Synthetic Biologic Application to T-cell Engineering

T-effector cells (T-cells) are immune cells whose major role is surveillance for and destruction of virally infected cells. These cells are capable of homing to the sites of infection where they exit the vasculature, divide and kill infected cells but leave uninfected cells unharmed. We have long sought to harness their potency and extreme selectivity for therapeutic purposes.

T-cells can be easily obtained from blood and cultured and expanded in vitro. Further, it has been possible to selectively expand T-cells specific for a particular virus in vitro. Administration of these specific T-cell populations are remarkably effective and non-toxic treatments for certain rare virally driven cancers. Until recently however, it has been difficult if not impossible to select and expand T-cell populations specific for more common cancers since cancer cells, unlike virally infected cells do not contain foreign proteins. Gene vector technology developed for gene-therapy have allowed us a radically solution: By introducing a new gene coding for an artificial receptor, we can easily generate large populations of T-cells specific for any antigen. This approach of using genetically engineered T-cells as a medical therapy, has been tested by us and others in early clinical studies with much promise.

The T-cell engineering field however is still in its infancy. Typically, we introduce a single new gene into T-cells to cause a simple change such as an alteration of specificity. Although a range of different engineering components have been made for example triggering homing to certain tissues, inducing enhanced proliferation etc. these components do not interconnect with each other. In addition, they are not well characterized - for instance triggering thresholds, dynamic range of signalling etc might be unknown. This means that T-cell engineering is inefficient, relying largely on trial error. Finally, in its current state, the tremendous potential of engineering T-cells with very complex new behaviours cannot be realized. Synthetic biology is a new area of biological research that combines science and engineering. It attempts to formalize the engineering of complex biological systems not found in nature by applying principles developed largely in electronic engineering. We believe the logical next step is to bring T-cell engineering into the synthetic biology era.

To achieve this, we plan the following: (1) generate a set of advanced inter-connectible T-cell engineering components (parts); (2) characterize their dynamic functional characteristics in detail; Once some of these parts are constructed and characterised we will apply for other funding to develop numeric methods to model systems developed from combinations of these components. This will allow us to develop complex systems based on these models first in silico, then in actuality.

with this work, we hope to advance the T-cell engineering field into the synthetic biology era. We anticipate that we will be able to then create advanced therapies based on heavily engineered T-cells leading to an entirely new field of therapeutics.

The administration of genetically modified immune effector cells (T-cells) is promising new form of cancer therapy. For instance, we have shown that administration of T-cells engineered to recognize a cancer antigen can result in clinical responses in children with neuroblastoma. T-cells have been engineered with a wide variety of disparate transgenes to alter their function for therapeutic effect: Typically, transgenes have altered the T-cell's specificity to a surface antigen (Chimeric Antigen Receptors, CAR), or to an epitope of an intracellular antigen (native TCR transfer). More recently, we and others have introduced transgenes which alter a T-cell's behaviour, for instance suicide genes, homing receptors and cytokines, or knocked out expression of single genes. To date however, this work has largely involved a single genetic modification. We propose to build on this work, increasing the complexity of genetic alteration to result in not only a single effect but to allow re-programming of T-cells with new more complex cellular behaviours for therapeutic application. We hope to achieve this by application of synthetic biology principles to T-cell engineering. We plan the development of new well characterized inter-connectable components. We ultimatley plan design, model and then build systems composed of combinations of these components. In this way we hope to develop therapeutics with heavily engineered cells which should exceed the complexity and refinement possible with traditional therapeutics such as small molecules or therapeutic proteins.

The application of synthetic biology principles to T-cell engineering will have impact on medical research, broad areas of biological science including systems biology. In addition, this work will lead to intellectual property of considerable commercial value.

*Translational (Clinical) Applications. We and others have already shown some promise of engineered T-cells in phase I clinical studies of cancer. With this work, we hope to improve the performance of these therapeutic T-cells to allow us to engineer cellular therapies that can solve therapeutic problems that are intractable with current technology. Cancer therapy is an illustrative example. Here, the challenge is essentially the ability to discriminate cancer cells from normal cells. Current cancer therapies are toxic since while they are selective to some extent for cancer cells, their broad biological effects damage normal tissues as well. However, cancer cells are distinguishable from normal cells: for instance expression of a particular antigen may be present in an unusual anatomical location, or the expression of a pattern of several surface antigens may be unique to the cancer etc. This type of recognition is clearly not achievable with a small molecule which disrupts a single metabolic pathway, or a therapeutic antibody which binds a single target. Conversely, this type of recognition could well be programmed into a T-cell. In this way, we hope to develop the technology which could lead to a sophisticated cellular therapies with a high degree of specificity, low toxicity and persistence. This approach has the potential to lead to whole new branch of medicine - namely advanced cellular therapeutics.

*Scientific Applications. ("What I cannot create, I do not understand", Richard Feynman, 1988). A detailed and precise understanding of these artificial components may prove of use to those in the systems biology field. The analytic and numerical methods used to study and model these components may also prove useful in their own right. For instance, the large numbers of fluorescent protein re-complementation and transcriptional reporters may prove useful to systems biology researchers.

*Biotechnological Applications. Although the primary aim of this work is therapeutics (see below), some of these components, and perhaps development of this approach in eukaryotic cells may prove useful to biotechnology in general. Synthetic biology is a growing area of research. With some notable exceptions, most of the researchers in the field are focusing on bacteria with a view to applications in material, chemical and environmental sciences. Very little synthetic biology work is done in eukaryotic cells. However, eukaryotic cells are invaluable for certain biotechnology applications. For instance, production of therapeutic proteins which require considerable post translational modification, cellular display systems for small-molecule drug development, tissue engineering, transgenic animals etc. This work may benefit these areas.

*Commercial Impact. the world-wide market for cancer therapeutics is considerable. Cellular therapies fall outside the usual paradigm of big pharma and were considered too complex to market. However, this is changing - cellular therapies are slowly being licensed and commercialized: For instance, Sipuleucel-T (APC8015, Provenge), a cellular therapeutic for Prostate cancer from Dendreon Corporation has been licensed by the FDA, costing approximately $93,000 a treatment. Osiris (a cellular therapy startup), has recently been purchased by Genzyme corporation the world's largest maker of drugs for rare genetic disorders, and well known for commercializing first-in-class biotechnologies. Closer to home, CellMedica a T-cell therapy company is rolling out its first phase III study. T-cells This project to engineer T-cells with complex therapeutic behaviours will create commercially relevant technology in an area of growing commercialization.