Safety and efficacy of ofatumumab, a fully human monoclonal anti-CD20 antibody, in patients with relapsed or refractory B-cell chronic lymphocytic leukemia: a phase 1-2 study

Ofatumumab, the first human anti-CD20 monoclonal antibody for the treatment of B cell hematologic malignancies

Ofatumumab is the first human anti-CD20 monoclonal antibody to be approved for patients in the United States and the European Union. Ofatumumab received accelerated approval from the U.S. Food and Drug Administration in October 2009 and was granted a conditional marketing authorization by the European Medicines Agency in April 2010 for the treatment of patients with chronic lymphocytic leukemia (CLL) refractory to fludarabine and alemtuzumab, based on interim results of a pivotal phase 2 trial. Preliminary positive results for ofatumumab in combination with chemotherapy in patients with CLL are currently being confirmed in larger randomized trials in both the frontline setting and the relapsed/refractory setting. Ofatumumab has also shown potential in treating B cell non-Hodgkin's lymphoma, such as follicular lymphoma (FL), diffuse large B cell lymphoma (DLBCL), and Waldenström's macroglobulinemia. Additional trials are ongoing to confirm activity of ofatumumab as monotherapy and in combination with chemotherapy in patients with FL or DLBCL.

Current status of targeted therapies for mantle cell lymphoma

Mantle cell lymphoma (MCL) is a type of non-Hodgkin's lymphoma (NHL) with treatment outcomes that have historically been poorer than those observed with other NHL subtypes. Patients typically present with advanced-stage disease and frequent extranodal involvement; the median age at diagnosis is >60 years. Recent improvements in progression-free and overall survival have been observed with more dose-intensive strategies, although at least half of patients diagnosed with MCL are not eligible for such treatment approaches based on age and co-morbidities. In addition, therapy options for relapsed MCL are limited. Only bortezomib is approved for treatment of relapsed MCL in the US. Development of targeted therapy approaches to minimize toxicities while preserving anti-neoplastic properties is of particular importance in MCL. Multiple ongoing studies are attempting to build on the known efficacy of bortezomib by evaluating combination regimens with other targeted agents or cytotoxic chemotherapy. The mammalian target of rapamycin (mTOR) inhibitor temsirolimus has known activity in MCL, making this an attractive class of agents for further investigation in combination regimens. Rituximab and other monoclonal antibodies are being evaluated for novel roles in MCL treatment, including as maintenance therapy. Other classes of drugs being investigated in MCL are immunomodulatory agents, inhibitors of the phosphoinositide 3-kinase/Akt and B-cell receptor signalling pathways, and inhibitors of bcl-2 and histone deacetylase. Although many of the agents appear to have modest single-agent activity, the favourable toxicity profile of many agents will make them best suited for incorporation into combination regimens.

Phase I study of the anti-CD40 humanized monoclonal antibody lucatumumab (HCD122) in relapsed chronic lymphocytic leukemia

Lucatumumab is a fully humanized anti-CD40 antibody that blocks interaction of CD40L with CD40 and also mediates antibody-dependent cell-mediated cytotoxicity (ADCC). We evaluated lucatumumab in a phase I clinical trial in chronic lymphocytic leukemia (CLL). Twenty-six patients with relapsed CLL were enrolled on five different dose cohorts administered weekly for 4 weeks. The maximally tolerated dose (MTD) of lucatumumab was 3.0 mg/kg. Four patients at doses of 4.5 mg/kg and 6.0 mg/kg experienced grade 3 or 4 asymptomatic elevated amylase and lipase levels. Of the 26 patients enrolled, 17 patients had stable disease (mean duration of 76 days, range 29-504 days) and one patient had a nodular partial response for 230 days. Saturation of CD40 receptor on CLL cells was uniform at all doses post-treatment but also persisted at trough time points in the 3.0 mg/kg or greater cohorts. At the MTD, the median half-life of lucatumumab was 50 h following the first infusion, and 124 h following the fourth infusion. In summary, lucatumumab had acceptable tolerability, pharmacokinetics that supported chronic dosing and pharmacodynamic target antagonism at doses of 3.0 mg/kg, but demonstrated minimal single-agent activity. Future efforts with lucatumumab in CLL should focus on combination-based therapy.

Treatment of relapsed or refractory chronic lymphocytic leukemia

BACKGROUND

Recent advances in the treatment of chronic lymphocytic leukemia (CLL) have moved beyond the traditional use of alkylating agents and purine analogs into regimens combining these two chemotherapy classes with monoclonal antibodies.

METHODS

This article reviews treatments options for patients with relapsed or refractory CLL.

RESULTS

Several studies have investigated novel agents in treating patients with 17p deletion, TP53 mutation, and fludarabine-refractory CLL, as well as patients with suboptimal response to intense treatment. These investigational agents include rituximab, alemtuzumab, ofatumumab, bendamustine, high-dose methylprednisolone, lenalidomide, lumiliximab, cyclin-dependent kinase inhibitors, small modular immunopharmaceuticals, Bcl-2 inhibitors, and histone deacetylase inhibitors. While these newer drugs and combination therapies have shown promise as treatment options for CLL, additional studies are needed to determine the immunosuppression, toxicities, and infections associated with their use.

CONCLUSIONS

Despite improvement in initial overall response rates, most patients relapse and require further treatment. CLL remains incurable with standard therapies due to development of disease refractoriness. As such, novel approaches such as those noted above warrant continued research to improve outcomes for patients with CLL.

State-of-the-Art Management of Patients Suffering from Chronic Lymphocytic Leukemia

The management of chronic lymphocytic leukemia (CLL) has evolved dramatically in the last decade. For the first time, clinical intervention has been shown to alter the natural history of the disease. Considerable efforts are focussing on better patient selection and response prediction, and it is expected that the publication of the first 200 CLL genomes will spark new insights into risk stratification of CLL patients. Besides, many new agents are being evaluated on their own and in combination therapy in early and late Phase clinical studies. Here, we provide a general clinical introduction into CLL including diagnosis and prognostic markers followed by a summary of the current state-of-the-art treatment. We point to areas of continued clinical research in particular for patients with co-morbidities and highlight the challenges in managing refractory disease.

Progress in the treatment of chronic lymphocytic leukemia: results of the German CLL8 trial

Until now, no approach that is able to improve overall survival of chronic lymphocytic leukemia (CLL) patients has been available. In the German CLL Study Group (GCLLSG) CLL8 trial, treatment-naive, physically fit patients (aged 30-81 years) with CD20(+) CLL were randomly assigned in a one-to-one ratio to receive six courses of intravenous fludarabine (25 mg/m(2) per day) and cyclophosphamide (250 mg/m(2) per day) for the first 3 days of each 28-day treatment course with or without rituximab (375 mg/m(2) on day 0 of first course and 500 mg/m(2) on day 1 of second to sixth courses). The two groups were well balanced with respect to baseline characteristics. The study was stopped at the preplanned interim analysis owing to an advantage in the median progression-free survival in the chemoimmunotherapy arm (51.8 vs 32.8 months; hazard ratio: 0.56; 95% CI: 0.46-0.69; p < 0.0001). Furthermore, at 3 years after randomization, 87% of patients in the chemoimmunotherapy group were alive compared with 83% in the chemotherapy group (hazard ratio: 0.67; 95% CI: 0.48-0.92; p = 0.01). In terms of toxicity, chemoimmunotherapy was more frequently associated with grade 3 and 4 neutropenia (p < 0.0001). There were eight (2%) treatment related-deaths in the chemoimmunotherapy arm compared with ten (3%) in the chemotherapy arm. The CLL8 trial has demonstrated that an association of rituximab, fludarabine and cyclophosphamide is effective in prolonging progression-free survival and overall survival of patients with symptomatic CLL, therefore establishing the new standard of treatment for physically fit patients.

Immunotherapy for B-cell lymphoma: current status and prospective advances

Therapy for non-Hodgkin's lymphoma has progressed significantly over the last decades. However, the majority of patients remain incurable, and novel therapies are needed. Because immunotherapy ideally offers target selectivity, an ever increasing number of immunotherapies, both passive and active, are undergoing development. The champion of passive immunotherapy to date is the anti-CD20 monoclonal antibody rituximab that revolutionized the standard of care for lymphoma. The great success of rituximab catalyzed the development of new passive immunotherapy strategies that are currently undergoing clinical evaluation. These include improvement of rituximab efficacy, newer generation anti-CD20 antibodies, drug-conjugated and radio labeled anti-CD20 antibodies, monoclonal antibodies targeting non-CD20 lymphoma antigens, and bispecific antibodies. Active immunotherapy aims at inducing long-lasting antitumor immunity, thereby limiting the likelihood of relapse. Current clinical studies of active immunotherapy for lymphoma consist largely of vaccination and immune checkpoint blockade. A variety of protein- and cell-based vaccines are being tested in ongoing clinical studies. Recently completed phase III clinical trials of an idiotype protein vaccine suggest that the vaccine may have clinical activity in a subset of patients. Efforts to enhance the efficacy of active immunotherapy are ongoing with an emphasis on optimization of antigen delivery and presentation of vaccines and modulation of the immune system toward counteracting immunosuppression, using antibodies against immune regulatory checkpoints. This article discusses results of the various immunotherapy approaches applied to date for B-cell lymphoma and the ongoing trials to improve their effect.

Monoclonal antibodies for the treatment of cancer

Over the past decade, the clinical utility of monoclonal antibodies has been realized and antibodies are now a mainstay for the treatment of cancer. Antibodies have the unique capacity to target and kill tumor cells while simultaneously activating immune effectors to kill tumor cells through the complement cascade or antibody-dependent cellular cytotoxicity (ADCC). This multifaceted mechanism of action combined with target specificity underlies the capacity of antibodies to elicit anti-tumor responses while minimizing the frequency and magnitude of adverse events. This review will focus on mechanisms of action, clinical applications and putative mechanisms of resistance to monoclonal antibody therapy in the context of cancer.

Monoclonal antibodies and recombinant immunoglobulins for the treatment of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and degenerative disease leading to demyelination and axonal damage in the CNS. Autoimmunity plays a central role in MS pathogenesis. Per definition, monoclonal antibodies are recombinant biological compounds with a well defined target, thus carrying the promise of targeting pathogenic cells or molecules with high specificity, avoiding undesired off-target effects. Natalizumab was the first monoclonal antibody to be approved for the treatment of MS. Several other monoclonal antibodies are in development and have demonstrated promising efficacy in phase II studies. They can be categorized according to their mode of action into compounds targeting (i) leukocyte migration into the CNS (natalizumab); (ii) cytolytic antibodies (rituximab, ocrelizumab, ofatumumab, alemtuzumab); or (iii) antibodies and recombinant proteins targeting cytokines and chemokines and their receptors (daclizumab, ustekinumab, atacicept, tabalumab [Ly-2127399], secukinumab [AIN457]). In this review, we discuss the specific molecular targets, clinical efficacy and safety of these compounds and discuss criteria to anticipate the position of monoclonal antibodies in the diversifying armamentarium of MS therapy in the coming years.

Update on novel monoclonal antibodies and immunoconjugates for the treatment of lymphoproliferative disorders

The year 1997 was pivotal in lymphoma research, as it was the year that the US FDA approved rituximab. Rituximab significantly altered clinical management and outcomes of patients with B-cell malignancies. Despite a high initial response rate, the majority of patients subsequently develop variable degrees of therapeutic resistance to rituximab. Research attempting to understand the mechanisms of rituximab resistance and potential ways to overcome them has given rise to the development of novel targeted immunotherapeutics. This article will update the readers on advances in bioengineering of monoclonal antibodies and immunoconjugates that target CD20, as well as other surface antigens. Some additional novel immunotherapeutics, including small modular immunopharmaceuticals, bispecific monoclonal antibodies, T-cell engaging antibodies and immunoconjugates, will also be discussed.

Leflunomide induces apoptosis in fludarabine-resistant and clinically refractory CLL cells

PURPOSE

Environmental conditions in lymph node proliferation centers protect chronic lymphocytic leukemia (CLL) cells from apoptotic triggers. This situation can be mimicked by in vitro stimulation with CD40 ligand (CD40L) and interleukin 4 (IL-4). Our study investigates the impact of the drug leflunomide to overcome apoptosis resistance of CLL cells.

EXPERIMENTAL DESIGN

CLL cells were stimulated with CD40L and IL-4 and treated with fludarabine and the leflunomide metabolite A771726.

RESULTS

Resistance to fludarabine-mediated apoptosis was induced by CD40 activation alone stimulating high levels of BCL-XL and MCL1 protein expression. Apoptosis resistance was further enhanced by a complementary Janus-activated kinase (JAK)/STAT signal induced by IL-4. In contrast, CLL proliferation required both a CD40 and a JAK/STAT signal and could be completely blocked by pan-JAK inhibition. Leflunomide (A771726) antagonized CD40L/IL-4-induced proliferation at very low concentrations (3 μg/mL) reported to inhibit dihydroorotate dehydrogenase. At a concentration of 10 μg/mL, A771726 additionally attenuated STAT3/6 phosphorylation, whereas apoptosis of CD40L/IL-4-activated ("resistant") CLL cells was achieved with higher concentrations (IC(50): 80 μg/mL). Apoptosis was also effectively induced by A771726 in clinically refractory CLL cells with and without a defective p53 pathway. Induction of apoptosis involved inhibition of NF-κB activity and loss of BCL-XL and MCL1 expression. In combination with fludarabine, A771726 synergistically induced apoptosis (IC(50): 56 μg/mL).

CONCLUSION

We thus show that A771726 overcomes CD40L/IL-4-mediated resistance to fludarabine in CLL cells of untreated as well as clinically refractory CLL cells. We present a possible novel therapeutic principle for attacking chemoresistant CLL cells.

Targeted treatment for chronic lymphocytic leukemia

The treatment of chronic lymphocytic leukemia (CLL) has evolved over the last few decades. Recognition has increased of several key components of CLL biology currently manipulated for therapeutics. A milestone in the treatment of CLL was reached with the incorporation of immunotherapy with conventional chemotherapy. The fludarabine/cyclophosphamide/rituximab combination has demonstrated survival advantage for the first time in the treatment of CLL. Several other biological compounds are being explored with the hope of improving responses, impacting survival, and ultimately curing CLL. Important agents being tested are targeted on CLL surface molecules and their ligands, signal transduction protein and oncogenes. This review provides a brief summary of the recent advances made in preclinical and clinical investigation of selected promising therapeutic agents, which lead the target-directed therapeutic approach.

Optimizing therapeutic antibody function: progress with Fc domain engineering

Since the establishment of monoclonal antibody production using hybridoma technology in the mid-1970s, there has been expanding progress and continuous technological improvement in the development of therapeutic antibodies. The initial technological breakthroughs involved reduction of immunogenicity and thus enabled repeated administration. The establishment of chimeric, humanized, and fully human antibodies has led to the great success of several ‘second-generation’ therapeutic antibodies, such as rituximab, trastuzumab, cetuximab, and bevacizumab. However, there still exists an urgent demand for improvement in the efficacy of the current antibody therapeutics, which is not yet fully satisfactory for patients. Based on the current understanding of the clinical mechanisms of several therapeutic antibodies, many now believe that Fc-mediated functions (e.g. antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and neonatal Fc receptor [FcRn]-mediated storage) will improve the clinical outcomes of therapeutic antibodies. The present review focuses on the recent progress in the development of ‘Fc engineering,’ which dramatically improves (and sometimes silences) Fc-mediated functions. These achievements can be classified into two technological approaches: (i) introducing amino acid mutations and (ii) modifying Fc-linked oligosaccharide structures. The effectiveness of multiple third-generation therapeutic antibodies armed with various engineered Fcs is now ready to be tested in clinical trials.

New anti-CD20 monoclonal antibodies for the treatment of B-cell lymphoid malignancies

Over the last few years, new generations of anti-CD20 monoclonal antibodies (mAbs) have been developed for potential benefits over the classical, first-generation mAb rituximab. Compared with rituximab, new mAbs have enhanced antitumor activity resulting from increased complement-dependent cytotoxicity (CDC) and/or antibody-dependent cellular cytotoxicity (ADCC) and increased Fc binding affinity for the low-affinity variants of the FcγRIIIa receptor (CD16) on immune effector cells. The second-generation mAbs, which include ofatumumab, veltuzumab, and ocrelizumab, are humanized or fully human to reduce immunogenicity, but with an unmodified Fc region. Ofatumumab is a fully human anti-CD20 IgG1 mAb in clinical development for hematological malignancies and autoimmune diseases. Ofatumumab specifically recognizes an epitope encompassing both the small and large extracellular loops of CD20 molecule, and is more effective than rituximab at CDC induction and killing target cells. Veltuzumab (IMMU-106, hA20) is a humanized anti-CD20 mAb with complementarity-determining regions similar to rituximab. This antibody has enhanced binding avidities and a stronger effect on CDC compared with rituximab. Ocrelizumab is a humanized mAb with the potential for enhanced efficacy in lymphoid malignancies compared with rituximab due to increased binding affinity for the low-affinity variants of the FcγRIIIa receptor. The third-generation mAbs are also humanized mAbs, but in addition they have an engineered Fc to increase their binding affinity for the FcγRIIIa receptor. The third-generation mAbs include AME-133v, PRO131921 and GA-101. AME-133v (LY2469298) is a type I, humanized IgG1 mAb with enhanced affinity for FcγRIIIa receptor and an enhanced ADCC activity compared with rituximab. PRO131921 is a humanized anti-CD20 mAb engineered to have improved binding to FcγRIIIa and better ADCC compared with rituximab. GA-101 (RO5072759) is a fully humanized, type II, IgG1 mAb derived from humanization of the parental B-Ly1 mouse antibody and subsequent glycoengineering using GlycoMab® technology. GA-101 was designed for enhanced ADCC and superior direct cell-killing properties, in comparison with currently available type I antibodies. TRU-015 is a small modular immunopharmaceutical (SMIP) derived from key domains of an anti-CD20 antibody. TRU-015 represents a novel biological compound that retains Fc-mediated effector functions and is smaller than mAbs. In this article we review data on new anti-CD20 mAbs that are potentially useful in the treatment of lymphoid malignancies.

CD40 stimulation sensitizes CLL cells to lysosomal cell death induction by type II anti-CD20 mAb GA101

Sensitivity of chronic lymphocytic leukemia (CLL) cells to anti-CD20 mAbs is low and, therefore, the efficacy of monotherapy with current anti-CD20 mAbs is limited. At present, it is not known whether sensitivity of CLL cells to CD20 mAbs is modulated by microenvironmental stimuli. We have shown previously that in vitro CD40 stimulation of peripheral blood-derived CLL cells results in resistance to cytotoxic drugs. In the present study, we show that, in contrast, CD40 stimulation sensitizes CLL cells to the recently described novel type II anti-CD20 mAb GA101. Cell death occurred without cross-linking of GA101 and involved a lysosome-dependent mechanism. Combining GA101 with various cytotoxic drugs resulted in additive cell death, not only in CD40-stimulated CLL cells, but also in p53-dysfunctional CLL cells. Our findings indicate that GA101 has efficacy against chemoresistant CLL, and provide a rationale for combining cytotoxic drugs with anti-CD20 mAbs.

Treatment of chronic lymphocytic leukemia requires targeting of the protective lymph node environment with novel therapeutic approaches

Chronic lymphocytic leukemia (CLL) remains associated with low complete response rates and high relapse rates. This is in part due to poor understanding of CLL biology and thus inadequate targeting of therapy. For years CLL has been proposed as bi-compartmental: the quiescent tumor in the periphery and the proliferating cells within specific microenvironments. Historically the bone marrow was considered the major tissue of the CLL microenvironment. However, many recent innovative studies have categorically shown that peripheral CLL cells are derived from the lymph nodes (LN). Proliferation here is largely driven by helper T cells via CD40-CD40L engagement. Critically, in vitro studies have shown that such engagement additionally protects LN CLLs from apoptosis. Agents inducing apoptosis in non-CD40 engaged CLL cells are frequently ineffective against those continually engaged with CD40L. This emphasizes that, in order to improve responses and prevent relapse, novel therapies must be assessed against CD40L engaged CLL cells to show effective targeting against the LN. This review discusses the evidence supporting the superior involvement of the LN in CLL, how CD40L engaged CLL studies should be conducted, and the novel therapies studied in vitro and in vivo that have been proposed to be effective in this setting.

Ofatumumab in the treatment of low-grade non-Hodgkin's lymphomas and chronic lymphocytic leukemia

Ofatumumab is a novel anti-CD20 monoclonal antibody recently approved for the treatment of chronic lymphocytic leukemia refractory to alemtuzumab and fludarabine. Ofatumumab has also demonstrated activity in other low-grade non-Hodgkin's lymphomas. However, the optimal time to use ofatumumab and in what patient population is debatable. This article will review some of the key clinical studies that led to the drug's approval, current recommended usage of the drug and significant future directions.

Ofatumumab: a novel anti-CD20 monoclonal antibody for treatment of refractory chronic lymphocytic leukemia

OBJECTIVE

To present the current clinical evidence on ofatumumab for use in refractory chronic lymphocytic leukemia (CLL).

DATA SOURCES

A literature search was performed using MEDLINE and PubMed (both 1966-May 2011), as well as the American Society of Hematology abstracts (2000-May 2011), using the primary search terms ofatumumab and HuMax-CD20.

STUDY SELECTION AND DATA EXTRACTION

Clinical studies and abstracts available in the English language, describing the pharmacology, pharmacokinetics, clinical activity, and safety of ofatumumab in CLL were included in this review.

DATA SYNTHESIS

Ofatumumab is a human immunoglobulin monoclonal antibody that binds to B-lymphocytes expressing CD-20 cell surface antigens. Ofatumumab was granted accelerated approval by the Food and Drug Administration in October 2009 for the treatment of CLL refractory to fludarabine and alemtuzumab. A Phase 1/2 trial has established the safety and tolerability of single-agent ofatumumab at an initial dose of 300 mg intravenously on week 1, followed by 2000 mg once weekly for 7 doses (weeks 2-8), followed by 2000 mg once every 4 weeks for 4 doses (weeks 9-12), for a total of 12 doses. The final analysis of a pivotal international multicenter trial has shown promising activity in patients with CLL refractory to fludarabine and alemtuzumab, demonstrating overall response rates of 44-51%, with prolonged progression-free and overall survival. Ofatumumab activity has also been shown in a variety of other malignant and nonmalignant conditions, including non-Hodgkin lymphoma, rheumatoid arthritis, and multiple sclerosis. The most common adverse effect is grade 1 and 2 infusion reactions. Other adverse effects include infection, neutropenia, anemia, rash, fever, and diarrhea.

CONCLUSIONS

Clinical evidence suggests that ofatumumab is an effective agent in patients with CLL refractory to fludarabine and alemtuzumab. Data are awaited comparing ofatumumab to other salvage regimens. Until results of head-to-head trials are conducted comparing ofatumumab to existing regimens, it cannot be said whether ofatumumab is more efficacious or tolerable than currently available therapies.

Ofatumumab for newly diagnosed and relapsed/refractory chronic lymphocytic leukemia

Monoclonal antibodies have become an increasingly utilized treatment option for many hematological malignancies, including chronic lymphocytic leukemia (CLL). Ofatumumab is a second-generation fully human anti-CD20 monoclonal antibody that binds to the small extracellular loop of CD20, thereby producing complement-dependent cell lysis and antibody-mediated cell cytotoxicity in cells expressing CD20. Ofatumumab has shown efficacy in the treatment for relapsed or refractory CLL. This success has resulted in the recent US FDA approval of ofatumumab for the treatment of CLL in patients who are refractory to fludarabine and alemtuzumab-based regimens. Major side effects of ofatumumab include infusion reactions, neutropenia and increased risk for infection. This article provides an overview of the current data supporting the use of ofatumumab for CLL and projects the future role of ofatumumab as monotherapy and combination therapy.

The in vivo mechanism of action of CD20 monoclonal antibodies depends on local tumor burden

BACKGROUND

CD20 monoclonal antibodies are widely used in clinical practice. Antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity and direct cell death have been suggested to be important effector functions for CD20 antibodies. However, their specific contributions to the in vivo mechanism of action of CD20 immunotherapy have not been well defined.

DESIGN AND METHODS

Here we studied the in vivo mechanism of action of type I (rituximab and ofatumumab) and type II (HuMab-11B8) CD20 antibodies in a peritoneal, syngeneic, mouse model with EL4-CD20 cells using low and high tumor burden.

RESULTS

Interestingly, we observed striking differences in the in vivo mechanism of action of CD20 antibodies dependent on tumor load. In conditions of low tumor burden, complement was sufficient for tumor killing both for type I and type II CD20 antibodies. In contrast, in conditions of high tumor burden, activating FcγR (specifically FcγRIII), active complement and complement receptor 3 were all essential for tumor killing. Our data suggest that complement-enhanced antibody-dependent cellular cytotoxicity may critically affect tumor killing by CD20 antibodies in vivo. The type II CD20 antibody 11B8, which is a poor inducer of complement activation, was ineffective against high tumor burden.

CONCLUSIONS

Tumor burden affects the in vivo mechanism of action of CD20 antibodies. Low tumor load can be eliminated by complement alone, whereas elimination of high tumor load requires multiple effector mechanisms.

Salvage therapy for relapsed chronic lymphocytic leukemia

Chronic lymphocytic leukemia is a common hematologic malignancy with a highly variable clinical course. While the median age at diagnosis is 72 years of age and fewer than 10% of patients are diagnosed before the age of 60 years, the majority of patients who require therapy will ultimately relapse. Advances in upfront therapy and supportive care have dramatically improved initial responses compared with traditional akylator-based chemotherapy. However, comparable results are not generally observed in the salvage setting. Careful planning that takes into account the duration of the initial response, patient age and/or comorbidities, and cytogenetic and molecular profiles are critical for the successful management of patients with relapsed chronic lymphocytic leukemia.

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.

Refractory chronic lymphocytic leukemia--new therapeutic strategies

Treatment outcome of chronic lymphocytic leukemia (CLL) has considerably improved since the introduction of fludarabine (F) as part of the standard therapy. Nevertheless, refractoriness to fludarabine occurs in a significant number of patients and is associated with an unfavorable prognosis. Important risk factors are 17p deletion and/or mutation of TP53. For this subgroup the CD52 antibody alemtuzumab (A) presents a new treatment approach and has already been approved. Meanwhile we have to face also refractoriness to alemtuzumab. Importantly, the monoclonal CD20 antibody ofatumumab has now shown efficacy in F and A double-refractory CLL. The next generation CD20 antibody GA-101 is currently compared to rituximab (R) and will possibly be its more potent successor. Further B-cell antigens are targeted by lumiliximab (CD23), TRU-016 (CD37) and blinatumomab (CD19). Apart from monoclonal antibody therapies, a great number of small molecules are examined for the treatment of refractory and relapsed CLL. Most of these agents aim to overcome apoptosis resistance in CLL cells or influence the microenvironment. Typical targets are regulators of the cell cycle and antiapoptotic molecules like the members of the Bcl-2 family. Up to now the most promising agents appear to be flavopiridol and lenalidomide among others.

Treatment options for high-risk chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common form of leukaemia in the Western world. The natural history of CLL is extremely variable with a survival time from initial diagnosis that ranges from 2 to more than 20 years. Understanding the clinical diversity and allowing the subclassification of CLL into various prognostic groups not only assists in predicting future outcome for patients, but also helps to direct treatment decisions. Chlorambucil and fludarabine were the standard therapy for CLL for decades. Randomized studies have reported superior overall response and progression-free survival (PFS) for fludarabine compared with alkylator-based therapy and for the fludarabine-cyclophospamide (FC) combination over fludarabine alone. More recently the addition of rituximab to the FC regimen (R-FC) has shown significant improvement in overall response, PFS and overall survival compared with FC alone. However, there are patients for whom this regimen still provides less satisfactory results. Within the above studies CLL patients who have some of the poorer prognostic markers, such as unmutated IgVH genes and/or high beta-2 microglobulin (B2M), and those who fail to achieve a minimal residual disease (MRD) negative remission are likely to have a shorter PFS compared with those without these features. Various strategies have been explored to improve the outcome for such patients. These include the addition of agents to a frontline R-FC regimen, use of consolidation and consideration of maintenance. The only group that can be clearly identified pretreatment for whom conventional fludarabine-based therapies produce significantly inferior response rates, PFS and overall survival are the patients who harbour a genetic fault; deletion or mutation or a combination of deletion and mutation of tumour protein p53 (TP53). TP53 inactivation is a less common finding at first treatment but becomes much more common in fludarabine-refractory patients. Alemtuzumab and high-dose corticosteroids have been shown to be effective in this group of CLL patients. Trials combining these two agents have shown improved responses, particularly for those patients with bulky nodal disease for whom alemtuzumab alone may be insufficient. Since the duration of responses remains relatively short, suitable patients should be considered for allogeneic stem cell transplantation according to the European Group for Blood and Marrow Transplantation (EBMT) guidelines. Furthermore, there are a number of other new treatments on the horizon, including humanized antibodies directed against novel targets and small-molecule inhibitors.

Personalizing treatment for chronic lymphocytic leukemia

Over the past few years, more effective therapies have emerged in the treatment of chronic lymphocytic leukemia (CLL); these are mainly combinations of immunotherapy with fludarabine-based regimens. Despite the higher response rates obtained with these more intensive treatments, they may not always be applicable. Patients with several comorbidities have an increased toxicity with these newer therapies. Effective tools to distinguish between fit and nonfit patients and new therapeutic approaches suitable for fragile patients with CLL are therefore necessary. Moreover, there is still a subset of patients who are refractory to standard fludarabine-based treatments who continue to have very poor survival. Efforts to understand the mechanisms of resistance to treatment in order to develop new therapeutic agents for those patients are mandatory. Finally, advances in the knowledge of the pathogenesis of CLL are promoting the emergence of drugs directed to new biological targets of this disease. Consequently, trials exploring the toxicity profile and efficacy of these new therapeutic agents, alone or in combination with standard treatments, are warranted.

Role of ofatumumab in treatment of chronic lymphocytic leukemia

The management of chronic lymphocytic leukemia (CLL) has dramatically improved in the past decade with the addition of anti-CD20 monoclonal antibodies to the treatment armamentarium. Ofatumumab is a novel anti-CD20 monoclonal antibody recently approved in the US and Europe for the treatment of CLL refractory to alemtuzumab and fludarabine. Preclinical data showed improved complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity compared with rituximab. Clinical studies have shown single-agent activity for ofatumumab in CLL and in other low-grade non-Hodgkin's lymphomas. Combination studies are being conducted to enhance the therapeutic efficacy of ofatumumab. This paper reviews some of the key clinical studies that led to approval of ofatumumab, and future directions.

Chemoimmunotherapy with O-FC in previously untreated patients with chronic lymphocytic leukemia

We conducted an international phase 2 trial to evaluate 2 dose levels of ofatumumab, a human CD20 mAb, combined with fludarabine and cyclophosphamide (O-FC) as frontline therapy for chronic lymphocytic leukemia (CLL). Patients with active CLL were randomized to ofatumumab 500 mg (n = 31) or 1000 mg (n = 30) day 1, with fludarabine 25 mg/m(2) and cyclophosphamide 250 mg/m(2) days 2-4, course 1; days 1-3, courses 2-6; every 4 weeks for 6 courses. The first ofatumumab dose was 300 mg for both cohorts. The median age was 56 years; 13% of patients had a 17p deletion; 64% had β2-microglobulin > 3.5 mg/L. Based on the 1996 National Cancer Institute Working Group (NCI-WG) guidelines, the complete response (CR) rate as assessed by an independent review committee was 32% for the 500-mg and 50% for the 1000-mg cohort; the overall response (OR) rate was 77% and 73%, respectively. Based on univariable regression analyses, β2-microglobulin and the number of O-FC courses were significantly correlated (P < .05) with CR and OR rates and progression-free survival (PFS). The most frequent Common Terminology Criteria (CTC) grade 3-4 investigator-reported adverse events were neutropenia (48%), thrombocytopenia (15%), anemia (13%), and infection (8%). O-FC is active and safe in treatment-naive patients with CLL, including high-risk patients. This trial was registered at www.clinicaltrials.gov as NCT00410163.

The emerging role of ofatumumab in the treatment of chronic lymphocytic leukemia

The treatment of chronic lymphocytic leukemia (CLL) has evolved over the past decade. Our better understanding of disease biology and risk stratification has allowed delivering more effective therapies. In fact, front-line chemoimmunotherapy has demonstrated improvement in overall survival when compared to chemotherapy in randomized studies. Yet, treatment of relapsed CLL remains challenging and few agents are effective in that setting. Ofatumumab (Ofa) is a humanized monoclonal antibody targeted against CD20 with demonstrable activity in rituximab-resistant CLL cell lines. This agent was recently approved for the treatment of relapsed/refractory CLL patients who have failed fludarabine and alemtuzumab. In this review, we provide a historical perspective on approaches to CLL as front-line and in the relapsed setting. We further summarize novel anti-CD20 antibodies with specific emphasis on ofa. We review studies that led to ofatumumab's approval including pre-clinical data, trials using ofa in combination therapies, and adverse events/toxicities reported with this agent.

Standard of care and novel treatments for chronic lymphocytic leukemia

PURPOSE

The standard of care and novel treatments for chronic lymphocytic leukemia (CLL) are reviewed.

SUMMARY

Recent advances in the treatment of CLL have dramatically changed the therapeutic landscape for both patients and health care professionals. The majority of conventional first-line therapies are noncurative and are only used to treat disease that is symptomatic or progressive and include chlorambucil, monotherapy with purine analogues, and combination chemotherapy. Immunotherapeutic agents such as rituximab and alemtuzumab may be indicated in select patient populations. However, because clinical trials have found that overall survival does not depend on the initial therapy, selection of first-line therapy should be based on patient-specific factors and the patient's goals for therapy with respect to response, survival, and symptom palliation. Progression-free survival time and time to treatment are critical endpoints for CLL treatment. An increasingly important endpoint is minimal residual disease (MRD), as it is considered to be the major cause of relapse in CLL. Finally, comparison of toxicities between different therapies is critical in CLL, as it is in other disease states. Several new agents are currently being evaluated for use in CLL, including alvocidib, oblimersen, and lumiliximab.

CONCLUSION

Chemotherapy remains the mainstay of treatment for the majority of patients with CLL. The introduction of rituximab, alemtuzumab, and bendamustine has improved the current outlook for patients with CLL. As overall survival does not appear to depend on the initial therapy, treatment should be selected based on patient-specific factors and goals. Challenges in CLL include determining when to initiate therapy, eradicating MRD, and managing therapeutic resistance.

Beyond chemotherapy: new agents for targeted treatment of lymphoma

An improved understanding of the molecular biology of cancer cell growth and survival and the role of the microenvironment in supporting the survival of cancer cells, including lymphoma cells, has led to the identification of a number of potential therapeutic targets. Despite these advances, drug development for lymphoma remains slow, inefficient, and frequently unfocused. Future work should focus on identifying 'driver' molecular defects of oncogenic pathways that can be targeted therapeutically, discovering predictive biomarkers for treatment response, and prioritizing promising drugs to accelerate their approval. This Review summarizes the current development status of novel agents for lymphoma and discusses strategies to move the field forward.

The future of anti-CD20 monoclonal antibodies: are we making progress?

The anti-CD20 monoclonal antibody (mAb) rituximab has revolutionized the treatment of B-cell malignancies. This unprecedented success has not only substantially changed the mindset of the clinical community about the ability of mAb to improve outcomes but has catalyzed the interest in the pharmaceutical industry to develop the next generation of anti-CD20 mAbs. Since the introduction of rituximab 15 years ago, we have learned much about the potential mechanisms underlying the therapeutic efficacy of anti-CD20 mAbs. In parallel, many novel anti-CD20 mAbs have entered the clinic, each designed with modifications to structure aimed at further improving efficacy. On review of the newer generation of anti-CD20 mAbs entering clinical trials, it appears that the link between the novel mechanistic insights and the development of these next-generation anti-CD20 mAbs is unclear. As we move into an era of personalized medicine, it will become increasingly important for us to develop closer links between the emerging mechanistic insights and the clinical development, to further enhance the potency of anti-CD20 mAbs beyond that achieved with rituximab.

Subcutaneous injections of low-dose veltuzumab (humanized anti-CD20 antibody) are safe and active in patients with indolent non-Hodgkin's lymphoma

BACKGROUND

Subcutaneous injections of anti-CD20 antibodies may offer benefits to both patients and the healthcare system for treatment of B-cell malignancies.

DESIGN AND METHODS

A pilot study was undertaken to evaluate the potential for subcutaneous dosing with 2(nd) generation anti-CD20 antibody veltuzumab in patients with CD20(+) indolent non-Hodgkin's lymphoma. Patients with previously untreated or relapsed disease received 4 doses of 80, 160, or 320 mg veltuzumab injected subcutaneously every two weeks. Responses were assessed by computed tomography scans, with other evaluations including adverse events, safety laboratories, B-cell blood levels, serum veltuzumab levels, and human anti-veltuzumab antibody (HAHA) titers.

RESULTS

Seventeen patients (14 follicular lymphoma; 13 stage III or IV disease; 5 treatment-naive) completed treatment with only occasional, mild-moderate, transient injection reactions and no other safety issues. Subcutaneous veltuzumab demonstrated a slow release pattern over several days, achieving a mean Cmax of 19, 25 and 63 μg/mL at 80, 160, and 320 mg doses for a total of 4 administrations, respectively. Depletion of circulating B cells occurred after the first injection. The objective response rate (partial responses plus complete responses plus complete responses unconfirmed) was 47% (8/17) with a complete response/complete response unconfirmed rate of 24% (4/17); 4 of 8 objective responses continued for 60 weeks or more. All serum samples evaluated for human anti-veltuzumab antibody were negative.

CONCLUSIONS

Subcutaneous injections of low-dose veltuzumab are convenient, well tolerated, and capable of achieving sustained serum levels, B-cell depletion, and durable objective responses in indolent non-Hodgkin's lymphoma. (Clinicaltrials.gov identifier: NCT00546793).

The European Medicines Agency review of ofatumumab (Arzerra®) for the treatment of chronic lymphocytic leukemia in patients refractory to fludarabine and alemtuzumab: summary of the scientific assessment of the European medicines agency committee for medicinal products for human use

On April 19, 2010, the European Commission issued a conditional marketing authorization valid throughout the European Union (EU) for ofatumumab (Arzerra®; Glaxo Group Ltd, Greenford, Middlesex, U.K.). The decision was based on the favorable opinion of the Committee for Medicinal Products for Human Use recommending a conditional marketing authorization for ofatumumab for the treatment of chronic lymphocytic leukemia (CLL) in patients refractory to fludarabine and alemtuzumab. A conditional marketing authorization means that additional data to confirm the benefit-risk balance of ofatumumab are awaited. The active substance of Arzerra® is ofatumumab, a monoclonal antibody medicinal product (ATC code L01XC10). The recommended dose is 300 mg of atumumab for the first infusion and 2,000 mg of atumumab for all subsequent infusions. The infusion schedule is eight consecutive weekly infusions, followed 4-5 weeks later by four consecutive monthly (i.e., every 4 weeks) infusions. Ofatumumab targets CD20, a cell surface marker of B lymphocytes, which is followed by cell lysis via complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity. The benefit of ofatumumab is the control of CLL in patients who are refractory to both fludarabine and alemtuzumab, which was indicated by a high response rate. The most common side effects are infections and infusion reactions. The objective of this paper is to summarize the scientific review of the application leading to approval in the EU. The detailed scientific assessment report and product information, including the summary of product characteristics, are available on the EMA website (http://www.ema.europa.eu).

New drugs for aggressive B-cell and T-cell lymphomas

Over the past decade an unprecedented number of new drugs for lymphomas have been developed. Most of these new drugs target molecules or pathways that are important for the growth and proliferation of lymphomas. The introduction of the B-lymphoma specific monoclonal anti-CD20 antibody, rituximab, has improved the prognosis of patients with B-cell lymphomas more than any other drug in the past 50 years; today less than half of the patients with aggressive B-cell lymphomas die of their disease than in the pre-rituximab era. Many new drugs are now available for clinical testing in addition to new CD20 antibodies and antibodies directed against other surface molecules specifically or preferentially expressed on the lymphoma-cell surface. A prerequisite for the development of these drugs was the recognition of aberrant cell-signal transduction involved in lymphoma pathogenesis and progression. New therapeutic targets include receptor tyrosine and cyclin-dependent kinases, histone deacetylases, and molecules involved in the regulation of apoptosis. The definition of the role of these new drugs alone or in combination with established chemotherapy regimens in adequately designed prospective trials represents one of the major challenges in clinical lymphoma research.

A complement-dependent cytotoxicity-enhancing anti-CD20 antibody mediating potent antitumor activity in the humanized NOD/Shi-scid, IL-2Rγ(null) mouse lymphoma model

Engineering the Fc region of monoclonal antibodies (mAb) in order to enhance effector functions such as antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity (CDC) is likely to a be promising approach for next-generation mAb therapy. Here, we report on such an antibody, 113F, a novel CDC-enhancing variant of rituximab, and determine the tumor-associated factors influencing susceptibility to 113F-induced CDC. The latter included the quantity of complement inhibitors present, such as CD55 and CD59. We report that compared to rituximab, 113F mediated highly enhanced CDC against primary CD20-expressing lymphoma cells in vitro. Currently, a major problem in the field of immunotherapy research is the lack of suitable small animal models to evaluate human CDC in vivo. Therefore, we established a novel human tumor-bearing NOD/Shi-scid, IL-2Rγ(null) mouse model, in which human complement functions as the CDC mediator. We demonstrated that rituximab exerted significant antitumor effects via human CDC in this humanized mouse. The finding of specific localization of human C1q on CD20-expressing tumor cell membranes was consistent with the observation that human CDC indeed contributed to the antitumor effect in this model. Moreover, 113F exerted significantly more potent antitumor effects than rituximab in this in vivo model. The detection of more abundant dense signals from C1q using 113F compared to rituximab was consistent with the concept that this reagent represented a CDC-enhancing mAb. In the near future, the efficacy of this type of CDC-enhancing antibody will be determined in clinical trials in humans.

γδ T-cell killing of primary follicular lymphoma cells is dramatically potentiated by GA101, a type II glycoengineered anti-CD20 monoclonal antibody

BACKGROUND

Anti-CD20 monoclonal antibodies are major therapeutic agents for patients with follicular lymphoma and work through complement-mediated cytotoxicity and antibody-dependent cellular cytotoxicity. Optimization of antibody-dependent cellular cytotoxicity, in particular by amplifying its effectors, could further increase the efficacy of anti-CD20 monoclonal antibodies.

DESIGN AND METHODS

We investigated the cytotoxic activity of Vγ9Vδ2 T cells against follicular lymphoma cells and whether this killing could be increased by promoting antibody-dependent cellular cytotoxicity with anti-CD20 monoclonal antibodies, in particular a type-II glycoengineered anti-CD20. Vγ9Vδ2 T cells were expanded in vitro in the presence of bromohydrin pyrophosphate (Phosphostim) and interleukin-2 and their ability to kill follicular lymphoma primary cells or cell lines was evaluated by flow cytometry cytotoxic T-lymphocyte assays in the presence or absence of three anti-CD20 monoclonal antibodies: the afucosylated GA101, the chimeric rituximab or the humanized ofatumumab. The ability of these cells to release perforin/granzyme and secrete interferon-γ when co-cultured with follicular lymphoma primary cells or cell lines in the presence or not of the three anti-CD20 monoclonal antibodies was also evaluated by CD107a staining and Elispot assays.

RESULTS

Phosphostim and interleukin-2 expanded Vγ9Vδ2 T cells were cytotoxic to primary follicular lymphoma cells and their cytotoxic potential was dramatically increased by GA101, a type II glycoengineered anti-CD20 monoclonal antibody, and to a lesser extent, by rituximab and ofatumumab. The increased cytotoxicity was associated with increased secretion of perforin/granzyme and interferon-γ.

CONCLUSIONS

In-vitro expanded Vγ9Vδ2 T cells efficiently kill primary follicular lymphoma cells and express CD16; anti-CD20 monoclonal antibodies, in particular GA101, dramatically increase the cytotoxic activity of expanded Vγ9Vδ2 T cells. These preclinical results prompt the development of clinical trials using this antibody dependent cellular cytotoxicity property of Vγ9Vδ2 T cells and anti-CD20 monoclonal antibodies.

The clinical application of monoclonal antibodies in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) represents the most prevalent adult leukemia. Treatment with chemotherapy over the past 3 decades has been palliative. The introduction of therapeutic antibodies has increased the number of treatment options for this disease. Despite this increase, our true understanding of the mechanism of action of antibody therapy in CLL remains limited. Rituximab, a CD20 antibody, is currently widely used in combination-based strategies for both previously untreated symptomatic CLL and as salvage therapy. Recent data suggest that the addition of rituximab to fludarabine with or without cyclophosphamide prolongs survival in younger patients with CLL. Other improved CD20 antibodies with promising clinical activity, including ofatumumab and GA-101, are coming forward. Alemtuzumab, a CD52 antibody, likewise has demonstrated benefit in both symptomatic, previously untreated CLL and in patients with relapsed disease but has less selectivity. Development of other therapeutic antibodies targeting alternative B-cell-specific antigens in CLL has been less successful, although many promising candidate antibodies and/or small modular immune pharmaceuticals (SMIPs) are coming forward. In addition, recent efforts to combine currently applied therapeutic antibodies with other biologic and targeted therapies with efficacy in CLL offers the potential to move toward alternative non-chemotherapy-based treatment approaches.

Refractory chronic lymphocytic leukemia--new therapeutic strategies

Treatment outcome of chronic lymphocytic leukemia (CLL) has considerably improved since the introduction of fludarabine (F) as part of the standard therapy. Nevertheless, refractoriness to fludarabine occurs in a significant number of patients and is associated with an unfavorable prognosis. Important risk factors are 17p deletion and/or mutation of TP53. For this subgroup the CD52 antibody alemtuzumab (A) presents a new treatment approach and has already been approved. Meanwhile we have to face also refractoriness to alemtuzumab. Importantly, the monoclonal CD20 antibody ofatumumab has now shown efficacy in F and A double-refractory CLL. The next generation CD20 antibody GA-101 is currently compared to rituximab (R) and will possibly be its more potent successor. Further B-cell antigens are targeted by lumiliximab (CD23), TRU-016 (CD37) and blinatumomab (CD19). Apart from monoclonal antibody therapies, a great number of small molecules are examined for the treatment of refractory and relapsed CLL. Most of these agents aim to overcome apoptosis resistance in CLL cells or influence the microenvironment. Typical targets are regulators of the cell cycle and antiapoptotic molecules like the members of the Bcl-2 family. Up to now the most promising agents appear to be flavopiridol and lenalidomide among others.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT). Treatment options for relapse have been inadequate, and the majority of patients ultimately die of their disease. There is no standard approach to treating relapse after alloHSCT. Withdrawal of immune suppression and donor lymphocyte infusions are commonly used for all diseases; although these interventions are remarkably effective for relapsed chronic myelogenous leukemia, they have limited efficacy in other hematologic malignancies. Conventional and novel chemotherapy, monoclonal antibody therapy, targeted therapies, and second transplants have been utilized in a variety of relapsed diseases, but reports on these therapies are generally anecdotal and retrospective. As such, there is an immediate need for well-designed, disease-specific trials for treatment of relapse after alloHSCT. This report summarizes current treatment options under investigation for relapse after alloHSCT in a disease-specific manner. In addition, recommendations are provided for specific areas of research necessary in the treatment of relapse after alloHSCT.

The Role of Monoclonal Antibodies in the Management of Leukemia

This article will review the monoclonal antibodies more commonly used in leukemias. In the last three decades, scientists have made considerable progress understanding the structure and the functions of various surface antigens, such as CD20, CD33. The introduction of rituximab, an anti CD20 monoclonal antibody, had a great impact in the treatment of lymphoproliferative disorders. Gemtuzumab, an anti CD 33 conjugated monoclonal antibody has activity in acute mylegenous leukemia (AML). As this field is undergoing a rapid growth, the years will see an increasing use of monoclonal antibodies in hematological malignancies.