Response to donor lymphocyte infusions for chronic myeloid leukemia is dose-dependent: the importance of escalating the cell dose to maximize therapeutic efficacy

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.

Spectral flow cytometry cluster analysis of therapeutic donor lymphocyte infusions identifies T cell subsets associated with outcome in patients with AML relapse

Identification of immune phenotypes linked to durable graft-versus-leukemia (GVL) response following donor lymphocyte infusions (DLI) is of high clinical relevance. In this prospective observational study of 13 AML relapse patients receiving therapeutic DLI, we longitudinally investigated changes in differentiation stages and exhaustion markers of T cell subsets using cluster analysis of 30-color spectral flow cytometry during 24 months follow-up. DLI cell products and patient samples after DLI were analyzed and correlated to the clinical outcome. Analysis of DLI cell products revealed heterogeneity in the proportions of naïve and antigen experienced T cells. Cell products containing lower levels of effector memory (eff/m) cells and higher amounts of naïve CD4⁺ and CD8⁺ T cells were associated with long-term remission. Furthermore, investigation of patient blood samples early after DLI showed that patients relapsing during the study period, had higher levels of CD4⁺ eff/m T cells and expressed a mosaic of surface molecules implying an exhausted functional state. Of note, this observation preceded the clinical diagnosis of relapse by five months. On the other hand, patients with continuous remission retained lower levels of exhausted CD4⁺ eff/m T cells more than four months post DLI. Moreover, lower frequencies of exhausted CD8⁺ eff/m T cells as well as higher amounts of CD4⁺temra CD45RO⁺ T cells were present in this group. These results imply the formation of functional long-term memory pool of T cells. Finally, unbiased sample analysis showed that DLI cell products with low levels of eff/m cells both in CD4⁺ and CD8⁺ T cell subpopulations associate with a lower relapse incidence. Additionally, competing risk analysis of patient samples taken early after DLI revealed that patients with high amounts of exhausted CD4⁺ eff/m T cells in their blood exhibited significantly higher rates of relapse. In conclusion, differentially activated T cell clusters, both in the DLI product and in patients post infusion, were associated with AML relapse after DLI. Our study suggests that differences in DLI cell product composition might influence GVL. In-depth monitoring of T cell dynamics post DLI might increase safety and efficacy of this immunotherapy, while further studies are needed to assess the functionality of T cells found in the DLI.

Healthy-like CD4+ Regulatory and CD4+ Conventional T-Cell Receptor Repertoires Predict Protection from GVHD Following Donor Lymphocyte Infusion

Donor lymphocyte infusion (DLI) can (re-)induce durable remission in relapsing patients after allogeneic hematopoietic stem-cell transplantation (alloHSCT). However, DLI harbors the risk of increased non-relapse mortality due to the co-occurrence of graft-versus-host disease (GVHD). GVHD onset may be caused or accompanied by changes in the clonal T-cell receptor (TCR) repertoire. To investigate this, we analyzed T cells in a cohort of 21 patients receiving DLI after alloHSCT. We performed deep T-cell receptor β (TRB) sequencing of sorted CD4+CD25+CD127low regulatory T cells (Treg cells) and CD4+ conventional T cells (Tcon cells) in order to track longitudinal changes in the TCR repertoire. GVHD following DLI was associated with less diverse but clonally expanded CD4+CD25+CD127low Treg and CD4+ Tcon TCR repertoires, while patients without GVHD exhibited healthy-like repertoire properties. Moreover, the diversification of the repertoires upon GVHD treatment was linked to steroid-sensitive GVHD, whereas decreased diversity was observed in steroid-refractory GVHD. Finally, the unbiased sample analysis revealed that the healthy-like attributes of the CD4+CD25+CD127low Treg TCR repertoire were associated with reduced GVHD incidence. In conclusion, CD4+CD25+CD127low Treg and CD4+ Tcon TRB repertoire dynamics may provide a helpful real-time tool to improve the diagnosis and monitoring of treatment in GVHD following DLI.

Analysis of Cell Subsets in Donor Lymphocyte Infusions from HLA Identical Sibling Donors after Allogeneic Hematopoietic Cell Transplant

Donor lymphocytes infusions (DLIs) are a major therapeutic approach to treat relapse and mixed chimerism after allogeneic hematopoietic cell transplant (alloHCT). The impact of the composition regarding different cell subsets in the development of graft-versus-host disease (GVHD) is not fully understood. We performed a cell subsets analysis of 56 DLIs from fully HLA-compatible identical matched sibling donors (MSDs) in 36 alloHCT patients and studied its association with GVHD. A median of one DLI was infused per patient. Fourteen patients (38%) developed GVHD. The cell composition analysis of the first DLI (DLI1) showed that a high dose of B cells (P = .03) and CD27⁺ B cells (P < .01) was associated with GVHD. We identified DLI dose cutoff points for several cell populations above which GVHD was more frequent (CD8⁺ T_N >3 × 10⁶ cells/kg, CD27⁺ B cells >2.6 × 10⁶/kg, CD27⁺ NK >0.35 × 10⁶ cells/kg, and mononuclear cells >0.83 × 10⁸/kg). Noteworthy, the proportion of CD4⁺ naive T cells (T_N) or unselected T_N was not linked with GVHD and a DLI1 containing a higher dose of regulatory T cells was not protective for GVHD. We studied several transplant clinical variables and did not find any association with GVHD. Altogether, this study provides a comprehensive analysis of the cell populations in a DLI from MSDs and identifies potential key cell subsets, which provides insight for the understanding of GVHD after DLI.

TCR Redirected T Cells for Cancer Treatment: Achievements, Hurdles, and Goals

Adoptive T cell therapy (ACT) is a rapidly evolving therapeutic approach designed to harness T cell specificity and function to fight diseases. Based on the evidence that T lymphocytes can mediate a potent anti-tumor response, initially ACT solely relied on the isolation, in vitro expansion, and infusion of tumor-infiltrating or circulating tumor-specific T cells. Although effective in a subset of cases, in the first ACT clinical trials several patients experienced disease progression, in some cases after temporary disease control. This evidence prompted researchers to improve ACT products by taking advantage of the continuously evolving gene engineering field and by improving manufacturing protocols, to enable the generation of effective and long-term persisting tumor-specific T cell products. Despite recent advances, several challenges, including prioritization of antigen targets, identification, and optimization of tumor-specific T cell receptors, in the development of tools enabling T cells to counteract the immunosuppressive tumor microenvironment, still need to be faced. This review aims at summarizing the major achievements, hurdles and possible solutions designed to improve the ACT efficacy and safety profile in the context of liquid and solid tumors.

Prophylactic donor lymphocyte infusion for relapse prevention: a meta-analysis

OBJECTIVE

Primary disease relapse (PDR) of malignant hematologic conditions after standard hematopoietic stem cell transplant (HSCT) is one of the most challenging diseases; therefore ongoing researches are aiming at relapse prevention and minimizing the transplant-related side effects. Prophylactic donor lymphocytes (pDLI) had been proposed as a valuable strategy for PDR prevention, but early studies had been discouraging due to the limited benefit and possible association with acute graft-versus-host disease (aGVHD). Therefore, we conducted a meta-analysis to evaluate the association between pDLI use, PDR, aGVHD and OS.

METHOD

We performed a comprehensive literature search in MEDLINE, Cochrane library and Embase database from inception to May 2019 for studies that evaluated the association between pDLI and PDR. We conducted a random effect meta-analysis of 9 studies involving a total of 748 participants (pDLI = 398, non-pDLI = 350) and reported the pooled odd ratio (OR) for association of pDLI use, PDR, aGVHD and OS.

RESULT

We found a significant decreased odd of PDR in the pDLI group (pooled OR = 0.42, 95% CI 0.30-0.58, I2 = 0%), but there was no significant increased odd of aGVHD (pooled OR of 0.98, 95% CI 0.56-1.72, I2 = 0.8%). We also found that there was an increased odd of overall survival (OS) (pooled OR 3.17, 95% CI 1.85-5.45, I2 = 50.2%).

CONCLUSION

There are significantly decreased odd of PDR and increased odd of OS in the pDLI group compared to the control group, but there is no statistically significant increased odd of aGVHD as suggested by previous studies. We concluded that pDLI is a potentially valuable method for post-transplant PDR prevention.

The Role of Donor Lymphocyte Infusion (DLI) in Post-Hematopoietic Cell Transplant (HCT) Relapse for Chronic Myeloid Leukemia (CML) in the Tyrosine Kinase Inhibitor (TKI) Era

Treatment for relapse of chronic myeloid leukemia (CML) following hematopoietic cell transplantation (HCT) includes tyrosine kinase inhibitors (TKIs) with or without donor lymphocyte infusions (DLIs), but the most effective treatment strategy is unknown. This study was performed through the Center for International Blood and Marrow Transplant Research (CIBMTR) database. We retrospectively reviewed all patients reported to the CIBMTR registry from 2002 to 2014 who underwent HCT for CML and were alive 30 days postrelapse. A total of 215 HCT recipients relapsed and were analyzed in the following groups: (1) TKI alone (n = 128), (2) TKI with DLI (n = 48), and (3) DLI without TKI (n = 39). In multivariate analysis, disease status prior to HCT had a significant effect on overall survival (OS). Patients who received a DLI alone compared with a TKI with a DLI had inferior survival (hazard ratio, 2.28; 95% confidence interval, 1.23 to 4.24; P= .009). Those who received a TKI alone had similar survival compared with those who received a TKI with a DLI (P = .81). These data support that despite use of TKIs pretransplantation, TKI salvage therapy continues to provide significant survival following relapse in patients with CML following HCT. These data do not suggest that adding a DLI to a TKI adds an improvement in OS.

Hematopoietic stem cell transplantation in its 60s: A platform for cellular therapies

Over the last 60 years, more than a million patients received hematopoietic cell transplantation. Having incorporated multiple changes in clinical practices, it remains a complex procedure facing a dual challenge: cure of the underlying disease and prevention of relapse while controlling potentially severe complications. Improved understanding of underlying biological processes resulted in the design of innovative therapies engineered from defined cell populations and testing of these therapies as addition or substitution at virtually every step of the procedure. This review provides an overview of these developments, many of them now applied outside the historical field of hematopoietic cell transplantation.

Preservation of Antigen-Specific Functions of αβ T Cells and B Cells Removed from Hematopoietic Stem Cell Transplants Suggests Their Use As an Alternative Cell Source for Advanced Manipulation and Adoptive Immunotherapy

Hematopoietic stem cell transplantation is standard therapy for numerous hematological diseases. The use of haploidentical donors, sharing half of the HLA alleles with the recipient, has facilitated the use of this procedure as patients can rely on availability of a haploidentical donor within their family. Since HLA disparity increases the risk of graft-versus-host disease, T-cell depletion has been used to remove alloreactive lymphocytes from the graft. Selective removal of αβ T cells, which encompass the alloreactive repertoire, combined with removal of B cells to prevent EBV-related lymphoproliferative disease, proved safe and effective in clinical studies. Depleted αβ T cells and B cells are generally discarded as by-products. Considering the possible use of donor T cells for donor lymphocyte infusions or for generation of pathogen-specific T cells as mediators of graft-versus-infection effect, we tested whether cells in the discarded fractions were functionally intact. Response to alloantigens and to viral antigens comparable to that of unmanipulated cells indicated a functional integrity of αβ T cells, in spite of the manipulation used for their depletion. Furthermore, B cells proved to be efficient antigen-presenting cells, indicating that antigen uptake, processing, and presentation were fully preserved. Therefore, we propose that separated αβ T lymphocytes could be employed for obtaining pathogen-specific T cells, applying available methods for positive selection, which eventually leads to indirect allodepletion. In addition, these functional T cells could undergo additional manipulation, such as direct allodepletion or genetic modification.

Specific removal of alloreactive T-cells to prevent GvHD in hemopoietic stem cell transplantation: rationale, strategies and perspectives

Hemopoietic stem cell transplantation (HSCT) is a standard procedure for treatment of malignant and non-malignant hematological diseases. HSCT donors include HLA-identical siblings, matched or mismatched unrelated donors and haploidentical related donors. Graft-versus-host disease (GvHD), mediated by donor alloreactive T-cells in the graft, can be triggered by minor histocompatibility antigens in HLA-identical pairs, by alleles at loci not considered for MUD-matching or by the mismatched haplotype in haplo-HSCT. Therefore, removal of donor T-cells, that contain the alloreactive precursors, is required, but T-cell depletion associates with opportunistic infections and with reduced graft-versus-leukemia effect. Selective T-cell depletion strategies have been introduced, like removal of αβ T-lymphocytes and of naive T-cells, two subsets including the alloreactive precursors, but the ultimate goal is specific removal of alloreactive T-cells. Here we review the different approaches to deplete alloreactive T-cells only and discuss pros and cons, specificity, efficiency and efficacy. Combinations of different methods and innovative approaches are also proposed for depleting specific alloreactive T-cells with high efficiency.

Strategies to accelerate immune recovery after allogeneic hematopoietic stem cell transplantation

The interplay existing between immune reconstitution and patient outcome has been extensively demonstrated in allogeneic hematopoietic stem cell transplantation. One of the leading causes of infection-related mortality is the slow recovery of T-cell immunity due to the conditioning regimen and/or age-related thymus damage, poor naïve T-cell output, and restricted T-cell receptor (TCR) repertoires. With the aim of improving posttransplantation immune reconstitution, several immunotherapy approaches have been explored. Donor leukocyte infusions are widely used to accelerate immune recovery, but they carry the risk of provoking graft-versus-host disease. This review will focus on sophisticated strategies of thymus function-recovery, adoptive infusion of donor-derived, allodepleted T cells, T-cell lines/clones specific for life-threatening pathogens, regulatory T cells, and of T cells transduced with suicide genes.

Characterization and targeting of neoplastic stem cells in Ph+ chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the presence of an oncogenic fusion gene, BCR–ABL1. This fusion gene produces a cytoplasmic protein with tyrosine kinase activity that acts as a main driver of oncogenesis and abnormal proliferation of myeloid cells in CML. Targeted therapy with BCR–ABL1 tyrosine kinase inhibitors (TKIs) such as imatinib is followed by long-term responses in most patients. However, despite continuous treatment, relapses occur, suggesting the presence of TKI-resistant neoplastic stem cells in these patients. Here, we discuss potential mechanisms and signaling molecules involved in the prosurvival and self-renewal capacity of CML neoplastic stem cells as well as antigens expressed by these cells. Several of these signaling molecules and cell surface antigens may serve as potential targets of therapy and their use may overcome TKI resistance in CML in the future.

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.

Impact of Chronic Graft-versus-Host Disease on Late Relapse and Survival on 7,489 Patients after Myeloablative Allogeneic Hematopoietic Cell Transplantation for Leukemia

PURPOSE

Malignancy relapse remains a major obstacle for successful allogeneic hematopoietic cell transplantation (HCT). Chronic graft-versus-host disease (cGVHD) is associated with fewer relapses. However, when studying effects of cGVHD on relapse, it is difficult to separate from acute GVHD effects as most cases of cGVHD occur within the first year after transplant at the time when acute GVHD is still active.

EXPERIMENTAL DESIGN

This study based on CIBMTR registry data investigated cGVHD and its association with the incidence of late relapse and survival in 7,489 patients with acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myelogenous leukemia (CML), and myelodysplastic syndromes (MDS), who were leukemia free at 12 months after myeloablative allogeneic HCT.

RESULTS

Forty-seven percent of the study population was diagnosed with cGVHD at 12 months after transplant. The protective effect of cGVHD on late relapse was present only in patients with CML [RR, 0.47; 95% confidence interval (CI), 0.37-0.59; P < 0.0001). cGVHD was significantly associated with higher risk of treatment-related mortality (TRM; RR, 2.43; 95% CI, 2.09-2.82; P < 0.0001) and inferior overall survival (RR, 1.56; 95% CI, 1.41-1.73; P < 0.0001) for all diseases. In patients with CML, all organ sites and presentation types of cGVHD were equally associated with lower risk of late relapse.

CONCLUSIONS

These results indicate that clinically relevant antileukemia effects of cGVHD on late relapses are present only in CML but not in AML, ALL, or MDS. Chronic GVHD in patients who are 1-year survivors after myeloablative allogeneic HCT is primarily associated with higher TRM and inferior survival.

Adoptive therapy with donor lymphocyte infusion after allogenic hematopoietic SCT in pediatric patients

The aim of this study was to analyse the experience of Polish Pediatric Group for Hematopoietic Stem Cell Transplantation in respect to donor lymphocyte infusion procedure. The study included 51 pediatric patients with malignant (45) and non-malignant (6) diseases treated with DLI in the period 1993-2012. The indications for DLI were as follows: (1) increasing recipient chimerism after non-ablative hematopoietic SCT (18 patients); (2) immunomodulation after a reduced intensity conditioning regimen (2 patients); (3) increase in minimal residual disease detection (3 patients); and (4) relapse (28 patients). DLI was carried out at a median of 6 (0.5-79) months after SCT. DLI was administered as either a single-dose (in 19 cases) or in escalating-dose regimens (in 32 cases). The median total dose of CD3-positive T cells was 28.0 (0.1-730.0) × 10(6)/kg body weight. The time for assessment of DLI efficacy ranged from 0 to 70 (median 3) months. At evaluation, 18 patients experienced CR, 3 achieved PR, 19 showed relapse and 11 rejected the graft. DLI was found to be effective in 39% of cases. Complications of the procedure occurred in 18 patients; of these, 2 died. To sum up DLI shows efficacy in a significant percentage of children. Mortality related to the therapy adverse effects is low. However, this method requires standardization.

HLA and KIR genotyping correlates with relapse after T-cell-replete haploidentical transplantation in chronic myeloid leukaemia patients

Background:

Conflicting results have been reported regarding the predicative roles of alloreactive natural killer (NK) cells on the outcomes of transplantation in leukaemia patients.

Methods:

We prospectively analysed the human leukocyte antigen (HLA) typing of donor–recipient pairs and the KIR typing of the donors in 97 CML patients to address the predictive roles of NK cells in relapse undergoing T-cell-replete haploidentical transplantation.

Results:

Patients with class I ligands for the donor-inhibitory KIR gene exhibited decreased molecular and haematologic relapse rates (P=0.003 and P=0.015, respectively). There was a significantly reduced risk of molecular and haematologic relapse in patients with HLA-C1C2 or C2C2 who accepted donors with KIR2DS1 or in patients with HLA-Bw4 who accepted donors with KIR3DS1 (‘recipient with relevant KIR ligand for donor-activating KIR', n=25), compared with the remaining transplants (n=72, P=0.009 and P=0.009, respectively). In addition, the presence of class I ligand in the recipients of donor-activating KIR contributed to a decreased relapse rate in patients lacking class I ligand in the recipient of donor-inhibitory KIR (P=0.04 and P=0.03, respectively).

Conclusions:

This study suggests that the presence of class I ligands for the donor-activating or donor-inhibitory KIR gene in the recipient might confer some protection against leukaemic relapse in T-cell-replete haploidentical transplantation.

Early administration of donor lymphocyte infusions upon molecular relapse after allogeneic hematopoietic stem cell transplantation for chronic myeloid leukemia: a study by the Chronic Malignancies Working Party of the EBMT

Patients with chronic myeloid leukemia relapsing after allogeneic hematopoietic stem cell transplantation may be treated by tyrosine kinase inhibitors and/or by donor lymphocyte infusions. The best strategies and timing of administration of lymphocytes are unclear. We analyzed 155 patients who relapsed after allogeneic stem cell transplantation with disease detectable only by molecular methods and who subsequently received lymphocytes. Transplants were performed in first chronic phase (n=125) or in advanced disease (n=29) from identical siblings (n=84) or unrelated donors (n=71) between 1986 and 2003. They received lymphocytes either during molecular relapse (n=85) or upon progression to more advanced disease (1993 to 2004). The median interval from relapse to lymphocyte infusion was 210 (0-1673) days. The median follow up after it was 46 (3-135) months. Overall survival was 76±4% at five years after lymphocyte infusions (89±8% with sibling donors and 63±13% with unrelated donors (P=0.003)). Survival was 69±14% when lymphocytes were given within six months of the detection of molecular relapse and 81±10% (P=0.061) when given later; 81±11% if given at molecular relapse versus 71±12% (P=0.26) with more advanced disease. In multivariate analysis survival was worse if the donor was unrelated (HR 2.54 (95% CI: 1.15-5.53), P=0.021) and better with lymphocyte infusions beyond six months from molecular relapse (HR 0.4 (95%CI: 0.19-0.84), P=0.018). These data confirm the remarkable efficacy of lymphocyte infusions for this disease. There appears to be no advantage from administering it early upon detection of molecular relapse in patients who received allogeneic stem cell transplantation for chronic myeloid leukemia.

Homozygosity for killer immunoglobin-like receptor haplotype A predicts complete molecular response to treatment with tyrosine kinase inhibitors in chronic myeloid leukemia patients

Several recent reports suggest a possible role for killer immunoglobulin-like receptors (KIR) in the onset of chronic myeloid leukemia (CML) and response to therapy with tyrosine kinase inhibitors (TKIs). To explore this hypothesis, we studied KIRs and their human leukocyte antigen class I ligands in 59 consecutive patients with chronic-phase CML (mean age, 53 years; range, 23-81 years) and a group of 121 healthy control participants belonging to the same ethnic group as the patients. The 2-year cumulative incidence of complete molecular response, obtained after a median of 27 months (range, 4-52 months), was 51.2%. An increased frequency of the activating receptor KIR2DS1 (pm = 0.05) and a reduced frequency of the KIR-ligand combination KIR2DS2/2DL2 absent/C1 present (pm = 0.001) were significantly associated with CML. Moreover, KIR repertoires in patients appeared to influence response to TKI therapy. Homozygosity for KIR haplotype A (pm = 0.01), a decreased frequency of the inhibitory KIR gene KIR2DL2 (pm = 0.02), and low numbers of inhibitory KIR genes (pm = 0.05) were all significantly associated with achievement of complete molecular remission. These data suggest that a decrease in properly stimulated and activated NK cells might contribute to the occurrence of CML and indicate homozygosity for KIR haplotype A as a promising immunogenetic marker of complete molecular response that could help clinicians decide whether to withdraw treatment in patients with CML.

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.

Management of chronic myeloid leukemia in childhood

Childhood chronic myelogenous leukemia (CML) is a rare malignancy, and experience with optimal treatment is very limited. Traditionally, allogeneic hematopoietic stem cell transplantation was considered the only curative treatment. Imatinib, a small-molecule inhibitor of the BCR-ABL tyrosine kinase (TKI), has been proven highly successful in adults with CML, resulting in prolonged molecular response with limited drug toxicity. This drug is now included as front-line therapy for CML in pediatrics as well, though valid concerns about serious late sequelae remain unresolved. Specific pediatric treatment guidelines have not yet been formulated, and most algorithms are derived from experience in adult CML. This overview attempts to summarize pediatric studies on issues such as dose, duration, adverse effects, and steering criteria for TKI treatment, adapting guidelines developed in adult medicine to pediatrics. Most importantly, pediatric patients with CML receiving TKI treatment should be enrolled into formal trials.

Adoptive T-cell therapy for B-cell malignancies

The success of allogeneic hematopoietic cell transplantation (HCT) for B-cell malignancies is evidence that these tumors can be eliminated by T lymphocytes. This has encouraged the development of specific adoptive T-cell therapy, both for augmenting the anti-tumor effect of HCT and for patients not undergoing HCT. T cells that are capable of recognizing antigens expressed on malignant B cells may be recruited from the endogenous repertoire or engineered to express tumor-targeting receptors. Critical insights into the qualities of T cells that enable their persistence and function in vivo have been derived, and obstacles to effective T-cell-mediated tumor eradication are being elucidated. These advances provide the tools to translate adoptive T-cell transfer into reliable clinical therapies.

Treatment of pediatric chronic myeloid leukemia in the year 2010: use of tyrosine kinase inhibitors and stem-cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-SCT) remains the only proven cure for chronic myeloid leukemia (CML), a rare malignancy in childhood. With the excellent results induced by the tyrosine kinase inhibitor (TKI) imatinib in adults in the last decade, the appropriate management of children with CML has also changed radically, and only a minority are now transplanted as a front-line treatment. Data on pediatric experiences with imatinib in CML from controlled trials remain very limited, but this review of available data describes the role of imatinib in children with CML, addressing: 1) the starting dose; 2) pharmacokinetics in childhood; 3) possible adverse effects, with a focus on the still-growing skeleton; 4) early monitoring of treatment efficacy in an attempt to avoid failure; 5) the timing of allo-SCT in children; and 6) treatment of CML relapse after allo-SCT. Because the characteristics of CML in children seem to overlap extensively with what is described in adult internal medicine, most answers and pediatric algorithms are adapted from the treatment of CML in adults. Today in 2010, allo-SCT in children should be postponed until CML becomes refractory to imatinib. The approach for young patients with suboptimal responses is unclear because data on the efficacy and safety of second-generation TKIs in childhood are almost entirely missing. Other than being included in a formal trial on second-generation TKIs, allo-SCT for patients failing imatinib remains the first choice.

Innovative approaches of targeted therapy for CML of childhood in combination with paediatric haematopoietic SCT

Allogeneic haematopoietic SCT (HSCT) induces CRs in most patients with CML. With the excellent short-term treatment results induced by imatinib (IMA), attitudes have changed and only a minority of children are now transplanted upfront. This review addresses the role of IMA in children with CML, focusing on the starting dose of IMA, possible adverse effects, timing of HSCT in children, duration of IMA treatment and monitoring of treatment efficacy to unravel failure of early treatment of IMA as well as treatment of CML relapse after HSCT. As the paediatric experience with IMA is still very limited, many answers and algorithms are adapted from CML in adults. Basically, HSCT should be postponed to achieve an optimal tumour cell reduction by IMA treatment. Children with a low-risk EBMT score should undergo HSCT within 2 years after diagnosis to avoid prolonged exposure and unknown late effects of IMA. Without a perfectly HLA-matched donor, HSCT may be postponed until CML becomes refractory to IMA. As realized in the presently activated international trial CML-paed II, this approach represents a risk-adapted therapy with the benefit of being tailored to the needs and profile of an individual patient.

Donor lymphocyte infusions: the long and winding road: how should it be traveled?

Donor lymphocyte infusions (DLI) often are used after allo-SCT to augment the graft-versus-tumor effect. Timing of infusion varies according to indication, for example to treat tumor recurrence, as a planned strategy to prevent disease relapse in the setting of T-cell-depleted grafts or non-myeloablative conditioning regimens, or as a method to convert mixed to full donor chimerism. The optimal strategy of timing, use of cytotoxic conditioning, cell dose and cell product composition, and so on, for DLI administration remains unclear. Despite varied techniques, DLI may lead to 3-year disease-free survivals (DFS) in excess of 60% for all CML patients and approach 90% in patients with only molecular or cytogenetic relapse. Other hematologic malignancies appear much less responsive, as less than 50% of patients respond and provide, at best, 3-year DFS rates of 20-50%. Multiple myeloma patients have overall response rates of 40-45% after DLI, suggesting benefit in relapsed disease, but limited experiences for diseases such as Hodgkin's lymphoma, myelodysplasia and ALL preclude recommendations for use of DLI at this time. Regardless of the indication, treatment-related mortality after DLI is 5-20% and more than one-third of patients will develop acute and/or chronic GVHD after DLI. The risks of these complications appear related, in part, to donor source, cell dose and therapy prior to DLI. Although there are no definitive answers, the information gleaned from published literature suggests that DLI should be administered early after relapse or as a prophylactic strategy in patients receiving T-cell-depleted grafts, and patients with bulky or aggressive disease may benefit from disease reduction prior to DLI.