A phase II multicenter study of CAMPATH-1H antibody in previously treated patients with nonbulky non-Hodgkin's lymphoma

Stem Cell Transplantation for Multiple Myeloma

BACKGROUND

Multiple myeloma (MM) is the second most common hematologic malignancy, affecting approximately 14,000 new patients in the United State per year. The median overall survival is 5 years, and cure is a realistic goal for only a small minority of patients.

METHODS

A review of the literature was conducted that focused on treatment strategies for MM involving administration of high doses of chemotherapy followed by autologous or allogeneic hematopoietic stem cell transplant.

RESULTS

For over three decades, the standard treatment for MM has been a regimen of melphalan and prednisone (MP). Complete responses (CRs) have been rare, and 50% of patients have had disease that was resistant to treatment with MP. Attempts have been made to improve the outcome of MM by administering other combinations of standard doses of chemotherapy, but these treatments are equivalent in terms of overall survival. For patients who are candidates, high-dose therapy followed by autologous stem cell transplantation results in higher CR rates and improved long-term survival compared to treatment with standard doses of chemotherapy alone. While this strategy represents an advance in the treatment of MM, evidence-based reviews indicate that there are a number of issues to consider regarding the induction therapy, the collection of stem cells, and the timing, type, and number of high-dose therapies to use in this type of treatment strategy.

CONCLUSIONS

Advances have been made in autologous transplantation, allogeneic transplantation, anti-MM agents, and immunotherapy for MM. Combining these different strategies to achieve synergistic responses is an exciting possibility.

Targeted Therapy for Hematologic Malignancies

Background:

The introduction of monoclonal antibodies, either as native molecules or conjugated to radioisotopes or other toxins, has led to new therapeutic options for patients with hematologic malignancies. In addition, the use of small molecules against specific cell surface receptors, enzymes, and proteins has become an important strategy in the treatment of such disorders.

Methods:

The author reviewed the published clinical trials of monoclonal antibody and other targeted therapies in hematologic malignancies.

Results:

Results from several trials demonstrate a therapeutic benefit for the use of monoclonal antibodies (either native or conjugated) and other targeted therapies, used alone or in combination with standard cytotoxic chemotherapy.

Conclusions:

Targeted therapy of hematologic malignancies seems to be an effective and less toxic approach to the treatment of such disorders. Nevertheless, additional studies are needed to determine where and when such management fits into a therapeutic regimen for any given disorder, whether upfront or as salvage therapy, alone or in combination with chemotherapy (concurrent or sequential).

Phase II Study of Alemtuzumab (CAMPATH-1) in Patients with HTLV-1-Associated Adult T-cell Leukemia/lymphoma

PURPOSE

Therapeutic regimens for adult T-cell leukemia/lymphoma (ATL) are limited with unsatisfactory results, thereby warranting development of novel therapies. This study investigated antitumor activity and toxicity of alemtuzumab with regard to response, duration of response, progression-free survival, and overall survival in patients with human T-cell lymphotropic virus-1 (HTLV-1)-associated ATL.

EXPERIMENTAL DESIGN

Twenty-nine patients with chronic, acute, and lymphomatous types of ATL were enrolled in a single-institution, nonrandomized, open-label phase II trial wherein patients received intravenous alemtuzumab 30 mg three times weekly for a maximum of 12 weeks.

RESULTS

Twenty-nine patients were evaluable for response and toxicity. The overall objective response was 15 of 29 patients [95% confidence interval (CI), 32.5%-70.6%]. The 15 patients who responded manifested a median time to response of 1.1 months. Median response duration was 1.4 months for the whole group and 14.5 months among responders. Median progression-free survival was 2.0 months. Median overall survival was 5.9 months. The most common adverse events were 2 with vasovagal episodes (7%) and 3 with hypotensive episodes (10%), leukopenia (41%) grade 3 and (17%) grade 4, lymphocytopenia (59%) grade 3, neutropenia (31%) grade 3, anemia (24%), and thrombocytopenia (10%). All patients developed cytomegalovirus antigenemia (CMV). Three were symptomatic and all responded to antiviral therapy. Grade 3 or 4 infections were reported in 4 (14%) of patients.

CONCLUSIONS

Alemtuzumab induced responses in patients with acute HTLV-1-associated ATL with acceptable toxicity, but with short duration of responses. These studies support inclusion of alemtuzumab in novel multidrug therapies for ATL. Clin Cancer Res; 23(1); 35-42. ©2016 AACR.

Cancer immunotherapy

Cancer immunotherapy consists of approaches that modify the host immune system, and/or the utilization of components of the immune system, as cancer treatment. During the past 25 years, 17 immunologic products have received regulatory approval based on anticancer activity as single agents and/or in combination with chemotherapy. These include the nonspecific immune stimulants BCG and levamisole; the cytokines interferon-α and interleukin-2; the monoclonal antibodies rituximab, ofatumumab, alemtuzumab, trastuzumab, bevacizumab, cetuximab, and panitumumab; the radiolabeled antibodies Y-90 ibritumomab tiuxetan and I-131 tositumomab; the immunotoxins denileukin diftitox and gemtuzumab ozogamicin; nonmyeloablative allogeneic transplants with donor lymphocyte infusions; and the anti-prostate cancer cell-based therapy sipuleucel-T. All but two of these products are still regularly used to treat various B- and T-cell malignancies, and numerous solid tumors, including breast, lung, colorectal, prostate, melanoma, kidney, glioblastoma, bladder, and head and neck. Positive randomized trials have recently been reported for idiotype vaccines in lymphoma and a peptide vaccine in melanoma. The anti-CTLA-4 monoclonal antibody ipilumumab, which blocks regulatory T-cells, is expected to receive regulatory approval in the near future, based on a randomized trial in melanoma. As the fourth modality of cancer treatment, biotherapy/immunotherapy is an increasingly important component of the anticancer armamentarium.

Involvement of neutrophils and natural killer cells in the anti-tumor activity of alemtuzumab in xenograft tumor models

Alemtuzumab is a recombinant humanized IgG1 monoclonal antibody directed against CD52, an antigen expressed on the surface of normal and malignant B and T lymphocytes. Alemtuzumab is approved for the treatment of B-cell chronic lymphocytic leukemia (B-CLL), but the exact mechanism by which the antibody depletes malignant lymphocytes in vivo is not clearly defined. To address this issue, the anti-tumor activity of alemtuzumab was studied in disseminated and subcutaneous xenograft tumor models. The density of CD52 target antigen on the surface of tumor cells appeared to correlate with the anti-tumor activity of alemtuzumab. Deglycosylation of alemtuzumab resulted in a loss of cytotoxicity in vitro and was found to abolish anti-tumor activity in vivo. Individual inactivation of effector mechanisms in tumor-bearing mice indicated that the protective activity of alemtuzumab in vivo was primarily dependent on ADCC mediated by neutrophils and to a lesser extent NK cells. Increasing the number of circulating neutrophils by treatment with G-CSF enhanced the anti-tumor activity of the antibody, thus providing further evidence for the involvement of neutrophils as effector cells in the activity of alemtuzumab.

Circulating CD33 and its clinical value in acute leukemia

OBJECTIVE

CD33 is a cell surface antigen for committed myelomonocytic lineage. We explored the potential of detecting CD33 as cell-free circulating protein in patients with leukemia.

MATERIALS AND METHODS

We developed a quantitative bead-based immunoflow cytometry assay to measure cell-free circulating CD33 (cCD33) levels in the plasma of patients with acute leukemia, and correlated these results with corresponding clinical behavior. We measured cCD33 levels in the plasma of 48 healthy subjects and in patients with acute myelogenous leukemia (n = 98), acute lymphoblastic leukemia (n = 46), myelodysplastic syndrome (MDS) (n = 50), and myeloproliferative disorder (n = 49).

RESULTS

Patients with acute myeloid leukemia and myeloproliferative disorders had significantly higher concentrations of cCD33 than the other patient groups and normal individuals (p = 0.0001), and among these groups, MDS patients displayed the lowest cCD33 levels (p = 0.02). Circulating CD33 values correlated positively with the CD33(+) blast cell counts in these patients. While there was no correlation between cCD33 levels and survival in acute myelogenous leukemia and MDS, higher cCD33 plasma concentrations did correlate with shorter survival in acute lymphoblastic leukemia (p = 0.03), and with shorter complete remission duration in acute myelogenous leukemia (p = 0.04) and MDS (p = 0.03).

CONCLUSION

Circulating CD33 can be detected in the plasma from patients with leukemias, and cCD33 levels may have clinical implication, e.g., predictive and prognostic value, in these patients.

Heterogeneous CD52 Expression among Hematologic Neoplasms: Implications for the Use of Alemtuzumab (CAMPATH-1H)

PURPOSE

CD52 is a GPI-linked glycoprotein expressed by B cells, T cells, monocytes, and macrophages. The humanized monoclonal antibody alemtuzumab (CAMPATH-1H) is specific for CD52 and is Food and Drug Administration - approved for the treatment of relapsed or refractory chronic lymphocytic leukemia (CLL). The utility of CAMPATH in the treatment of other hematologic neoplasms has been explored; however, a comprehensive survey of CD52 expression among a broad spectrum of WHO-defined tumor types has not been completed.

EXPERIMENTAL DESIGN

We evaluated 294 hematologic neoplasms for the presence of CD52 using standard immunohistochemical techniques on paraffin-embedded biopsy specimens fixed with formalin, B-Plus, Zenker's acetic acid, or B5-formalin.

RESULTS

The vast majority of low-grade B cell lymphoproliferative disorders (CLL/small lymphocytic leukemia, follicular lymphoma, lymphoplasmacytic lymphoma, hairy cell leukemia, and mucosa-associated lymphoid tissue lymphomas) express CD52. In addition, we found that the majority of precursor B cell acute lymphoblastic leukemia/lymphomas express this antigen. In contrast, there is surprising heterogeneity in CD52 expression among more aggressive B cell lymphomas, with 25% of cases of diffuse large B cell lymphoma and Burkitt lymphoma demonstrating no detectable CD52. In addition, the majority of neoplasms of the T cell lineage are negative for the antigen, including most cases of precursor T cell acute lymphoblastic leukemia/lymphoma, anaplastic large cell lymphoma, and peripheral T cell lymphoma, not otherwise specified. Finally, the vast majority of cases of acute myeloid leukemia, Hodgkin lymphoma, and multiple myeloma are negative for CD52 expression.

CONCLUSION

In contrast with CLL, the variable expression of CD52 among other hematologic malignancies suggests that target validation on a case-by-case basis will likely be necessary to guide the rational analysis of CAMPATH therapy.

Development of Antibodies and Chimeric Molecules for Cancer Immunotherapy

Monoclonal antibodies are among the most rapidly expanding class of therapeutics for cancer treatment. Monoclonal antibodies targeting non-Hodgkin's lymphoma (NHL), Her-2/neu highly expressing metastatic breast cancer, colorectal cancer, acute myelogenous leukemia, and B-cell chronic lymphocytic leukemia (CLL) have received FDA approval. Promising new targets for antibody therapy include cellular growth factor receptors, mediators of tumor-driven neo-angiogenesis, as well as host negative immunoregulatory checkpoints that impede an effective immune response to neoplasia. Antibody efficacy has been increased by genetic engineering to humanize the antibodies and to increase their effector functions including antibody dependent cellular cytotoxicity. Furthermore, antibodies have been armed with cytokines, chemotherapeutic agents, toxins, and radionuclides to augment their efficacy as tumor cytotoxic agents. As a consequence of these advances, 30 years after their first development, monoclonal antibodies have become an important standard approach for the therapy of neoplasia with 19 therapeutic monoclonal antibodies now approved by the FDA including 8 for the treatment of cancer.

Management of Central Nervous System Lymphomas Using Monoclonal Antibodies: Challenges and Opportunities

Monoclonal antibodies (mAb) may change the management of central nervous system (CNS) lymphomas. This is due to the fact that traditional chemotherapies lack specificity for B-lymphoma cells and blood-brain barrier prevents adequate chemotherapy dosing in the CNS without significant systemic side effects. But in the past 5 years, the emergence of mAbs against specific receptors on B-lymphoma cells, either as a single agent or in combination with cytotoxic chemotherapies, may offer a better therapeutic index than conventional chemotherapies. The advantages of mAbs include high affinity to targets on lymphoma cells, their lack of pharmacodynamic or pharmacokinetic interactions with other drugs, and a potential for a synergistic therapeutic response when combined with conventional chemotherapies. Our review summarizes the biological behaviors of CNS lymphomas and the challenges and opportunities in using mAbs for CNS lymphomas.

Monoclonal antibody therapy for central nervous system lymphomas: an emerging treatment paradigm

The management of CNS lymphomas is poised for another revolution due to the emergence of therapeutic monoclonal antibodies. As the technology for generating monoclonal antibodies matures and obstacles are solved, therapeutic monoclonal antibodies will play an increasing role in the management of cancer. This article will review the biology of CNS lymphomas, monoclonal antibody technology, limitation of existing chemotherapies and the application of therapeutic monoclonal antibodies for the treatment of CNS lymphomas.

Monoclonal antibody therapy of B cell lymphoma

Studies in the early 1980s with anti-idiotype mAbs provided clinical proof that mAbs could be safe and effective antilymphoma agents; however, mAb therapy of lymphoma did not become practical until the chimaeric anti-CD20 mAb rituximab was developed. As a single agent, rituximab is well-tolerated and has clinical efficacy in select patient populations. A number of mechanisms of action have been identified that appear to contribute to the observed antilymphoma effects of mAb. Growing evidence suggests that multiple interacting mechanisms are likely to be involved. Anti-CD20-based radioimmunotherapy and combinations of mAb and chemotherapy are showing promise. mAbs that recognise other target antigens and immunotoxins have been evaluated clinically. It remains unclear whether these other mAbs provide value added beyond rituximab. Research geared towards understanding mAb mechanisms of action and the rational design of the next generation of mAb-based regimens will allow us to take full advantage of this exciting new mode of therapy.

Alemtuzumab in the Treatment of Chronic Lymphocytic Leukemia

Alemtuzumab is a humanized therapeutic monoclonal antibody (MAb) that recognizes the CD52 antigen, expressed on normal and neoplastic lymphocytes, monocytes, and natural killer cells. In 2001, alemtuzumab was approved in the US and Europe to treat B-cell chronic lymphocytic leukemia (CLL) that had been treated previously with alkylating agents and was refractory to fludarabine. In heavily pretreated patients this MAb is able to produce response rates of about 40%, and in symptomatic, previously untreated patients response rates of more than 80% can be achieved. Alemtuzumab can also be used in patients with CLL as a preparative regimen for stem cell transplantation (SCT) and to prevent graft versus host disease. Moreover its in vivo use before or after SCT may also potentially result in depletion of residual leukemia cells, especially in the autologous setting. Adverse events associated with alemtuzumab include acute first-dose reaction, hematologic toxicity, and infectious complications. Usually they are predictable, manageable, and acceptable in the context of CLL. However, in a significant percentage of patients, cytomegalovirus reactivation occurs during alemtuzumab therapy, and routine weekly monitoring with the polymerase chain reaction methodology is indicated. Moreover, antiviral and antibacterial prophylaxis is mandatory.

Antibody therapy for chronic lymphocytic leukemia: a promising new modality

Therapeutic options for chronic lymphocytic leukemia (CLL) have been limited, with low complete response rates (CR) and no treatments demonstrating a survival advantage. The recent introduction of the monoclonal antibodies rituximab and alemtuzumab into clinical trials for patients with CLL has generated promising results. Rituximab targets the CD20 antigen and demonstrates varied single-agent activity that is highly dependent upon the dosing schedule and treatment status of the patient. More importantly, when rituximab is combined with fludarabine or fludarabine and cyclophosphamide, a high frequency of CR and prolonged progression-free survival are observed without an appreciable increase in significant toxicity. Alemtuzumab targets the more ubiquitously expressed CD52 antigen and is therefore associated with a higher frequency of toxicity, particularly immunosuppression, but has appreciable activity in fludarabine refractory CLL. Additionally, alemtuzumab is effective against CLL clones that have p53 mutations or deletions. Future efforts in developing combination strategies with rituximab, alemtuzumab, and potentially other new antibodies offer great promise for the future treatment of CLL.

Advances in follicular lymphoma

Follicular lymphoma is a usually indolent lymphoma that responds well to chemotherapy. While multiple treatments show a good response rate, most patients relapse. Emerging therapies, such as antibody therapy and stem cell transplantation, are increasingly being used to try to lengthen response time. This article will review the available treatments for follicular lymphoma and discuss the studies supporting newer strategies of treatment.

Homing and mobilization of hematopoietic stem cells and hematopoietic cancer cells are mirror image processes, utilizing similar signaling pathways and occurring concurrently: circulating cancer cells constitute an ideal target for concurrent treatment with chemotherapy and antilineage-specific antibodies

Adhesion molecules and stromal cell-derived factor-1 (SDF-1)/CXCR4 signaling play key role in homing and mobilization of hematopoietic progenitor (HPC) and hematopoietic cancer clonogenic cells (HCC). High expression of VLA-4 is required for homing of HPC and HCC, whereas downregulation of these molecules is required for successful mobilization of HPC and HCC. Upregulation and activation of the SDF-1/CXCR4 signaling is required for homing of HPC and HCC, whereas disruption of the SDF-1 signaling is required for mobilization of HPC and HCC. Hence, mobilizations of HPC and HCC occur concurrently. It is proposed that drug resistance evolves as a result of repeated cycles of chemotherapy. Following each cycle of chemotherapy, HCC lose adhesion molecules and SDF-1 signaling. Surviving cells, released from tumor sites, circulate until re-expression of adhesion molecules and CXCR4 occurs, then homing to stroma of distal tissues occurs. Cytokines secreted by cells in the new microenvironment induce proliferation and drug resistance of HCC. This process is amplified in each cycle of chemotherapy resulting in disease progression. A novel model for treatment is proposed in which circulating HCC are the target for clinical intervention, and concurrent treatment with chemotherapy and antilineage-specific antibodies will result in abrogation of the 'vicious cycle' of conventional anticancer therapy.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is one of the most commonly diagnosed leukemias managed by practicing hematologists. For many years patients with CLL have been viewed as similar, with a long natural history and only marginally effective therapies that rarely yielded complete responses. Recently, several important observations related to the biologic significance of V(H) mutational status and associated ZAP-70 overexpression, disrupted p53 function, and chromosomal aberrations have led to the ability to identify patients at high risk for early disease progression and inferior survival. Concurrent with these investigations, several treatments including the nucleoside analogues, monoclonal antibodies rituximab and alemtuzumab have been introduced. Combination of these therapies in clinical trials has led to high complete and overall response rates when applied as initial therapy for symptomatic CLL. Thus, the complexity of initial risk stratification of CLL and treatment has increased significantly. Furthermore, when these initial therapies do not work, approach of the CLL patient with fludarabine-refractory disease can be quite challenging. This session will describe the natural history of a CLL patient with emphasis on important decision junctures at different time points in the disease. In Section I, Dr. Stephan Stilgenbauer focuses on the discussion that occurs with CLL patients at their initial evaluation. This includes a review of the diagnostic criteria for CLL and prognostic factors utilized to predict the natural history of the disease. The later discussion of risk stratification focuses on molecular and genomic aberrations that predict rapid progression, poor response to therapy, and inferior survival. Ongoing and future efforts examining early intervention strategies in high risk CLL are reviewed. In Section II, Drs. Ian Flinn and Jesus G. Berdeja focus on the discussion of CLL patients when symptomatic disease has developed. This includes an updated review of monotherapy trials with nucleoside analogs and recent trials that have combined these with monoclonal antibodies and/or alternative chemotherapy agents. Appropriate application of more aggressive therapies such as autologous and allogeneic immunotherapy and less aggressive treatments for appropriate CLL patient candidates are discussed. In Section III, Dr. John Byrd focuses on the discussion that occurs with CLL patients whose disease is refractory to fludarabine. The application of genetic risk stratification in choosing therapy for this subset of patients is reviewed. Available data with conventional combination based therapies and monoclonal antibodies are discussed. Finally, alternative promising investigational therapies including new antibodies, kinase inhibitors (CDK, PDK1/AKT, PKC) and alternative targeted therapies (DNA methyltransferase inhibitors, histone deacetylase inhibitors, etc.) are reviewed with an emphasis on the most promising agents for this patient population.

Phase I/II trial of epratuzumab (humanized anti-CD22 antibody) in indolent non-Hodgkin's lymphoma

PURPOSE

This single-center, dose-escalation study examines the safety, efficacy, and pharmacokinetics of epratuzumab (anti-CD22 humanized monoclonal antibody) in patients with recurrent indolent non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Patients had indolent NHL and recurrent disease after at least one chemotherapy regimen. Epratuzumab was administered intravenously at 120 to 1,000 mg/m2 over 30 to 60 minutes weekly for four treatments.

RESULTS

Fifty-five patients received epratuzumab and were assessable for safety; 51 patients were assessable for response. Patients were heavily pretreated (50% had at least four prior regimens) and 49% had bulky disease (> or = 5 cm). Epratuzumab was well tolerated, with no dose-limiting toxicity. Circulating B cells transiently decreased without significant effects on T cells or immunoglobulin levels. More than 95% of infusions were completed in approximately 1 hour. Mean serum half-life was 23 days. Across all dose levels and histologies, nine patients (18%; 95% confidence interval, 8% to 31%) achieved objective response, including three complete responses (CRs). All responses were in patients with follicular NHL: 24% of these patients responded, including 43% in the 360 mg/m2 dose group and 27% in the 480 mg/m2 dose group. No responses were observed in other indolent histologies. Median duration of objective response was 79.3 weeks (range, 11.1 to 143.3 weeks), with median time to progression for responders of 86.6 weeks by Kaplan-Meier estimate.

CONCLUSION

Epratuzumab was well tolerated at up to 1,000 mg/m2/wk (for 4 weeks) and had clinical activity. One third of responding patients achieved CR. A 43% objective response rate in follicular NHL patients treated at 360 mg/m2/wk indicates that this dose should be explored in additional studies.

Alemtuzumab therapy in B-cell lymphoproliferative disorders

Alemtuzumab (Campath-1H, Ilex Pharmaceuticals, San Antonio, TX) is a humanized monoclonal antibody that recognizes the CD52 antigen expressed on malignant and normal B lymphocytes. It has come to be used therapeutically in B-cell malignancies. Responses are seen in non-Hodgkin's lymphoma (NHL), and alemtuzumab can induce molecular remissions in relapsed chronic lymphocytic leukaemia (CLL), even when refractory to purine analogues. Most studies reveal the responses to be superior in the absence of bulky disease. Infusion-related side effects such as rigors, hypotension, and nausea are reduced by using the subcutaneous route of administration. Infectious complications are the most important toxicity seen and are related to the depletion of normal lymphocytes. The clinical efficacy in combination with both fludarabine and rituximab is under investigation.

Treatment of low-grade B-cell lymphoma with the monoclonal antibody rituximab

The anti-CD20 chimeric monoclonal antibody has been a tremendous addition to the therapeutic armamentarium against low-grade lymphoma. In indolent lymphoma, rituximab as a single agent is associated with 50% to 60% objective response rates in the relapsed setting and 60% to 75% as front-line therapy. Chemotherapy plus rituximab combinations have been associated with response rates of 85% to 95% and randomized trials have confirmed a higher response rate for various chemotherapy plus rituximab combinations compared to the same chemotherapy alone. Concurrent chemotherapy with rituximab does not increase toxicity and appears superior to sequences of chemotherapy followed by rituximab. Repeated intermittent therapy is associated with higher response rates and longer duration of remission. When used alone, the activity of rituximab is probably due to a combination of complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, and regulatory effects that enhance apoptosis. Dosing could probably be optimized by monitoring serum levels of rituximab in individual patients, because of the tremendous variability in lymphoma tumor burden, rates of tumor proliferation, rates of CD20 antigen production and expression, and clearance of rituximab. Combinations of rituximab with other monoclonal antibodies are currently being tested.

CD22-directed monoclonal antibody therapy for lymphoma

Immunotherapy directed against the CD20 antigen has had a profound impact on the management of patients with B-cell non-Hodgkin's lymphoma (NHL). Antibody-based treatments offer a favorable side effect profile, as well as alternate mechanisms of action that may complement those of cytotoxic modalities. Targeting other antigens, such as CD22, may also result in antilymphoma effects. This B-cell-specific molecule is widely expressed in NHL and mediates important functions in B-cell biology. Preclinical and early clinical data suggest that epratuzumab, a humanized anti-CD22 monoclonal antibody, demonstrates antilymphoma effects in both unlabeled and radiolabeled forms, as well as a favorable safety profile. Ongoing and future studies will further determine the role of epratuzumab among the array of antilymphoma therapies, both as a single agent and in combination with other agents.

New approaches in the immunotherapy of haematological malignancies

Advances in the management of haematological malignancies have allowed to obtain improved remission rates. Nonetheless, relapses impair these results and justify the search for novel therapeutic strategies. Clinical data demonstrate that the immune system plays an important role in the control of haematological malignancies. An increased frequency of haematological malignancies is observed in immunodeficiency states. Reversal of the immunosuppression is sometimes sufficient to induce tumour regression (withdrawal of cyclosporine in post-transplant lymphoproliferations, highly active anti-retroviral treatment in human immunodeficiency virus related Kaposi's disease). Another line of evidence for the involvement of the immune system in the anti-tumour response comes from the observation of spontaneous anti-tumour responses that parallel the occurrence of paraneoplastic immune-mediated syndromes. Finally, the efficiency of allogeneic transplantation in the haematological field has been clearly demonstrated to depend on the immune-mediated graft vs. leukaemia effect. Nonetheless, tumours develop in immune competent patients because of various tumour escape mechanisms, such as loss of human leucocyte antigen class I antigens, absence of target recognition by deficient adhesion/co-stimulatory molecule expression, tumour cell counterattack against immune effectors, direct (contact-dependent) or indirect (cytokine-mediated) impairment of T-lymphocyte activation. Novel immunotherapy approaches are now orientated in a convergent direction, i.e. the reversal of immune escape mechanisms either via the correction of deficient phases of the immune response or by the amplification of physiological mechanisms.

Circulating CD20 is detectable in the plasma of patients with chronic lymphocytic leukemia and is of prognostic significance

CD20 is a 33- to 36-kDa transmembrane phosphoprotein involved in the activation, proliferation, and differentiation of B lymphocytes. The predicted amino acid sequence of the CD20 suggests 4 transmembrane-spanning regions with both N- and C-termini located in the cytoplasm. We demonstrate herein that significant levels of circulating CD20 (cCD20) can be detected in the plasma of patients with chronic lymphocytic leukemia (CLL) and that cCD20 interferes with the binding of rituximab, a humanized anti-CD20 monoclonal antibody, to CLL cells. An enzyme-linked immunosorbent assay (ELISA) was developed to measure circulating cCD20 levels in the plasma. We measured cCD20 levels in the plasma of 180 patients with CLL and correlated these levels with clinical characteristics and outcome. Circulating CD20 levels correlated positively with beta(2)-microglobulin level (p =.006) and percentage of CD38(+) cells (p =.03) and negatively with platelet count (p =.004) and hemoglobin level (p =.02). Patients with advanced Rai (III/IV) or Binet (C) stage disease had significantly higher levels of cCD20 than did patients with earlier-stage disease (P =.01 and P =.006, respectively). There was no correlation between cCD20 level and age, lymphocyte count, or white blood cell count. Using a recursive classification method, we found that patients with a cCD20 level more than 1875 nM/L had significantly shorter survival than those with cCD20 1875 nM/L or below (P =.01). The prognostic value of cCD20 was independent of Rai staging or hemoglobin level. Prospective evaluation is indicated to establish whether rituximab dosing should be adjusted according to cCD20 levels.

Immunological effects and safe administration of alemtuzumab (MabCampath) in advanced B-cLL

Alemtuzumab (MabCampath) can purge both B- and T-cells in a variety of clinical situations, as seen in the treatment of autoimmune disorders and of lymphoid malignancies such as B-cell chronic lymphocytic leukemia (B-CLL). One of the characteristics of advanced B-CLL is an increased susceptibility to infection, which may improve in patients whose disease responds to alemtuzumab, particularly when immune reconstitution by non-malignant stem cells is successful. However, at initiation of treatment, patients with advanced disease are likely to have poor immune function, and need careful management during and after treatment. Here, we present results showing the nature of immune reconstitution after alemtuzumab and the ways in which alemtuzumab may affect white cell counts during and after treatment. The management of B-CLL patients is discussed both in the context of minimizing acute "first-dose" events and with reference to the health risks already existing in this patient population. With protocols in place for dose escalation, for dose postponement in the event of cytopenia, and for anti-infective prophylaxis, alemtuzumab can be used effectively and safely in high-risk B-CLL patients.

Immunotherapy of Non-Hodgkin's lymphomas

Recent years have witnessed the development of a variety of promising immunotherapies for treating patients with non-Hodgkin's lymphomas. Foremost among these advances is the exciting success of monoclonal antibodies directed against lymphocyte surface antigens. Rituximab is a chimeric (human-mouse) anti-CD20 antibody that induces responses in approximately half of the patients with relapsed indolent lymphomas and a third of patients with relapsed aggressive lymphomas when used as a single agent. Response rates appear even higher (up to 70%) for newly diagnosed patients treated with Rituximab monotherapy. Other promising antibodies for treatment of B cell malignancies include epratuzumab (anti-CD22), CAMPATH-1H (anti-CD52w), and Hu1D10 (anti-class II HLA). Even more exciting than antibody monotherapy is the prospect of combination antibody therapy (e.g. rituximab + epratuzumab) or combination chemotherapy and antibody therapy. In this regard, a recent phase III randomized trial from the GELA group in France demonstrated statistically significantly superior complete and overall response rates and superior event-free and overall survivals for elderly patients with newly diagnosed diffuse aggressive B cell lymphomas treated with CHOP + rituximab compared with CHOP alone. Confirmatory cooperative group trials combining chemotherapy with antibody therapies are currently underway. Another approach to augment the efficacy of antibodies is to deploy them in radiolabeled form. Iodine-131, Yttrium-90, and Copper-67 labeled monoclonal antibodies targeting CD-20, CD-22, HLA class II, and other cell surface antigens have been tested and demonstrate higher overall response rates (50-80%) and complete response rates (20-40%) than unlabeled antibodies. Pilot studies combining radiolabeled antibodies with either standard dose chemotherapy or myeloablative chemoradiotherapy with stem cell transplantation also appear very promising. Lymphoma vaccines have also produced very encouraging results in single institution studies at Stanford and the National Cancer Institute, with responding patients demonstrating superior event-free and overall survival than historical controls. Phase III randomized trials of idiotype vaccines are currently underway and novel new vaccine approaches are also being tested.