Relapsed or drug-resistant leukemia and/or lymphoma are very difficult to cure using the traditional work horses of cancer therapy, surgery, radiation and chemotherapy. New classes of therapies need to be developed. In my laboratory we are using the patient’s immune system to directly attack the disease. This therapy harnesses the power of T cells, a type of immune cell, and uses gene therapy to redirect the function of the T cell so that it can target a patient’s leukemia and/or lymphoma. These are exciting times for immune-based therapy and we expect that the experiments funded by ACGT will provide critical insights into designing new ways of using T-cells to treat patients.

ACGT funds were used to genetically modify T cells to redirect their specificity to desired tumor-associated antigens (TAA).  This was accomplished by the development of a chimeric antigen receptor (CAR) that redirects specificity to TAA displayed on the cell surface independent of the major histocompatibility complex (MHC).  Over the course of our funding we developed a 1st generation CAR that relies solely on CD3-ζ endodomain to activate T cells for CAR-dependent lysis (major finding #1).  This resulted in our first gene therapy trial infusing CD19-specific CAR+ T cells after lymphodepleting chemotherapy (major finding #2).  This trial showed that the design of the CAR was insufficient to fully-activate T cells for a fully competent signal and that the presence of bacterial and viral transgenes in the expression vector led to deleterious immune-mediated clearance.  Therefore, a 2nd generation CAR was designed that could not only lyse CD19+ tumor targets, but could activate the T cells for sustained proliferation by signaling through CD28 as well as CD3-ζ (major finding #3).  We developed a new non-viral gene transfer strategy based on the Sleeping Beauty (SB) system (major finding #4) to improve the efficiency of CAR integration and together with the development of CD19+ artificial antigen presenting cells (aAPC, major finding #5), we developed an approach to generate T cells without the need to express immunogenic transgenes.  A next-generation clinical trial for first-in-human application of the SB system and CD19+ aAPC has been favorably reviewed by NIH-OBA (major finding #6) and is currently being reviewed by the FDA (major finding #7).  This upcoming trial will infuse autologous 2nd generation CD19-specific T cells in patients who are undergoing autologous hematopoietic stem-cell transplantation.  In addition to developing the scientific rational for targeted therapy using CAR+ T cells we also developed the infrastructure to translate basic immunology into applied practice by establishing a laboratory within a laboratory that operates in compliance with current good laboratory practices. This group works seamlessly with the manufacturing team to generate clinical-grade T cells in compliance with current good manufacturing practice. Furthermore, we established a clinical trials team to be able to conduct gene therapy trials, including a regulatory affairs group to handle the administrative burden of reporting to institutional and federal regulatory oversight bodies.  And, we put in place a group to undertake correlative studies to help understand the biologic impact of adoptive transfer of T cells.  In aggregate, with the help of ACGT funding we were able to develop a program to genetically modify T cells with desired specificity for CD19+ tumors and initiate a series of gene therapy trials to test the safety and feasibility of infusing CAR+ T cells.

Recently, the use of tumor-killing viruses has gained favor in cancer gene therapy in an approach that has become known as “virotherapy.” Virotherapy exploits viruses that are able to target and destroy cancer cells, while sparing the surrounding normal tissue. We are developing a virotherapy approach for the treatment of prostate cancer based on infection with Sindbis virus.  

The ability of Sindbis virus to travel rapidly throughout the body in the bloodstream will improve access to metastasized cancer cells. We intend first to develop and test these agents in cultured cells. We will then test and optimize the ability of the virus to cure prostate cancer.

Since most human tumors must recruit new blood vessels in order to grow and move, anti-angiogenic therapies have been viewed as a potential complement to more traditional cancer treatments. We have identified a genetic element that allows genes to be expressed in a group of bone marrow derived cells that contribute to cancer-associated blood vessels.  

The cells are called “endothelial cell precursors” (ECPs). ECPs are a special type of stem cell that play a role in the formation of new blood vessels. We propose to create a simple virus designed to carry genes to ECPs and prevent them from helping tumors to grow. 

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.

A promising approach in cancer treatment is to vaccinate patients against molecules expressed by cancer in hopes of starting or awakening an immune response that will kill tumor cells. One leading strategy bases the center of such vaccines on the patient’s own immune cells, which are removed from the body and re-engineered outside the body before re-injection.  

With this grant, we will evaluate a novel gene therapy vaccine specifically designed for children with cancer, for whom very few attempts at cancer vaccination have been undertaken. This work will establish the scientific and manufacturing rationale for translating this gene therapy technology to the clinic, especially for children with cancer.