved to evaluate three routes of locoregional T cell administration (intratumoral (ICT), intraventricular (ICV) and dual ICT/ICV) and two manufacturing platforms, culminating in arm 5, which utilized dual ICT/ICV delivery and an optimized manufacturing process. Locoregional CAR-T cell administration was feasible and well tolerated, and as there were no dose-limiting toxicities across all arms, a maximum tolerated dose was not determined. Probable treatment-related grade 3+ toxicities were one grade 3 encephalopathy and one grade 3 ataxia. A clinical maximum feasible dose of 200 × 106 CAR-T cells per infusion cycle was achieved for arm 5; however, other arms either did not test or achieve this dose due to manufacturing feasibility. A recommended phase 2 dose will be refined in future studies based on data from this trial. Stable disease or better was achieved in 50% (29/58) of patients, with two partial responses, one complete response and a second complete response after additional CAR-T cycles off protocol. For rGBM, median overall survival for all patients was 7.7 months and for arm 5 was 10.2 months. Central nervous system increases in inflammatory cytokines, including IFNγ, CXCL9 and CXCL10, were associated with CAR-T cell administration and bioactivity. Pretreatment intratumoral CD3 T cell levels were positively associated with survival. These findings demonstrate that locoregional IL-13Rα2-targeted CAR-T therapy is safe with promising clinical activity in a subset of patients. ClinicalTrials.gov Identifier: NCT02208362 .

Abstract 59: CAR T cell therapy reshapes the tumor microenvironment to promote host antitumor immune repsonses in glioblastoma

CAR T cell therapy is emerging as a promising strategy to treat cancer and may offer new therapeutic options for individuals diagnosed with glioblastoma (GBM) and other solid tumors. While early clinical studies evaluating CAR T cell therapy in GBM have established evidence of safety and bioactivity, objective clinical responses have been limited. It remains unclear whether productive CAR T cell therapy for solid tumors requires solely CAR T cell engagement with tumor antigen, or if it also necessitates the stimulation of a patient's endogenous immune response. Focusing on our preclinical and clinical program evaluating IL13Rα2-targeted CAR-T cells for the treatment of IL13Rα2-positive glioblastoma (GBM), we set out to mechanistically interrogate the interplay between CAR T cell therapy and the host tumor microenvironment. We designed a murine CAR T cell syngeneic platform in C57BL/6 immunocompetent mice and demonstrate that single intratumoral infusion of IL13Rα2-CAR T cells mediate potent antitumor activity against established KR158 tumors, a highly invasive and poorly immunogenic murine glioma model. We demonstrate that CAR T cell treatment of mouse syngeneic GBM alters the tumor immune landscape, activates intratumoral myeloid cells and induces endogenous T cell memory responses coupled with feed forward propagation of CAR T responses. IFNγ production by CAR T cells and IFNγ-responsiveness of host immune cells is critical for tumor immune landscape remodeling to promote a more activated and less suppressive tumor microenvironment. The clinical relevance of these findings was explored in patient samples from our on-going IL13Rα2-CAR T cell phase I clinical trial [NCT02208362]. Consistent with our preclinical findings, we show that locoregional CAR T cell infusions result in spikes in inflammatory cytokines and an influx of endogenous immune cells into the cerebrospinal fluid (CSF) and resected tumor cavity. Single cell RNA-sequencing revealed unique genes upregulated in immune cells from blood and CSF samples after treatment. One patient of particular interest, who presented with recurrent multifocal GBM, remarkably achieved a complete response (CR) following locoregional delivery of IL13Rα2-CAR T cells, despite heterogeneous IL13Rα2 tumor expression (PMID: 28029927). In this responding patient, we now show the induction of endogenous tumor-specific T cell reactivity and T cell clones whose dynamics contracted with tumor volume following IL13Rα2-targeted CAR T therapy. These studies establish that CAR T cell therapy has the potential to re-shape the tumor microenvironment, creating a context permissible for eliciting endogenous antitumor immunity and emphasize the importance of the host innate and adaptive immunity in productive CAR T cell therapy of solid tumors.

Citation Format: Christine E. Brown, Darya Alizadeh, Vanessa Jonsson, Jonathan Hibbard, Stephanie Yahn, Robyn A. Wong, Xin Yang, Rachel Ng, Natalie Dullerud, Madeleine Maker, Sharahreh Gholamin, Renate Starr, Nicholas Banovich, Stephen J. Forman, Behnam Badie. CAR T cell therapy reshapes the tumor microenvironment to promote host antitumor immune repsonses in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 59.

Betacellulin drives therapy resistance in glioblastoma

BACKGROUND

The transcription factor signal transducer and activator of transcription 3 (STAT3) drives progression in glioblastoma (GBM), suggesting STAT3 as a therapeutic target. Surprisingly however, GBM cells generally show primary resistance to STAT3 blockade.

METHODS

Human glioblastoma cell lines LN229, U87, SF767, and U373, and patient-derived xenografts (PDXs) GBM8 and GBM43 were used to evaluate epidermal growth factor receptor (EGFR) activation during STAT3 inhibition. Protein and gene expression experiments, protein stability assays, cytokine arrays, phospho-tyrosine arrays and EGFR-ligand protein arrays were performed on STAT3 inhibitor-treated cells. To evaluate antitumor activity, we administered a betacellulin (BTC)-neutralizing antibody alone and in combination with STAT3 inhibition. BTC is an EGFR ligand. We therefore treated mice with orthotopic xenografts using the third-generation EGFR inhibitor osimertinib, with or without STAT3 knockdown.

RESULTS

We demonstrate that both small-molecule inhibitors and knockdown of STAT3 led to expression and secretion of the EGFR ligand BTC, resulting in activation of EGFR and subsequent downstream phosphorylation of nuclear factor-kappaB (NF-κB). Neutralizing antibody against BTC abrogated activation of both EGFR and NF-κB in response to inhibition of STAT3; with combinatorial blockade of STAT3 and BTC inducing apoptosis in GBM cells. Blocking EGFR and STAT3 together inhibited tumor growth, improving survival in mice bearing orthotopic GBM PDXs in vivo.

CONCLUSION

These data reveal a feedback loop among STAT3, EGFR, and NF-κB that mediates primary resistance to STAT3 blockade and suggest strategies for therapeutic intervention.

IFNγ Is Critical for CAR T Cell-Mediated Myeloid Activation and Induction of Endogenous Immunity

Chimeric antigen receptor (CAR) T cells mediate potent antigen-specific antitumor activity; however, their indirect effects on the endogenous immune system are not well characterized. Remarkably, we demonstrate that CAR T-cell treatment of mouse syngeneic glioblastoma (GBM) activates intratumoral myeloid cells and induces endogenous T-cell memory responses coupled with feed-forward propagation of CAR T-cell responses. IFNγ production by CAR T cells and IFNγ responsiveness of host immune cells are critical for tumor immune landscape remodeling to promote a more activated and less suppressive tumor microenvironment. The clinical relevance of these observations is supported by studies showing that human IL13Rα2-CAR T cells activate patient-derived endogenous T cells and monocytes/macrophages through IFNγ signaling and induce the generation of tumor-specific T-cell responses in a responding patient with GBM. These studies establish that CAR T-cell therapy has the potential to shape the tumor microenvironment, creating a context permissible for eliciting endogenous antitumor immunity. SIGNIFICANCE: Our findings highlight the critical role of IFNγ signaling for a productive CAR T-cell therapy in GBM. We establish that CAR T cells can activate resident myeloid populations and promote endogenous T-cell immunity, emphasizing the importance of host innate and adaptive immunity for CAR T-cell therapy of solid tumors.This article is highlighted in the In This Issue feature, p. 2113.

Cooperative Blockade of PKCα and JAK2 Drives Apoptosis in Glioblastoma

The mTOR signaling is dysregulated prominently in human cancers including glioblastoma, suggesting mTOR as a robust target for therapy. Inhibitors of mTOR have had limited success clinically, however, in part because their mechanism of action is cytostatic rather than cytotoxic. Here, we tested three distinct mTOR kinase inhibitors (TORKi) PP242, KU-0063794, and sapanisertib against glioblastoma cells. All agents similarly decreased proliferation of glioblastoma cells, whereas PP242 uniquely induced apoptosis. Apoptosis induced by PP242 resulted from off-target cooperative inhibition of JAK2 and protein kinase C alpha (PKCα). Induction of apoptosis was also decreased by additional on-target inhibition of mTOR, due to induction of autophagy. As EGFR inhibitors can block PKCα, EGFR inhibitors erlotinib and osimertinib were tested separately in combination with the JAK2 inhibitor AZD1480. Combination therapy induced apoptosis of glioblastoma tumors in both flank and in patient-derived orthotopic xenograft models, providing a preclinical rationale to test analogous combinations in patients. SIGNIFICANCE: These findings identify PKCα and JAK2 as targets that drive apoptosis in glioblastoma, potentially representing a clinically translatable approach for glioblastoma.

IL15 Enhances CAR-T Cell Antitumor Activity by Reducing mTORC1 Activity and Preserving Their Stem Cell Memory Phenotype

Improvements in the quality and fitness of chimeric antigen receptor (CAR)-engineered T cells, through CAR design or manufacturing optimizations, could enhance the therapeutic potential of CAR-T cells. One parameter influencing the effectiveness of CAR-T cell therapy is the differentiation status of the final product: CAR-T cells that are less-differentiated and less exhausted are more therapeutically effective. In the current study, we demonstrate that CAR-T cells expanded in IL15 (CAR-T/IL15) preserve a less-differentiated stem cell memory (Tscm) phenotype, defined by expression of CD62L⁺CD45RA⁺ CCR7⁺, as compared with cells cultured in IL2 (CAR-T/IL2). CAR-T/IL15 cells exhibited reduced expression of exhaustion markers, higher antiapoptotic properties, and increased proliferative capacity upon antigen challenge. Furthermore, CAR-T/IL15 cells exhibited decreased mTORC1 activity, reduced expression of glycolytic enzymes and improved mitochondrial fitness. CAR-T/IL2 cells cultured in rapamycin (mTORC1 inhibitor) shared phenotypic features with CAR-T/IL15 cells, suggesting that IL15-mediated reduction of mTORC1 activity is responsible for preserving the Tscm phenotype. CAR-T/IL15 cells promoted superior antitumor responses in vivo in comparison with CAR-T/IL2 cells. Inclusion of cytokines IL7 and/or IL21 in addition to IL15 reduced the beneficial effects of IL15 on CAR-T phenotype and antitumor potency. Our findings show that IL15 preserves the CAR-T cell Tscm phenotype and improves their metabolic fitness, which results in superior in vivo antitumor activity, thus opening an avenue that may improve future adoptive T-cell therapies.

A Kinase Inhibitor Targeted to mTORC1 Drives Regression in Glioblastoma

Although signaling from phosphatidylinositol 3-kinase (PI3K) and AKT to mechanistic target of rapamycin (mTOR) is prominently dysregulated in high-grade glial brain tumors, blockade of PI3K or AKT minimally affects downstream mTOR activity in glioma. Allosteric mTOR inhibitors, such as rapamycin, incompletely block mTORC1 compared with mTOR kinase inhibitors (TORKi). Here, we compared RapaLink-1, a TORKi linked to rapamycin, with earlier-generation mTOR inhibitors. Compared with rapamycin and Rapalink-1, TORKi showed poor durability. RapaLink-1 associated with FKBP12, an abundant mTOR-interacting protein, enabling accumulation of RapaLink-1. RapaLink-1 showed better efficacy than rapamycin or TORKi, potently blocking cancer-derived, activating mutants of mTOR. Our study re-establishes mTOR as a central target in glioma and traces the failure of existing drugs to incomplete/nondurable inhibition of mTORC1.

STAT3 Blockade Inhibits Radiation-Induced Malignant Progression in Glioma

High grade gliomas (HGG) are classified into four subgroups based on transcriptional signatures and phenotypic characteristics. In particular, the proneural-to-mesenchymal transition (PMT) is associated with increased malignancy, poor prognosis, and disease recurrence, but the underlying causes of PMT are still unclear. In this study, we investigated whether radiotherapy promotes PMT using a genetically engineered mouse model of proneural HGG. We found that cranial ionizing radiation induced robust and durable PMT in tumors. Additionally, we isolated primary proneural HGG cells from mouse and human tumors and demonstrate that radiation induced a sustained cell-intrinsic mesenchymal transition associated with increased invasiveness and resistance to the alkylating agent temozolomide. Expectedly, irradiation-induced PMT was also associated with activation of the STAT3 transcription factor, and the combination of STAT3 blockade using JAK2 inhibitors with radiation abrogated the mesenchymal transition and extended survival of mice. Taken together, our data suggest that clinical JAK2 inhibitors should be tested in conjunction with radiation in patients with proneural HGG as a new strategy for blocking the emergence of therapy-resistant mesenchymal tumors at relapse.

EGFR phosphorylates tumor-derived EGFRvIII driving STAT3/5 and progression in glioblastoma

EGFRvIII, a frequently occurring mutation in primary glioblastoma, results in a protein product that cannot bind ligand, but signals constitutively. Deducing how EGFRvIII causes transformation has been difficult because of autocrine and paracrine loops triggered by EGFRvIII alone or in heterodimers with wild-type EGFR. Here, we document coexpression of EGFR and EGFRvIII in primary human glioblastoma that drives transformation and tumorigenesis in a cell-intrinsic manner. We demonstrate enhancement of downstream STAT signaling triggered by EGFR-catalyzed phosphorylation of EGFRvIII, implicating EGFRvIII as a substrate for EGFR. Subsequent phosphorylation of STAT3 requires nuclear entry of EGFRvIII and formation of an EGFRvIII-STAT3 nuclear complex. Our findings clarify specific oncogenic signaling relationships between EGFR and EGFRvIII in glioblastoma.

Clinical presentation and management of iatrogenic colon perforations

BACKGROUND

Because iatrogenic colonic perforation is uncommon, surgical management of this complication has been based on the civilian trauma experience. In this study, we determine the incidence, clinical presentation, and management of colonic perforations resulting from colonoscopy or barium enema.

PATIENTS AND METHODS

The medical records of all patients with colorectal perforations due to barium enema or colonoscopy seen over a 5-year period were reviewed.

RESULTS

Twenty-one patients, 12 males and 9 females aged 66 +/- 16 years, undergoing evaluation for polyps and bleeding (11), diverticulosis (4), diarrhea (2), or miscellaneous indications (4) sustained colonic perforation from colonoscopy (18; 0.20%) or barium enema (3; 0.10%). Abdominal pain, 66% (13), and fever, 24% (5), were the most frequent symptoms encountered and extraluminal air, 67% (14), the most common radiologic finding. The site of perforation was the rectosigmoid in 62% (13) of patients. Eighteen patients underwent surgery; 11 within 24 hours (group I) and 7 patients within 6.0 +/- 4 days (group II). Fifty percent (9 of 18) had primary repair or resection with anastomosis without mortality. Of the 6 patients initially treated nonoperatively, 3 subsequently underwent surgery. Both deaths, one in group I and one in group II, occurred in patients who had colonic diversion for perforation following colonoscopy.

CONCLUSION

We conclude that in the absence of significant contamination either primary repair or resection and anastomosis can be performed with acceptable morbidity for iatrogenic perforations of the colon.

In vivo proliferation of adoptively transferred tumor-infiltrating lymphocytes in mice

The adoptive transfer of tumor-infiltrating lymphocytes (TILs) in conjunction with interleukin-2 (IL-2) administration can mediate a reduction in established pulmonary and hepatic metastases of a variety of murine tumors as well as in patients with metastatic melanoma. To characterize further the fate of adoptively transferred TILs, the uptake of the thymidine analog 5-[125I]iodo-2-deoxyuridine ([125I]UdR) into the DNA of dividing cells was used to study the in vivo proliferation and migration patterns of transferred TILs in C57BL/6N mice. Animals received 500 rad of total body irradiation prior to cell transfer to separate incorporation of radiolabel into endogenous lymphoid cells from that into transferred TILs. Mice were subsequently treated with i.v. injections of TILs or no cells followed by i.p. injections of Hanks' balanced salt solution or IL-2. At various time points, mice received [125I]UdR, and 20 h later tissues were removed and counted on a gamma analyzer. A proliferation index (PI) was calculated by dividing the mean cpm of organs of experimentally treated mice by the mean cpm of organs of control mice. Animals receiving TILs alone demonstrated small increases in [125I]UdR in the lungs, liver, and spleen of saline-treated controls (PI = 1.4, 1.6, and 1.7, respectively, on day 4), while animals treated with 50,000 U of IL-2 alone showed greater increases in the lungs, liver, kidneys, and spleen (PI = 3.9, 6.1, 3.3, and 15.8). Mice receiving TILs plus IL-2 demonstrated the highest levels of radiolabel incorporation in the same organs (PI = 10.5, 19.4, 10.2, and 22.4). Over a period of 10 days, TIL plus IL-2 treated animals continued to incorporate significantly greater amounts of [125I]UdR for as long as high-dose IL-2 was administered. Animals treated with TILs demonstrated increased incorporation of radiolabel with increasing doses of IL-2. Injection of irradiated TILs did not result in an increased uptake of [125I]UdR into these tissues, thus confirming that TIL proliferation is responsible for the radiolabel uptake in animals receiving TILs alone or TILs plus IL-2. Additionally, fluorescein-labeled anti-Thy-1.1 antibody identified proliferating TILs derived from congenic B6.PL Thy 1a/CY (Thy-1.1) animals in the lungs, spleen, and liver of recipient C57BL/6N (Thy 1.2) mice. In summary, we have demonstrated that adoptively transferred TILs distribute widely after i.v. injection and can proliferate in various tissues especially under the influence of exogenous IL-2.

Geriatrics emphasis in physical therapy. A historical survey

The number of elderly individuals and the health care needs of elderly persons are rapidly growing. Are physical therapists interested and involved in meeting the needs of this geriatric group? One measure of physical therapists' interest is the quantity of geriatrics-related articles that appear in our profession's journal. The purpose of this study was to conduct a historical review of the number of geriatrics-related articles published in Physical Therapy. All articles indexed under "geriatrics" between January 1921 and June 1987 were identified and categorized in five-year time intervals to assess trends over time. Geriatrics-indexed articles generally appeared infrequently in the Journal, averaging one article every two years. All Physical Therapy articles published between January 1980 and June 1987 were read to determine whether they exhibited a geriatrics orientation. An average of six geriatrically oriented articles appeared in the Journal annually (about 5% of all articles annually). An increased number of geriatrics articles appeared in the Journal between 1980 and 1987. An imbalance clearly exists when an age group that comprises 25% of our patient population receives attention in only 5% of the Journal articles. As a profession, we must examine our attitudes toward and perceptions about elderly persons if we are to address their needs responsibly.

High voltage versus low voltage electrical stimulation. Force of induced muscle contraction and perceived discomfort in healthy subjects

High voltage pulsed galvanic stimulation (HVPGS) and low voltage neuromuscular stimulation (LVNMS) techniques were compared for peak torque of an induced isometric contraction, perceived discomfort, and subjective preference of treatment. The high voltage current used a 40-microseconds monophasic waveform, and the low voltage current used a 300-microseconds biphasic waveform. Both currents used a pulse rate of 50 pps. Both HVPGS and LVNMS were administered to one muscle group, either knee extensors or plantar flexors, of 24 healthy subjects. An isokinetic dynamometer was used to assess peak torque. The perceived discomfort experienced with each type of electrical stimulation was quantified by the use of a visual analog scale. For all dependent measures, data first were analyzed for the whole treatment group and then analyzed for each subgroup. Correlated t tests for the whole group and the plantar flexor muscle subgroup demonstrated that HVPGS produced a significantly greater average peak force of muscle contraction than LVNMS and HVPGS was perceived to be significantly less uncomfortable than LVNMS. No significant differences were found between treatments in the knee extensor muscle subgroup for these dependent variables. Chi-square analysis revealed a subject preference for HVPGS in the whole group and in both subgroups. This study indicates that HVPGS can produce a stronger, less uncomfortable, induced isometric muscle contraction than LVNMS.

Changes in sympathetic tone associated with different forms of transcutaneous electrical nerve stimulation in healthy subjects

The purpose of this study was to determine the effect of four different forms of transcutaneous electrical nerve stimulation (TENS) on sympathetic tone in healthy subjects. Twelve subjects received high frequency, low frequency, burst frequency, and placebo stimulation to one upper extremity. Treatments were given on different days. Ipsilateral and contralateral fingertip skin temperatures were measured at three intervals for each treatment: 1) after a 25-minute rest period before stimulation, 2) after a 25-minute treatment, and 3) 25-minutes posttreatment. High, low, and burst frequency TENS significantly increased sympathetic activity in the ipsilateral extremity immediately after treatment. Similar trends in temperature change were seen on the contralateral side. The effects of the three nonplacebo treatments did not differ from each other. Further research is needed to assess sympathetic effects of TENS on patient groups. The results suggest that monitoring skin temperature as part of a TENS assessment may be warranted, especially in patients with distal vascular impairments.

Automated microdensitometry and quantification of lipoproteins by agarose gel electrophoresis

A major obstacle in the application of quantitative microelectrophoresis has been tedious manipulations and calculations. To overcome these difficulties, we have developed an automatic system for the microdensitometry and calculations as part of a quantitative agarose gel electrophoresis facility. Results are internally standardized by serum cholesterol and/or triglyceride measurements. The hardware consists of a densitometer, an analog to digital converter, a cathode ray tube terminal, a teleprinter, and a small computer. A program in 4K words allows sample coding, electrophoretic scan display, indexing, and systematic identification of each peak. Data are acquired from scans of electrophoretic patterns of serum alone or in combination with the 1.006 gm/ml VLDL top and/or bottom preparative lipoprotein fractions. As many as 30 scans can be stored in 4K words of memory and then sent via high-speed telephone line to a larger computer for remote processing. The analysis corrects for baseline drifts and pre-beta asymmetry and will properly identify and quantify the amount of VLDL, LDL, and HDL with corrections for "sinking pre-beta" and "floating beta" in LDL and VLDL, respectively. Results are given in milligrams per 100 milliliter as well as percentile rank and standard deviation score ranking of each lipoprotein class as compared to an appropriate normal reference population. The latter data are in a form more meaningful to the physician and patient and provide a quantitative dimension to lipoprotein phenotyping.