Brain Tumor SPORE Projects

Maciej S. Lesniak, MD
Roger Stupp, MD
Adam Sonabend, MD

Glioblastoma remains resilient to therapy and recurrence is almost universal. In particular, targeted therapies fail given the heterogeneity in the expression or presence of molecular targets for these therapies across tumors. Oncolytic virotherapy (OV) is an anti-tumoral strategy where viruses selectively replicate and kill tumor cells in the brain and potentially, activate anti-tumoral immune response. Initial studies showed that a bottleneck for the efficacy of OV was poor distribution of virus in the human brain. To overcome this challenge, over the last SPORE funding period, we investigated the feasibility and safety of delivering oncolytic adenovirus to the peri-tumoral brain of malignant glioma patients using neural stem cells (NSC) which can carry OV, and migrate to distant tumor pockets infiltrating the brain. We conducted a Phase 1 trial in which we showed the feasibility, safety and established a maximally-tolerated dose for this therapy (NCT03072134) and published the results in Lancet Oncology. The next step in this program is to perform a phase II trial to investigate the efficacy of OV using overall survival as an endpoint for efficacy. However, a phase II trial needs to be optimized via additional studies proposed in this continuation of funding by 1) enabling multiple injections over time, to be accomplished through a novel brain parenchymal catheter-based delivery system (Renishaw ®). 2) maximizing NSC viability and OV production using N-acetylcystein Amide (NACA), which we showed to enhance delivery and efficacy of this therapy, and 3) a priori-identification of patients with tumors that are susceptible to OV. We hypothesize that only a subset of patients might have tumors that are susceptible to OV, and that identification of susceptible tumors will allow elucidation of an efficacy signal.  In this continued renewal of Project 1, we now propose the following specific aims:

Specific Aim 1: Conduct a phase 1B expansion trial utilizing a novel catheter method to deliver multiple injections of product in newly diagnosed malignant gliomas

Specific Aim 2: Examine the pre-existing tumor microenvironment, the effect of NACA on viral replication, and the immune response during NSC-OV therapy in malignant glioma patients.

Specific Aim 3:  Validate genes that are implicated in glioma susceptibility to oncolytic virus using paired analysis of pre-treatment and during-treatment human glioma specimens

Amy Heimberger, MD, PhD
Rimas V. Lukas, MD
Irina V. Balyazsnikova, PhD

The glioblastoma (GBM) microenvironment is dominated by myeloid cell infiltrates. Results from multiple studies indicate these tumor-associated myeloid cells (TAMS) as supporting GBM growth. The goal of this project is to reprogram TAMS for immunologic anti-tumor activity. Stimulator of interferon genes (STING) is a widely expressed sensor of cellular stress that is activated by the presence of DNA in the cytoplasm. Distinct from most other immune agonists, STING activation re-educates tumor supportive M2 macrophage TAMS toward a proinflammatory anti-tumor M1 phenotype. Macrophage proinflammatory phenotypic conversion, in turn, promotes cytotoxic T cell infiltration of and activity against tumor. We have developed a high potency STING agonist, IACS-8803, with marked antitumor activity when tested in humanized mice bearing human GBM, and in canines with spontaneously arising high-grade gliomas. In addressing the clinical potential of this agonist in treating GBM, we will first determine its effect on interferon responses, using [¹⁸F]FLT PET, when IACS-8803 is administered to patients with recurrent tumor. This first-in-man Phase I clinical trial will inform regarding the range in IACS-8803 activity that is observed across the cohort of treated patients, with activity results compared against tumor molecular characteristics, and patient clinical data. The clinical trial will include analysis of several unique endpoints, among which are target engagement and longitudinal kinetics of IACS-8803 induced T cell chemokine expression such as CXCL10. In addition, a window-of-opportunity patient cohort will receive direct intratumoral administration of IACS-8803, and whose results will be compared against those from patients that have received systemic administration of standard-of-care therapeutics. The PET Imaging results will be analyzed with respect to inflammatory immune response in resected tumors from active vs. non-active tracer regions in post-STING treated subjects, using multiplex immunofluorescence, CyTOF, and/or mass cytometry. This clinical study will ultimately provide sufficient data to make a clear go/no go determination for later-stage clinical trials based on sufficient target engagement in the tumor microenvironment. While conducting this clinical trial, we will move forward with preclinical research by evaluating the efficacy of combined IAC-8803 + radiation in orthotopic models of GBM. Results from these preclinical studies will inform whether STING agonist and radiation treatment should be tested in patients with newly diagnosed GBM, and whose tumors have unmethylated MGMT promoter, and as such, do not require treatment with temozolomide

Catalina Lee-Chang, PhD
Roger Stupp, MD
Maciej S. Lesniak, MD

Immunotherapy has significantly improved the clinical outcome of many cancer patients. However, most glioblastoma (GBM) patients have not, so far, benefited from immunotherapeutic intervention. To explore alternative ways to potentiate the anti-GBM immunity, we've developed a B-cell-based vaccine (B_Vax) that consists of 4-1BBL⁺ B cells activated with CD40 agonism, BAFF, and IFNg stimulation. In our preclinical study, B_Vax migrates to critical secondary lymphoid organs and is proficient at antigen cross-presentation, promoting the survival and functionality of tumor-infiltrating CD8⁺ T cells. In addition, B_Vax produces immunoglobulins (humoral immune response) reactive to the tumor. These immunoglobulins elicited a potent therapeutic effect.  A combination of radiation, B_Vax, CD8 T cells and PD-L1 blockade conferred tumor eradication in 80% of treated tumor-bearing animals. This research proposal aims to translate B_Vax to the clinic to treat newly diagnosed malignant gliomas. To effectively implement this therapy in the clinic, we propose to perform IND-enabling studies to manufacture autologous B_Vax and CD8 T cells (Aim 1). Upon FDA approval, we aim to conduct a first-in-human B_Vax trial (Aim 2) and evaluate the effect on the immune response (Aim 3). We hypothesize that the proposed autologous cellular therapy is safe and effective at eliciting protective anti-GBM immunity via cellular and humoral immune responses. Overall, our study provides a novel alternative to current immunotherapeutic approaches.

Atique Ahmed, PhD
Priya Kumthekar, MD

Glioblastoma (GBM), a grade IV tumor, is one of the most aggressive and infiltrative brain cancer forms. Patients currently diagnosed with Glioblastoma (GBM) have an abysmal prognosis. The median survival is around 8-10 months, even after the standard care protocol of surgical resection followed by alkylating chemotherapy (typically temozolomide or TMZ) and radiotherapy. This is because, in nearly all patients, the tumor recurs after treatment since GBM cells can become resistant to therapy. Our laboratory's goal is to develop a treatment for GBM that will reduce the recurrence rate and improve the prognosis for patients. One of the distinguishing characteristics of cancer is its uncontrolled cell division. Since cancer cells divide more rapidly than normal cells, they require more purines, the building blocks of DNA and RNA. Purines are either synthesized from amino acids and other small molecules through the de novo biosynthesis pathway or are recycled from the microenvironment through the salvage pathway. Cancer cells use the de novo biosynthesis pathway, whereas the central nervous system usually relies more on the salvage pathway. We have identified ARL13B as a novel regulator of the purine biosynthesis pathway during chemotherapy through initial analysis. ARL13B, a member of the ADP-ribosylation factor-like family protein accountable for cilia maintenance, directly interacts with inosine monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme purine biosynthesis. Our initial studies knocking down ARL13B inhibited GBM cells' utilization of the de novo pathway after TMZ treatment and increased utilization of the salvage biosynthesis pathway. The effectiveness of TMZ treatment was also elevated in vitro and in vivo following ARL13B knockdown. We, therefore, proposed that the ARL13B-IMPDH2 regulated switch from the salvage pathway to the de novo purine biosynthesis pathway is necessary for GBM cells' adaptation to alkylating-based chemotherapy. Based on this, we hypothesize that therapeutic transformation in GBM involves interaction between ciliary protein ARL13B and rate-limiting purine biosynthesis enzyme IMPDH2 Mycophenolate mofetil (MMF), an FDA-approved drug in the organ-transplant setting, inhibits IMPDH2 activity and allows for increased the therapeutic efficacy of TMZ and extended the survival of patient-derived xenograft (PDX) models across multiple GBM subtypes. This provides a clinically translatable opportunity to overcome chemoresistance in GBM.

In this proposal, we set to conduct a Phase 1/1b clinical trial of MMF combined with standard chemo- and radiotherapy for newly diagnosed GBM. The primary objectives are to evaluate this novel combination's safety and toxicity and establish the maximally tolerated dose (MTD). Exploratory secondary endpoints include progression-free and overall survival. Furthermore, we intend to investigate mycophenolic acid, an immediate metabolite of MMF that can serve as a biomarker for such therapy.