CD8+ T-cell-depleted, matched unrelated donor, allogeneic bone marrow transplantation for advanced AML using busulfan-based preparative regimens

T cell-depleted unrelated donor stem cell transplantation provides favorable disease-free survival for adults with hematologic malignancies

We report a prospective phase II clinical trial in 35 adult patients (median age 40.5 years) with hematologic malignancies who received T cell-depleted, hematopoietic stem cell transplants from HLA-compatible, unrelated donors. The cytoreductive regimen consisted of hyperfractionated total-body irradiation, thiotepa, and fludarabine. The preferred graft source was granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSC). PBSC were CD34(+) selected, followed by sheep erythrocyte rosetting to deplete residual T cells. Anti-thymocyte globulin provided graft rejection prophylaxis. No additional graft-versus-host disease (GVHD) prophylaxis was planned. Estimated disease-free survival at 4 years is 56.8% for the entire group and 75% in patients with standard-risk disease. The cumulative incidence of relapse is 6%. Acute GVHD grade II-III developed in 9% and chronic GVHD in 29% of patients. Fatal infections occurred in 5 of 35 (14%) patients. There was 1 late graft failure. This study demonstrates durable engraftment with a low overall incidence of GVHD. Its curative potential is reflected in the remarkably low relapse rate at 4 years.

BU- vs TBI-based conditioning for adult patients with ALL

Evidence suggests an advantage for TBI over BU as a component of conditioning regimens for allogeneic hematopoietic cell transplant in patients with ALL. We have employed both TBI and BU for conditioning in ALL and reviewed our experience to compare outcomes. From July 1989 to June 2008, we identified 86-adult ALL patients treated with either a TBI- or BU-based regimen and transplanted with either a well-matched sibling or unrelated donor. Data including demographics, immunophenotype, disease status and cytogenetic risk were examined by Cox proportional hazards analysis. Patients treated with TBI were older (median age 40 vs 33 years; P=0.018), had a higher-risk cytogenetic profile (P=0.010), were more often transplanted using an unrelated donor (P=0.038) and were treated more recently (P<0.001). There was a significant improvement in EFS (P=0.046), and a trend to improved OS (P=0.08) in patients treated with TBI compared with those treated with BU. However, the advantage for TBI could not be confirmed by multivariable analysis where only disease status retained statistical significance.

Emerging drugs for acute graft-versus-host disease

The number of allogeneic hematopoietic cell transplantations (HCT) continues to increase. More than 15,000 allogeneic transplantations are performed annually. The graft-versus-leukemia/tumor effect during allogeneic HCT effectively eradicates many hematological malignancies. The development of novel strategies that use donor leukocyte infusions, nonmyeloablative conditioning and umbilical cord blood transplantation have helped expand the indications for allogeneic HCT over the past several years, especially among older patients. Yet the major complication of allogeneic HCT, graft-versus-host disease, remains lethal and limits wider application of allogeneic HCT. In this article, we review current practice and recent advances made in prevention and treatment of graft-versus-host disease.

Prophylaxis of acute GVHD: manipulate the graft or the environment?

Graft-versus-host disease (GVHD) is the immune response of donor T lymphocytes responding to the recipient's alloantigens. The cellular and cytokine mechanisms driving GVHD are now well defined and have led to several prophylactic approaches. Selective allodepletion techniques promise to prevent GVHD without causing immune deficiency provoked by global T-cell depletion. Targeted dosing of other (non-T-cells) cells in the graft - such as CD34+ progenitors, regulatory T cells, natural killer cells and mesenchymal stromal cells - can also lead to transplants designed to retain immune capability without causing GVHD. Immunosuppressive drugs such as methotrexate, cyclosporine and anti-lymphocyte antibodies are the mainstay in the prevention of GVHD and can be used in conjunction with engineered grafts to eliminate GVHD. In future it is anticipated that further refinements in targeting the elimination or suppression of the GVHD reacting T cells should be selective enough to preserve the important graft-versus-leukemia effect which contributes to the cure of malignant diseases by allogeneic stem-cell transplantation.

T-cell therapy after hematopoietic stem cell transplantation

PURPOSE OF REVIEW

The separation of graft versus host disease from graft versus leukaemia reactivity and the reconstitution of immunity to infectious agents are the main goals of T-cell therapy after allogeneic hematopoietic stem cell transplantation. We describe how an improved understanding of T-cell mediated graft versus leukemia and of antiviral responses is providing effective approaches to T-cell immunotherapy.

RECENT FINDINGS

Over the past several years, researchers have developed strategies to eliminate alloreactive T cells from the graft, to expand naturally occurring regulatory T cells, and to select and expand antigen-specific T cells specific for tumor-associated or viral antigens. Incorporation of suicide genes allows the selective destruction of allodepleted or antigen-selected cells after infusion, further increasing the safety and potential applicability of these approaches.

SUMMARY

In this review we describe current strategies for adoptive T-cell immunotherapy after hematopoietic stem cell transplantation.

Improving outcome of allogeneic stem cell transplantation by immunomodulation of the early post-transplant environment

There has been great progress in understanding the alloresponse and the process of immune recovery after stem cell transplantation. Here, we highlight ways in which transplant outcome is determined by unique immunological features of the early post-transplant period that modulate the growth and function of the grafted donor T cells and stem cells. Better understanding of these early events and more detailed knowledge of the phenotype and function of transplanted donor cells facilitate strategies to optimize immune recovery, prevent graft-versus-host disease (GVHD) and boost immunity to viruses and leukemia. Approaches that optimize CD34 cell dose, techniques to remove GVHD-reacting T cells by T cell subset selection, suicide gene insertion or selective allodepletion, and the adoptive transfer of antigen-specific T cells have reached the stage of clinical trials. Furthermore, murine transplant experiments indicate ways to prevent GVHD while preserving immune function by depletion of naïve cells, T cytotoxic 1 and T helper 1 cells, or by enrichment of regulatory T cells. Many of these approaches appear feasible in clinical transplantation and have yielded promising initial results, but proof that the goal of controlled selective immune reconstitution can be achieved is still awaited.

High Disease Burden Is Associated with Poor Outcomes for Patients with Acute Myeloid Leukemia Not in Remission Who Undergo Unrelated Donor Cell Transplantation

Results were analyzed for 48 consecutive patients with acute myeloid leukemia not in remission who underwent unrelated donor bone marrow or stem cell transplantation between 1991 and February 2003 at 2 transplant centers. Forty-six were adults with a median age of 32 years (range, 4-58 years). Forty-two were HLA-A, -B, and -DR matched with their respective donors, and 6 were mismatched at 1 of these loci. The conditioning regimen was myeloablative in all cases: busulfan/cyclophosphamide/etoposide in 34 patients, busulfan/cyclophosphamide in 10 patients, and total body irradiation based in 4 patients. Median follow-up for survivors was 540 days (range, 145-2716 days). Only patients with <5000 peripheral blood blasts per microliter at the time of transplantation survived 2 years (18% versus 0%; P = .003). Similarly, patients with <20% blasts in the marrow at the time of transplantation had superior 2-year survival compared with those who had > or =20% (33% versus 5%; P = .04). Patients with <20% blasts who had > or =3 prior therapies also fared poorly. Cause of death was more commonly treatment related rather than relapse related. This study confirms that patients with acute myeloid leukemia not in remission can achieve prolonged survival with myeloablative conditioning and unrelated donor cell transplantation. However, sustained survival occurs only in patients with a low disease burden at the time of unrelated donor stem cell transplantation, and patients with a high disease burden may benefit from added counseling regarding the high risk of death due to both treatment-related toxicities and disease relapse.