ADOPTIVE T CELL THERAPY Presented by Md. Farhadur Rahman Phase A Student Department of Microbiology BSMMU

OUTLINE BACKGROUND IMMUNE BIOLOGY HISTORY SCIENTIFIC CONCEPT ENGINEERED T CELLS AUGMENTATION OF EFFICACY OF ACT ADVERSE EFFECTS

The transfusion of lymphocytes, referred to as adoptive T cell therapy, is being tested for the treatment of cancer. The cells may have originated in the same or in a different individual. Adoptive T cell therapy has the potential to enhance antitumor immunity, augment vaccine efficacy, and limit graft-versus-host disease (GVHD).

This form of personalized medicine is now in various early- and late-stage clinical trials. These trials are currently testing strategies to infuse tumor-infiltrating lymphocytes (TIL), CTLs, Th cells, and Tregs. Improved molecular biology techniques have also increased the enthusiasm and feasibility for testing genetically engineered T cells.

Background The most common treatment for cancer is chemotherapy Chemotherapy, though helpful, also causes unwanted side effects Chemotherapy focuses on inhibition of tumor cells in order to decrease growth rate

Adoptive cell therapy (ACT) However, some natural cells have high growth rate, such as the skin and GIT mucosa, these cells can be adversely effected by chemotherapy An alternative solution has developed called: Adoptive cell therapy (ACT)

Immune Biology Cells Of Tumor Immunity T Lymphocytes Lymphocytes express highly specific antigen receptors on their surface and thus are highly specific for a given epitope. CD8+ cells kill target cells by recognizing foreign peptide-MHC molecules on the target cell membrane. IL-2 causes proliferation and activation of T cells.

Natural Killer Cells Macrophages By detecting reduced number of MHC molecule on the cancer cell surface By ADCC Macrophages

Tumors Cancer cells must express antigens recognizable and accessible to the immune system. The immune system must in turn be able to mount a response against cells bearing such antigens. Tumors possess a varying degree of Immune “Antigenicity” that is unique to each tumor and thus be rejected by Immunocompetent hosts.

HISTORY In the 1960s, syngeneic lymphocytes were transferred from rodents heavily immunized against the tumor to inhibit growth of small established tumors, the first example of ACT. In 1976, description of T cell growth factor interleukin-2 (IL-2) allowed T lymphocytes to be grown in vitro.

In 1985, IL-2 administration produced durable tumor regressions in some patients with metastatic melanoma. In 1986, human TILs from resected melanomas were found to contain cells that could recognize autologous tumors. In 1988, autologous TILs were shown to reduce metastatic melanoma tumors.

In 1989, Israeli scientist Zelig Eshhar published a study in which he replaced the T cell’s natural receptor. In 2002, lymphodepletion using a nonmyeloablative chemotherapy regimen administered immediately before TIL transfer increased cancer regression.

In 2006, administration of normal circulating lymphocytes transduced with a retrovirus encoding a T-cell receptor (TCR) that recognized the melanoma-associated antigen recognized by T cells 1 (MART-1) antigen, mediated tumor regression. In 2010, administration of lymphocytes genetically engineered to express a chimeric antibody receptor (CAR) against B cell antigen CD19 was shown to mediate regression of an advanced B cell lymphoma.

By 2010, doctors had begun treating leukemia patients with CD19-targeting T cells with added DNA to stimulate cells division. In August 2012, Novartis donated $20 million to the University of Pennsylvania to build a cell-therapy center.

To date, engineered T cells seem to quickly disappear from many patients. However, genetic engineering has allowed T cells to disable molecules called Programmed death-ligand 1 (PD-L1) that turn T cells off, called checkpoint therapy.

Scientific Concept Basic steps: Collection of T cells that Are highly specific for cancer cells Last a long time Proliferation of T cells in vitro Transfusion of T cells

Collection of T cells From peripheral blood: After vaccination, by apheresis, peripheral blood lymphocytes are collected, polyclonal in vitro activation and expansion is performed and are reinfused. From draining lymph nodes: Patients are primed with tumor vaccine, lymphocytes are collected from draining lymph nodes, harvested and reinfused.

3. Tumor-infiltrating lymphocytes: Isolation of T cells from fresh patient biopsy specimens and the progressive selection of tumor-specific T cells ex vivo using high levels of IL-2 and various cell culture approaches and then reinfused.

TIL Tumor-infiltrating Lymphocytes TIL enrichment IL-2

4. Allogeneic T cells: Host is immunosuppressed by chemotherapy and haemopoitic stem cells (HSCs) are transfused from donor. Then T cells are collected from donor, harvested and transfused into host. Here is chance of GVHD.

Engineered T cells T cells engineered to express suicide molecules: To prevent severe and potentially lethal GVHD, T cells with an inducible suicide phenotype has been developed. Expression of herpes simplex virus thymidine kinase (HSV-TK) in T cells provides a means of ablating transduced T cells in vivo by the administration of acyclovir or ganciclovir.

T cells engineered to express tumor antigen-specific receptors: 1. Bispecific T cells are created by the introduction of genes that encode proteins that recognize antigens expressed by target tumor cells. 2. Chimeric Antigen Receptor (CAR) T cells: Here genes can encode chimeric tumor antigen-specific receptors, or T bodies, that target surface antigens in an MHC-independent fashion.

It is constructed by linking the variable regions of the antibody heavy and light chains to intracellular signaling chains such as CD3-zeta, potentially including costimulatory domains encoding CD28 or CD137.

T cells engineered for enhanced survival: A limitation to adoptive transfer of CTLs is that they have short-term persistence in the host in the absence of antigen-specific Th cells and/or cytokine infusions. CTLs with chimeric GM-CSF–IL-2 receptors that deliver an IL-2 signal when they bind GM-CSF.

Stimulation of the CTLs with antigen causes GM-CSF secretion and resulted in an autocrine growth loop such that the CTL clones proliferated in the absence of exogenous cytokines.

Augmentation of Efficacy of ACT Strategies to augment the efficacy of adoptively transferred T cells 1. Lymphodepletion by chemothrapy before transfusion 2. Antibody infusion to prevent CTLA-4 inhibitory effect 3. Antibody infusion to block PD L-1 – PD-1 interaction

4. Cytokines administration e. g. IL-2, IL-7, IL-12, IL-15, or IL-21 5 4. Cytokines administration e.g. IL-2, IL-7, IL-12, IL-15, or IL-21 5. Host Treg depletion or inhibition 6. Vaccine therapy

Adverse Effects Toxicity: Targeting normal, nonmutated antigenic targets that are expressed on normal tissues, but overexpressed on tumors has led to severe on-target, off-tumor toxicity. Cytokine release syndrome: As the tumor is destroyed, it turns into large quantities of smaller molecules that have proven fatal to at least seven patients.

Adoptive T cell therapy is the ultimate challenge to implementation of personalized medicine. To be commercially aviable, adoptive T cell therapy has to be clinically effective, scalable, reproducibly manufactured, and appropriately priced and marketed. However the major challenge facing the field at present is to conduct randomized clinical trials demonstrating sufficient clinical benefit to justify the logistics and expense of customized cellular therapies.