M.D., University of Manitoba, 1986.
B.Sc., University of Manitoba, Medicine, 1986.
Adoptive T Cell Therapy
Introduction and Synopsis
Adoptive cellular therapy involves the ex vivo isolation, enrichment and expansion of tumor-reactive T cells for infusion into patients with cancer. Unlike most conventional therapies, adoptive cellular therapy represents a non-cross-resistant modality that offers minimal toxicity and the potential for long-term immunoprotection from disease recurrence.
The T cells can come from the peripheral blood, tumor infiltrating lymphocyte population or may be engineered to express the antigen receptor by genetic modification.
Our work over the last 15 years has been focused on the generation of autologous antigen-specific T cells from the peripheral blood of patients; we have performed several first-in-man studies using ex vivo expanded antigen-specific T cells.
We developed strategies to isolate rare high-affinity tumor-reactive T cells from the peripheral blood of patients, expand these to several tens of billions and infuse them for the treatment of refractory, progressive metastatic melanoma. Our studies demonstrate long-term persistence of infused T cells with encouraging clinical results, sometimes complete long-lasting responses, and more often a significant delay in time to progression.
We have formulated a path forward to translate our work into a treatment modality that can become more widely applicable to other malignancies (breast cancer, ovarian cancer, sarcoma and others), to a larger pool of patients, and with relatively modest infrastructure requirements. Our research is focused on developing adoptive T cell therapy in combination with other immunomodulatory reagents including checkpoint inhibitors, vaccines and biologicals, and defining the intrinsic and extrinsic immune parameters for an effective, durable response. Below, we summarize our work to date and include a few selected footnote references.Tumor-reactive T cells circulate in peripheral blood of patients
These cells are present in rare numbers in the circulation but can be identified using peptide-MHC tetramers, which are several cross-linked monomers of the peptide-MHC complex. The peptide-MHC complex is the natural ligand for a specific T cell receptor (TCR). As a monomer, its dissociation rate is too high for binding; as a multimer conjugated to a fluorescent molecule, it can be used to tag antigen-specific T cells for flow cytometry and cell sorting.
We demonstrated in 1996 that melanoma-specific T cells could be isolated from patients with melanoma.1
We demonstrated in 1999 that there are circulating populations of melanoma-specific T cells in patients that can be detected using these tetramers2 and that it was possible to sort them, retain their viability and expand them to large numbers, sufficient for adoptive therapy. 3Adoptive therapy using CD8 T cell clones
At that time (1980s) the NCI was pursuing TIL therapy for patients, using lymphocytes collected from excisional tumor biopsies from patients with melanoma, growing these in vitro with high dose IL-2 (6000 U/ml) and treating patients with expanded TIL and high-dose IL-2.
We pursued a different approach by starting with patient peripheral blood as a source of T cells and trying to grow T cell clones so that we could examine more rigorously the fate of the infused T cell clones we had expanded in the lab. We used autologous dendritic cells pulsed with a peptide representing the target epitope of melanoma associated antigens, MART-1, tyrosinase or gp100, to stimulate the T cells in vitro. Because the antigen-specific T cells were present at frequencies of 1:10,000 or less, this required iterative cycles of in vitro stimulation, followed by limiting dilution cloning and then two cycles of expansion. We were able to generate 10-20 billion T cell clones from a single clone (4-5000 fold expansion per cycle) and then infuse these into patients with metastatic melanoma 4. Although it took 2-3 months to get a T cell product for therapy, we were able to treat several patients and demonstrate
The CD8+ T cell clones survived in vivo and did respond to low-dose IL-2, but they only persisted for 2-3 weeks at most.
Adoptive therapy with CD4 T cells
We then pursued a study using CD4 + T cell clones reasoning that CD4 T cells produce their own IL-2 and may persist longer by an antigen-driven autocrine mechanism.5 We targeted tyrosinase, a melanocyte-associated tumor antigen and NY-ESO-1 a cancer-testis antigen expressed in melanoma but also many other solid tumors, such as gastric cancer, breast cancer and head and neck cancer.
We found that these antigen-specific tumor-reactive CD4 T cell clones lasted for more than 3 weeks (up to 8 months) in the patient’s peripheral circulation and that no IL-2 was required.
We found clinical responses in 5 of 9 patients including one patient with a complete response within 4 weeks of therapy. In that patient, we discovered that although we were targeting only NY-ESO-1, endogenous responses to MART-1 and MAGE-A3 were also elicited, likely through a process of antigen-spreading whereby, the initial tumor damage led to the release of non-targeted tumor antigens that were processed and presented by local antigen presenting cells and could elicit a broad endogenous T cell response to non-targeted antigens like MART-1, and MAGE-A3.
This was a first-in-man study using adoptively transferred CD4 T cells for the treatment of cancer.
More recently, we implemented three clinical trials to address three specific questions about adoptive T cell therapy:
Lymphodepletion and Adoptive therapy with CD8 T cells leads to clinical response
The first study has been completed and will be published in the Proceedings of the National Academy of Science.6 We demonstrate that a short relatively low-toxicity course of cyclophosphamide conditioning was sufficient and necessary to mediate significant clinical responses (see CT/PET scans on right). We observed one durable complete response with elimination of transverse colon metastasis within 4 weeks (now disease-free with no other therapy 3 years later) and 7 other patients presenting with progressive refractory cancer whose disease has stabilized) .
More importantly, this study demonstrated that T cells could revert to a more de-differentiated state and impart central memory-like properties that render these tumor-reactive CTL, helper-independent.
The second study using anti-CTLA4 has already produced provocative data demonstrating the ability to boost anti-tumor T cell responses, both transferred and endogenous, by anti-CTLA4 administration. In this example the frequency of transferred NY-ESO-1-specific CTL which had plateaued at < 1 %, within a week, demonstrated a rapid 3-fold increase to more than 4% with anti-CTLA4 alone.
Path ForwardT cell therapy has been highly effective in metastatic melanoma. It has induced clinical responses, sometimes durable complete responses where conventional therapy failed.
Treatment of other cancers with T cell therapy is feasible. We have treated patients with ovarian cancer and breast cancer and are beginning studies in patients with sarcoma. Antigens, such as NY-ESO-1 are expressed in many solid tumor malignances and can be targeted with T cell therapy.
Future studies will address two major challenges:
1. Increase the availability
To further enrich the population of NY –ESO-1 specific CTL, we recently acquired, modified and received regulatory approval to use a BD Influx cell sorter under clinical grade conditions. With a cell sorter, we have been able to enrich, from a single round of in vitro stimulation, a 0.2% population of tetramer-staining antigen-specific T cells to > 80% after sorting and in vitro expansion. We have succeeded in generating NY-ESO-1-specific CTL for adoptive therapy from 5 patients so far using this 3-pronged strategy; an autologous T cell infusion product can now be attained in 24-28 days.2. Develop combinational strategies
The development of a coherent strategy to enhance the efficacy of adoptive T cell therapy will involve judicious manipulation of intrinsic and extrinsic factors. Intrinsic factors describe cell-associated features such as subset selection, for CD4/CD8 phenotypes, memory properties, cytokine or biological modulation or genetic modification to enhance safety, efficacy or function. One example of intrinsic manipulation is exposure to IL-21 (described above).
Extrinsic features include pre- or post-infusion immunomodulation and represent a combinational approach that encompasses the use of reagents that influence the immune response in order to:
These extrinsic components are represented by previously approved chemotherapy or radiation therapy (e.g. for lymphodepletion conditioning) or the newly emerging class of biologic and chemical reagents, that can augment the survival, function and anti-tumor efficacy of the transferred T cells.
1. Adoptive T cell therapy of melanoma
2. Adoptive T cell therapy of ovarian cancer
3. Murine model of tumor immunity (or lack thereof)
4. Novel methods in immune monitoring
5. Novel methods in isolation and expansion of tumor-specific T cells
American Association for Cancer Research
American Association of Immunologists
American Society for Clinical Investigation
Society for Biological Therapy
1995-1998, Associate, Fred Hutchinson Cancer Research Center, Clinical Research
1989-1991, Resident, Stanford University
1987-1989, Postdoctoral Fellow, Ontario Cancer Institute