A prospective study of positive/negative ex vivo B-cell depletion in patients with chronic lymphocytic leukemia

Efficient depletion of chronic lymphocytic leukemia B cells using serial rounds of immunomagnetic depletion

Functional studies of cellular immunity in patients with leukemia often require separation of leukemic cells from other peripheral blood mononuclear cells (PBMCs). This can pose a challenge when the number of leukemic cells is very high, such as in untreated patients with chronic lymphocytic leukemia (CLL). We found that when leukemia cell frequency was very high, anti-CD19 coated immunomagnetic beads did not thoroughly deplete B cells when used according to manufacturer's instructions. In this study, we depleted leukemic B cells using a modified protocol comprising serial rounds of depletion using immunomagnetic beads at reduced bead to cell ratios. This resulted in more effective B cell depletion with the use of fewer immunomagnetic beads, and without affecting viability or yield of non-B cells. CD19- PBMC subsets were retained, and serial depletion rounds did not activate T cells and monocytes. The positively isolated CLL cells were of high purity and were available for downstream analysis. This is a convenient and cost-effective method to enable in vitro analysis of immunocompetent cells from patients with leukemia.

Early autologous stem cell transplantation for chronic lymphocytic leukemia: long-term follow-up of the German CLL Study Group CLL3 trial

The CLL3 trial was designed to study intensive treatment including autologous stem cell transplantation (autoSCT) as part of first-line therapy in patients with chronic lymphocytic leukemia (CLL). Here, we present the long-term outcome of the trial with particular focus on the impact of genomic risk factors, and we provide a retrospective comparison with patients from the fludarabine-cyclophosphamide-rituximab (FCR) arm of the German CLL Study Group (GCLLSG) CLL8 trial. After a median observation time of 8.7 years (0.3-12.3 years), median progression-free survival (PFS), time to retreatment, and overall survival (OS) of 169 evaluable patients, including 38 patients who did not proceed to autoSCT, was 5.7, 7.3, and 11.3 years, respectively. PFS and OS were significantly reduced in the presence of 17p- and of an unfavorable immunoglobulin heavy variable chain mutational status, but not of 11q-. Five-year nonrelapse mortality was 6.5%. When 110 CLL3 patients were compared with 126 matched patients from the FCR arm of the CLL8 trial, 4-year time to retreatment (75% vs 77%) and OS (86% vs 90%) was similar despite a significant benefit for autoSCT in terms of PFS. In summary, early treatment intensification including autoSCT can provide very effective disease control in poor-risk CLL, although its clinical benefit in the FCR era remains uncertain. The trial has been registered with www.clinicaltrials.gov as NCT00275015.

Antibody-based therapy of leukaemia

Over the past decade, monoclonal antibodies have dramatically impacted the treatment of haematological malignancies, as evidenced by the effect of rituximab on the response rate and survival of patients with follicular and diffuse large B cell non-Hodgkin's lymphoma. Currently, only two monoclonal antibodies - the anti-CD33 immunotoxin gemtuzumab ozogamicin and the CD52-directed antibody alemtuzumab - are approved for treatment of relapsed acute myeloid leukaemia in older patients and B cell chronic lymphocytic leukaemia, respectively. Although not approved for such treatment, alemtuzumab is also active against T cell prolymphocytic leukaemia, cutaneous T cell lymphoma and Sézary syndrome, and adult T cell leukaemia and lymphoma. In addition, rituximab has demonstrated activity against B cell chronic lymphocytic and hairy cell leukaemia. Monoclonal antibodies targeting CD4, CD19, CD20, CD22, CD23, CD25, CD45, CD66 and CD122 are now being studied in the clinic for the treatment of leukaemia. Here, we discuss how these new antibodies have been engineered to reduce immunogenicity and improve antibody targeting and binding. Improved interactions with Fc receptors on immune effector cells can enhance destruction of target cells through antibody-dependent cellular cytotoxicity and complement-mediated cell lysis. The antibodies can also be armed with cellular toxins or radionuclides to enhance the destruction of leukaemia cells.

Hematopoietic stem cell transplantation for chronic lymphocytic leukemia: potential cure for an incurable disease

Hematopoietic stem cell transplantation (HSCT) has been used as a treatment modality in patients with chronic lymphocytic leukemia (CLL). Allogeneic HSCT is the only therapy at present that has curative potential in patients with CLL. Allogeneic HSCT using standard myeloablative regimens has been generally associated with high treatment mortality rates and autologous HSCT with high relapse rates. Over the last decade the use of reduced intensity conditioning (non-myeloablative) regimens have reduced the treatment-related mortality after allogeneic-HSCT without affecting the graft-versus-leukemia effectiveness. In addition, the development of molecular and biologic markers has identified high-risk CLL patients that may benefit from earlier treatment with HSCT. This review summarizes the use of existing prognostic markers in CLL and their use in HSCT, and the advances, indications and clinical outcomes of both autologous HSCT and allogeneic HSCT.

Systematic review of high dose chemotherapy and autologous haematopoietic stem cell transplantation for chronic lymphocytic leukaemia: what is the published evidence?

Despite improved responses, chronic lymphocytic leukaemia (CLL) remains incurable with conventional chemotherapy. Patients with poor-risk factors or who fail conventional chemoimmunotherapy are offered autografts, preferably after achieving remission. This report presents the totality of evidence through a systematic review that assessed the efficacy of autografts in CLL. A search of MEDLINE databases from 1966-2006 and hand-search of references identified 82 prospective-randomized, non-randomized comparisons or single-arm trials, of which only nine met our inclusion criteria: two trials were funded by public/government, one by private foundations, one jointly by private/public, and was unclear in five. No randomized controlled trials comparing autografts versus conventional chemotherapy (or chemoimmunotherapy) were found. Six studies were single-arm and three were non-randomized with a control-arm (autologous versus allogeneic). Overall, 361 patients were enrolled, but only 292 were transplanted. Transplant-related mortality ranged from 0% to 9%. Complete responses ranged from 74% to 100% and molecular responses ranged from 57% to 88%. Overall survival ranged from 68% at 3 years to 58% at 6 years. It is uncertain whether autograft is superior to conventional therapy. The high incidence of myelodysplastic syndrome (9-12%) is particularly concerning in CLL, where median survival is 9 years.

Positive selection and transplantation of autologous highly purified CD133(+) stem cells in resistant/relapsed chronic lymphocytic leukemia patients results in rapid hematopoietic reconstitution without an adequate leukemic cell purging

We assessed the capacity of positively selected autologous CD133(+) hematopoietic stem cells (HSCs) to reconstitute lymphomyelopoiesis in chronic lymphocytic leukemia (CLL) patients receiving myeloablative chemotherapy. Ten resistant/relapsed CLL patients underwent HSC mobilization with chemotherapy and granulocyte-colony stimulating factor (G-CSF). Positive selection of circulating CD133(+) HSCs was performed by immunomagnetic technique. Highly purified HSCs were reinfused after busulphan/melphalan myeloablative treatment. A median number of 4.2 x 10(6) CD34(+) cells/kg and of 3.14 x 10(6) CD133(+) cells/kg were collected. Immunomagnetic selection resulted in the reinfusion of a median number of 2.45 x 10(6) CD133(+) cells/kg (median purity: 94.8%; median recovery: 84%) and 2.4 x 10(6) CD34(+) cells/kg (median purity: 93%; median recovery: 71%). HSC selection resulted in a median T cell and CD19(+)/CD5(+) cell depletion of 3.85 log and 2.8 log, respectively. At the molecular level, however, 7 of 8 valuable purified HSC fractions were contaminated by leukemic cells. All CLL patients showed rapid and sustained myeloid engraftment after reinfusion of purified CD133(+) cells. Immunologic reconstitution was comparable to that routinely observed in patients reinfused with unmanipulated leukapheresis products and no late infectious complications were observed. With a median follow-up of 28 months for transplanted patients, 5 patients are in clinical complete remission, 3 are in partial remission, and 1 is in progression. In conclusion, the reinfusion of highly purified CD133(+) HSCs allowed the rapid and sustained recovery of hematopoiesis after myeloablative treatment in resistant/relapsed CLL patients. However, the purging potential of positive selection of CD133(+) cells is not adequate to achieve tumor-free autografts.

Hematopoietic Cell Transplantation for Chronic Lymphocytic Leukemia: An Evolving Concept

Recent years have brought major strides to our understanding of prognostic pathobiologic factors in patients with chronic lymphocytic leukemia. This has allowed identification of high-risk patients who may benefit from more aggressive therapies, including hematopoietic cell transplantation. High-dose chemotherapy followed by autologous hematopoietic cell transplantation is feasible, and results in encouraging responses, including molecular responses, with low transplant-associated mortality. However, it has failed to show a plateau effect on survival curves. On the other hand, there is convincing evidence that immunologically mediated graft-versus-leukemia effect of donor T cells are responsible for lowering the incidence of relapse and allowing possible "cure" in allograft recipients, albeit at the expense of high treatment-associated mortality using conventional myeloablation. Reducing the intensity of conditioning regimens has translated into lesser toxicity with reasonable preservation of its curative potential. Autologous or allogeneic hematopoietic cell transplantation in high-risk chronic lymphocytic leukemia remain promising and evolving treatment options. Treatment of CLL should consider stratification according to modern prognostic markers.

Revisiting the role of hematopoietic stem cell transplantation in chronic lymphocytic leukemia

Since the advent of hematopoietic stem cell transplantation more than 40 years ago, numerous methods of transplantation have been developed, modified and improved upon. Although hematopoietic stem cell transplantation has been used in a variety of malignant diseases since then, its use in the treatment of chronic lymphocytic leukemia has recently started to gain interest. Patients with chronic lymphocytic leukemia are generally elderly, and because of its relatively benign course, they were not considered suitable candidates for hematopoietic stem cell transplantation. Nonetheless, there have been marked improvements in transplantation techniques, including better conditioning regimens that have decreased treatment-related morbidity and mortality. In this article, the authors review the most recent data on hematopoietic stem cell transplantation in chronic lymphocytic leukemia as well as the change in risk stratification based on newer prognostic factors and its impact on treatment decisions in chronic lymphocytic leukemia.

A one-step large-scale method for T- and B-cell depletion of mobilized PBSC for allogeneic transplantation

BACKGROUND

The presence of T and B cells in allogeneic grafts contributes to GvHD and to EBV-associated lymphoproliferative disease (LPD). Depletion of T and B cells from the graft decreases the risk of these complications.

METHODS

T and B cells were depleted from mobilized peripheral stem cells from volunteer donors (n=5) using anti-CD3 and anti-CD19 Abs conjugated to magnetic microbeads, and the CliniMACS device. The function of the stem cells after depletion was evaluated using colony assays and non-obese diabetic (NOD)/SCID repopulating experiments.

RESULTS

The mean mononuclear cell (MNC) count prior to T- and B-cell depletion was 2.19x10(10) (range 1.48-3.53). After depletion, the mean percentage of contaminating T cells was 0.02% (range 0.01-0.04%) with a mean log(10) depletion of 3.4 (range 3-3.8). The mean percentage of contaminating B cells was 0.1% (range 0.01-0.4%) with a mean log(10) depletion of 2.2 (range 1.4-3). The mean recovery of CD3- and CD19-negative MNCs after depletion was 70% (range 54-88%) and the mean recovery of CD34(+) stem cells was 69% (range 52-98%). The mean number of natural killer (NK) cells after T- and B-cell depletion was 5.2x10(8) (range 2-10x10(8)). In vitro colony assays and in vivo NOD/SCID repopulation assays showed no negative impact of this method on the function of the hematopoietic stem cells.

DISCUSSION

Our results show that the CliniMACS system can be used to efficiently deplete PBSC of T and B cells simultaneously, without adverse effect on the graft.

Quantitative Molecular Evaluation of Minimal Residual Disease in Patients with Chronic Lymphocytic Leukemia

Although novel therapies for chronic lymphocytic leukemia have resulted in higher hematologic response rates, the complete eradication of disease rarely occurs. Alemtuzumab (Campath-1H) seems to be extremely effective in this role in pretreated patients. The authors used a molecular semiquantitative polymerase chain reaction (PCR) method to assess the ability of alemtuzumab to induce PCR negativity in eight patients pretreated with fludarabine. IgH rearrangement was coamplified with a housekeeping gene and fluorescent PCR products were analyzed on a DNA automatic sequencer. Each patient was evaluated at diagnosis, after fludarabine, and after Campath-1H. The median interval between the last therapy course with fludarabine and the start of Campath-1H was 14 weeks. Patients received subcutaneous doses up to 10 mg, three times a week, for 12 weeks, with a median dose of 190 mg. After six cycles with fludarabine, only one patient (12.5%) achieved molecular remission, and in three other patients IgH levels decreased by 0.5 to 1 log. At the beginning of Campath-1H administration, all patients were PCR positive, including the one previously found to be negative. At the end of treatment, five patients achieved molecular remission (62.5%), four of them within 1 month after the end of therapy. Seventy-two percent of responses, with 43% of complete responses, were documented on bone marrow smears. A significant reduction of lymph node and spleen diameters was noted in 50% and 33% of patients, respectively. Four patients showed grade 2 skin reaction at the site of the subcutaneous injection and grade 1 or 2 fever. Two patients developed neutropenia (grade 2 and 3) and two hemolytic episodes. Three patients showed cytomegalovirus and one herpes zoster and Epstein-Barr virus reactivation. These results show that Campath-1H represents an efficacious in vivo purging tool with a safe profile.

Impaired stem cell function of CD34+ cells selected by two different immunomagnetic beads systems

We have been investigating the hematopoietic stem cell (HSC) activity of peripheral blood-derived CD34(+) cells selected by two different laboratory immunomagnetic beads systems (MiniMACS and Isolex 50). In this study, the quality of purified CD34(+) cells was directly compared using clonal cell culture, a cobblestone area-forming cell (CAFC) assay, and an in vivo severe combined immunodeficiency (SCID)-repopulating cell (SRC) assay. It was found that CD34(+) cells selected by these two immunomagnetic methods showed a reduced yield of colony-forming cells and CAFCs compared with cells enriched by the StemSep device (a negative selection method). However, these CD34(+) cells still showed significant SRC activity, including multilineage lymphomyeloid reconstitution. The percentage of human CD45(+) cells in murine bone marrow after transplanting 5 x 10(5) CD34(+) cells selected by the Isolex 50 was significantly lower than after transplanting cells selected by the MiniMACS or the StemSep. Our findings clearly demonstrated that CD34(+) cells selected by the MiniMACS system had superior HSC functions, including SRC activity, compared with cells separated by the Isolex 50 system. More detailed functional analysis of immunomagnetically separated CD34(+) cells may provide useful knowledge for basic research on HSCs as well as for clinical HSC transplantation.

CD34+-enriched-CD19+-depleted autologous peripheral blood stem cell transplantation for chronic lymphoproliferative disorders: high purging efficiency but increased risk of severe infections

OBJECTIVE

The main objective of this work was to decrease the incidence of relapse after autologous stem cell transplantation with a "double purging" procedure.

METHODS

We used a "positive" (CD34) and "negative" (CD19) double selection method to improve the efficacy of "single purging" of hematopoietic harvests in poor-prognosis lymphoproliferative disorders. All patients included in the study had a positive molecular marker of their disease. Minimal residual disease (MRD) was studied by flow cytometry and PCR techniques during the purging procedure and after transplantation.

RESULTS

Twenty-six patients fulfilled entry criteria. Median age of patients was 50 years (range: 33-66); 17 were male and 9 female. Thirteen (50%) of the patients mobilized an adequate number of CD34+ cells (>or=3 x 10(6)/kg) to proceed with the double-selection protocol. Twelve of the 13 harvests became PCR negative after purging. Ten patients were grafted with the selected products and all but one engrafted without delay. After a median follow-up of 30 months, 2 of 10 patients suffered a molecular relapse at 7 and 19 months respectively. The earlier relapse was observed in the patient who received a MRD+ product. Only one patient experienced a clinical relapse. Three patients died due to obliterans bronchiolitis, pneumococcal sepsis, and septic shock of unknown origin, respectively, and three others presented life-threatening infections.

CONCLUSION

Therefore, CD34+/CD19+ positive/negative selection is an effective purging approach in patients with chronic lymphoproliferative disorders. This favorable effect is, however, counterbalanced by the high frequency of life-threatening infections.

Combined isolation of CD34+ progenitor cells and reduction of B cells from peripheral blood by use of immunomagnetic methods

BACKGROUND

Malignant cells may contribute to relapse after autologous hematopoietic cell transplantation The effectiveness of a double immunomagnetic purging strategy combining CD34-positive with B-negative cell selection to purge peripheral blood progenitor cells (PBPCs) from patients with chronic lymphoproliferative disorders has been analyzed.

STUDY DESIGN AND METHODS

Twenty-two CD34+ cell selections from patients with follicular lymphoma (n = 14), chronic lymphocytic leukemia (n = 6), mantle cell lymphoma (n = 1), and splenic marginal zone lymphoma (n = 1) were performed by use of a magnetic cell selector followed by a negative cell selection step with anti-CD19 monoclonal antibody bound to immunomagnetic beads.

RESULTS

The PBPC components contained median CD34+ cells of 1.24 percent (range, 0.38-3.92%) and CD19+ cells of 1.83 percent (range, 0.06-69.7%). After positive selection (n = 22), 49 percent (range, 16-72%) of CD34+ cells were recovered with a purity of 93 percent (range, 24-99%). The double-positive and -negative selections (n = 20) yielded 57.5 percent of CD34+ cells (range, 33.4-79.4%) with a purity of 95 percent (range, 63-99%). Logarithms of B-cell reduction in the CD34+-cell-enriched B-cell-depleted component had a median value of 3.63 (range, 2.74-4.84 log) and CD19+ and CD5+ cells for chronic lymphocytic leukemia patients with more than 4.56 log (>3.6-5.6 log). Of 13 PBPC components that had a tumor-specific clonal signal, 10 became PCR negative after the double-selection procedure.

CONCLUSION

Combined positive and negative magnetic cell selection achieves a high grade of tumor cell reduction with up to 77 percent of the grafts being negative for tumor-specific clonal signal by PCR analysis. This technique preserves an adequate recovery of progenitor cells able to engraft.

Autologous and allogeneic stem cell transplantation for chronic lymphocytic leukemia

Allogeneic and autologous stem cell transplantation (SCT) are increasingly considered for treatment of patients with chronic lymphocytic leukemia (CLL). In order to assess the potential therapeutic value of SCT for CLL, the present article aims at answering the following crucial questions: (1) Is SCT a curative treatment? (2) Does SCT improve the prognosis of poor-risk CLL? (3) Do risk factors exist which are useful for defining prognostic groups in terms of feasibility and post-transplant outcome? The efficacy of auto-SCT relies exclusively on the cytotoxic therapy administered. To date, there is only limited hope that autotransplantation can cure the disease. Nevertheless, the results of the published series suggest that auto-SCT is capable of improving the prognosis of CLL with poor-risk features. Well defined favorable conditions for successful autografting are the status of the disease (CR or VGPR) and the number of lines of therapy (<2) before transplantation. The crucial anti-leukemic principle of allo-SCT consists in the immune-mediated GVL effects conferred with the graft. The GVL activity explains that allografting seems to be curative for at least a subset of patients. However, as long as allo-SCT in CLL is still associated with an excessively high treatment-related mortality, only selected patients with advanced poor-risk disease should be considered for allografting. The development of conditioning regimens with reduced intensity may allow extending the indications of allogeneic SCT for CLL in the near future.

Surface immunoglobulin on B lymphocytes as a potential target for specific peptide ligands in chronic lymphocytic leukaemia

With the aim of producing unique targets for malignant cells we have identified peptide ligands for the clonal surface immunoglobulin isolated from the B cells of a chronic lymphocytic leukaemia (CLL) patient. The peptides were identified from random-peptide phage-display libraries. The obtained ligands bound specifically to the surface of the target lymphocytes as well as to clonal immunoglobulin in lysate from the same cells. Peptide-based antigen mimotopes may have a future use in targeted therapy of CLL and other B-cell-derived malignancies displaying surface immunoglobulin.

Recent publications in hematological oncology

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of hematological oncology. Each bibliography is divided into 14 sections: 1 Books, Reviews & Symposia; 2 General; Leukemias: 3 Lymphoblastic; 4 Myeloid & Myelodysplastic Syndromes; 5 Chronic; 6 Others; Lymphomas: 7 Hodgkin's; 8 Non-Hodgkin's; 9 Plasmacytomas/Multiple Myelomas; 10 Others; 11 Bone Marrow Transplantation; 12 Cytokines; 13 Diagnosis; 14 Cytogenetics. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted.