Factors predicting response and graft-versus-host disease after donor lymphocyte infusions: a study on 593 infusions

Donor Lymphocyte Infusion and Molecular Monitoring for Relapsed Myelofibrosis After Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) is a curative approach for myelofibrosis patients, but relapse is a major cause of treatment failure. We investigated the effect of donor lymphocyte infusion (DLI) in 37 patients with molecular (n = 17) or hematological relapse (n = 20) after HCT. Patients received median of 2 (range, 1-5) cumulative DLI (total of 91 infusions). Median starting dose was 1 × 10⁶ cells/kg, escalated by half-log ≥6 weeks if no response nor graft-versus-host disease (GvHD) occurred. Median time to first DLI was 40 weeks for molecular relapse versus 145 weeks for hematological relapse. Overall molecular complete response (mCR) at any time was 73% (n = 27) and was significantly higher for initial molecular relapse (88%) versus hematological relapse (60%; P = 0.05). The 6-year overall survival was 77% versus 32% (P = 0.03). Acute GvHD 2-4 occurred in 22% and half of the patients achieved mCR without any GvHD. All patients who relapsed from mCR achieved after first DLI could be salvaged with subsequent DLI, showing long-term survival. No second HCT was needed for molecular relapse versus 6 for hematological relapse. This comprehensive and largest study to date suggests molecular monitoring together with DLI as standard of care and a crucial approach to achieve excellent outcomes in relapsed myelofibrosis.

Potential to Improve Therapy of Chronic Myeloid Leukemia (CML), Especially for Patients with Older Age: Incidence, Mortality, and Survival Rates of Patients with CML in Switzerland from 1995 to 2017

BACKGROUND

Tyrosine kinase inhibitors (TKI) substantially improved chronic myeloid leukemia (CML) prognosis. We aimed to describe time period- and age-dependent outcomes by reporting real-world data of CML patients from Switzerland.

METHODS

Population-based incidence, mortality, and survival were assessed for four different study periods and age groups on the basis of aggregated data from Swiss Cantonal Cancer Registries.

RESULTS

A total of 1552 new CML cases were reported from 1995 to 2017. The age-standardized rate (ASR) for the incidence remained stable, while the ASR for mortality decreased by 50-80%, resulting in a five-year RS from 36% to 74% over all four age groups. Importantly, for patients <60 years (yrs), the five-year RS increased only in earlier time periods up to 92%, whereas for older patients (+80 yrs), the five-year RS continued to increase later, however, reaching only 53% until 2017.

CONCLUSIONS

This is the first population-based study of CML patients in Switzerland confirming similar data compared to other population-based registries in Europe. The RS increased significantly in all age groups over the last decades after the establishment of TKI therapy. Interestingly, we found a more prominent increase in RS of patients with older age at later observation periods (45%) compared to patients at younger age (10%), implicating a greater benefit from TKI treatment for elderly occurring with delay since the establishment of TKI therapy. Our findings suggest more potential to improve CML therapy, especially for older patients.

60 Years Young: The Evolving Role of Allogeneic Hematopoietic Stem Cell Transplantation in Cancer Immunotherapy

The year 2020 marked the 30th anniversary of the Nobel Prize in Medicine awarded to E. Donnall Thomas for the development of allogeneic hematopoietic stem cell transplantation (allo-HSCT) to treat hematologic malignancies and other blood disorders. Dr. Thomas, "father of bone marrow transplantation," first developed and reported this technique in 1957, and in the ensuing decades, this seminal study has impacted fundamental work in hematology and cancer research, including advances in hematopoiesis, stem cell biology, tumor immunology, and T-cell biology. As the first example of cancer immunotherapy, understanding the mechanisms of antitumor biology associated with allo-HSCT has given rise to many of the principles used today in the development and implementation of novel transformative immunotherapies. Here we review the historical basis underpinning the development of allo-HSCT as well as advances in knowledge obtained by defining mechanisms of allo-HSCT activity. We review how these principles have been translated to novel immunotherapies currently utilized in clinical practice and describe potential future applications for allo-HSCT in cancer research and development of novel therapeutic strategies.

Repetitively Administered Low-Dose Donor Lymphocyte Infusion for Prevention of Relapse after Allogeneic Stem Cell Transplantation in Patients with High-Risk Acute Leukemia

Simple Summary

Patients with high-risk acute leukemia (AL) have a high risk of relapse after allogeneic stem cell transplantation (allo-SCT). Prophylactic donor lymphocyte infusion (pro-DLI) has shown significant efficacy in reducing relapse rate but its widespread application has been limited due to concerns of graft versus host disease (GVHD) development. In the present study, we tested the safety and efficacy of a novel method of pro-DLI based on repetitive administration of low lymphocyte doses. Low-dose pro-DLI was administered every two months for at least 3-years. Forty-four high-risk AL patients with a median age of 53-years who underwent allo-SCT from a matched-sibling (38pts) or a matched-unrelated donor (6pts) received pro-DLI. Acute and chronic-GVHD developed in 14% and 12% of patients. With a median follow-up of 44-months, the cumulative incidence of relapse and non-relapse mortality was 12% and 13%, while the overall survival was 78%. Prolonged up to 3-years low-dose pro-DLI administered every two months is safe and effective in reducing relapse rate in patients with high-risk AL. The low-dose repetitive administration DLI strategy reduced the risk of DLI-mediated GVHD, while the prolonged repeated administration helped in preventing relapse, possibly by inducing a sustained and prolonged immunological pressure on residual leukemic cells.

Abstract

Background: Patients with high-risk acute leukemia have a high risk of relapse after allogeneic stem cell transplantation (allo-SCT). In an effort to reduce the relapse rate, various therapeutic methods have been implemented into clinical practice. Among them, prophylactic donor lymphocyte infusion (pro-DLI) has shown significant efficacy. However, the widespread application of pro-DLI has been restricted mostly due to concerns regarding the development of graft versus host disease (GVHD). In the present study, we tested the safety and efficacy of a novel method of prophylactic-DLI based by repetitive administration of low lymphocyte doses. Methods: DLI was administered to patients with high-risk acute leukemia at a dose of 2 × 10⁶/kg CD3-positive cells. DLI at the same dose was repeated every two months for at least 36 months post-allo-SCT, or until relapse or any clinical or laboratory feature suggested GVHD, whichever occurred first. Forty-four patients with a median age of 53 years (range 20–67) who underwent allo-SCT between 2011 and 2020 were included in our study. Thirty-three patients with high-risk acute myeloid leukemia (AML) and 11 with high-risk acute lymphoblastic leukemia (ALL) after allo-SCT from a matched sibling (MSD, no = 38 pts) or a matched-unrelated donor (MUD, no = 6 pts) received pro-DLI. Twenty-three patients were in CR1, all with unfavorable genetic features; 12 patients were in CR2 or beyond; and 9 patients had refractory disease at the time of transplant. Ten out of 23 patients in CR1 had detectable minimal residual disease (MRD) at the time of allo-SCT. Disease risk index (DRI) was high and intermediate in 21 and 23 patients, respectively. Conditioning was myeloablative (MAC) in 36 and reduced intensity (RIC) in 8 patients, while GVHD prophylaxis consisted of cyclosporine-A in combination with low-dose alemtuzumab in 39 patients or with low-dose MTX in 5 patients, respectively. Results: Thirty-five patients completed the scheduled treatment and received a median of 8 DLI doses (range 1–35). Fifteen out of 35 patients received all planned doses, while DLI was discontinued in 20 patients. Reasons for discontinuation included GVHD development in nine, donor unavailability in seven, disease relapse in three, and secondary malignancy in one patient, respectively. Nine patients were still on treatment with DLI, and they received a median of four (range 2–12) doses. Fourteen percent of patients developed transient grade-II acute GVHD while 12% developed chronic GVHD post-DLI administration. Acute GVHD was managed successfully with short course steroids, and four out of five patients with cGVHD were disease-free and off immunosuppression. With a median follow-up of 44 months (range 8–120), relapse-free (RFS) and overall survival (OS) were 74%, (95% CI, 54–87%) and 78%, (95% CI, 58–89%) respectively, while the cumulative incidence of non-relapse mortality (NRM) was 13% (95% CI, 4–28%). The cumulative incidence of relapse in patients with intermediate and high DRI is 7% and 15%, respectively. Conclusion: Prolonged—up to three years—low-dose pro-DLI administered every two months is safe and effective in reducing relapse rate in patients with high-risk acute leukemia. The low-dose repetitive administration DLI strategy reduced the risk of DLI-mediated GVHD, while the prolonged repeated administration helped in preventing relapse, possibly by inducing a sustained and prolonged immunological pressure on residual leukemic cells. This novel strategy deserves testing in larger cohort of patients with high-risk acute leukemia.

Donor Lymphocyte Infusions After Allogeneic Stem Cell Transplantation in Acute Leukemia: A Survey From the Gruppo Italiano Trapianto Midollo Osseo (GITMO)

We conducted a retrospective multicenter study including pediatric and adult patients with acute leukemia (AL) who received donor lymphocyte infusions (DLIs) after allogeneic hematopoietic stem cell transplantation (HCT) between January 1, 2010 and December 31, 2015, in order to determine the efficacy and toxicity of the immune treatment. Two hundred fifty-two patients, median age 45.1 years (1.6–73.4), were enrolled from 34 Italian transplant centers. The underlying disease was acute myeloid leukemia in 180 cases (71%). Donors were HLA identical or 1 locus mismatched sibling (40%), unrelated (40%), or haploidentical (20%). The first DLI was administered at a median time of 258 days (55–3,784) after HCT. The main indication for DLI was leukemia relapse (73%), followed by mixed chimerism (17%), and pre-emptive/prophylactic use (10%). Ninety-six patients (38%) received one single infusion, whereas 65 (26%), 42 (17%), and 49 patients (19%) received 2, 3, or ≥4 infusions, respectively, with a median of 31 days between two subsequent DLIs. Forty percent of evaluable patients received no treatment before the first DLI, whereas radiotherapy, conventional chemotherapy or targeted treatments were administered in 3, 39, and 18%, respectively. In informative patients, a few severe adverse events were reported: grade III–IV graft versus host disease (GVHD) (3%), grade III–IV hematological toxicity (11%), and DLI-related mortality (9%). Forty-six patients (18%) received a second HCT after a median of 232 days (32–1,390) from the first DLI. With a median follow-up of 461 days (2–3,255) after the first DLI, 1-, 3-, and 5- year overall survival (OS) of the whole group from start of DLI treatment was 55, 39, and 33%, respectively. In multivariate analysis, older recipient age, and transplants from haploidentical donors significantly reduced OS, whereas DLI for mixed chimerism or as pre-emptive/prophylactic treatment compared to DLI for AL relapse and a schedule including more than one DLI significantly prolonged OS. This GITMO survey confirms that DLI administration in absence of overt hematological relapse and multiple infusions are associated with a favorable outcome in AL patients. DLI from haploidentical donors had a poor outcome and may represent an area of further investigation.

Chemotherapy plus DLI for relapse after haploidentical HSCT: the biological characteristics of relapse influences clinical outcomes of acute leukemia patients

This study investigated the prognostic factors in patients (n = 89) who experienced relapse and received chemotherapy plus donor leukocyte infusion (Chemo-DLI) after haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Patients with early relapse (< 6 vs. > 6 months after haplo-HSCT), higher bone marrow blast count before chemo-DLI (> 20% vs. 5-19%), and without chronic graft-versus-host disease (cGVHD) after chemo-DLI had a higher rate of progressive disease (PD) and worse progression-free survival (PFS) and overall survival (OS). In multivariate analysis, non-cGVHD after Chemo-DLI and high blast count predicted a higher risk of PD and poorer PFS, and non-cGVHD after Chemo-DLI and early relapse predicted poorer OS. The patients were stratified into three groups according to these three risk factors. Patients with all three risk factors (n = 14) had the highest PD rate and poorest survival compared with those with one or two risk factors (n = 63) or no risk factors (n = 12). Thus, early relapse, high leukemia burden before Chemo-DLI, and non-cGVHD after Chemo-DLI can predict outcomes in patients who have experienced relapse and received Chemo-DLI after haplo-HSCT. New therapeutic strategies should be identified for these patients.

Multicenter phase 1/2 application of adenovirus-specific T cells in high-risk pediatric patients after allogeneic stem cell transplantation

BACKGROUND

Adenovirus (ADV) reactivation can cause significant morbidity and mortality in children after allogeneic stem cell transplantation. Antiviral drugs can control viremia, but viral clearance requires recovery of cell-mediated immunity.

METHOD

This study was an open-label phase 1/2 study to investigate the feasibility of generating donor-derived ADV-specific T cells (Cytovir ADV, Cell Medica) and to assess the safety of pre-emptive administration of ADV-specific T cells in high-risk pediatric patients after allogeneic hematopoietic stem cell transplantation (HSCT) to treat adenoviremia. Primary safety endpoints included graft-versus-host disease (GvHD), and secondary endpoints determined antiviral responses and use of antiviral drugs.

RESULTS

Between January 2013 and May 2016, 92 donors were enrolled for the production of ADV T cells at three centers in the United Kingdom (UK), and 83 products were generated from 72 mobilized peripheral blood harvests and 20 steady-state whole blood donations. Eight children received Cytovir ADV T cells after standard therapy and all resolved ADV viremia between 15 and 127 days later. ADV-specific T cells were detectable using enzyme-linked immunospot assay (ELISpot) in the peripheral blood of all patients analyzed. Serious adverse events included Grade II GvHD, Astrovirus encephalitis and pancreatitis.

CONCLUSION

The study demonstrates the safety and feasibility of pre-emptively manufacturing peptide pulsed ADV-specific cells for high-risk pediatric patients after transplantation and provides early evidence of clinical efficacy.

CTLA4-CD28 chimera gene modification of T cells enhances the therapeutic efficacy of donor lymphocyte infusion for hematological malignancy

Donor lymphocyte infusion (DLI) followed by hematopoietic stem cell transplantation has served as an effective prevention/treatment modality against the relapse of some hematologic tumors, such as chronic myeloid leukemia (CML). However, the therapeutic efficacies of DLI for other types of leukemia, including acute lymphocytic leukemia (ALL), have been limited thus far. Therefore, we examined whether increasing the reactivity of donor T cells by gene modification could enhance the therapeutic efficacy of DLI in a murine model of ALL. When a CTLA4-CD28 chimera gene (CTC28) in which the intracellular signaling domain of CTLA4 was replaced with the CD28 signaling domain was introduced into CD4 and CD8 T cells in DLI, the graft-versus-tumor (GVT) effect was significantly increased. This effect was correlated with an increased expansion of donor CD8 T cells in vivo, and the depletion of CD8 T cells abolished this effect. The CD8 T cell expansion and the enhanced GVT effect were dependent on the transduction of both CD4 and CD8 T cells with CTC28, which emphasizes the role of dual modification in this therapeutic effect. The CTC28-transduced T cells that expanded in vivo also exhibited enhanced functionality. Although the potentiation of the GVT effect mediated by the CTC28 gene modification of T cells was accompanied by an increase of graft-versus-host disease (GVHD), the GVHD was not lethal and was mitigated by treatment with IL-10 gene-modified third-party mesenchymal stem cells. Thus, the combined genetic modification of CD4 and CD8 donor T cells with CTC28 could be a promising strategy for enhancing the therapeutic efficacy of DLI.

Flow cytometry minimal residual disease after allogeneic transplant for chronic lymphocytic leukemia

OBJECTIVES

This study investigates whether achieving complete remission (CR) with undetectable minimal residual disease (MRD) after allogeneic stem cell transplantation (allo-SCT) for chronic lymphocytic leukemia (CLL) affects outcome.

METHODS

We retrospectively studied 46 patients transplanted for CLL and evaluated for post-transplant MRD by flow cytometry.

RESULTS

At transplant time, 43% of the patients were in CR, including one with undetectable MRD, 46% were in partial response, and 11% had refractory disease. After transplant, 61% of the patients achieved CR with undetectable MRD status. By multivariate analysis, reaching CR with undetectable MRD 12 months after transplant was the only factor associated with better progression-free survival (P = 0.02) and attaining undetectable MRD, independently of the time of negativity, was the only factor that correlated with better overall survival (P = 0.04).

CONCLUSION

Thus, achieving undetectable MRD status after allo-SCT for CLL is a major goal to improve post-transplant outcome.

Immunothérapie et greffe de cellules souches hématopoïétiques allogéniques

IMMUNOTHERAPY AND ALLOGENEIC STEM CELLS TRANSPLANTATION

Allogeneic stem cell transplantations represent perfect example of immunotherapy. Its positive aspects are due to the graft versus tumor effect. Unfortunately, this therapeutic advantage is usually associated with graft versus host effects. While the mechanism of these two graft reactions remain unclear, this is possible to modulate these immunologic effects. The type of conditioning regimen, the source of donor and the use of donor cells after the transplantation may influence the toxicity and the tumor response, leading to a better optimization of the procedure. This paper is presenting all the parameters which may contribute to improve allogeneic stem cell transplantations.

Minimal residual disease- and graft-vs.-host disease-guided multiple consolidation chemotherapy and donor lymphocyte infusion prevent second acute leukemia relapse after allotransplant

BACKGROUND

Persons with acute leukemia relapsing after allotransplant and who respond to anti-leukemia interventions are at high risk of a second relapse. We studied the impact of minimal residual disease (MRD)- and graft-vs.-host disease (GvHD)-guided multiple consolidation chemotherapy and donor lymphocyte infusions (DLIs) to prevent second relapse in patients with acute leukemia relapsing post-transplant and who achieved complete remission after induction chemotherapy and DLI.

METHODS

Forty-seven subjects with acute leukemia relapsing after an allotransplant and who achieved complete remission after post-relapse induction chemotherapy and DLI were eligible. The use of consolidation chemotherapy and DLI was guided by the results of MRD testing and whether or not DLI caused acute and/or chronic GvHD. Outcomes were compared with those of 34 similar historical controls who did not receive consolidation chemotherapy and DLIs after induction chemotherapy and DLI.

RESULTS

One-year cumulative incidence of relapse (CIR; 22 % 95 % confidence interval (10, 35 %) vs. 56 % (39, 73 %); P < 0.0001), leukemia-free survival (LFS; 71 % (57, 84 %) vs. 35 % (19, 51 %); P < 0.0001), and survival (78 % (66, 90 %) vs. 44 % (27, 61 %); P < 0.0001) was significantly better in subjects than controls. In multivariate analyses, no chronic GvHD after therapy (hazard ratio (HR) = 3.56 (1.09, 11.58); P = 0.035) and a positive MRD test after therapy (HR = 21.04 (4.44, 94.87); P < 0.0001) were associated with an increased CIR.

CONCLUSION

These data suggest MRD- and GvHD-guided multiple consolidation chemotherapy and DLIs reduce CIR and increase LFS and survival compared with controls in persons relapsing after allotransplant for acute leukemia.

TRIAL REGISTRATION

ChiCTR-ONC-12002912 . Donor lymphocyte infusion for the treatment of leukemia relapse following allogeneic hematopoeitic stem cell transplant.

Manufacture of GMP-compliant functional adenovirus-specific T-cell therapy for treatment of post-transplant infectious complications

BACKGROUND AIMS

In pediatric patients, adenovirus (ADV) reactivation after allogeneic hematopoietic stem cell transplantation (allo HSCT) is a major cause of morbidity and mortality. For patients who do not respond to antiviral drug therapy, a new treatment approach using ADV-specific T cells can present a promising alternative. Here we describe the clinical scale Good Manufacturing Practice (GMP)-compliant manufacture and characterization of 40 ADV-specific T-cell products, Cytovir ADV, which are currently being tested in a multi-center phase I/IIa clinical trial. This process requires minimal intervention, is high yield, and results in a pure T-cell product that is functional.

METHODS

Mononuclear cells (2 × 10(7)) were cultured in a closed system in the presence of GMP-grade ADV peptide pool and cytokines for 10 days. On day 10, the T-cell product was harvested, washed in a closed system, counted and assessed for purity and potency. Additional characterization was carried out where cell numbers allowed.

RESULTS

Thirty-eight of 40 products (95%) met all release criteria. Median purity of the cell product was 88.3% CD3+ cells with a median yield of 2.9 × 10(7) CD3+ cells. Potency analyses showed a median ADV-specific interferon (IFN)γ response of 5.9% of CD3+ and 2345 IFNγ spot-forming cells/million. CD4 and CD8 T cells were capable of proliferating in response to ADV (63.3 and 56.3%, respectively). These virus-specific T cells (VST) were heterogenous, containing both effector memory and central memory T cells. In an exemplar patient with ADV viremia treated in the open ASPIRE trial, ADV-specific T-cell response was detected by IFNγ enzyme-linked immunospot from 13 days post-infusion. ADV DNA levels declined following cellular therapy and were below level of detection from day 64 post-infusion onward.

CONCLUSIONS

The clinical-scale GMP-compliant One Touch manufacturing system is feasible and yields functional ADV-specific T cells at clinically relevant doses.

Strategies for improving the efficacy of donor lymphocyte infusion following stem cell transplantation

Donor lymphocyte infusion (DLI) is an effective immunotherapeutic approach with significant activity in the treatment and prevention of relapse after allogeneic stem cell transplantation. DLI is associated with significant toxicity mainly due to graft-versus-host disease. Moreover, DLI does not produce durable responses in aggressive malignancies like acute leukemia. Improvement in DLI efficacy requires dissociation of graft-versus-leukemia effect from graft-versus-host disease. Minor histocompatibility antigens with tissue restriction and leukemia or tumor-associated antigens represent ideal antigenic targets. A brief overview of the existing methods of DLI administration is the topic of this article. T cells transduced with genes encoding for T-cell receptors with reactivity against minor histocompatibility antigens or leukemia-associated antigens is a promising option.

Salvage treatment for relapsed/refractory Hodgkin lymphoma: role of allografting, brentuximab vedotin and newer agents

INTRODUCTION

Second-line, salvage chemotherapy followed by high-dose chemotherapy and autologous stem cell transplantation (AUTO-SCT) is the standard of care for patients with relapsed/refractory (R/R) Hodgkin lymphoma (HL). Approximately 50% of patients relapse after AUTO-SCT and their prognosis is generally poor. Brentuximab Vedotin (BV) has demonstrated efficacy in this setting and allogeneic (ALLO)-SCT represents an option with curative potential in this subgroup of patients.

AREAS COVERED

A systematic review has been conducted to explore the actual knowledge on ALLO-SCT, BV and newer agents in R/R HL.

EXPERT OPINION

The introduction of BV in clinical practice has significantly improved the management of post-AUTO-SCT relapses and the drug can induce durable remissions in a subset of R/R HL. Allografting select patients has been used to improve clinical outcomes and recent case series have begun to explore BV as a potential 'bridge' to allo-SCT, even though the optimal timing of ALLO-SCT after BV response remains undetermined. However, reduced tumor burden at the time of ALLO-SCT is a key factor to decrease relapse risk. Based on the unique composition of the tumor, more recently new agents such as PD-1 inhibitors have been developed. The potential role of PD-1 inhibitors with ALLO-SCT remains to be explored.

Donor Lymphocyte Infusions for Chronic Myeloid Leukemia Relapsing after Allogeneic Stem Cell Transplantation: May We Predict Graft-versus-Leukemia Without Graft-versus-Host Disease?

Donor lymphocyte infusions (DLI) are an effective treatment for relapsed chronic myeloid leukemia (CML) after allogeneic stem cell transplantation (alloSCT). Leukemia resistance and secondary graft-versus-host disease (GVHD) are major obstacles to success with DLI. The aim of this study was to identify pre-DLI factors associated with prolonged survival in remission without secondary GVHD. We retrospectively analyzed 500 patients treated with DLI for CML relapse (16% molecular, 30% cytogenetic, and 54% hematological) after alloSCT. The overall probabilities of failure- and secondary GVHD-free survival (FGFS) were 29% and 27% at 5 and 10 years after DLI, respectively. The type of relapse was the major factor influencing FGFS (40% for molecular and/or cytogenetic relapse and 20% for hematological relapse at 5 years, P < .001). Chronic GVHD before DLI and an interval <1 year between alloSCT and first DLI were independently associated with inferior FGFS in patients with molecular and/or cytogenetic relapse. Consequently, FGFS was 13%, 35%, to 56% at 5 years in patients with 2, 1, and 0 adverse features, respectively. In patients with hematological relapse, independent adverse prognostic factors for FGFS were initial dose of CD3(+) cells ≥ 50 × 10(6)/kg, donor-recipient sex mismatch, and chronic GVHD before DLI. FGFS was 0%, 17%, 33%, to 37% in patients with 3, 2, 1, and 0 adverse features, respectively. The probability of survival in remission without secondary GVHD was highest (>50% at 5 years) when DLI were given beyond 1 year from alloSCT for molecular and/or cytogenetic CML relapse that was not preceded by chronic GVHD.

Immunotherapy in acute myeloid leukemia

Treatment of acute myeloid leukemia (AML) with current chemotherapy regimens is still disappointing, with overall survival rates of ≤40% at 5 years. It is now well established that AML cells can evade the immune system through multiple mechanisms, including the expression of the enzyme indoleamine 2,3 dioxygenase. Immunotherapeutic strategies, including both active, such as vaccination with leukemia-associated antigens, and passive, such as adoptive transfer of allogeneic natural killer cells, may overcome leukemia escape and lead to improved cure. Allogeneic hemopoeitic stem cell transplantation, the most effective treatment of AML, is the best known model of immunotherapy. Following transplant, recipient AML cells are eradicated by donor immune cells through the graft-versus-leukemia (GVL) effect. However, GVL is clinically associated with graft-versus-host disease, the major cause of mortality after transplant. GVL is mediated by donor T cells recognizing either leukemia-associated antigens or minor as well as major histocompatibility antigens. Several innovative strategies have been devised to generate leukemia reactive T cells so as to increase GVL responses with no or little graft-versus-host disease.

Chemotherapy followed by modified donor lymphocyte infusion as a treatment for relapsed acute leukemia after haploidentical hematopoietic stem cell transplantation without in vitro T-cell depletion: superior outcomes compared with chemotherapy alone and an analysis of prognostic factors

We retrospectively compared the antileukemic effects of chemotherapy alone and chemotherapy followed by modified donor lymphocyte infusion (DLI) in 82 patients with relapsed acute leukemia after haploidentical hematopoietic stem cell transplantation (HSCT) without in vitro T-cell depletion. We also investigated prognostic factors in patients receiving chemotherapy followed by modified DLI. Thirty-two patients received chemotherapy alone, and the remaining 50 patients received chemotherapy followed by modified DLI. In patients receiving chemotherapy followed by modified DLI, complete remission rate was significantly higher (64.0% vs. 12.5%, P = 0.000), the incidence of relapse was significantly lower (50.0% vs. 100.0%, P = 0.000), and disease-free survival was significantly improved (36.0% vs. 0.0%, P = 0.000) compared with patients receiving chemotherapy alone. Multivariate analysis demonstrated that patients with chronic graft-versus-host disease (GVHD) after intervention (P = 0.000) and patients receiving chemotherapy followed by modified DLI (P = 0.037) were associated with a lower relapse rate. Furthermore, in patients receiving chemotherapy followed by modified DLI, multivariate analysis demonstrated that chronic GVHD after modified DLI (P = 0.039) and duration of minimal residual disease (MRD) (-) ≥4 months after modified DLI (P = 0.001) were associated with a lower relapse rate. Our study is the first to suggest that chemotherapy followed by modified DLI is associated with stronger antileukemic effects and better survival in relapsed acute leukemia after haploidentical HSCT without in vitro T-cell depletion. Furthermore, our study suggests that lack of chronic GVHD and duration of MRD (-) <4 months after modified DLI are associated with higher relapse rates in patients receiving chemotherapy followed by modified DLI.

Is Imatinib Maintenance Required for Patients with Relapse Chronic Myeloid Leukemia Post-Transplantation Obtaining CMR? A Pilot Retrospective Investigation

Imatinib can induce complete molecular remission (CMR) in relapse chronic myelogenous leukemia (CML) after allogeneic hematopoietic stem cell transplantation, but it is indefinite whether imatinib is required to maintain CMR. We retrospectively reviewed 37 relapse CML post-transplants treated with imatinib (n = 20) or donor lymphocyte infusion (DLI) (n = 17). The rate of CMR was 85% and 76.47% (P = 0.509) and treatment-related mortality was 0% and 29.4% (P = 0.019), respectively, in imatinib and DLI groups. Fifteen patients obtaining CMR voluntarily ceased imatinib, and did not experience relapse. The 8-year overall survival (OS) after relapse was 85%±8% and 40.3±12.1% (P = 0.017), and disease-free survival (DFS) after relapse was 85%±8% and 40.3±12.1% (P = 0.011), respectively, in imatinib and DLI groups. Imatinib resulted in higher OS and DFS than that of DLI in relapse CML. Imatinib maintenance might not be required for patients with relapse CML post-transplants after they achieved full donor chimerism and CMR.

Cellular therapy following allogeneic stem-cell transplantation

Allogeneic hematopoietic stem-cell transplantation (HSCT) is the most effective approach for many patients with hematologic malignancies. Unfortunately, relapse remains the most common cause of death after allogeneic HSCT, and the prognosis of relapsed disease is poor for most patients. Induction of a graft-versus-leukemia (GVL), or graft-versus-tumor, effect through the use of donor leukocyte infusion (DLI), or donor lymphocyte infusion, has been remarkably successful for relapsed chronic myelogenous leukemia. Unfortunately, response to DLI in other hematologic malignancies is much less common and depends on many factors including histology, pace and extent of relapse, and time from HSCT to relapse. Furthermore, graft-versus-host disease (GVHD) is common after DLI and often limits successful immunotherapy. Ultimately, manipulations to minimize GVHD while preserving or enhancing GVL are necessary to improve outcomes for relapse after allogeneic HSCT.

Cytotoxic T cells induce proliferation of chronic myeloid leukemia stem cells by secreting interferon-γ

Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasia arising from the oncogenic break point cluster region/Abelson murine leukemia viral oncogene homolog 1 translocation in hematopoietic stem cells (HSCs), resulting in a leukemia stem cell (LSC). Curing CML depends on the eradication of LSCs. Unfortunately, LSCs are resistant to current treatment strategies. The host's immune system is thought to contribute to disease control, and several immunotherapy strategies are under investigation. However, the interaction of the immune system with LSCs is poorly defined. In the present study, we use a murine CML model to show that LSCs express major histocompatibility complex (MHC) and co-stimulatory molecules and are recognized and killed by leukemia-specific CD8(+) effector CTLs in vitro. In contrast, therapeutic infusions of effector CTLs into CML mice in vivo failed to eradicate LSCs but, paradoxically, increased LSC numbers. LSC proliferation and differentiation was induced by CTL-secreted IFN-γ. Effector CTLs were only able to eliminate LSCs in a situation with minimal leukemia load where CTL-secreted IFN-γ levels were low. In addition, IFN-γ increased proliferation and colony formation of CD34(+) stem/progenitor cells from CML patients in vitro. Our study reveals a novel mechanism by which the immune system contributes to leukemia progression and may be important to improve T cell-based immunotherapy against leukemia.

Immunoregulatory CD4(-)CD8(-) T cells as a potential therapeutic tool for transplantation, autoimmunity, and cancer

A central objective in organ transplantation and the treatment or prevention of autoimmune disease is the achievement of antigen-specific immune tolerance. An additional challenge in bone marrow transplantation for the treatment of hematological malignancies is the prevention of graft-vs-host disease (GVHD) while maintaining graft-vs-tumor activity. Interestingly, CD4^-CD8^- (double negative, DN) T cells, which exhibit a unique antigen-specific immunoregulatory potential, appear to exhibit all of the properties to respond to these challenges. Herein, we review the therapeutic potential of immunoregulatory DN T cells in various immunopathological settings, including graft tolerance, GVHD, cancer, and autoimmunity.

Treatment of relapsed adult T-cell leukemia/lymphoma after allogeneic hematopoietic stem cell transplantation: the Nagasaki Transplant Group experience

Adult T-cell leukemia/lymphoma (ATL) relapse is a serious therapeutic challenge after allogeneic hematopoietic stem cell transplantation (allo-SCT). In the present study, we retrospectively analyzed 35 patients who experienced progression of or relapsed persistent ATL after a first allo-SCT at 3 institutions in Nagasaki prefecture (Japan) between 1997 and 2010. Twenty-nine patients were treated by the withdrawal of immune suppressants as the initial intervention, which resulted in complete remission (CR) in 2 patients. As the second intervention, 9 patients went on to receive a combination of donor lymphocyte infusion and cytoreductive therapy and CR was achieved in 4 patients. Of 6 patients who had already had their immune suppressants discontinued before the relapse, 3 patients with local recurrence received local cytoreductive therapy as the initial treatment, which resulted in CR for more than 19 months. Donor lymphocyte infusion-induced remissions of ATL were durable, with 3 cases of long-term remission of more than 3 years and, interestingly, the emergence or progression of chronic GVHD was observed in all of these cases. For all 35 patients, overall survival after relapse was 19.3% at 3 years. The results of the present study suggest that induction of a graft-versus-ATL effect may be crucial to obtaining durable remission for ATL patients with relapse or progression after allo-SCT.

Donor lymphocyte infusions and second transplantation as salvage treatment for relapsed myelofibrosis after reduced-intensity allografting

Thirty myelofibrosis patients (21 males, nine females) with relapse (n = 27) or graft-rejection (n = 3) after dose-reduced allografting underwent a salvage strategy including donor lymphocyte infusions (DLIs) and/or second allogeneic haematopoietic stem cell transplantation (HSCT). Twenty-six patients received a median number of three (range, 1-5) DLIs in a dose-escalated mode starting with a median dose of 1·2 × 10(6) (range, 0·003-8 × 10(6) ) up to median dose of 40 × 10(6) T-cells/kg (range, 10-130 × 10(6) ). 10/26 patients (39%) achieved complete response (CR) to DLIs. Acute (grade II-IV) and chronic graft-versus-host (GvHD) disease occurred in 12% and 36% cases. Thirteen non-responders to DLI and four patients who did not receive DLI due to graft-rejection or acute transformation of the blast phase underwent a second allogeneic HSCT from alternative (n = 15) or the same (n = 2) donor. One patient (6%) experienced primary graft-failure and died. Acute (II-IV) and chronic GvHD were observed in 47% and 46% of patients. Overall responses after second HSCT were seen in 12/15 patients (80%: CR: n = 9, partial response: n = 3). The 1-year cumulative incidence of non-relapse mortality for recipients of a second allograft was 6%, and the cumulative incidence of relapse was 24%. After a median follow-up of 27 months, the 2-year overall survival and progression-free survival for all 30 patients was 70% and 67%, respectively. In conclusion, our two-step strategy, including DLI and second HSCT for non-responding or ineligible patients, is an effective and well-tolerated salvage approach for patients relapsing after reduced-intensity allograft after myelofibrosis.

High alloreactivity of low-dose prophylactic donor lymphocyte infusion in patients with acute leukemia undergoing allogeneic hematopoietic cell transplantation with an alemtuzumab-containing conditioning regimen

The value of prophylactic donor lymphocyte infusion (pDLI) is unclear and differs among diseases and transplantation protocols. Experience with this approach in patients with acute leukemia undergoing hematopoietic cell transplantation (HCT) with an alemtuzumab-incorporating conditioning protocol is lacking. We conducted a single-center prospective study to investigate the applicability and efficacy of prophylactic donor lymphocyte infusion (pDLI) in patients with leukemia undergoing HCT with a low-dose alemtuzumab-containing conditioning regimen. Inclusion criteria were high-risk acute myelogenous leukemia, acute lymphoblastic leukemia, or increasing mixed chimerism. All patients included were tapered off of immunotherapy. Exclusion criteria were a history of ≥ grade II or active graft-versus-host disease (GVHD). Of the 56 consecutive patients who underwent HCT with an alemtuzumab-containing regimen, 15 patients (8 with acute myelogenous leukemia and 7 with acute lymphoblastic leukemia) met the study inclusion criteria and received prophylactic DLI (total of 45 infusions) from 7 sibling donors and 8 unrelated donors. The first infusion was given at a median of 162 days posttransplantation. The median number of DLIs was 3, and the median cumulative CD3(+) cell dose was 2 × 10(6)cells/kg. Six of the 8 patients (75%) who received pDLI while in mixed chimerism converted to stable, complete donor chimerism. Some 47% of DLI recipients developed GVHD (4 acute GVHD and 3 with chronic GVHD) after a median cumulative dose of 2 × 10(6) CD3(+) cells/kg. After a median follow-up of 575 days, 11 (73%) pDLI recipients were alive. All 4 deaths were due to GVHD-related causes. None of the patients who received pDLIs relapsed. Patients with leukemia who received low-dose pDLI after conditioning with alemtuzumab are at low risk for relapse; however, this approach is associated with a relatively high incidence of severe GVHD.

Clinical options after failure of allogeneic hematopoietic stem cell transplantation in patients with hematologic malignancies

Disease recurrence is the single most common cause of death after allogeneic or autologous hematopoietic stem cell transplantation (HSCT). Disease status and chemosensitivity at the time of transplantation, as well as the development of graft-versus-host disease (GVHD), are factors known to influence the risk of relapse post-HSCT. Both acute and chronic GVHD have been associated with decreased relapse rates; however, owing to toxicity, overall survival is not consistently improved in these patients. Furthermore, there is a transient period of immunodeficiency after HSCT, which may permit residual malignant cells to proliferate early in the post-transplant course, before the donor immune system can establish a graft-versus-tumor response. Patients who fail an initial HSCT have an extremely poor outcome; therefore, maneuvers to prevent, identify and treat recurrent disease as early as possible in these situations are necessary. Strategies to distinguish graft-versus-tumor from GVHD, to enhance both general and disease-specific immune reconstitution after transplantation, and to increase donor-mediated anti-host immune reactions are being investigated in clinical trials. Single agent nontoxic post-HSCT chemotherapy, cellular therapies and second allogeneic HSCT using reduced intensity regimens are among the modalities under investigation.

Relapse after allogeneic stem cell transplantation

Since allogeneic stem cell transplantation (SCT) represents an intensive curative treatment for high-risk malignancies, its failure to prevent relapse leaves few options for successful salvage treatment. While many patients have a high early mortality from relapse, some respond and have sustained remissions, and a minority has a second chance of cure with appropriate therapy. The prognosis for relapsed hematological malignancies after SCT depends on four factors: the time elapsed from SCT to relapse (with relapses occurring within 6 months having the worst prognosis), the disease type (with chronic leukemias and some lymphomas having a second possibility of cure with further treatment), the disease burden and site of relapse (with better treatment success if disease is treated early), and the conditions of the first transplant (with superior outcome for patients where there is an opportunity to increase either the alloimmune effect, the specificity of the antileukemia effect with targeted agents or the intensity of the conditioning in a second transplant). These features direct treatments toward either modified second transplants, chemotherapy, targeted antileukemia therapy, immunotherapy or palliative care.

Donor Lymphocyte Infusions Modulate Relapse Risk in Mixed Chimeras and Induce Durable Salvage in Relapsed Patients After T-Cell–Depleted Allogeneic Transplantation for Hodgkin's Lymphoma

Purpose

Reduced-intensity conditioning has minimized nonrelapse-related mortality rates after allogeneic transplantation in patients with Hodgkin's lymphoma, and relapse has now become the major cause for treatment failure. We aimed to assess the impact of donor lymphocyte infusions (DLIs) on relapse incidence when administered for mixed chimerism and their utility as salvage therapy when given for relapse.

Patients and Methods

This study reports the outcomes of 76 consecutive patients with multiply relapsed or refractory Hodgkin's lymphoma who underwent allogeneic transplantation that incorporated in vivo T-cell depletion. Forty-two patients had related donors and 34 had unrelated donors. DLIs were administered in a dose-escalating fashion to 22 patients for mixed chimerism (median time of first dose, 9 months post-transplantation) and to 24 patients for relapse.

Results

Three-year donor lymphocyte–related mortality was 7%, relating mainly to the induction of graft-versus-host disease. Nineteen (86%) of 22 patients receiving donor lymphocytes for mixed chimerism converted to full donor status. Four-year relapse incidence was 5% in these 22 patients compared with 43% in patients who remained relapse free but full donor chimeras at 9 months post-transplantation (P = .0071). Nineteen (79%) of 24 patients receiving donor lymphocytes for relapse responded (14 complete responses, five partial responses). Four-year overall survival from relapse was 59% in recipients of donor lymphocytes, contributing to a 4-year overall survival from transplantation of 64% and a 4-year current progression-free survival of 59% in all 76 patients.

Conclusion

These data demonstrate the potential for allogeneic immunotherapy with donor lymphocytes both to reduce relapse risk and to induce durable antitumor responses in patients with Hodgkin's lymphoma after hematopoietic stem-cell transplantation that incorporates in vivo T-cell depletion.

Chronic myeloid leukemia: a historical perspective

Patients with splenomegaly and abnormally high leukocyte counts were first recognized in France, Germany, and Scotland in the 1840s. The only well-documented therapy in the 19th century was use of arsenic in one or other form, which did undoubtedly reduce the leukocyte count but probably did little or nothing to prolong life. These early cases were probably examples of chronic myeloid leukemia (CML) (then called chronic granulocytic leukemia). In the 20th century important steps in unraveling the pathogenesis of CML were the discovery of the Philadelphia chromosome in 1960, and of the (9;22) translocation in 1973. There followed definition of the breakpoint cluster region on chromosome 22 in 1984 and the demonstration of the BCR-ABL transcript in CML in 1985. In the first half of the 20th century patients were treated predominantly with radiotherapy, and later on with busulfan, hydroxycarbamide, or interferon-alfa (IFN-α). From 1980 onwards allogeneic stem cell transplantation (SCT) became the treatment of choice for eligible patients. The era of tyrosine kinase inhibitors (TKI) began in 1998 and today the use of the original TKI, imatinib, has replaced SCT as initial therapy for patients who present with CML in chronic phase.

Donor lymphocyte infusion following allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (SCT) is the treatment of choice for many malignant hematological disorders. Following recent improvements in non-relapse-related mortality rates, relapse has become the commonest cause of treatment failure. Infusion of donor lymphocytes can potentially enhance immune-mediated antitumor activity and offers a salvage option for some patients. This paper reviews the current literature on the efficacy of this therapeutic strategy.

AREAS COVERED

The biology of adoptive cellular therapy with allogeneic immune cells to treat relapse across a spectrum of diseases in both the full intensity and reduced intensity hematopoietic SCT settings is explored. The review discusses the current limitations of the approach and reviews several new experimental strategies which aim to segregate the desired graft-versus-tumor effect from the deleterious effects of more widespread graft-versus-host reactivity.

EXPERT OPINION

Durable responses to DLI have been noted in chronic myeloid leukemia and responses have also been described in acute leukemia, multiple myeloma and chronic lymphoproliferative disorders. The new challenge in transplantation is to optimize DLI therapy in order to further improve patient outcomes.

CD4+CD25+ regulatory T cell depletion improves the graft-versus-tumor effect of donor lymphocytes after allogeneic hematopoietic stem cell transplantation

Donor T cells play a pivotal role in the graft-versus-tumor effect after allogeneic hematopoietic stem cell transplantation. Regulatory T cells (T(reg)s) may reduce alloreactivity, the major component of the graft-versus-tumor effect. In the setting of donor lymphocyte infusion after hematopoietic stem cell transplantation, we postulated that T(reg) depletion could improve alloreactivity and likewise the graft-versus-tumor effect of donor T cells. The safety and efficacy of T(reg)-depleted donor lymphocyte infusion was studied in 17 adult patients with malignancy relapse after hematopoietic stem cell transplantation. All but one had previously failed to respond to at least one standard donor lymphocyte infusion, and none had experienced graft-versus-host disease. Two of the 17 patients developed graft-versus-host disease after their first T(reg)-depleted donor lymphocyte infusion and experienced a long-term remission of their malignancy. Four of the 15 patients who did not respond after a first T(reg)-depleted donor lymphocyte infusion received a second T(reg)-depleted donor lymphocyte infusion combined with lymphodepleting chemotherapy aimed to also eliminate recipient T(reg)s. All four developed acute-like graft-versus-host disease that was associated with a partial or complete and durable remission. In the whole cohort, graft-versus-host disease induction through T(reg) depletion was associated with improved survival. These results suggest that T(reg)-depleted donor lymphocyte infusion is a safe, feasible approach that induces graft-versus-host or graft-versus-tumor effects in alloreactivity-resistant patients. In patients not responding to this approach, the combination of chemotherapy-induced lymphodepletion of the recipient synergizes with the effect of T(reg)-depleted donor lymphocyte infusion. These findings offer a rational therapeutic approach for cancer cellular immunotherapy.

NCI First International Workshop on The Biology, Prevention and Treatment of Relapse after Allogeneic Hematopoietic Cell Transplantation: report from the committee on prevention of relapse following allogeneic cell transplantation for hematologic malignancies

Prevention of relapse after allogeneic hematopoietic stem cell transplantation is the most likely approach to improve survival of patients treated for hematologic malignancies. Herein we review the limits of currently available transplant therapies and the innovative strategies being developed to overcome resistance to therapy or to fill therapeutic modalities not currently available. These novel strategies include nonimmunologic therapies, such as targeted preparative regimens and posttransplant drug therapy, as well as immunologic interventions, including graft engineering, donor lymphocyte infusions, T cell engineering, vaccination, and dendritic cell-based approaches. Several aspects of the biology of the malignant cells as well as the host have been identified that obviate success of even these newer strategies. To maximize the potential for success, we recommend pursuing research to develop additional targeted therapies to be used in the preparative regimen or as maintenance posttransplant, better characterize the T cell and dendritic cells subsets involved in graft-versus-host disease and the graft-versus-leukemia/tumor effect, identify strategies for timing immunologic or nonimmunologic therapies to eliminate the noncycling cancer stem cell, identify more targets for immunotherapies, develop new vaccines that will not be limited by HLA, and develop methods to identify populations at very high risk for relapse to accelerate clinical development and avoid toxicity in patients not at risk for relapse.

Adoptive antifungal T cell immunotherapy--into the clinic?

The morbidity and mortality rates of invasive fungal infection in allogeneic stem cell recipients are still unacceptably high and have not been significantly improved by alternative antifungal strategies to date. Over the last few years, rapid methods for the clinical-scale generation of functionally active and well characterized antifungal T(H)1 cells have become available. In addition, current data on the use of donor-derived virus-specific T cells in allogeneic stem cell transplantation suggest that the risk of severe adverse events, in particular the risk of graft-versus-host disease, is negligible. Therefore, adoptive antifungal immunotherapeutic strategies should be evaluated in clinical trials. However, one has to recognize that these trials are only meaningful with sufficiently large and homogenous cohorts of patients and if the settings of adoptive antifungal immunotherapy are comparable. Ultimately, the strategy of adoptively transferring antifungal immune responses might improve the outcome in hematopoietic stem cell recipients suffering from invasive fungal infection.

Donor lymphocyte infusion for leukemia relapse after hematopoietic stem cell transplantation

Leukemia relapse is a serious therapeutic challenge following hematopoietic stem cell transplantation (HSCT). In this retrospective study, 23 patients [15 (65.2%) AML, 8 (34.8%) ALL] who received DLI+/-reinduction chemotherapy for post-transplant relapse were reviewed. The overall response rate of DLI was 66.7% for AML and 50% for ALL. A total of 15 patients (65.2%) developed acute graft versus host disease (GVHD). Response rates were higher in patients with GVHD (80% versus 25%; p=0.01; OR: 12.0). The probability of OS was better in patients who respond to DLI (p=0.04). Further strategies are required to improve the anti-tumor properties of alloreactive donor lymphocytes and to obtain durable responses with DLI in patients with relapsed acute leukemia after allogeneic HSCT.

Pediatric immunohematopoietic stem cell transplantation at a tertiary care center in Cape Town

INTRODUCTION AND STUDY DESIGN: We conducted a retrospective analysis of consecutive referrals of patients under 18 years of age undergoing immunohematopoietic stem cell transplantation to assess the influence of age, diagnosis, graft type and gender on survival. We also contrasted program activity and outcome to that reported from a state hospital in the same geographical area over a comparable period.

METHODS

Conditioning employed either a sequential combination of fractionated 12Gy whole body and 6Gy total nodal irradiation separated by 120mg/kg of cyclophosphamide in patients over 15 years of age. Alternatively, the latter agent was combined initially with oral busulphan and later the intravenous equivalent. Neuroblastoma cases were prepared using a different regimen. In allografts the harvested product underwent ex vivo T-cell depletion with the humanized version of anti-CD 52 monoclonal antibody designated Campath 1H. No additional immunosuppression was given except where matched unrelated volunteer donors were employed.

RESULTS

Sixty-eight procedures were carried out in 61 patients over a 6-year period. Of 11 with acute myeloid leukemia, 8 are alive and well whereas 8 of the 14 with the lymphoblastic variant have died. Of the remaining 12 with hematologic malignancy, all but 2 are alive. Ten of the 17 with aplasia are alive as are all with thalassemia or sickle cell disease. None of the four variables tested affected survival.

CONCLUSION

Our analysis indicates that the standardized preparative regimen, coupled with a now well-established immunosuppressive regimen, is as effective in patients under 18 years of age as in adults. Our analysis also indicates that in a resource-scarce or developing country, it is mandatory to limit high-risk and relatively expensive procedures to active teams that enjoy international accreditation, whether these be in the state or private sector.

Phase I study of high-stringency CD8 depletion of donor leukocyte infusions after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Donor leukocyte infusions (DLI) are given after hematopoietic stem-cell transplantation to eradicate persistent tumor or correct mixed chimerism (MC). The drawback of DLI is the risk of graft-versus-host disease (GVHD). In this phase I study, we examined the potential of highly extensive CD8 depletion of DLI as a means of improving its safety profile.

METHODS

High-stringency immunomagnetic CD8 depletion of DLI was performed after steady state donor apheresis. Patients with persistent disease or MC received escalated dose CD8-depleted DLI at 3-month intervals starting from 6 months posttransplantation. The starting dose was 1 x 10(6) CD4 cells/kg in recipients of unrelated and 3 x 10(6) CD4 cells/kg in recipients of related donor transplantations.

RESULTS

Twenty-eight patients received CD8-depleted DLI (n=16 unrelated or mismatched, n=12 human leukocyte antigen-identical sibling). Median CD8 depletion was more than 4 log. The median overall dose of CD4+ cells/kg given was 4 x 10(6) (range 1 x 10(6)-43 x 10(6)). Conversion from MC to full donor chimerism was observed in 8 of 16 evaluable patients, and disease responses occurred in 5 of 11 patients (complete response in four and partial response in one). Five of 28 patients developed severe acute pattern (grade II-IV) GVHD. Two patients died as a result of complications relating to GVHD.

CONCLUSIONS

Graft-versus-tumor effects can be observed after high-stringency CD8-depleted DLI, although the major toxicity remains GVHD in this high-risk patient group. The safety and efficacy profile of this approach will require testing in a randomized controlled study.

The allogeneic graft-versus-cancer effect

Allogeneic haematological stem cell transplantation (HSCT) has developed into immunotherapy. Donor CD4+, CD8+ and natural killer (NK) cells have been reported to mediate graft-versus-leukaemia (GVL) effects, using Fas-dependent killing and perforin degranulation to eradicate malignant cells. Cytokines, such as interleukin-2, interferon-gamma and tumour necrosis factor-alpha potentiate the GVL effect. Post-transplant adoptive therapy of cytotoxic T-cells (CTL) against leukaemia-specific antigens, minor histocompatibility antigens, or T-cell receptor genes may constitute successful approaches to induce anti-tumour effects. Clinically, a significant GVL effect is induced by chronic rather than acute graft-versus-host disease (GVHD). An anti-tumour effect has also been reported for myeloma, lymphoma and solid tumours. Reduced intensity conditioning enables HSCT in older and disabled patients and relies on the graft-versus-tumour effect. Donor lymphocyte infusions promote the GVL effect and can be given as escalating doses with response monitored by minimal residual disease. A high CD34+ cell dose of peripheral blood stem cells increases GVL. There is a balance between effective immunosuppression, low incidence of GVHD and relapse. For instance, T-cell depletion of the graft increases the risk of relapse. This paper reviews the current knowledge in graft-versus-cancer effects. Future directions, such as immunotherapy using leukaemia-specific CTLs, allo-depleted T-cells and suicide gene manipulated T-cells, are presented.