Focus: Gioblastoma

Ahmed

Glioblastoma (GBM) is the most common brain cancer and remains largely incurable. The recent identification of chemotherapy and radiotherapy resistant stem cells in GBMs may help explain why conventional therapies are ineffective.  

Immunotherapy may be able to kill GBM stem cells since immune-mediated killing does not rely on the conventional mechanisms of cell killing. HER2 is tumor protein is positive in >80% of GBMs, but not by the normal brain, making it an attractive target for immunotherapy.  

We have shown that HER2-specific T cells from GBM patients kill GBM stem cells and induce remission of GBMs grown in mice. We now wish to evaluate our approach clinically and test if HER2-specific T cells can be safely given to patients with HER2-positive GBMs (Aim 1) and intend to study their will persistence and antitumor activity in the human body (Aim 2).  

While our preclinical studies demonstrated the potent antitumor activity of HER2-specific T cells, tumors recurred in several treated animals. This limitation in T-cell efficacy is most likely due to the inhibitory tumor environment. GBMs (including GBM stem cells) contain high level of the STAT3, a protein which is not only necessary for GBM stem cell survival but also induces the expression of T cell suppressive factors. Thus, Aim 3 will test in preclinical models our hypothesis that combining STAT3 inhibition with HER2-specific T cells will more effectively eradicate GBMs than T cells alone.  

Cooper

Scatter factor/hepatocyte growth factor is a pleiotropic growth factor that binds to c-Met, a proto-oncogene encoded tyrosine kinase receptor ubiquitously present on most malignant gliomas. This grant application seeks to infuse thawed allogeneic T cells that have been rendered c-Met-specific for the treatment of gliomas.  

Buidling upon on our experience infusing autologous and allogeneic T cells genetically modified to express a chimeric antigen receptor (CAR) to redirect specificity for a desired cell-surface antigen (such as CD19 on B-cell malignancies) and our novel platform technologies that have been adapted for clinical translation using (i) the Sleeping Beauty (SB) transposon/transposase system to stably express CAR transgenes and (ii) artificial antigen presenting cells (aAPC) derived from K562 cells to propagate genetically modified T cells in a CAR-dependent manner to clinically-sufficient numbers.  

We have designed a 2nd generation CAR, designated cMetRCD28, to render T cells specific for c-Met independent of MHC. To conditionally activate cMetRCD28+ T cells under conditions of hypoxia thereby limiting deleterious targeting of normal tissues expressing c-Met, this CAR has been fused to the oxygen-dependent degradation domain (ODDD) which results in degradation of cell-surface CAR-ODDD protein under conditions of normoxia, but not hypoxia found in the tumor microenvironment.  

To generate allogeneic T cells from a 3rd party to be infused “on demand” we will co-express the CAR-ODDD with designer zinc finger nuclease (ZFN) (or inhibiting RNA species) to eliminate endogenous expression of alpha/beta T-cell receptor (TCR). The cMetRCD28-ODDD and ZFN transgenes will be electro-transferred into T cells using the SB system and selectively propagated on c-Met+ aAPC.  

This approach will be further developed to co-express a mutein of thymidine kinase (sr39TK) from herpes simplex virus-1 for in vivo conditional ablation with ganciclovir and imaging by positron emission tomography (PET). Aim #1 evaluates whether cMetRCD28+TK+TCRneg T cells lyse gliomas. The ability for these T cells to survive/propagate under hypoxia will be determined.  

Aim #2 evaluates the ability of cMetRCD28+TK+TCRneg T cells to selectively eliminate hypoxic c-Met+ glioma in an orthotopic xenogeneic mouse tumor model, using bioluminescent imaging and micro-PET to asses T-cell persistence and anti-tumor effect. Aim #3 evaluates in a human Phase I clinical trial the safety, feasibility, persistence and efficacy of thawed allogeneic cMetRCD28+TK+TCRneg T cells delivered loco-regionally after initial resection. PET/CT imaging using [18F]-FHBG metabolized by sr39TK will be used to evaluate the distribution of adoptively transferred T cells.  

In aggregate, these studies will develop new targeted cell and gene therapy for gliomas using our established clinical platform technologies and as c-Met is expressed on many extra-cranial solid tumors this approach may have broad application.  

Davidoff

Brain tumors are among the leading causes of cancer-related death in both adults and children, with malignant gliomas being one of the most aggressive and difficult to treat. Clearly, new strategies for treating patients with this disease are desperately needed. Type I interferons (IFN) have potent, pleiotropic anti-tumor activity. Despite exciting pre-clinical results, however, the anti-tumor efficacy of IFN in clinical trials has been limited.  

Important contributing factors have included a very short half-life, making effective dosing problematic, and significant systemic toxicity at therapeutic doses. We hypothesize that an alternative method and schedule of drug administration in which there is continuous, local delivery should avoid the systemic toxicity of IFN while maximizing its potent anti-tumor activities.  

We believe that a gene therapy approach in which adeno-associated virus (AAV) vectors are used to transfer an expression cassette for IFN-B to target cells is the safest and most effective way to establish continuous, local delivery of IFN. Because GBM, unlike most human cancers, is problematic locally, rarely being metastatic, it is a tumor particularly well suited for this approach. The overriding goal is to obtain sufficient preclinical safety and efficacy data to support and initiate a clinical trial of local AAV IFN-B mediated gene transfer for patients with recurrent malignant glioma. 

 The major specific aims are: Aim 1: To complete the demonstration of anti-tumor synergy between AAV-mediated local delivery of IFN-B and adjuvant cytotoxic therapy, in relevant brain tumor models. Aim 2: To assess the safety of AAV-mediated continuous local delivery of IFN-B in the brain using relevant rodent and nonhuman primate models. Aim 3: To perform a Phase I dose-escalating clinical trial of local administration of AAV IFN-B to the resection bed in patients with recurrent glioblastoma multiforme following surgical removal of recurrent disease. 

 We feel that our approach has a high likelihood of resulting in a successful clinical trial for the following reasons: 

 1. Pre-clinical data. We have very encouraging pre-clinical data using a highly relevant orthotopic rat resection model that AAV-IFN-B has significant anti-tumor activity against residual human GBM xenografts.  

2. GMP vector production facility. We have our own GMP facility on campus to make clinical grade AAV vectors. In addition, we have developed a baculovirus-mediated production system that generates AAV at very high titer. 

 3. Toxicity studies. We have access to nonhuman primates on campus to perform relevant, pre-clinical toxicity studies. 

 4. Experience with gene transfer clinical trials. We have just opened a clinical trial of AAV-mediated, liver-targeted gene transfer for hemophilia B.  

5. Access to patients. Through our collaboration with the Neurosurgery Department at the University of Tennessee Health Science Center, Memphis, we have access to a large number of patients.