Harnessing a patient’s own immune system to attack blood cancers has recently enjoyed remarkable success. In one strategy, a patient’s T cells are harvested, reprogrammed to recognize the cancer as foreign, and then returned to the body. The reprogrammed T cells produce a novel artificial protein, a chimeric antigen receptor commonly called a CAR, which brings together the ability of two other proteins: one that recognizes the tumor cells and another which can stimulate the T cell to attack.
These so-called CAR-T cells are highly effective and specific anti-tumor agents that kill tumor cells and further stimulate other parts of the immune system. In several recent clinical trials, approximately 70% of terminally ill patients, refractory to standard treatments, were cured by CAR-T therapy. However, most protocols reprogram the T cells to express the CAR by permanently altering their DNA using retroviruses.
We have developed an alternate system, using RNA, which transiently reprograms the T cells to attack the cancer. This approach has many benefits including increased safety, speed, control and the ability to deliver multiple beneficial proteins at the same time. The flexibility to accurately adjust therapeutic conditions and introduce different proteins into T cells at different times according to the needs of the patient makes this a useful tool for individualized medicine. Moreover, RNA reprogramming is essentially transient. After conclusion of the therapeutic treatment all of the RNAs and the proteins they make are degraded and the T cells return to their normal state, which minimizes any possible side effects of the treatment. Our technology has wide applicability for many different tumors and a high potential for further development.
Despite the success of CAR-T cells in blood cancers, duplicating these achievements in solid cancers like breast cancer, melanoma and sarcoma remains a “holy grail” for the field. Two key barriers to success are (1) most CAR-T cells that recognize solid cancers also recognize normal tissues, and (2) solid tumors have the ability to prevent the activation of T cells. The ability of our RNA approach to make multiple helpful proteins in the patient’s T cells in one-shot has the potential to overcome both of these obstacles. In addition to the CAR, our RNA approach provides proteins that limit the T cell’s ability to attack normal tissues, and other proteins that will help the T cell survive and be active while it avoids the suppressive signals being sent to it from the solid tumor. Collectively, this approach will induce the CAR-T cells to become more sensitive, specific and effective killers of solid tumors.
This Alliance for Cancer Gene Therapy Research Fellow is funded in part by Swim Across America.
Re-activating and directing a cancer patient’s immune system to reject their tumors and eradicate the cancer with minimal toxicity to the patient is the ultimate goal of the cancer immunotherapy field. The field has made great progress, with multiple immunomodulatory antibody therapies already approved and more in the therapeutic pipeline. Additional progress has been seen in recent successful cancer treatment using genetically modified T cell-based therapy. These advances in cancer immunotherapy represent the clinical translation of research into the signals that activate and inhibit cells of the immune system, particularly T cells.
We believe that through understanding the molecular mechanisms by which recent translational approaches have been successful we can establish a strong foundation for the rational design of new approaches to T cell cancer immunomodulatory therapy.
Specifically, we believe that by investigating connections between two of the signaling molecules targeted in developing antibody and cell based Immunotherapeutics, PD-1 and 4-1BB, and two transcription factors critical to effective and durable T cell immune responses, T-bet and Eomesodermin (Eomes), we will identify T cell molecules and signaling pathways representing promising future targets in cancer immunotherapy.
Our prior work has described the functions of T-bet and Eomes in determining T cell behavior in immune responses. Our preliminary data show that Eomes is essential to cancer immunotherapeutic approaches targeting either PD-1 or 4-1BB on T cells. In the proposed project we will determine how Eomes contributes to T cell anti-tumor activity and determine what, if anything, is needed in T cells beyond Eomes to enact a strong and durable anti-cancer response. The Alliance for Cancer Gene Therapy funded research will provide new insights into the mechanisms of cellular cancer immuno-modulatory therapy that we will use to design and test novel cancer immunotherapeutic approaches.
This Alliance for Cancer Gene Therapy Research Fellow is funded in part by Swim Across America.
Ovarian cancer is the leading cause of gynecologic cancer death, and though most patients respond to initial chemotherapy, the majority will eventually relapse and die of chemotherapy resistant disease. Despite the advent of newer chemotherapies, the five-year survival for patients with advanced disease remains only 25 percent, and few patients are cured.
In preliminary studies, we have developed genetically engineered T cells as a complementary immunotherapy to augment traditional treatment strategies. The engineered T cells eradicate large tumors in pre-clinical experiments.
In this project, we will conduct FDA-mandated pre-clinical experiments, manufacture clinical grade vector, obtain local IRB approval and FDA and NIH/OBA RAC federal approval for the protocol, and then conduct the clinical protocol.
The protocol will test whether the T cells that are designed to withstand the toxic effects of the tumor are able to mediate tumor regression in patients with advanced ovarian cancer that has failed to regress after chemotherapy.
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.
