T-Cell–Depleted Allogeneic Bone Marrow Transplantation as Postremission Therapy for Acute Myelogenous Leukemia: Freedom From Relapse in the Absence of Graft-Versus-Host Disease

Thiotepa/cyclophosphamide/TBI as a conditioning regimen for allogeneic hematopoietic stem cell transplantation in patients with myelodysplastic syndrome

In all, 18 patients (30-56 years; median 49) with MDS underwent allogeneic HSCT from related (n=12) or unrelated (n=6) donors after a conditioning regimen comprising thiotepa, cyclophosphamide, and TBI. GVHD prophylaxis consisted of cyclosporine (n=15) or tacrolimus (n=3) with short-course methotrexate. Four patients had low-risk disease (refractory anemia or complete remission after chemotherapy) and 14 patients had high-risk disease (RAEB, RAEB-t, or AML). Grade II-IV acute GVHD developed in six patients and chronic GVHD in 10. With a median follow-up of 31 months, the 2-year survival probability is 75% for low-risk patients and 57% for high-risk patients. One patient died of leukemia and six of treatment-related causes. This conditioning regimen requires further study in patients with MDS.

Phenotypic analysis of human BM T-cell depleted by soybean lectin agglutination and E rosetting with sheep RBC: relative enrichment of NK cells and a CD3(+),CD2(-dim) population

BACKGROUND

T-cell depletion (TCD) of BM allows transplantation across HLA barriers. Although different methods are used throughout the world, the optimal application of TCD still remains unclear, partly due to the lack of thorough analyses of the cellular fractions eliminated or retained in each method, and their possible implications regarding GvHD, GvL, or engraftment. We have analyzed the phenotype of the successive fractions of 19 BM samples depleted by soybean lectin agglutination and sheep erythrocyte rosetting (elimination of T cells that form rosettes through CD2), focusing on the final fraction infused to patients.

METHODS

Analysis was performed using three-color flow cytometry and strategies for optimal staining and individualism of the subsets of interest.

RESULTS

The relative composition of the lymphoid population varied significantly along the successive steps in TCD: at the agglutination step, B cells and CD4 T cells are greatly reduced, while natural killer cells (NK) and TCRgammadelta+ T are augmented. The rosetting steps imply the relative enrichment of CD2-dim T cells, together with a further rise in the proportion of NK and double-negative T cells frequently TCRgammadelta+.

DISCUSSION

The presence of minor subsets of CD2- TCRgammadelta+ and CD2- TCRalphabeta T cells has already been described in the peripheral blood of normal individuals. We report that, by using this method of TCD, CD2-dim T cells, frequently TCRgammadelta+, are retained in the grafts and infused in patients, together with NK cells as the main lymphoid population. We discuss the possible implications of these populations in the biology of the graft, regarding GvHD, GvL and engraftment.

Cytoreduction with iodine-131-anti-CD33 antibodies before bone marrow transplantation for advanced myeloid leukemias

The monoclonal antibodies M195 and HuM195 target CD33, a glycoprotein found on myeloid leukemia cells. When labeled with iodine-131 ((131)I), these antibodies can eliminate large disease burdens and produce prolonged myelosuppression. We studied whether (131)I-labeled M195 and HuM195 could be combined safely with busulfan and cyclophosphamide (BuCy) as conditioning for allogeneic BMT. A total of 31 patients with relapsed/refractory acute myeloloid leukemia (AML) (n=16), accelerated/myeloblastic chronic myeloid leukemia (CML) (n=14), or advanced myelodysplastic syndrome (n=1) received (131)I-M195 or (131)I-HuM195 (122-437 mCi) plus busulfan (16 mg/kg) and cyclophosphamide (90-120 mg/kg) followed by infusion of related-donor bone marrow (27 first BMT; four second BMT). Hyperbilirubinemia was the most common extramedullary toxicity, occurring in 69% of patients during the first 28 days after BMT. Gamma camera imaging showed targeting of the radioisotope to the bone marrow, liver, and spleen, with absorbed radiation doses to the marrow of 272-1470 cGy. The median survival was 4.9 months (range 0.3-90+ months). Three patients with relapsed AML remain in complete remission 59+, 87+, and 90+ months following bone marrow transplantation (BMT). These studies show the feasibility of adding CD33-targeted radioimmunotherapy to a standard BMT preparative regimen; however, randomized trials will be needed to prove a benefit to intensified conditioning with radioimmunotherapy.

Regimen-related toxicity after fludarabine-melphalan conditioning: a prospective study of 31 patients with hematologic malignancies

A total of 31 consecutive patients with hematologic malignancies who were considered poor candidates for TBI underwent allogeneic stem cell transplantation after conditioning with fludarabine and melphalan. A total of 25 matched sibling recipients received fludarabine 25 mg/m(2) x 5 days and melphalan 70 mg/m(2) x 2 days. For unrelated and haploidentical donor recipients, fludarabine was increased to 30 mg/m(2) and ATG 30 mg/kg x 4 days was added. Graft-versus-host disease prophylaxis consisted of tacrolimus and mini methotrexate. All patients engrafted. Regimen-related toxicity was considerable and included mainly renal, hepatic and mucosal toxicity. There were seven regimen-related-deaths including two VOD, two pulmonary, one renal, one cardiac and one mucosal toxicity. One case of fatal pulmonary toxicity death could be attributed to pre-existing pulmonary damage. Progression-free survival at 12 months was 44% (90% CI: 30-58%) for recipients of HLA-identical sibling transplants and 33% (90% CI: 21-45%) for all patients. In conclusion, the fludarabine-melphalan regimen leads to consistent engraftment. The regimen-related toxicity is considerable and cannot be explained solely by patient selection. Cardiac toxicity is emerging as a unique toxicity of this regimen. Despite toxicity, fludarabine-melphalan has considerable activity and leads to durable remission in a proportion of patients.

Acute myeloid leukemia

In this chapter, Drs. Keating and Willman review recent advances in our understanding of the pathophysiology of acute myeloid leukemia (AML) and allied conditions, including the advanced myelodysplastic syndromes (MDS), while Drs. Goldstone, Avivi, Giles, and Kantarjian focus on therapeutic data with an emphasis on current patient care and future research studies. In Section I, Dr. Armand Keating reviews the role of the hematopoietic microenvironment in the initiation and progression of leukemia. He also discusses recent data on the stromal, or nonhematopoietic, marrow mesenchymal cell population and its possible role in AML. In Section II, Drs. Anthony Goldstone and Irit Avivi review the current role of stem cell transplantation as therapy for AML and MDS. They focus on data generated on recent Medical Research Council studies and promising investigation approaches. In Section III, Dr. Cheryl Willman reviews the current role of molecular genetics and gene expression analysis as tools to assist in AML disease classification systems, modeling of gene expression profiles associated with response or resistance to various interventions, and identifying novel therapeutic targets. In Section IV, Drs. Hagop Kantarjian and Francis Giles review some promising agents and strategies under investigation in the therapy of AML and MDS with an emphasis on novel delivery systems for cytotoxic therapy and on targeted biologic agents.

Nonmyeloablative therapy and allogeneic hematopoietic stem cell transplantation

The toxicities associated with conventional myeloablative therapy and allogeneic hematopoietic stem cell transplantation (SCT) limit the use of this potentially curative approach to relatively healthy young patients. The risk of treatment-related morbidity and mortality with conventional allogeneic SCT ranges from 10% to 50%, depending on the age of the patient, HLA histocompatibility, diagnosis and disease status, and presence or absence of comorbid conditions. The main goals of conventional high-dose preparative regimens are to eradicate the malignancy and induce adequate host immunosuppression to prevent graft rejection. However, accumulated data indicate that the currently used myeloablative regimens frequently do not eradicate the malignant clone, and that an immune-mediated effect between donor immunocompetent T lymphocytes and host tumor cells seems to induce a major therapeutic benefit, accounting for the significantly lower incidence of leukemic relapse seen with allogeneic SCT compared to autologous or syngeneic SCT. These observations have led to the development of newer treatment modalities focusing on the induction of host tolerance to donor cells followed by the administration of scheduled donor T-lymphocyte infusions. Preliminary clinical data are encouraging but need to be confirmed in well-designed prospective controlled trials with direct comparison to conventional allogeneic SCT and extended follow-up to determine the durability of responses and the consequences of late complications such as chronic graft-vs-host disease on the patient's quality of life.

Early lymphocyte recovery is an important determinant of outcome following allogeneic transplantation with CD34+ selected graft and limited T-cell addback

We evaluated the outcome of 29 patients (age 22-60 years), who received a CD34+selected related (n=16) or unrelated graft (n=13) with limited T-cell addback (TCAB) (median 5.9 x 10(4)/kg) following full-intensity conditioning for haematological malignancies. In all, 16 patients (55%) had either advanced disease or previous transplants. The cumulative incidences of grade 2-4 acute GVHD were 15.4 and 19.2% and that for chronic extensive GVHD were 35 and 37% in related and unrelated graft recipients, respectively. The strongest predictor of nonrelapse mortality and overall survival was the absolute lymphocyte count (ALC) at 30 days; patients with ALC<0.35 x 10(9)/l having an NRM and OS of 59.2 and 24.7%, compared to 10 and 90% in those with a higher ALC. Patients with acute leukaemia had poorer survival and this was associated with a lower ALC as well. Thus, TCAB with a CD34+ selected graft resulted in a comparable outcome in both older and younger patients, but the survival was strongly influenced by early lymphocyte recovery.

High incidence of graft failure in children receiving CD34+ augmented elutriated allografts for nonmalignant diseases

T-cell depletion of the marrow graft using counterflow centrifugal elutriation reduces the risk of graft-versus-host disease (GVHD). However, because of high rates of graft failure and relapse, elutriation alone has not improved survival. We have carried out a phase II clinical trial in 54 pediatric patients to determine if CD34+ selection to rescue pluripotent stem cells from the small lymphocyte fraction improves engraftment. The processed grafts contained a mean of 5.5 x 10(7) cells/kg IBW, 4.7 x 10(6) CD34+ cells/kg IBW, and 6.3 x 10(5) CD3+cells/kg IBW. Patients achieved an ANC >500 at a median of 16 days and platelet count >20 000 at a median of 28 days. The incidence of clinically significant GVHD was 19%. In total, 10 patients enrolled in this study experienced graft failure, with eight of the 14 patients transplanted for nonmalignant indications failing to engraft stably. Graft failure was statistically significantly associated with nonmalignant diagnosis (P<0.001), but was not associated with CMV seropositivity, donor gender, or cell counts of the allograft. We conclude that although time to engraftment is similar to that seen with unmanipulated grafts, graft failure remains a significant problem in patients with hereditary, nonmalignant diseases. Future efforts will seek to preserve the benefits of elutriation with CD34+ selection by increasing immune ablation of the preparative regimen and/or increasing posttransplant immune suppression.

T-cell depletion with Campath-1H "in the bag" for matched related allogeneic peripheral blood stem cell transplantation is associated with reduced graft-versus-host disease, rapid immune constitution and improved survival

We studied the outcome of 24 peripheral blood stem cell (PBSC) graft recipients, who were T-cell depleted (TCD) with either 20 mg (n = 14) or 10 mg (n = 10) Campath-1H in vitro, in comparison with a retrospective cohort of 23 unmanipulated (UM) PBSC recipients. While the neutrophil engraftment was similar, the platelet engraftment occurred earlier in the TCD group (d 11 vs 14). The incidence of acute and chronic graft-versus-host-disease (GVHD) was 8.7% and 4.4% in the TCD group, respectively, compared with 47.7% and 56.3% in UM group (P < 0.001). In the TCD group, 5/6 chronic myeloid leukaemia (CML) and 4/18 non-CML patients relapsed (vs 0/6 and 3/17 in UM group, P = 0.06). All four molecular or cytogenetic relapses of CML were disease-free survivors following donor lymphocyte infusion. There was no difference in the incidence of serious infection between the TCD and UM groups and the lymphocyte recovery at 100 d was comparable. In the TCD cohort, the lymphocyte recovery was quicker in the 10 mg Campath-1H group. The non-relapse mortality (19.1%vs 66.3%) and 3 year survival (73.1 vs 19.2) were improved in the TCD group (P = 0.05). Thus elimination of late mortalities related to chronic GVHD and a rapid immune reconstitution, limiting either infection or relapse related deaths, contributed to an improved outcome following T-cell depletion with Campath-1H "in the bag".

Systemic nocardiosis following allogeneic bone marrow transplantation

Five cases of systemic Nocardia infection were diagnosed among 301 allogeneic bone marrow transplant recipients. A sixth case included in this report received her transplant at another institution. The cumulative annual incidence rate of this infection was 1.75%. All patients had been treated previously for acute graft-versus-host disease (GVHD). At the time of diagnosis of systemic Nocardia infection, a median of 198 (range 148-1121) days after transplantation, all patients had extensive chronic GVHD and were taking 2 to 3 immunosuppressive medications. Prior to diagnosis of Nocardia infection patients had experienced multiple opportunistic infections, including infections with Mycobacterium avium-intracellulare, Pneumocystis carinii, and cytomegalovirus antigenemia. Treatment with trimethoprim-sulfamethoxazole (TMP-SMX), ceftriaxone, or carbapenem antibiotics resulted in a median survival of 219 days from the time of diagnosis and an actuarial 1-year survival of 40%. All patients who received more than 2 weeks of therapy were cured of their infections. Notably, 5/6 patients in this cohort were unable to take TMP-SMX because of myelosuppression. In comparison with randomly selected control patients, the use of pentamidine for prevention of P. carinii infection was associated with a marginal increase in the risk of Nocardia infection. We postulate that the use of TMP-SMX may be of benefit in the prophylaxis of infections other than P. carinii in patients with chronic GVHD.

Allogeneic hematopoietic stem cell transplantation--yesterday, today, and tomorrow

During the past 50 years, intensive studies into the use of hematopoietic stem cell transplantation (HSCT) for therapy of cancer and nonmalignant hematologic diseases have changed this treatment modality from one that was thought to be plagued by insurmountable complications to one that is now standard therapy for some diseases. More-recent research has opened up the way to include elderly patients with a wide variety of hematologic malignant diseases. Continued research by transplant teams worldwide is likely to allow continued progress toward developing novel and improved treatment modalities and even wider application of the use of pluripotent hematopoietic stem cells in the treatment of human diseases.

Unrelated donor umbilical cord blood transplantation in adults

Umbilical cord blood (UCB) has emerged as an appealing alternative source of hematopoietic stem cells for unrelated donor transplantation. Shorter time to transplant and an improved chance of finding a suitable graft are evident advantages over bone marrow transplantation from unrelated donors. The majority of UCB transplants from unrelated donors have been performed in children, but the number in adults has been growing steadily in recent years. We review herein the reported experience with that source of hematopoietic stem cells in adults with hematological malignancies. The available data support the use of UCB transplantation from unrelated donors for young adults with hematological malignancies and no appropriate bone marrow donor, especially for those requiring urgent transplantation.

Regulation of alloresponses after bone marrow transplantation using donor T cells expressing a thymidine kinase suicide gene

Donor T cells have a critical role in promoting engraftment after allogeneic bone marrow transplantation (BMT), but also cause graft versus host disease (GVHD). Ex vivo T cell depletion has been an effective strategy to reduce GVHD but has been associated with impaired alloengraftment and host immunity. Using an MHC-mismatched murine model, we have examined an alternative approach to GVHD prevention whereby donor T cells are selectively eliminated in vivo after BMT using transgenic T cells in which a thymidine kinase (TK) suicide gene is targeted to the T cell. Lethally irradiated AKR/J (H-2k) mice transplanted with TCD C57BL/6 (B6)(H-2b) bone marrow (BM) plus B6 TK+ T cells and then treated with GCV post-BMT had significantly less GVHD severity and improved immune reconstitution compared to untreated mice, providing proof of principle that this strategy could mitigate GVHD. To assess the impact of GCV administration on alloengraftment, sublethally irradiated AKR mice were transplanted with TCD B6 BM alone or admixed with limiting numbers (5 x 10(5)) of B6 TK+ T cells. When tested 3-4 weeks post-transplant, control TCD BM mice all rejected their grafts. Conversely, > 80% of GCV-treated mice had sustained donor T cell engraftment comparable to what was observed in untreated animals. Notably, GCV-treated mice were more likely to have mixed T cell chimerism early post-BMT than untreated animals, however, nearly all GCV-treated mice progressed to complete donor T cell engraftment by 2-3 months post-transplant. Preservation of engraftment was critically dependent upon the GCV administration schedule and required that GCV be delayed for at least one week post-transplant. These studies demonstrate that specific incorporation of a suicide gene into donor T cells is a viable strategy that can be employed to reduce GVHD without compromising alloengraftment.

Direct evidence for new T-cell generation by patients after either T-cell–depleted or unmodified allogeneic hematopoietic stem cell transplantations

Successful allogeneic hematopoietic stem cell transplantation (HSCT) requires reconstitution of normal T-cell immunity. Recipient thymic activity, biologic features of the allograft, and preparative regimens all contribute to immune reconstitution. We evaluated circulating T-cell phenotypes and T-cell receptor rearrangement excision circles (TRECs) in 331 blood samples from 158 patients who had undergone allogeneic HSCTs. All patients had received myeloablative conditioning regimens and were full donor chimeras in remission. Younger patients exhibited more rapid recovery and higher TRECs (P = .02). Recipients of T-cell–depleted allografts initially had lower TRECs than unmodified allograft recipients (P < .01), but the difference abated beyond 9 months. TREC level disparities did not achieve significance among adults with respect to type of allograft. Measurable, albeit low, TREC values correlated strongly with severe opportunistic infections (P < .01). This finding was most notable during the first 6 months after transplantation, when patients are at greatest risk but before cytofluorography can detect circulating CD45RA+ T cells. Low TRECs also correlated strongly with extensive chronic graft-versus-host disease (P < .01). Recipients of all ages of either unmodified or T-cell–depleted allografts therefore actively generate new T cells. This generation is most notable among adult recipients of T-cell–depleted allografts, most of whom had also received antithymocyte globulin for rejection prophylaxis. Low TREC values are significantly associated with morbidity and mortality after transplantation. T-cell neogenesis, appropriate to age but delayed in adult recipients of T-cell– depleted allografts, justifies interventions to hasten this process and to stimulate desirable cellular immune responses.

Minor histocompatibility antigens--targets of graft versus leukemia responses

Immune-mediated elimination of tumor cells by donor T cells recognizing recipient minor H antigens contributes to the curative potential of allogeneic HCT. The importance of the allogeneic response to a successful outcome is clearly illustrated by the results of stem cell transplant for malignancy after nonmyeloablative conditioning. Remarkably little is understood about the molecular nature of minor H antigens and this has impeded efforts to determine the role of specific disparities in graft versus tumor reactions or to manipulate T cell responses to augment antitumor activity without exacerbating GVHD. The isolation of minor H antigen-specific CD8+ and CD4+ T cell clones from recipients of allogeneic HCT has provided the reagents to characterize their expression on leukemic progenitors and to identify the genes encoding these antigens. Using cDNA expression cloning, genetic polymorphisms in the human IFI-75, Uty, KIAA0020, and UGT2B17 genes have been identified to encode new minor H antigens presented by HLA A3, B8, A2, and A29 respectively. Two of these genes are preferentially expressed in hematopoietic cells including leukemic progenitors suggesting it may be possible to augment T cell responses to promote a selective graft versus leukemia effect. A third gene, UGT2B17 is highly expressed in liver and GI tract and may be a target for GVHD in these organs. The studies to identify the molecular nature of minor H antigens have provided insights into the complexities of the graft versus host response associated with allogeneic HCT, but the challenge for the future will be to develop strategies that can selectively induce durable graft versus tumor effects without GVHD. A critical issue in developing specific immunotherapy to augment GVL responses is to determine which minor H antigens are expressed on leukemic stem cells. Studies using transplantation of human AML into SCID mice have identified a putative leukemic stem cell which is contained in the CD34+ CD38- subset of the blast population and is present in very low frequency (<1/200,000) in blood or bone marrow from AML patents. We have examined the ability of minor H antigen-specific CTL to prevent engraftment of human AML in NOD/SCID mice. These studies show that engraftment of leukemias derived from individuals encoding the minor H antigen can be specifically prevented demonstrating that AML stem cells express minor H antigens and are targets for CTL. One approach to determine directly which minor H antigens can be selectively targeted to induce a GVL effect without GVHD is to adoptively transfer T cell clones of defined specificity and function to patients who relapse after HCT. Studies of this approach are now in progress in acute leukemia and have provided important insights into potential obstacles of T cell therapy for relapsed leukemia after HCT.

Donor-derived interferon gamma separates graft-versus-leukemia effects and graft-versus-host disease induced by donor CD8 T cells

The graft-versus-leukemia (GVL) effects and graft-versus-host disease (GVHD)-inducing activity of CD8 T cells was compared in murine recipients of wild-type (WT) or interferon gamma (IFN-gamma)-deficient (GKO) allogeneic donor cells. CD8 T cells (or CD4-depleted splenocytes) from GKO donor mice induced more severe GVHD in lethally irradiated allogeneic recipients compared to the same cell populations from WT donors. Consistent with GVHD severity, donor CD8 T-cell expansion in allogeneic recipients was augmented in the absence of IFN-gamma. These results demonstrate that IFN-gamma does not stimulate but instead down-modulates GVHD induced by donor CD8 T cells. Remarkably, antihost lymphohematopoietic reactions, including GVL effects against host leukemia/lymphoma cells, of CD8 T cells correlated inversely with their GVHD-inducing activity, and those of GKO donors were markedly weaker than those mediated by WT donor CD8 T cells. These data show for the first time that GVHD-inducing activity and GVL effects of allogeneic CD8 T cells can be separated by a single cytokine, IFN-gamma. (Blood. 2002;99:4207-4215)

Induction of immunologic tolerance for allogeneic hematopoietic cell transplantation

The ability to achieve complete hematopoietic engraftment in the allogeneic setting without intensive myeloablative chemotherapy will have a profound effect on the practice of allogeneic hematopoietic cell transplantation (HCT). Novel methods to induce antigen-specific T-cell tolerance provide promise to ensure engraftment and reduce GVHD without producing generalized and other toxicities caused by myeloablative conditioning regimens. Compelling experimental evidence indicates that the antigen receptors on T-lymphocytes have dual potential to transmit crucial activation signals for initiating immune responses and to discharge equally potent inactivating signals to abort or inhibit immune responses. Many events impact on this fundamental decision-making process and one of the great challenges for modern immunology is to decipher the molecular wiring that integrates and converts the extrinsic and intrinsic variables into positive or negative cellular responses termed immunity and anergy, respectively. Our currently expanding understanding of the biochemical and molecular basis of T-cell anergy provides great promise to improve our ability to design novel clinical therapeutic approaches in order to induce antigen-specific tolerance in vivo. Importantly, strategies now exist to segregate graft versus tumor (GVT) effects from GVHD. Therefore, achievement of limited and specific tolerance to host alloantigens by selectively inactivating the indicated subsets of alloantigen-specific T-lymphocytes will prevent GVHD but retain the GVT effect of the graft. Such treatment approaches will expand the donor pool, because they will allow transplantation between individuals with increasing human leukocyte antigen (HLA) disparity, enable reduction of the need for non-specific immunosuppression, and reduce the risk of opportunistic infections and relapse of leukemia.

Listeriosis in recipients of allogeneic blood and marrow transplantation: thirteen year review of disease characteristics, treatment outcomes and a new association with human cytomegalovirus infection

Listeriosis is uncommon in recipients of allogeneic blood, marrow and organ transplantation. Six patients with systemic Listeria monocytogenes infection during 1985-1997 at Bone Marrow Transplantation Service, Memorial Sloan-Kettering Cancer Center are described. In two male and four female patients, the median duration from transplantation to isolation of L. monocytogenes was 62.5 (range 29 to 821) days. Among five allogeneic marrow transplant recipients, four (80%) received HLA antigen matched, T cell-depleted grafts from three unrelated and a single related donor. One patient underwent mismatched-related marrow graft transplant. Cord stem cell transplantation was performed in a single patient. Two required therapy for graft-versus-host disease (GVHD). The 13 year incidence of systemic Listeria infections was 0.47 percent. All six presented with fever (>39 degrees C), and L. monocytogenes bloodstream invasion. Mental status changes and meningioencephalitis were observed in two (33.3%). A concurrent primary opportunistic infection was present in five individuals (83.3%), and four (80%) were being treated for acute human cytomegalovirus (HCMV) viremia. Sixty-six percent responded to therapy and two died from unrelated, non-listeric causes. Systemic listeriosis was uncommon in our high-risk allogeneic blood and marrow transplantation population, and response to therapy with parenteral ampicillin and gentamicin was excellent. The association between primary HCMV reactivation and subsequent listeric infection emphasizes the significance of HCMV-related dysfunction in hosts' cellular immune responses, especially in the setting of allogeneic transplantation.

In vivo T cell depletion with pretransplant anti-thymocyte globulin reduces graft-versus-host disease without increasing relapse in good risk myeloid leukemia patients after stem cell transplantation from matched related donors

One-hundred and two patients with good risk myeloid leukemia (CML first chronic phase or AML first CR) were transplanted from HLA-related donors after conditioning with (n = 45) or without anti-thymocyte globulin (ATG) (n = 57). One graft failure was observed in the non-ATG and none in the ATG group. The median time to leukocyte engraftment (> 1 x 10(9)/l) was 16 (range 12-33) in the ATG group and 17 days (range 11-29) in the non-ATG group (NS) and for platelet engraftment (> 20 x 10(9)/l) 24 and 19 days (P = 0.002), respectively. Acute GVHD grade II-IV was observed in 47% of the non-ATG and in 20% of the ATG group (P = 0.004). Grade III/IV GVHD occurred in 7% of the ATG and in 32% of the non-ATG group (P = 0.002). Chronic GVHD was seen in 36% and 67% (P = 0.005), respectively. After a median follow-up of 48 months (range 2-128), the 5-year estimated OS is 66% (95% KI: 51-81%) for the ATG group and 59% (95% KI: 46-72%) for the non-ATG group (NS). The 5-year estimated DFS is 64% (95% KI: 50-78%) for ATG and 55% (95% KI: 43-67%) for the non-ATG regimen (NS). The 5-year probability of relapse was 5% in the ATG and 15% in the non-ATG group (NS). ATG as part of the conditioning regimen leads to a significant reduction in GVHD without increase of relapse in patients with myeloid leukemia after stem cell transplantation from HLA-related donors.

History of haematopoietic stem-cell transplantation

After fifty years of investigations into the use of pluripotent haematopoietic stem-cell transplantation for cancer therapy, this procedure has progressed from one that was thought to be plagued with insurmountable complications to a standard treatment for many haematological malignancies. How have these hurdles been overcome, and how can the therapy be expanded to include patients who are too old or medically infirm to tolerate conventional transplant approaches?

Is there an upper age limit for bone marrow transplantation?

Advances in hematopoietic cell transplantation have reduced the toxicity of both allogeneic and autologous transplantation. Decisions regarding the feasibility of transplantation should be individualized, and based upon physiological rather than chronological age.

Transplants across human leukocyte antigen barriers

Clinical experience with full haplotype-mismatched stem cell transplants has a 20-year history. Early results in leukemia patients were disappointing because of a high incidence of severe graft-versus-host disease (GvHD) in T-replete transplants or high rejection rates in T-cell-depleted transplants. The breakthrough came with introduction of a megadose T-cell-depleted progenitor cell transplant following a high-intensity conditioning regimen and the realization that donor natural killer (NK) cell alloreactivity also plays a role in facilitating engraftment and in preventing relapse. Treating end-stage patients inevitably confounded clinical outcome in early pilot studies. Today, high-risk acute leukemia patients are treated at less advanced stages of disease, receive a reasonably well-tolerated conditioning regimen, and benefit from advances in post-transplant immunological reconstitution. These factors have markedly reduced transplant-related mortality. Overall, event-free survival (EFS) and transplant-related mortality (TRM) compare favorably with reports from unrelated matched transplants. T-cell-depleted megadose stem cell transplant from a mismatched family member, who is immediately available, can now be offered as a viable option to candidates with high-risk acute leukemias.

Exploiting graft-versus-tumour responses using donor leukocyte infusions

Allogeneic stem cell transplantation (SCT) has become the treatment of choice for some patients with haematological malignancies, allowing dose escalation of chemo-radiotherapy beyond the limits imposed by bone marrow toxicity. However, it is now apparent that dose escalation alone does not eradicate the malignancy in many cases and that an associated immune-mediated graft-versus-malignancy effect may be equally important. Its presence is supported by the following observations: anecdotal reports that patients with relapsed leukaemia following SCT may re-enter remission after withdrawal of immunosuppressive drugs; the lower risk of relapse associated with the development of graft-versus-host-disease (GVHD); and an increased risk of relapse in patients receiving syngeneic transplants or T-cell depleted allogeneic marrow grafts. More directly compelling evidence has been provided by the efficacy of donor lymphocyte infusions, particularly for relapsed chronic-phase CML. Issues that remain to be resolved include the precise nature of the effector cells and their target antigens, the best strategies for separating graft-versus-malignancy from GVHD, the role of adjuvant chemotherapy/cytokines, and the role of non-myeloablative transplantation.

Allogeneic transplantation for leukaemia using unrelated donors

This chapter describes the current role of unrelated donor stem cell transplantation (UD-SCT) in the management of leukaemia. The available data are scant and incomplete and there are few randomized studies comparing UD-SCT with alternative therapies. Patients with many of the leukaemias require prolonged follow-up after allogeneic SCT to determine whether they are cured; the registry-based comparisons that have been initiated reflect the results achievable some years ago and may not help us in deciding what is best in 2001. In addition, new therapies such as ST1571, even though the long-term outcome of patients treated with this agent is uncertain, may affect which patients with chronic myeloid leukaemia we decide to recommend for transplant. The focus here is on acute and chronic myeloid leukaemia, acute lymphoblastic leukaemia and chronic lymphocytic leukaemia, as well as the myelodysplastic syndromes. Patient selection, conditioning strategies, comparison with other therapies, timing of transplant and the major causes of treatment failure are discussed, and there is an exploration of where improvement will come from.

Allogeneic transplantation of CD34+-selected cells from peripheral blood in patients with myeloid malignancies in early phase: a case control comparison with unmodified peripheral blood transplantation

An allogeneic transplantation of CD34(+)-selected cells from peripheral blood (allo-PBT/CD34(+)) from HLA-identical sibling donors was performed in 50 adult patients with acute myeloid leukemia in first complete remission (AML CR1) (n = 29), myelodysplastic syndrome (MDS) (n = 4), or chronic myeloid leukemia in first chronic phase (CML CP1) (n = 17). Clinical results were compared to a concurrent group of 50 patients transplanted with unmodified peripheral blood progenitor cells (allo-PBT), matched for age, diagnosis, and disease stage. The median follow-up period was 29 months (range 1-69). The actuarial probability of developing acute GVHD clinical grade II to IV was 16% (95%CI: 6-26) for the allo-PBT/CD34(+) group and 41% (95%CI: 29-57) for the allo-PBT group (P = 0.002). The actuarial probability of developing extensive chronic GVHD was 22% (95%CI: 8-36) for the allo-PBT/CD34(+) group and 47% (95%CI: 31-63) for the allo-PBT group (P = 0.02). Recipients of allo-PBT/CD34(+) had less toxicity associated with the transplant and better Karnofsky index at the last follow-up. For AML/MDS patients, the actuarial probability of disease-free survival (DFS) for recipients of allo-PBT/CD34(+) and allo-PBT was 65% (95%CI: 45-85) vs43% (95%CI: 28-58) (P = 0.05), respectively. These data provide a rationale for a randomised trial of allo-PBT/CD34(+) vs allo-PBT in AML/MDS patients in early stage of the disease.

Rhenium 188-labeled anti-CD66 (a, b, c, e) monoclonal antibody to intensify the conditioning regimen prior to stem cell transplantation for patients with high-risk acute myeloid leukemia or myelodysplastic syndrome: results of a phase I-II study

The conditioning regimen prior to stem cell transplantation in 36 patients with high-risk acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) was intensified by treating patients with a rhenium 188-labeled anti-CD66 monoclonal antibody. Dosimetry was performed prior to therapy, and a favorable dosimetry was observed in all cases. Radioimmunotherapy with the labeled antibody provided a mean of 15.3 Gy of additional radiation to the marrow; the kidney was the normal organ receiving the highest dose of supplemental radiation (mean 7.4 Gy). Radioimmunotherapy was followed by standard full-dose conditioning with total body irradiation (12 Gy) or busulfan and high-dose cyclophosphamide with or without thiotepa. Patients subsequently received a T-cell-depleted allogeneic graft from a HLA-identical family donor (n = 15) or an alternative donor (n = 17). In 4 patients without an allogeneic donor, an unmanipulated autologous graft was used. Infusion-related toxicity due to the labeled antibody was minimal, and no increase in treatment-related mortality due to the radioimmunoconjugate was observed. Day +30 and day +100 mortalities were 3% and 6%, respectively, and after a median follow-up of 18 months treatment-related mortality was 22%. Late renal toxicity was observed in 17% of patients. The relapse rate of 15 patients undergoing transplantation in first CR (complete remission) or second CR was 20%; 21 patients not in remission at the time of transplantation had a 30% relapse rate. (Blood. 2001;98:565-572)

Relationship between graft-versus-host disease and graft-versus-leukaemia in partial T cell-depleted bone marrow transplantation

The success of allogeneic bone marrow transplantation (BMT) is limited by the major complications, graft-versus-host disease (GVHD) and relapse. The very beneficial effect of maximal T-cell depletion of the graft for prevention of GVHD has been counterbalanced by an increase in graft failure and relapse of disease. Therefore, we started an approach of partial T-cell depletion of the graft. GVHD and graft-versus-leukaemia (GVL) are strongly correlated after non-T cell-depleted BMT. Here, we report whether the correlation between GVHD and GVL also exists in partial T cell-depleted BMT from sibling donors. We retrospectively studied 117 adult patients with early haematological malignancies. Our method of partial T-cell depletion gave a relapse rate in patients with acute leukaemias similar to that observed in non-T cell-depleted BMT. However, patients with chronic myeloid leukaemia had a relapse rate that was similar to that observed in maximal T cell-depleted BMT. We found a significant correlation between the presence of chronic GVHD and an improved disease-free survival. Nevertheless, overall survival was lower in patients with chronic GVHD. There was no correlation between the occurrence of acute GVHD and disease-free or overall survival.

Chronic graft-versus-host disease: clinical manifestation and therapy

Chronic graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in long-term survivors of allogeneic stem cell transplantation. The immunopathogenesis of chronic GVHD is, in part, TH-2 mediated, resulting in a syndrome of immunodeficiency and an autoimmune disorder. The most important risk factor for chronic GVHD is prior history of acute GVHD and strategies that prevent acute GVHD also decrease the risk of chronic GVHD. Other important risk factors are the use of a non-T cell-depleted graft, and older age of donor and recipient. Whether recipients of peripheral blood stem cells are at increased risk of chronic GVHD remains unsettled. There are no known pharmacologic agents which can specifically prevent development of chronic GVHD. Agents which have efficacy in the treatment of autoimmune disorders have been utilized as therapy for established chronic GVHD and are associated with response rates of 20% to 80%. Most responses are confined to skin, soft tissue, oral mucosa and occasionally liver. Bronchiolitis obliterans responds infrequently to therapy and is associated with a dismal prognosis. Newer, promising therapeutic strategies under investigation include thalidomide, photopheresis therapy, anti-tumor necrosis factor and B cell depletion with anti-CD20 monoclonal antibody.

Treatment of post-transplanted, relapsed patients with hematological malignancies by infusion of HLA-matched, allogeneic-dendritic cells (DCs) pulsed with irradiated tumor cells and primed T cells

Patients with hematological malignancies who relapse after bone marrow transplantation (BMT) are often treated with donor lymphocyte infusion. However, this procedure often results in graft-versus-host disease (GVHD). While, Dendritic cells (DCs), which present antigens to naive T cells, have been used in the immunotherapy of cancer, this approach has been logistically difficult due to limiting numbers of DCs. We have now developed a method for obtaining a large number of DCs by treating the granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood stem cells (PBSCs) from healthy donors with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4), and tumor necrosis factor-alpha (TNF-alpha). The resulting cells possess the morphologic, phenotypic, and functional characteristics of mature DCs. In in vitro studies, culture of these HLA-matched donor derived-DCs with irradiated each patient's tumor cells as an antigen source, followed by incubation with T cells from the patient, induced the production of highly cytotoxic T lymphocytes (CTLs) specific for the respective tumor cells in the semi-allogeneic setting. A transient, but objective clinical response was obtained in the absence of GVHD when we injected the DCs which had been pulsed with irradiated tumor cells as well as primed T cells from the same original donor of related- allogeneic stem cell transplantation into the relapsed patients. Our findings suggest that treatment of relapsed patients with such donor-derived DCs, and primed T cells may be effective as an adjunctive immunotherapy.

Haematopoietic cell transplantation as immunotherapy

The graft-versus-tumour effect seen after allogeneic (genetically different) haematopoietic cell transplantation for human malignancies represents the clearest example of the power of the human immune system to eradicate cancer. Recent advances in our understanding of the immunobiology of stem-cell engraftment, tolerance and tumour eradication are allowing clinicians to better harness this powerful effect.

Nonmyeloablative preparative regimens for allogeneic hematopoietic transplantation

Allogeneic hematopoietic transplantation is an effective therapy for a range of malignancies. High doses of myelosuppressive chemotherapy or radiation have been used in preparative regimens with the goal of preventing graft rejection and eradicating malignancy. Much of the benefit of transplantation, however, results from graft-versus-malignancy effects, mediated by donor immunocompetent cells. An alternative approach is to utilize less toxic, nonmyeloablative preparative regimens to achieve engraftment and allow graft-versus-malignancy effects to develop. This strategy reduces the risk of treatment-related mortality and allows transplantation for elderly or medically infirm patients not eligible for myeloablative therapy. Nonmyeloablative preparative regimens appear promising in diagnoses sensitive to graft-versus-malignancy effects and provide a platform for further development of cellular immunotherapy. Controlled clinical trials are warranted to define the role of nonmyeloablative allogeneic transplants in a range of hematologic malignancies and selected solid tumors.

CD6+ donor marrow T-cell depletion as the sole form of graft-versus-host disease prophylaxis in patients undergoing allogeneic bone marrow transplant from unrelated donors

PURPOSE

The role of donor marrow T-cell depletion (TCD) in preventing graft-versus-host disease (GVHD) after transplantation of unrelated allogeneic marrow remains undefined. Because different TCD methodologies differ in the degree and specificity with which T cells are removed, it is likely that transplant outcomes would depend on which technique is used. Herein, we report results in the first 48 recipients of unrelated marrow using CD6+ TCD as the sole form of GVHD prophylaxis.

PATIENTS AND METHODS

Median age of patients was 46 years (20 to 58 years). Donors were matched at A/B HLA loci. Ablation consisted of cyclophosphamide and fractionated total-body irradiation (TBI; 14 Gy). To facilitate engraftment, patients also received 7.5 Gy (22 patients) [corrected] or 4.5 Gy (26 patients) [corrected] of total lymphoid irradiation (TLI) before admission. No additional immune suppressive prophylaxis was administered. Granulocyte colony-stimulating factor was administered daily from day +1 to engraftment.

RESULTS

All 48 patients demonstrated neutrophil engraftment. An absolute neutrophil count of 500 x 10(6)/L was achieved at a median of 12 days (range, 9 to 23 days). There were no cases of late graft failure. The number of CD34+ cells infused/kg was associated with speed of platelet and neutrophil recovery. The dose of TLI did not influence engraftment. Grades 2-4 acute GVHD occurred in 42% of patients (95% confidence interval [CI], 0.28 to 0.57). Mortality at day 100 was 19%. There have been only five relapses. Estimated 2-year survival was 44% (95% CI, 0.28 to 0.59) for the entire group, 58% for patients less than 50 years of age. In multivariable analysis, age less than 50 years (P =.002), cytomegalovirus seronegative status (P =.04), and early disease status at bone marrow transplant (P =.05) were associated with superior survival.

CONCLUSION

CD6+ TCD does not impede engraftment of unrelated bone marrow after low-dose TLI, cyclophosphamide, and TBI. CD6+ TCD as the sole form of GVHD prophylaxis results in an incidence of GVHD that compares favorably with many adult studies of unrelated transplantation using unmanipulated marrow and immune-suppressive medications, especially in light of the median age of our patients (46 years). Although event-free survival in patients less than 50 years of age is very encouraging, older patients experience frequent transplantation-related complications despite TCD.

Non-myeloablative transplants for malignant disease

This article discusses changes in the way hematopoietic stem cell allotransplants may be carried out in the future to treat patients with malignant hematological diseases. Specifically, the focus has shifted away from attempts at eradicating underlying diseases through toxic high-dose chemoradiation therapy towards using the stem cell donor's immune cells for that purpose (allogeneic graft-versus-tumor effect). The non-myeloablative transplant approaches hold promise in reducing the morbidity and mortality associated with conventional high-dose chemoradiation therapy, and they allow allogeneic transplants in elderly or medically infirm patients who are at present not candidates for transplantation. In the future, specific graft-versus-tumor responses may become possible by eliciting donor T cell responses to tumor-associated minor histocompatibility antigens. In Section I, Dr. Rainer Storb describes experimental studies in random-bred dogs that rely on non-cytotoxic immunosuppressive agents to establish stable allografts. Powerful postgrafting immunosuppression, traditionally directed at preventing graft-versus-host disease (GVHD), is also used to overcome host-versus-graft (HVG) reactions, thereby dramatically reducing the need for intensive immunosuppressive conditioning programs. Preclinical canine studies have been translated into the clinical setting for treatment of elderly or medically infirm patients with malignant hematological diseases. The pretransplant conditioning has been reduced to a single dose of 2 Gy total body irradiation (TBI) with or without fludarabine. The lack of toxicity makes it possible for transplants to be conducted in the outpatient setting. Multicenter trials have been initiated, and more than 300 patients have been successfully treated with hematopoietic stem cell grafts both from related and unrelated HLA-matched donors. In Section II, Dr. Richard Champlin describes clinical studies with therapeutic strategies that utilize relatively non-toxic, nonmyeloablative disease-specific preparative regimens incorporating fludarabine, together with other chemotherapeutic agents, to achieve disease suppression and engraftment of allogeneic hematopoietic cells and to allow subsequent infusions of donor lymphocytes. Remissions have been seen in patients with acute myelocytic, chronic myelocytic, chronic lymphocytic, leukemias, lymphomas, and myelomas. In Section III, Dr. Stanley Riddell and colleagues describe studies on isolation of T cells reactive with minor histocompatibility (H) antigens and involved both in GVHD and graft-versus-leukemia (GVL) responses. For example, the gene encoding a novel H-Y antigen in humans has been identified and shown to exhibit restricted tissue expression. Acute myelocytic leukemia stem cells were demonstrated to express the H-Y antigen and additional minor H antigens, and engraftment of such cells in NOD/SCID mice could be selectively prevented by minor antigen-specific T-cell clones. An autosomal encoded human minor H antigen associated with chronic GVHD has been demonstrated. A trial evaluating therapy of relapsed acute myelocytic leukemia or acute lymphoblastic leukemia after allogeneic stem cell transplantation with T-cell clones specific for recipient minor H antigens has been initiated.

Evolving strategies to address adverse transplant outcomes associated with T cell depletion

Graft-versus-host disease (GVHD) is the major complication of allogeneic bone marrow transplantation (BMT). The most effective strategy to reduce GVHD has been T cell depletion (TCD) of the donor marrow graft. Although TCD has reduced both the incidence and severity of GVHD, it has been associated with an increased rate of graft rejection and an impairment in immune reconstitution after transplant. Relapse rates in selected hematologic malignancies have also been higher after TCD allogeneic BMT. Over the past several years, a number of clinical strategies have been developed in an effort to reduce adverse transplant outcomes associated with TCD. This review examines some of the strategies designed to promote alloengraftment, prevent relapse, and enhance immune reconstitution after TCD.

Immunology and immunotherapy of human cancer: present concepts and clinical developments

Immunotherapy of cancer is entering into a new phase of active investigation both at the pre-clinical and clinical level. This is due to the exciting developments in basic immunology and tumour biology that have allowed a tremendous increase in our understanding of mechanisms of interactions between the immune system and tumour cells. This review briefly summarizes the state of the art in basic tumour immunology before discussing the clinical applications of the new concepts in the clinical setting. Clinical approaches are diverse but can now be based on strong scientific rationales. The analysis of the available clinical results suggests that, despite some disappointments, there is room for optimism that both active immunotherapy (vaccination) and adoptive immunotherapy may soon become part of the therapeutic arsenal to combat cancer in a more efficient way.

Transplantation of hematopoietic stem cells from alternate donors in acute myelogenous leukemia

The number of allogeneic transplants from unrelated donors has grown in the past decade in part because of the expansion of the donor registry size. Patient survival has improved due to the selection of more closely matched donors and the development of effective infection prophylaxis. Relapse-free survival remains limited in patients with a large tumor burden at the time of transplantation. A higher marrow cell dose is the major factor to minimize transplant-related death. Future studies of peripheral blood stem cell transplants should be considered for patients with acute leukemia with the goal of enhancing the stem cell dose and improving survival.

Is there a best transplant conditioning regimen for acute myeloid leukemia?

The outcome of marrow transplantation is largely determined by the effectiveness of the transplant preparative regimen. Nonetheless, there have been startlingly few randomized trials attempting to identify optimal regimens for specific conditions and, at present, no single approach has emerged as superior for the treatment of acute myeloid leukemia (AML) in the few trials that have been performed. Newer approaches that appear encouraging in phase II studies include substituting etoposide for cyclophosphamide, adding thiotepa to the traditional cyclophosphamide plus total body irradiation combination in the setting of T cell depletion, and using antibody-based targeted radiotherapy as part of the transplant regimen. The ability to obtain allogeneic engraftment with nonablative regimens may open the door to additional innovative approaches, combining very specific antileukemia therapy with relatively nontoxic measures to ensure engraftment.

Graft-vs.-malignancy with allogeneic blood stem cell transplantation: a potential primary treatment modality

The high-dose chemotherapy and radiation typically used as the preparative regimen for bone marrow transplantation produces considerable morbidity and mortality. An alternative strategy is to utilize a low-dose, non-myeloablative, preparative regimen designed not to eradicate the malignancy, but to provide sufficient immunosuppression to achieve engraftment of an allogeneic hematopoietic graft and allow subsequent development of a graft-vs.-malignancy effect. We studied this approach in patients who were ineligible for standard myeloablative preparative regimens because of advanced age or comorbidities and demonstrated that purine analog (fludarabine or 2-CDA) containing non-myeloablative chemotherapy allows engraftment of HLA-compatible hematopoietic progenitor cells, and extended remissions were observed in approximately half of chemosensitive patients with recurrent AML or CML. Patients with CLL or lymphoma have been effectively treated using a non-myeloablative regimen of fludarabine/cyclophosphamide of fludarabine, cytarabine, cisplatin. This chemotherapy is known to be non-myeloablative and mixed chimerism was anticipated. All patients with engraftment have responded and 67% have achieved complete remission. Maximal responses are slow to develop and occur gradually over a period of several months to one year. Long-term efficacy must still be determined and controlled trials are necessary comparing this approach with alternative therapies as well as standard transplantation regimens.

Allogeneic hematopoietic stem-cell engraftment and graft failure

Two immunologically mediated reactions, the graft-versus-host (GvH) and host-versus-graft (HvG) responses, form primary and opposing barriers to successful transplantation of allogeneic hematopoietic stem-cells (HSC). The HvG barrier is set by the strength of the allogeneic immune response, which is determined by antigenic stimulation provided by donor cells, owing to differences in histocompatibility antigens, and the capacity of host immune cells to generate a response. Risk of graft failure must be viewed as the interplay of multiple factors, including degree of human leukocyte antigen and minor histocompatibility antigen disparity, capacity of host immune response, and the capacity of donor hematopoietic and immunologic cells for overcoming residual host immunity.