What is the optimal initial treatment for chronic lymphocytic leukemia?

For decades, initial therapy for chronic lymphocytic leukemia (CLL) consisted of alkylators such as chlorambucil (Leukeran). The introduction of nucleoside analogs such as fludarabine and monoclonal antibodies such as rituximab (Rituxan) markedly changed the initial therapy of CLL, particularly in the United States. Fludarabine and combination regimens such as fludarabine/cyclophosphamide (FC) have achieved higher complete response (CR) rates and progression-free survival (PFS) than chlorambucil in previously untreated CLL, but long-term overall survival has not improved, due to concurrent improvement in salvage therapy of relapsed CLL patients. Upfront chemoimmunotherapy regimens such as fludarabine/rituximab (FR) and fludarabine/cyclophosphamide/rituximab (FCR) have similarly improved CR rates and PFS in previously untreated CLL patients, but it is unclear whether overall survival is improved. Advances in cytogenetic analysis and other biologic prognostic factors have greatly enhanced clinicians' ability to risk-stratify newly diagnosed CLL patients, and knowledge of such prognostic factors is necessary to properly interpret results of clinical treatment studies. The choice of initial therapy for an individual patient should depend upon the patient's age and medical condition, cytogenetic and other prognostic factors, and whether the goal of therapy is maximization of CR and PFS or palliation of symptoms with minimal toxicity.     

New agents in chronic lymphocytic leukemia

Opinion statement For many years, alkylating agents, especially chlorambucil, have been considered the drugs of choice for first-line treatment of progressive and symptomatic chronic lymphocytic leukemia (CLL). More recently, treatment approaches have included purine nucleoside analogs (PNAs), fludarabine or cladribine (2-CdA), and monoclonal anti-bodies (MoAbs). PNAs are highly active in patients with CLL, previously treated and untreated. Significantly higher overall response and complete response in patients treated initially with fludarabine or 2-CdA than in those treated with chlorambucil- or cyclophosphamide-based combination regimens have been recently confirmed in prospective, randomized trials. However, the median survival times do not differ among the patients treated with PNA and alkylating agents. The MoAbs directed against CD52 antigen (alemtuzumab) and CD20 antigen (rituximab) also demonstrate significant activity in CLL and should be used in patients with disease that is refrac-tory to PNAs. Combination therapies with PNAs and cyclophosphamide, and especially with rituximab, are more active than monotherapy with PNAs in regard to response rate and possible survival. Because most patients are older and there is no survival time advantage for alkylating agents or PNA therapies, we recommend chlorambucil as the first-line treatment, with PNAs for consideration as the second-line therapy. PNAs alone or in combination with cyclophosphamide and rituximab as first-line treatment are an option in younger patients, who may be candidates for consolidation therapy with alemtuzumab and/or stem cell transplantation. Alemtuzumab may be an effective treatment for patients refractory to PNAs. Several biological parameters have been gaining increasing importance to evaluate the prognosis of patients with CLL and define optimal therapeutic strategy. Moreover, novel therapies are being evalu-ated, especially in patients refractory to PNAs, including those targeting the anti-apoptotic bcl-2 family of proteins and receptors, vaccines, and allogenic stem cell transplantation, especially after nonmyeloablative chemotherapy.     

Combination therapy with fludarabine and rituximab followed by alemtuzumab in the first-line treatment of patients with chronic lymphocytic leukemia or small lymphocytic lymphoma: a phase 2 trial of the Minnie Pearl Cancer Research Network

BACKGROUND: The purpose of the current study was to evaluate the efficacy and toxicity of the combination of fludarabine and rituximab, followed by alemtuzumab, as first-line treatment for patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). METHODS: In a nonrandomized phase 2 trial, 41 patients who had previously untreated CLL or SLL and required treatment received 4 cycles of the fludarabine and rituximab combination followed 5 weeks later by 4 weeks (12 doses) of intravenous alemtuzumab therapy. The response to treatment was evaluated after completion of treatment with fludarabine and rituximab, and again after the completion of alemtuzumab consolidation. RESULTS: Initial treatment with the combination of fludarabine and rituximab was well tolerated, and produced a 71% overall response rate (13% complete response). Thirty-four patients began treatment with intravenous alemtuzumab, but this drug was relatively poorly tolerated when given at a short interval after fludarabine and rituximab, and only 20 patients (49% of total) were able to complete the prescribed course. Five patients had an improvement in their response with alemtuzumab; the final complete response rate was 21%. The median progression-free survival for the entire group was 42 months. Toxicity with alemtuzumab included infusion-related toxicity, myelosuppression, and opportunistic infections. CONCLUSIONS: The intravenous schedule of alemtuzumab employed in the trial was relatively poorly tolerated in this community-based trial. The relatively low complete response rates after treatment with the combination of fludarabine and rituximab and after the completion of treatment suggest that these abbreviated courses may compromise efficacy. The generalized use of alemtuzumab as consolidation therapy cannot yet be recommended for community practice. However, optimization of the route of administration, duration of treatment, and interval after completion of induction therapy may improve efficacy, and further investigation is ongoing.     

Role of CD20 Monoclonal Antibodies in Previously Untreated Chronic Lymphocytic Leukemia

Monoclonal antibodies (MoAbs) directed against the CD20 antigen on B cells have dramatically altered the treatment landscape for patients with chronic lymphocytic leukemia (CLL). Rituximab, a chimeric mouse/human MoAb, was the first antibody to be approved for the treatment of indolent B-cell lymphomas. Although single-agent, standard-dose rituximab has limited activity as first-line therapy for patients with CLL, it has synergistic therapeutic activity when combined with chemotherapy. Indeed, chemoimmunotherapy with combined fludarabine (F), cyclophosphamide (C), and rituximab was shown to improve both progression-free and overall survival in a randomized phase III clinical trial compared with FC in previously untreated patients with CLL. In this article, we review important clinical trials that have incorporated rituximab with other agents for treatment-naive patients with CLL. We also highlight second- and third-generation CD20 MoAbs approved or in development for the treatment of CLL.     

Ofatumumab: a new CD20 monoclonal antibody therapy for B-cell chronic lymphocytic leukemia

Though most patients with chronic lymphocytic leukemia (CLL) respond to first-line therapy, all patients eventually relapse, after which therapeutic options are limited. Fludarabine-refractory patients have a particularly poor prognosis. The addition of the CD20 monoclonal antibody (MoAb) rituximab to chemotherapy in CLL has improved outcomes, particularly in early lines of therapy; however, the efficacy of rituximab monotherapy in CLL is limited, potentially in part because of reduced cell lysis via complement-dependent cytotoxicity (CDC) in this setting. Rituximab CDC is dependent on CD20 expression; CLL cells underexpress CD20. Ofatumumab is a human MoAb that targets an epitope encompassing the membrane-proximal small-loop on the CD20 molecule, which differs from the binding location of rituximab. In vitro studies with ofatumumab have demonstrated that it is significantly more effective than rituximab at corresponding dose levels at lysing CLL cells and B-cell lines, especially those with low CD20 copy numbers. In patients with CLL refractory to both fludarabine and alemtuzumab or refractory to fludarabine with bulky lymphadenopathy and, therefore, less suitable for treatment with the CD52 MoAb alemtuzumab, results from the planned interim analysis showed an encouraging response rate with ofatumumab (Independent Endpoint Review Committee evaluated) and survival parameters, which seemed to be higher than those reported from a historical assessment of other salvage therapies in a corresponding group of patients. Ofatumumab was also well tolerated; the most common adverse events were transient grade 1 or 2 infusion reactions and infections. Ongoing trials will help confirm the role of ofatumumab in CLL, in addition to the effect of this agent in combination with chemotherapies and other MoAbs.     

Recent progress in the management of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a clonal disease characterized by proliferation and accumulation of small CD5-positive B cells. More than 50% of patients are asymptomatic at diagnosis and usually require no treatment. However, treatment is needed in the advanced and progressive disease. Chlorambucil with or without steroids has been the drug of choice for many years in previously untreated patients with CLL. The purine nucleoside analogs (PNAs), fludarabine (FA), cladribine (2-CdA-chlorodeoxyadenosine) and pentostatin (DCF, 2'-deoxycoformycin) also have been introduced for treatment of CLL. Significantly higher overall response (OR) and complete response (CR) and longer progression free survival (PFS) in patients with CLL treated with FA or 2-CdA have been confirmed in randomized, multicenter trials and more recently in meta-analysis. However, the median survival time did not differ between patients treated with PNA and alkylating agents. Combination therapies with PNAs and cyclophosphamide and especially with cyclophosphamide and rituximab are more active than monotherapy in terms of OR, CR and PFS. Several reports have shown significant activity of alemtuzumab in previously untreated and pretreated patients even when refractory to FA. Alemtuzumab also can be used in CLL as a preparative regimen before stem cell transplantation (SCT) and to eliminate minimal residual disease (MRD). Recently, several new agents have shown promise in treating CLL, including new monoclonal antibodies, agents targeting bcl-2 family of proteins, antisense oligonucleotides and other agents. Moreover, autologous and allogenic hematopoietic cell transplantations are increasingly considered for treatment of patients with CLL. In this review current therapeutic strategies in CLL are presented.     

Alemtuzumab (Campath-1H) in the treatment of chronic lymphocytic leukemia

Alemtuzumab (Campath-1H) is a humanized IgG1 monoclonal antibody that targets the human CD52 antigen. CD52 is expressed by a variety of lymphoid neoplasms and most human mononuclear cell subsets. In 2001, alemtuzumab was approved for marketing in the United States and Europe for use in patients with fludarabine-refractory chronic lymphocytic leukemia (CLL). In heavily pretreated patients with CLL, the overall response rate (ORR) is approximately 35%, and in previously untreated patients the ORR is greater than 80%, with a recent randomized study suggesting it is superior to alkylator-based therapy. Importantly, alemtuzumab is effective in patients with high-risk del(17p13.1) and del(11q22.3) CLL. Alemtuzumab combination studies with fludarabine and/or monoclonal antibodies such as rituximab have demonstrated promising results. Alemtuzumab is also being studied in CLL patients as consolidation therapy for treatment of minimal residual disease, in preparation for stem cell transplantation and to prevent acute and chronic graft versus host disease. Alemtuzumab is frequently associated with acute 'first-dose' reactions when administered intravenously, but is much better tolerated when administered subcutaneously without loss of therapeutic efficacy. Additional potential adverse events associated with alemtuzumab administration include myelosuppression as well as profound cellular immune dysfunction with the associated risk of viral reactivation and other opportunistic infections. Additional studies detailing the mechanism of action of alemtuzumab as well as new strategies for prevention of opportunistic infections will aid in the future therapeutic development of this agent.     

Treatment of fludarabine‐refractory chronic lymphocytic leukemia

The development of resistance to purine analogs defines a poor‐risk subset of patients with chronic lymphocytic leukemia (CLL). Although in recent years chemoimmunotherapeutic combinations such as fludarabine, cyclophosphamide, and rituximab have induced response rates of 95% in previously untreated patients and increased the rates of failure‐free survival, CLL remains incurable for many patients because of a lack of disease response or the development of refractoriness to fludarabine. Fludarabine‐refractory disease is defined as CLL that does not respond to fludarabine or that recurs within 6 months of treatment with a fludarabine‐containing regimen. The natural course of the disease is associated with poor survival. Salvage therapeutic strategies include alemtuzumab‐containing regimens, targeted agents, and allogeneic stem cell transplantation. Single‐agent alemtuzumab induces response in up to 40% of patients with fludarabine‐refractory CLL, but responses are not durable, and the median survival is approximately 1 to 2 years. Alemtuzumab is also combined with fludarabine, cyclophosphamide, and/or rituximab, and other agents such as lenalidomide and flavopiridol, as well as targeted agents, and used in fludarabine‐refractory CLL. Cumulative evidence suggests that allogeneic stem cell transplantation is an efficacious therapeutic strategy for patients who do not respond to fludarabine or who develop disease recurrence within 12 months after purine analog treatment. In conclusion, chemoimmunotherapy regimens that include alemtuzumab and/or rituximab and allogeneic stem cell transplantation improve the prognosis of this disease, but there is a continued need for novel, more effective therapies. Cancer 2009. © 2009 American Cancer Society.     

Chronic lymphocytic leukemia

Opinion statement Historically, treatment of chronic lymphocytic leukemia (CLL) essentially had been palliative. During the past two decades, effective new therapies for the treatment of CLL have emerged. The advent of fludarabine, a purine analog with activity against chlorambucil-resistant CLL, showed promising results with high response rates in previously untreated patients. These improvements in response and delays in disease progression have not translated into a survival benefit, indicating that chlorambucil may be the preferred first-line therapy when treatment is indicated. Allogeneic hematopoietic stem cell transplantation, by combining the cytoreductive effects of conditioning with a potent graft-versus-tumor effect, is the only treatment modality with the prospect of cure for patients with CLL. However, conventional hematopoietic stem cell transplantation can be offered only to select patients with CLL because of older age and comorbid conditions. Novel methods of transplantation exploiting the graft-versus-leukemia effect while reducing the toxicity of the pretransplant conditioning are promising approaches that may enable more patients to benefit from this therapy. Monoclonal antibodies such as rituximab or alemtuzumab (Campath-1H; llex Pharmaceuticals, San Antonio, TX) are agents with activity in untreated and resistant CLL. Efforts are being focused on combining these monoclonal antibodies with chemotherapy and the development of rationally designed drugs.     

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.     

Antik?rpertherapie bei malignem Lymphom

The availability of monoclonal antibodies has revolutionized the therapy of malignant lymphoma. By adding rituximab to the therapeutic arsenal, response rates, progression-free survival and even overall survival could be improved for several lymphoma entities. Ritxuimab is used as part of induction and maintenance therapy as well as in the relapse situation for follicular lymphoma, mantle cell lymphoma, diffuse large B cell lymphoma and chronic lymphocytic leukemia (CLL). The successors, ofatumumab and obinutuzumab are currently being tested in clinical trials. Other antibodies target CD22, CD52 and CD80. The CD52 targeting antibody alemtuzumab is approved for fludarabine refractory CLL by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) and is also effective in patients with high risk cytogenetics. Apart from conventional antibodies, the bispecific T-cell engager (BiTE) single-chain variable fragments (scFv) antibody blinatumomab is currently being tested in clinical trials. This review gives an overview of antibody therapy for malignant lymphoma.     

Evolving Strategies for the Treatment of Chronic Lymphocytic Leukemia in the Upfront Setting

Chronic lymphocytic leukemia (CLL) is a disease of marked clinical heterogeneity, and while some patients have a normal life expectancy, others develop rapidly progressive disease shortly after diagnosis. The current standard for upfront treatment of CLL is chemoimmunotherapy for younger fit patients, FCR (fludarabine, cyclophosphamide, and rituximab) being the prototype. For older patients, BR (bendamustine and rituximab) exhibits excellent activity with decreased toxicity. For the frailest patients, CD20 monoclonal antibodies with or without chlorambucil have proven to be efficacious. The novel oral kinase inhibitors ibrutinib and idelalisib are FDA-approved in the relapsed/refractory setting, and ibrutinib is approved upfront for those with del(17p). These drugs have produced long-term durable responses in the relapsed/refractory setting, and studies are underway using these as single agent upfront or in combination with both chemotherapy and monoclonal antibodies. Here, we review standard upfront therapies and new agents and combinations that are on the horizon for CLL.     

Monoclonal antibodies in the treatment of chronic lymphocytic leukemia

Traditional therapy for chronic lymphocytic leukemia (CLL) has consisted of alkylating agents, purine analogs, or a combination of these drugs. These agents are effective at producing remissions but are not curative. Thus, new drugs are still needed to improve the outcome of patients with CLL. The introduction of monoclonal antibodies, such as rituximab and alemtuzumab, provides a novel therapeutic modality. Rituximab is an active agent in CLL. Standard doses of rituximab result in higher response rates in previously untreated than in relapsed patients but low complete response (CR) rates. Rituximab is most effective in combination with chemotherapy, especially fludarabine-based regimens in the first-line and salvage setting. Rituximab is also useful in the treatment of complications of CLL, such as pure red cell aplasia, autoimmune thrombocytopenia, and autoimmune hemolytic anemia. Alemtuzumab has impressive activity in patients with refractory CLL and may play an important role in the consolidation treatment of CLL. Alemtuzumab is most efficacious at clearing disease in the peripheral blood and bone marrow. Bulky lymphadenopathy is less sensitive to therapy. Because of the significant lymphopenia associated with alemtuzumab, antibacterial and antiviral prophylaxis should always be used.     

The role of fludarabine in the treatment of follicular and mantle cell lymphoma

Advanced-stage follicular lymphoma (FL) and mantle cell lymphoma (MCL) cannot be cured using conventional chemotherapy. Fludarabine, the most widely used purine analog, exhibits a particularly high level of activity against small lymphocytic lymphoma and chronic lymphocytic leukemia (CLL). Numerous studies have investigated the efficacy of fludarabine as a single agent or in combination with other cytostatic compounds in the treatment of FL and MCL. Hematologic toxicity is the most commonly observed adverse event in patients treated with fludarabine, but serious infectious complications are relatively rare. Fludarabine monotherapy has proven to be particularly effective in the treatment of FL; however, complete responses (CRs) are observed in only approximately 20-40% of all cases. In contrast, combinations containing fludarabine and anthracyclines or alkylating agents have yielded superior response rates and longer periods of progression-free survival (PFS), and the addition of the anti-CD20 antibody rituximab appears to yield even better results. In a randomized trial, an immunochemotherapy regimen consisting of a fludarabine-containing combination and rituximab resulted in superior remission and survival rates compared with the fludarabine-containing combination alone. In summary, fludarabine has proven to be a safe and effective agent in the treatment of indolent lymphoma. In particular, combinations containing fludarabine, anthracyclines and/or alkylating agents, and rituximab have yielded remarkable CR and PFS rates. Consequently, current research efforts have focused on the use of fludarabine-containing combinations in the first-line treatment of FL and MCL.     

Targeted therapy for chronic lymphocytic leukemia

The introduction of targeted agents such as the monoclonal antibodies rituximab (anti-CD20) and alemtuzumab (anti-CD52) has brought about a remarkable change in the therapy of chronic lymphocytic leukemia (CLL). Although it is unclear whether overall survival has been improved, the incorporation of these monoclonal antibodies into chemoimmunotherapy regimens has dramatically improved complete response rates and progression-free survival in patients with both newly-diagnosed and relapsed CLL. The success of rituximab and alemtuzumab has spurred the development of other monoclonal antibodies targeting distinct proteins and epitopes on the surface of CLL cells and an exciting array of novel immunotherapeutics. The judicious use of these agents provides the opportunity to develop risk-adapted therapeutic strategies to optimize responses and quality of life in patients with CLL.     

Refractory Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a common malignancy often managed by the practicing oncologist rather than at a tertiary referral center. Since no standard treatment has been shown to be curative, patients are frequently observed without treatment for many years. In the past, first-line therapy with an alkylating agent, particularly chlorambucil, was standard when treatment became necessary. Because of its superior activity in achieving remission and extending the time to relapse and disease progression compared with alkylating agents, the purine nucleoside analog fludarabine is now commonly used as first-line treatment. Historically, salvage treatment with combination chemotherapy included an alkylating agent, anthracycline, vinca alkyloid, and/or corticosteroid. Currently, salvage regimens often incorporate a purine nucleoside analog and an alkylating agent. Two monoclonal antibodies, rituximab and alemtuzumab, have become available and have made further advances in both first-line and salvage treatment of patients with CLL. In this article we review the agents and regimens that have been studied as salvage treatment of CLL. With the development of purine nucleoside analogs and monoclonal antibodies, incremental progress has been made in the therapy of previously treated patients with CLL. Newer strategies will aim to further improve the complete remission rate, which may have a positive impact on survival.     

Screening and early diagnosis in lung cancer

Over the last few years, several monoclonal antibodies have been investigated in patients with B-cell lymphoid malignancies. Rituximab is the most important monoclonal antibody of clinical value in these disorders. Rituximab is an IgG1 chimeric antibody containing murine light- and heavy-chain variable region sequences and human constant region sequences. Since approval in 1997, rituximab has become the standard of care in follicular B-cell lymphoma, chronic lymphocytic leukemia (CLL) and aggressive lymphoma when combined with chemotherapy. Higher clinical benefits of rituximab can be seen in patients with CLL when it is added to other chemotherapeutic agents. Several recent reports have suggested that in patients with CLL, rituximab combined with purine nucleoside analogs (PNAs) or PNAs and cyclophosphamide may improve the results with acceptable toxicity, both in previously untreated and refractory/relapsed patients. The randomized, multinational Phase III study (REACH trial) has shown that rituximab combined with fludarabine and cyclophosphamide (R-FC regimen) results in 10 months longer progression-free survival, and higher overall response and complete response rates than fludarabine and cyclophosphamide (FC regimen) in previously treated patients. The German CLL study group initiated a multicenter, multinational Phase III trial, CLL8, to evaluate the efficacy and tolerability of R-FC versus FC for the first-line treatment of patients with advanced CLL. The overall response rate was significantly higher in the R-FC arm (95%) compared with FC (88%). The complete response rate in the R-FC arm was 44% compared with 27% in the FC arm. The recently updated analysis has demonstrated longer overall survival in the R-FC group. Recent clinical observations have revealed that combinations of rituximab with pentostatin and cyclophosphamide, or cladribine and cyclophosphamide are also highly active regimens in previously untreated CLL. In addition, the results of treatment with high-dose methylprednisolone in combination with rituximab in advanced CLL resistant to fludarabine have been reported recently by several groups. However, available therapies are only partially effective in CLL, exposing an obvious need to develop new, more specific and active drugs. Recently, several new anti-CD20 monoclonal antibodies have been developed and are now being evaluated in clinical trials.     

Rituximab plus fludarabine and cyclophosphamide or other agents in chronic lymphocytic leukemia

Over the last few years, several monoclonal antibodies have been investigated in patients with B-cell lymphoid malignancies. Rituximab is the most important monoclonal antibody of clinical value in these disorders. Rituximab is an IgG1 chimeric antibody containing murine light- and heavy-chain variable region sequences and human constant region sequences. Since approval in 1997, rituximab has become the standard of care in follicular B-cell lymphoma, chronic lymphocytic leukemia (CLL) and aggressive lymphoma when combined with chemotherapy. Higher clinical benefits of rituximab can be seen in patients with CLL when it is added to other chemotherapeutic agents. Several recent reports have suggested that in patients with CLL, rituximab combined with purine nucleoside analogs (PNAs) or PNAs and cyclophosphamide may improve the results with acceptable toxicity, both in previously untreated and refractory/relapsed patients. The randomized, multinational Phase III study (REACH trial) has shown that rituximab combined with fludarabine and cyclophosphamide (R-FC regimen) results in 10 months longer progression-free survival, and higher overall response and complete response rates than fludarabine and cyclophosphamide (FC regimen) in previously treated patients. The German CLL study group initiated a multicenter, multinational Phase III trial, CLL8, to evaluate the efficacy and tolerability of R-FC versus FC for the first-line treatment of patients with advanced CLL. The overall response rate was significantly higher in the R-FC arm (95%) compared with FC (88%). The complete response rate in the R-FC arm was 44% compared with 27% in the FC arm. The recently updated analysis has demonstrated longer overall survival in the R-FC group. Recent clinical observations have revealed that combinations of rituximab with pentostatin and cyclophosphamide, or cladribine and cyclophosphamide are also highly active regimens in previously untreated CLL. In addition, the results of treatment with high-dose methylprednisolone in combination with rituximab in advanced CLL resistant to fludarabine have been reported recently by several groups. However, available therapies are only partially effective in CLL, exposing an obvious need to develop new, more specific and active drugs. Recently, several new anti-CD20 monoclonal antibodies have been developed and are now being evaluated in clinical trials.     

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.     

Monoclonal antibodies in the treatment of chronic lymphoid leukemias

In recent years preclinical and clinical studies have been undertaken with selected monoclonal antibodies (MoAbs) either alone or coniugated to toxins in patients with several lymphoid malignancies, including chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL) and hairy cell leukemia (HCL). Two MoAbs, directed against CD20 antigen (Rituximab, RIT) and CD52 antigen (Campath-1H, alemtuzumab, ALT) demonstrate significant activity in CLL. The most notable success to data has been achieved with ALT, both in previously treated and untreated patients with CLL. ALT is a humanized rat IgG1 antibody that binds to the cell membrane of virtually all normal as well as malignant lymphocytes. In the vast majority of CLL patients ALT causes constant reduction of abnormal blood lymphocytes, usually in less than 4 weeks, and disappearance of CD5/CD19 co-expression cells from blood. The regression of lymphoid infiltration from other sites is less clear. ALT is also highly active in patients with CLL in progression, even refractory to fludarabine (FA). Hematological toxicity, especially long-lasting lymphocytopenia, was noted in the majority of patients. The most important clinical side effects of ALT treatment were infections, mainly herpes simplex virus and cytomegalovirus reactivation. RIT is also active in CLL in conventional doses. However some studies suggest that higher doses are more effective than standard doses, used routinely in other lymphoid malignancies. The activity of ALT and RIT in CLL patients resistant to FA and their synergistic interactions with cytotoxic drugs suggests that a combination of these agents may lead to further progress in the treatment of this disease. The T-cell variant of PLL has demonstrated impressive responses to ALT in several trials even if the patients were refractory to deoxycoformycin (DCF) and other agents. However, this MoAb is not curative, because all patients eventually relapsed. Consequently, treatment with ALT may need to be associated with stem cell transplantation to consolidate and maintain long-term remissions. Recently anti-CD22 and anti-CD25 immunotoxins have been investigated in purine analogues refractory or relapsed HCL. The presented results indicate that these agents are highly active and well tolerated even if the patients were resistant to 2-CdA or DCF.