Anti-CD20-based therapy of B cell lymphoma: state of the art

The interaction of innate immune and adaptive immune system

The innate immune system serves as the body's first line of defense, utilizing pattern recognition receptors like Toll-like receptors to detect pathogens and initiate rapid response mechanisms. Following this initial response, adaptive immunity provides highly specific and sustained killing of pathogens via B cells, T cells, and antibodies. Traditionally, it has been assumed that innate immunity activates adaptive immunity; however, recent studies have revealed more complex interactions. This review provides a detailed dissection of the composition and function of the innate and adaptive immune systems, emphasizing their synergistic roles in physiological and pathological contexts, providing new insights into the link between these two forms of immunity. Precise regulation of both immune systems at the same time is more beneficial in the fight against immune-related diseases, for example, the cGAS-STING pathway has been found to play an important role in infections and cancers. In addition, this paper summarizes the challenges and future directions in the field of immunity, including the latest single-cell sequencing technologies, CAR-T cell therapy, and immune checkpoint inhibitors. By summarizing these developments, this review aims to enhance our understanding of the complexity interactions between innate and adaptive immunity and provides new perspectives in understanding the immune system.

Myasthenia gravis: the changing treatment landscape in the era of molecular therapies

Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junction, leading to muscle weakness and fatigue. MG is caused by antibodies against the acetylcholine receptor (AChR), the muscle-specific kinase (MuSK) or other AChR-related proteins that are expressed in the postsynaptic muscle membrane. The standard therapeutic approach for MG has relied on acetylcholinesterase inhibitors, corticosteroids and immunosuppressants, which have shown good efficacy in improving MG-related symptoms in most people with the disease; however, these therapies can carry a considerable burden of long-term adverse effects. Moreover, up to 15% of individuals with MG exhibit limited or no response to these standard therapies. The emergence of molecular therapies, including monoclonal antibodies, B cell-depleting agents and chimeric antigen receptor T cell-based therapies, has the potential to revolutionize the MG treatment landscape. This Review provides a comprehensive overview of the progress achieved in molecular therapies for MG associated with AChR antibodies and MuSK antibodies, elucidating both the challenges and the opportunities these therapies present to the field. The latest developments in MG treatment are described, exploring the potential for personalized medicine approaches.

Nanotechnological engineering of extracellular vesicles for the development of actively targeted hybrid nanodevices

Background

We propose an efficient method to modify B-cell derived EVs by loading them with a nanotherapeutic stimuli-responsive cargo and equipping them with antibodies for efficient targeting of lymphoma cells.

Results

The post-isolation engineering of the EVs is accomplished by a freeze–thaw method to load therapeutically-active zinc oxide nanocrystals (ZnO NCs), obtaining the so-called TrojanNanoHorse (TNH) to recall the biomimetism and cytotoxic potential of this novel nanoconstruct. TNHs are further modified at their surface with anti-CD20 monoclonal antibodies (TNH^CD20) achieving specific targeting against lymphoid cancer cell line. The in vitro characterization is carried out on CD20+ lymphoid Daudi cell line, CD20-negative cancerous myeloid cells (HL60) and the healthy counterpart (B lymphocytes). The TNH shows nanosized structure, high colloidal stability, even over time, and good hemocompatibility. The in vitro characterization shows the high biocompatibility, targeting specificity and cytotoxic capability. Importantly, the selectivity of TNH^CD20 demonstrates significantly higher interaction towards the target lymphoid Daudi cell line compared to the CD20-negative cancerous myeloid cells (HL60) and the healthy counterpart (lymphocytes). An enhanced cytotoxicity directed against Daudi cancer cells is demonstrated after the TNH^CD20 activation with high-energy ultrasound shock-waves (SW).

Conclusion

This work demonstrates the efficient re-engineering of EVs, derived from healthy cells, with inorganic nanoparticles and monoclonal antibodies. The obtained hybrid nanoconstructs can be on-demand activated by an external stimulation, here acoustic pressure waves, to exploit a cytotoxic effect conveyed by the ZnO NCs cargo against selected cancer cells.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00784-9.

Extracellular Vesicles Tropism: A Comparative Study between Passive Innate Tropism and the Active Engineered Targeting Capability of Lymphocyte-Derived EVs

Cellular communications take place thanks to a well-connected network of chemical–physical signals, biomolecules, growth factors, and vesicular messengers that travel inside or between cells. A deep knowledge of the extracellular vesicle (EV) system allows for a better understanding of the whole series of phenomena responsible for cell proliferation and death. To this purpose, here, a thorough immuno-phenotypic characterization of B-cell EV membranes is presented. Furthermore, the cellular membrane of B lymphocytes, Burkitt lymphoma, and human myeloid leukemic cells were characterized through cytofluorimetry assays and fluorescent microscopy analysis. Through cytotoxicity and internalization tests, the tropism of B lymphocyte-derived EVs was investigated toward the parental cell line and two different cancer cell lines. In this study, an innate capability of passive targeting of the native EVs was distinguished from the active targeting capability of monoclonal antibody-engineered EVs, able to selectively drive the vesicles, enhancing their internalization into the target cancer cells. In particular, the specific targeting ability of anti-CD20 engineered EVs towards Daudi cells, highly expressing CD20 marker on their cell membrane, was proved, while almost no internalization events were observed in HL60 cells, since they did not express an appreciable amount of the CD20 marker on their plasma membranes.

Current status and perspective of CAR-T and CAR-NK cell therapy trials in Germany

Chimeric antigen receptor (CAR)-T cell therapies are on the verge of becoming powerful immunotherapeutic tools for combating hematological diseases confronted with pressing medical needs. Lately, CAR-NK cell therapies have also come into focus as novel therapeutic options to address hurdles related to CAR-T cell therapies, such as therapy-induced side effects. Currently, more than 500 CAR-T and 17 CAR-NK cell trials are being conducted worldwide including the four CAR-T cell products Kymriah, Yescarta, Tecartus and Breyanzi, which are already available on the market. Most CAR-T cell-based gene therapy products that are under clinical evaluation consist of autologous enriched T cells, whereas CAR-NK cell-based approaches can be generated from allogeneic donors. Besides modification based on a second-generation CAR, more advanced CAR-immune cell therapeutics are being tested, which utilize precise insertion of genes to circumvent graft-versus-host disease (GvHD) or employ a dual targeting approach and adapter CARs in order to avoid therapy resistance caused by antigen loss. In this review, we are going to take a closer look at the commercial CAR-T cell therapies, as well as on CAR-T and CAR-NK cell products, which are currently under evaluation in clinical trials, that are being conducted in Germany.

CD20 as a gatekeeper of the resting state of human B cells

Worldwide about one million patients are given anti-CD20 antibodies such as rituximab (RTX) for the treatment of B cell-associated diseases. Despite the success of this first therapeutic antibody, little is known about the function of its target. The role of CD20 only becomes clear in the context of the nanoscale compartmentalization of the B lymphocyte membrane. We found that CD20 is an organizer of the IgD-class nanocluster on the B cell membrane. The loss of CD20 on human B cells results in a dissolution of the IgD-class nanocluster and a transient B cell activation inducing a B cell-to-PC differentiation. Thus, CD20 is an essential gatekeeper of a membrane nanodomain and the resting state of naive B cells.

CD20 is a B cell-specific membrane protein and represents an attractive target for therapeutic antibodies. Despite widespread usage of anti-CD20 antibodies for B cell depletion therapies, the biological function of their target remains unclear. Here, we demonstrate that CD20 controls the nanoscale organization of receptors on the surface of resting B lymphocytes. CRISPR/Cas9-mediated ablation of CD20 in resting B cells resulted in relocalization and interaction of the IgM-class B cell antigen receptor with the coreceptor CD19. This receptor rearrangement led to a transient activation of B cells, accompanied by the internalization of many B cell surface marker proteins. Reexpression of CD20 restored the expression of the B cell surface proteins and the resting state of Ramos B cells. Similarly, treatment of Ramos or naive human B cells with the anti-CD20 antibody rituximab induced nanoscale receptor rearrangements and transient B cell activation in vitro and in vivo. A departure from the resting B cell state followed by the loss of B cell identity of CD20-deficient Ramos B cells was accompanied by a PAX5 to BLIMP-1 transcriptional switch, metabolic reprogramming toward oxidative phosphorylation, and a shift toward plasma cell development. Thus, anti-CD20 engagement or the loss of CD20 disrupts membrane organization, profoundly altering the fate of human B cells.

Novel combination immunochemotherapy beyond CD20 for B-cell lymphomas

Despite substantially improved survival with rituximab-based treatment regimens, there is an unmet medical need for better treatments of B-cell lymphoma, particularly for patients with relapsed or refractory disease. Retreatment with rituximab exerts a limited effect in these patients, and platinum-based salvage treatment followed by autologous stem cell transplantation remains the only curative option. Recent strategies have focused on targeting novel B-cell surface markers, inhibiting B-cell receptor signaling, and enhancing the cytotoxicity of effector cells. The current article will review the recent progress in immunochemotherapy targeting other than CD20 for B-cell lymphomas.

Current Development of Monoclonal Antibodies in Cancer Therapy

Exploiting the unique specificity of monoclonal antibodies has revolutionized the treatment and diagnosis of haematological and solid organ malignancies; bringing benefit to millions of patients over the past decades. Recent achievements include conjugating antibodies with toxic payloads resulting in superior efficacy and/or reduced toxicity, development of molecular imaging techniques targeting specific antigens for use as predictive and prognostic biomarkers, the development of novel bi- and tri-specific antibodies to enhance therapeutic benefit and abrogate resistance and the success of immunotherapy agents. In this chapter, we review an overview of antibody structure and function relevant to cancer therapy and provide an overview of pivotal clinical trials which have led to regulatory approval of monoclonal antibodies in cancer treatment. We further discuss resistance mechanisms and the unique side effects of each class of antibody and provide an overview of emerging therapeutic agents.

Cardiovascular Adverse Events Complicating the Administration of Rituximab: Report of Two Cases

Rituximab is a murine/human chimeric monoclonal antibody directed against the CD20 antigen. It is widely used in combination with polychemotherapy regimens for the treatment of hematological disorders. There is no evidence of direct cardiotoxicity of the drug but a few cases of cardiovascular adverse events have been reported in the literature.

We report on two patients affected by stage IV non-Hodgkin lymphoma with bone marrow infiltration and peripheral blood involvement who experienced cardiovascular accidents temporally related to rituximab infusion. In both cases the monoclonal antibody was administered in association with a polychemotherapy regimen but administration was postponed several days later in order to avoid severe cytokine release syndrome because of the high tumor burden.

The first case concerns an episode of atrial fibrillation in a patient with a diagnosis of small B-cell lymphoma. The episode happened immediately after rituximab infusion. In the second case there was an episode of chest pain associated with fever and chills during rituximab infusion in a patient with a diagnosis of mantle cell lymphoma. In both cases we noticed an unusual correlation between symptom recurrence and the speed of rituximab infusion. Both patients presented several cardiovascular risk factors but preliminary cardiac function assessment excluded signs of heart dysfunction.

The pathogenesis of cardiovascular events during rituximab infusion remains unclear. A key role might be played by cytokine release from B cells as a consequence of rituximab activity. Moreover, pre-existing silent cardiac damage could be co-responsible for the clinical manifestations we reported.

We consider our clinical experience relevant because it raises an issue of good clinical practice: despite rituximab's good tolerability profile, patients with cardiovascular risk factors should undergo accurate cardiac assessment so that silent heart disease can be detected. If the suspicion of cardiac damage is high, more extensive cardiac assessment is recommended.

Theranostic Radiolabeled Anti-CD20 sdAb for Targeted Radionuclide Therapy of Non-Hodgkin Lymphoma

Anti-CD20 radioimmunotherapy is an effective approach for therapy of relapsed or refractory CD20^pos lymphomas, but faces limitations due to poor tumor penetration and undesirable pharmacokinetics of full antibodies. Camelid single-domain Ab fragments (sdAb) might circumvent some of the limitations of radiolabeled full antibodies. In this study, a set of hCD20-targeting sdAbs was generated, and their capacity to bind hCD20 was evaluated in vitro and in vivo A lead sdAb, sdAb 9079, was selected on the basis of its specific tumor targeting and significant lower kidney accumulation compared with other sdAbs. SdAb 9079 was then radiolabeled with ⁶⁸Ga and ¹⁷⁷Lu for PET imaging and targeted therapy. The therapeutic potential of ¹⁷⁷Lu-DTPA-sdAb was compared with that of ¹⁷⁷Lu-DTPA-rituximab and unlabeled rituximab in mice bearing hCD20^pos tumors. Radiolabeled with ⁶⁸Ga, sdAb 9079 showed specific tumor uptake, with very low accumulation in nontarget organs, except kidneys. The tumor uptake of ¹⁷⁷Lu-DTPA-sdAb 9079 after 1.5 h was 3.4 ± 1.3% ID/g, with T/B and T/M ratios of 13.3 ± 4.6 and 32.9 ± 15.6. Peak tumor accumulation of ¹⁷⁷Lu-DTPA-rituximab was about 9 times higher, but concomitantly with high accumulation in nontarget organs and very low T/B and T/M ratios (0.8 ± 0.1 and 7.1 ± 2.4). Treatment of mice with ¹⁷⁷Lu-DTPA-sdAb 9079 significantly prolonged median survival compared with control groups and was as effective as treatment with rituximab or its ¹⁷⁷Lu-labeled variant. Taken together, sdAb 9079 displays promising features as a theranostic drug to treat CD20^pos lymphomas. Mol Cancer Ther; 16(12); 2828-39. ©2017 AACR.

Molecular markers in oral lichen planus: A systematic review

Oral lichen planus (OLP) is a chronic inflammatory mucosal disease that is usually detected in 0.5–2.2% of the human population. Among these, only 0.5–2.9% of the lesions progress to carcinoma. However, there are no prognostic markers available presently to recognize the increased risk in malignant transformation of the lesions. Selected markers for cell proliferation, adhesion, apoptosis and lymphocytic infiltration were analyzed by immunohistochemistry in addition to static cytometry for DNA content. The concept linking OLP and oral squamous cell carcinoma states that chronic inflammation results in crucial DNA damage, which further progresses to development of carcinoma. Even though in the past decade, enormous information has been accumulated on malignant potential of OLP, its transformation still remains unclear. Hence, the purpose of this article was to review cellular and molecular markers to understand the pathogenesis of OLP and its progression toward malignancy.

Rituximab maintenance improves survival in male patients with diffuse large B-cell lymphoma. Results of the HD2002 prospective multicentre randomized phase III trial

In the multicentre prospective randomized HD2002 trial, rituximab maintenance therapy (375 mg/m(2) every 3 months for 2 years) versus observation was evaluated for CD20(+) B-cell lymphoma. Out of 321 patients [161 randomized to the treatment group (TG), 160 to the observation group (OG)], 295 data sets were evaluable for statistical analysis. Estimated 5-year relapse-free survival (RFS) was 81% in the TG and 70% in the OG (logrank test, P = 0·047). In the diffuse large B-cell lymphoma (DLBCL) subgroup (n = 152), 5-year RFS was excellent, at 87% in the TG and 84% in the OG (logrank test, P = 0·35). Of note, only in male patients of the DLBCL subgroup was RFS significantly superior in the TG in comparison to the OG (5-year RFS: 88% vs. 74%; logrank test, P = 0·05). Cox regression analysis showed a significant interaction between treatment and gender regarding overall survival (OS) (P = 0·006) and RFS (P = 0·02), with a lower hazard in females than males in the OG [OS: hazard ratio (HR) (female:male) = 0·11; 95% confidence interval (CI) = 0·00-1·03; RFS: HR (female:male) = 0·27; 95% CI = 0·05-0·97], and no significant differences between males and females in the TG. We conclude that Rituximab maintenance therapy improves survival in male patients with DLBCL.

High contrast tumor imaging with radio-labeled antibody Fab fragments tailored for optimized pharmacokinetics via PASylation

Although antigen-binding fragments (Fabs) of antibodies constitute established tracers for in vivo radiodiagnostics, their functionality is hampered by a very short circulation half-life. PASylation, the genetic fusion with a long, conformationally disordered amino acid chain comprising Pro, Ala and Ser, provides a convenient way to expand protein size and, consequently, retard renal filtration. Humanized αHER2 and αCD20 Fabs were systematically fused with 100 to 600 PAS residues and produced in E. coli. Cytofluorimetric titration analysis on tumor cell lines confirmed that antigen-binding activities of the parental antibodies were retained. The radio-iodinated PASylated Fabs were studied by positron emission tomography (PET) imaging and biodistribution analysis in mouse tumor xenograft models. While the unmodified αHER2 and αCD20 Fabs showed weak tumor uptake (0.8% and 0.2% ID/g, respectively; 24 h p.i.) tumor-associated radioactivity was boosted with increasing PAS length (up to 9 and 26-fold, respectively), approaching an optimum for Fab-PAS₄₀₀. Remarkably, 6- and 5-fold higher tumor-to-blood ratios compared with the unmodified Fabs were measured in the biodistribution analysis (48 h p.i.) for αHER2 Fab-PAS₁₀₀ and Fab-PAS₂₀₀, respectively. These findings were confirmed by PET studies, showing high imaging contrast in line with tumor-to-blood ratios of 12.2 and 5.7 (24 h p.i.) for αHER2 Fab-PAS₁₀₀ and Fab-PAS₂₀₀. Even stronger tumor signals were obtained with the corresponding αCD20 Fabs, both in PET imaging and biodistribution analysis, with an uptake of 2.8% ID/g for Fab-PAS₁₀₀vs. 0.24% ID/g for the unmodified Fab. Hence, by engineering Fabs via PASylation, plasma half-life can be tailored to significantly improve tracer uptake and tumor contrast, thus optimally matching reagent/target interactions.

Treatment of chronic lymphocytic leukemia with monoclonal antibodies, where are we heading?

Chronic lymphocytic leukemia (CLL) is the most prevalent leukemia in the western world and monoclonal antibodies (mAbs) are important part of CLL treatment. The goal of this article was to summarize current literature on the position of mAbs in CLL treatment and to mention factors influencing effectiveness of mAbs in CLL. Several new mAbs have been developed and investigated in CLL over the past few years. Mainly anti-CD20 monoclonal antibodies are still used routinely in CLL therapy. Unfortunately, the clinical application of mAbs needs to be further improved. Novel combinations and sequences of mAbs with other compounds need to be studied in clinical trials in order to increase overall response rate and prolong remission duration. Mechanisms of action of mAbs or mechanisms of resistance to mAbs have to be also investigated to predict effectiveness of mAb in particular patient.

Ofatumumab: a novel, fully human anti-CD20 monoclonal antibody for the treatment of chronic lymphocytic leukemia

Ofatumumab is a fully human, IgG anti-CD20 monoclonal antibody codeveloped by GlaxoSmithKline (Brentford, UK) and Genmab (Copenhagen, Denmark). In preclinical studies, ofatumumab exhibited more potent in vitro activity than rituximab against B-cell malignancies and prolonged survival in in vivo animal models compared with rituximab. Ofatumumab is clinically well tolerated with initial infusion reactions being the predominant associated toxicity. Ofatumumab has demonstrated efficacy in relapsed/refractory chronic lymphocytic leukemia (CLL) and has received regulatory approval in both Europe and the USA for treatment of fludarabine and alemtuzumab refractory disease. Single-agent ofatumumab has resulted in overall response rates of 42-51% in relapsed/refractory CLL and up to 80% when combined with chemotherapy. In de novo CLL, overall response rates of 77-78% have been achieved.

The immune potential and immunopathology of cytokine-producing B cell subsets: a comprehensive review

B lymphocytes are generally recognized for their potential to mediate humoral immunity by producing different antibody isotypes and being involved in opsonization and complement fixation. Nevertheless, the non-classical, antibody-independent immune potential of B cell subsets has attracted much attention especially in the past decade. These B cells can release a broad variety of cytokines (such as IL-2, IL-4, IL-6, IL-10, IL-17, IFN-α, IFN-γ, TNF-α, TGF-β, LT), and can be classified into distinct subsets depending on the particular cytokine profile, thus emerging the concept of cytokine-producing B cell subsets. Although there is still controversy surrounding the key cell surface markers, intracellular factors and cellular origins of cytokine-producing B cell subsets, accumulating evidence indicates that these B cells are endowed with great potential to regulate both innate and adaptive arms of immune system though releasing cytokines. On the one hand, they promote immune responses through mounting Th1/Th2/Th17 and neutrophil response, inducing DC maturation and formation of lymphoid structures, increasing NK cell and macrophage activation, enhancing development of themselves and sustaining antibody production. On the other hand, they can negatively regulate immune responses by suppressing Th cell responses, inhibiting Tr1 cell and Foxp3(+) Treg differentiation, impairing APC function and pro-inflammatory cytokine release by monocytes, and inducing CD8(+) T cell anergy and CD4(+) T cell apoptosis. Therefore, cytokine-producing B cell subsets have multifunctional functions in health and diseases, playing pathologic as well as protective roles in autoimmunity, infection, allergy, and even malignancy. In this review, we revisit the history of discovering cytokine-producing B cells, describe the identification of cytokine-producing B cell subsets, introduce the origins of cytokine-producing B cell subsets as well as molecular and cellular mechanisms for their differentiation, and summarize the recent progress made toward understanding the unexpectedly complex and potentially opposing roles of cytokine-producing B cells in immunological disorders.

Radiolabeling of rituximab with (188)Re and (99m)Tc using the tricarbonyl technology

INTRODUCTION

The most successful clinical studies of immunotherapy in patients with non-Hodgkin's lymphoma (NHL) use the antibody rituximab (RTX) targeting CD20(+) B-cell tumors. Rituximab radiolabeled with β(-) emitters could potentiate the therapeutic efficacy of the antibody by virtue of the particle radiation. Here, we report on a direct radiolabeling approach of rituximab with the (99m)Tc- and (188)Re-tricarbonyl core (IsoLink technology).

METHODS

The native format of the antibody (RTX(wt)) as well as a reduced form (RTX(red)) was labeled with (99m)Tc/(188)Re(CO)(3). The partial reduction of the disulfide bonds to produce free sulfhydryl groups (-SH) was achieved with 2-mercaptoethanol. Radiolabeling efficiency, in vitro human plasma stability as well as transchelation toward cysteine and histidine was investigated. The immunoreactivity and binding affinity were determined on Ramos and/or Raji cells expressing CD20. Biodistribution was performed in mice bearing subcutaneous Ramos lymphoma xenografts.

RESULTS

The radiolabeling efficiency and kinetics of RTX(red) were superior to that of RTX(wt) ((99m)Tc: 98% after 3 h for RTX(red) vs. 70% after 24 h for RTX(wt)). (99m)Tc(CO)(3)-RTX(red) was used without purification for in vitro and in vivo studies whereas (188)Re(CO)(3)-RTX(red) was purified to eliminate free (188)Re-precursor. Both radioimmunoconjugates were stable in human plasma for 24 h at 37 °C. In contrast, displacement experiments with excess cysteine/histidine showed significant transchelation in the case of (99m)Tc(CO)(3)-RTX(red) but not with pre-purified (188)Re(CO)(3)-RTX(red). Both conjugates revealed high binding affinity to the CD20 antigen (K(d) = 5-6 nM). Tumor uptake of (188)Re(CO)(3)-RTX(red) was 2.5 %ID/g and 0.8 %ID/g for (99m)Tc(CO)(3)-RTX(red) 48 h after injection. The values for other organs and tissues were similar for both compounds, for example the tumor-to-blood and tumor-to-liver ratios were 0.4 and 0.3 for (99m)Tc(CO)(3)-RTX(red) and for (188)Re(CO)(3)-RTX(red) 0.5 and 0.5 (24 h pi).

CONCLUSION

Rituximab could be directly and stably labeled with the matched pair (99m)Tc/(188)Re using the IsoLink technology under retention of the biological activity. Labeling kinetics and yields need further improvement for potential routine application in radioimmunodiagnosis and therapy.

Drug-free macromolecular therapeutics: induction of apoptosis by coiled-coil-mediated cross-linking of antigens on the cell surface

A new paradigm was designed for apoptosis induction mediated by the biorecognition of coiled-coil motifs at the Raji B cell surface. The heterodimerization of complementary peptides, one bound to Fab’ antibody fragment, the other as grafts to HPMA copolymer, results in crosslinking of CD20 target antigens, and consequently, initiation of apoptosis.

Rituximab Followed by Cladribine in the Treatment of Heavily Pretreated Patients with Indolent Lymphoid Malignancies

The purpose of this study was to determine the efficacy and toxicity of combined therapy consisting of rituximab (RIT), an anti-CD20 monoclonal antibody, and cladribine (2-chlorodeoxyadenosine, 2-CdA) (RC regimen) in patients with refractory or relapsed indolent lymphoproliferative disorders. Twenty six CD20 antigen positive patients, 15 with B-cell chronic lymphocytic leukemia (B-CLL) and 11 with low grade non-Hodgin's lymphoma (LG-NHL) were enrolled to the study. Fourteen patients (53.8%) had refractory disease, the other 12 (46.2%) were recurrent after prior chemotherapy. RC regimen consisted of RIT at a dose of 375 mg/m2 in 6 h infusion on day 1 and 2-CdA at a dose of 0.12 mg/kg, in 2 h infusion, given on days 2-6. The RC courses were repeated at 4 week intervals or longer if severe myelosuppression occurred. Seventy eight cycles of RC with median of 3 cycles per patient were administered (range 1-5 cycles). Four patients (15.4%) (95% CI 1.5-29.3%), 1 with B-CLL and 3 with LG-NHL, achieved a complete response (CR). Fourteen patients (53,8%) (95%CI 34.6-72.9%), including 10 with B-CLL and 4 with LG-NHL, had a partial response (PR). Overall response rate (OR) was 69.2% (95%CI 51.4-86.9%) in the whole group, from 63.6% (95% CI 35.2 92.0%) in LG-NHL to 73.3% (95%CI 50.1-95.7%) in B-CLL patients. Twelve of 18 patients with CR/PR are still in remission, with the median follow up 10 (7-28 months). The median failure-free survival (FFS) of responders was 6.5 months. Hypersensitivity to RIT was the major toxicity of RC regimen, and occurred in 9 patients (34.6%), mostly only during the first infusion of RIT. Severe neutropenia (grade III) was seen in 3 patients (11.5%). Anemia and thrombocytopenia associated with RC treatment were observed in 5 (19.2%) and 2 patients (7.7%), respectively. Four episodes (15.4%) of grade III-IV infections were observed. There was no treatment related mortality. During the follow-up six patients (23.1%) died from the disease progression. In conclusion, the combination of RIT and 2-CdA is an effective and well tolerated treatment, even for heavily pre-treated patients, and the results seem to be better than in patients previously treated in our institution with 2-CdA alone. This regimen can be considered as an alternative treatment of CD-20 positive indolent lymphoproliferative disorders.

Ofatumumab

Ofatumumab is an anti-CD20 IgG1kappa human monoclonal antibody that is being considered by the US Food and Drug Administration and the European Medicines Agency for marketing approval as a treatment for chronic lymphocytic leukemia. The mAb is also being studied as a treatment for lymphoma, rheumatoid arthritis and multiple sclerosis. The candidate targets the same antigen as rituximab, but ofatumumab binds a novel, membrane-proximal epitope, and dissociates from its target at a slower rate compared to rituximab. Ofatumumab might be approved in the US by August 2009.

Quantitative determination of humanized monoclonal antibody rhuMAb2H7 in cynomolgus monkey serum using a Generic Immunoglobulin Pharmacokinetic (GRIP) assay

Preclinical pharmacokinetic (PK) assays are important to help evaluate the safety and efficacy of a potential biotherapeutic before clinical studies. The assay typically requires a biotherapeutic-specific reagent to minimize matrix effects especially when the host species are non-human primates such as cynomolgus monkeys and the biotherapeutic is a humanized monoclonal antibody (MAb). Recombinant humanized mAb 2H7 (rhuMAb2H7) binds to the extracellular domain of CD20 that is expressed on B cells and results in B cell depletion. It is currently being evaluated for its therapeutic potential in rheumatoid arthritis (RA) in clinical studies. During the early development of rhuMAb2H7, a cynomolgus monkey PK assay was needed to help assess the pharmacokinetic parameters of rhuMAb2H7 in a pilot cynomolgus monkey study. However, development of a cynomolgus monkey PK assay was challenging due to lack of rhuMAb2H7-specific reagents. Here we describe an alternative method for detection of rhuMAb2H7 in cynomolgus monkey serum using polyclonal antibodies against human IgGs. This assay quantifies rhuMAb2H7 in 10% cynomolgus monkey serum with high sensitivity, accuracy, and precision. This assay successfully supported the rhuMAb2H7 development, and has the potential to be used to quantify other humanized MAb biotherapeutics in serum from a variety of non-human species.

The 'short' history of regulatory B cells

The maintenance of tolerance is the sine qua non of a sophisticated regulatory apparatus to prevent or dampen overzealous immune responses. In addition to the ability of B cells to prime and activate the immune system, B cells with regulatory function (Bregs) have been identified in experimental models of autoimmunity, infections, and cancer, supporting the notion that, similar to regulatory T cells (Tregs), Breg-mediated suppression is an important means for the maintenance of peripheral tolerance. This regulatory function appears to be directly mediated by the production of IL-10 and/or TGFbeta and by the ability of B cells to interact with pathogenic T cells to inhibit harmful immune responses. The identification of their existence is of great relevance to the understanding of autoimmune diseases and to the development of new therapeutic strategies.

Rituximab plus cladribine with or without cyclophosphamide in patients with relapsed or refractory chronic lymphocytic leukemia

OBJECTIVES

The aim of our study was to determine the feasibility, effectiveness and toxicity of combined regimens consisting of rituximab and cladribine (2-CdA) (RC) and RC plus cyclophosphamide (RCC) in the treatment of patients with recurrent or refractory chronic lymphocytic leukemia (CLL).

METHODS

The RC regimen consisted of rituximab given on day 1 and 2-CdA (days 2-6). The RCC protocol included rituximab (day 1), 2-CdA (days 2-4) and cyclophosphamide given on days 2-4. The courses were re-administered at time intervals of 4 weeks or longer if severe myelosuppression occurred.

RESULTS

Forty-six patients with CLL entered the study. Eighteen patients were treated with RC and 28 with RCC regimen. The median number of courses administered were three cycles (range 1-6). Three (6.5%) patients (95% CI: 1-14%) achieved a complete response and 31 (67%) patients (95% CI: 50-83%) a partial response. According to the particular regimen, the overall response rate was obtained in 12 (67%) patients treated with RC (95% CI: 45-89%) and in 22 patients (78%) treated with RCC (95% CI: 62-93%). The median progression free survival of responders to RC/RCC regimens was 12 months (range 4-46). Hypersensitivity to rituximab occurred in 16 (33%) patients, mostly during the first infusion of the drug. Grade 3/4 neutropenia was seen in six (13%) patients, grade 3/4 thrombocytopenia in three (9%) patients and grade 3/4 infections were observed in ten (28%) patients.

CONCLUSIONS

These data indicate that both RC and RCC regimens are feasible in heavily pretreated patients with CLL, showing also distinct therapeutic activity and relatively low toxicity, even in patients previously treated with cladribine-based protocols.

Antiproliferative activity of RAD001 (everolimus) as a single agent and combined with other agents in mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive form of B-cell non-Hodgkin's lymphoma, with a mean survival of only 3-5 years and suboptimal therapeutic options. MCL is characterized by a balanced translocation t(11;14)(q13;q32), resulting in overexpression of cyclin D1, a G(1) cyclin regulated by the PI3K/Akt/mammalian target of rapamycin (mTOR) signaling pathway. As improved therapy for MCL is required and the mTOR pathway may be involved in its pathophysiology, the antiproliferative effects of RAD001 (everolimus), an mTOR inhibitor, against three MCL cell lines were investigated. As a single agent, RAD001 inhibited proliferation in MCL cell lines (Jeko1, SP49 and NCEB1) approximately 40-65% compared to diluent control cells. This was associated with G(1) cell-cycle arrest and reduced phosphorylation of the mTOR downstream target, 4E-BP1. Furthermore, combination drug studies revealed predominantly synergistic cytotoxicity with RAD001 and several secondary agents, including doxorubicin, vincristine or rituximab (components of the standard MCL regimen), as well as paclitaxel, vorinostat and bortezomib. These data indicate that single agent RAD001 is effective in inhibiting growth of MCL cells in vitro and combination studies with secondary agents further demonstrate synergistic cytotoxicity. Thus, these findings support future clinical studies of RAD001 in the treatment of MCL.

Rituximab combined with cladribine or with cladribine and cyclophosphamide in heavily pretreated patients with indolent lymphoproliferative disorders and mantle cell lymphoma

BACKGROUND

In vitro studies have shown synergistic or additive interactions between rituximab and purine nucleoside analogues. The results of recent clinical trials seem to confirm these preclinical observations.

METHODS

For the current study, the authors evaluated the feasibility, efficacy, and toxicity of combined regimens that consisted of either rituximab plus cladribine (2-CdA) (the RC regimen) or RC plus cyclophosphamide (the RCC regimen) in the treatment of patients with heavily pretreated, indolent lymphoid malignancies. Fifty-four adult patients with recurrent or refractory, low-grade non-Hodgkin lymphoma (LG-NHL) and B-cell chronic lymphocytic leukemia (B-CLL) were treated according to the RC/RCC regimens. The RC protocol consisted of intravenous rituximab at a dose of 375 mg/m(2) on Day 1 and 2-CdA at a dose of .12 mg/kg per day on Days 2 through 6. The RCC protocol consisted of rituximab at a dose of 375 mg/m(2) on Day 1, 2-CdA at a dose of 0.12 mg/m(2) on Days 2 through 4, and intravenous cyclophosphamide at a dose of 250 mg/m(2) per day on Days 2 to 4. The RC/RCC courses were repeated at 4-week intervals.

RESULTS

Thirty-three patients with B-CLL, 12 patients with LG-NHL and 9 patients with mantle cell lymphoma (MCL) entered the study. Thirty-three patients (61%) had recurrent disease after prior therapy, and 21 patients (39%) had refractory disease. Thirty-one patients were treated on the RC regimen, and 23 patients were treated on the RCC regimen. Six patients (11%) achieved a complete response, and 33 patients (60%) achieved a partial response. The median failure-free survival of responders was 10.5 months. The treatment revealed tolerability, with episodes of severe neutropenia (Grade 3 and 4 [according to World Health Organization criteria]) observed in 6 patients (11%), episodes of Grade 3 and 4 infections observed in 11 patients (20%), and episodes of Grade 3-4 thrombocytopenia observed in 4 patients (7%).

CONCLUSIONS

The RC and RCC regimens were highly effective and well tolerated modalities of treatment in heavily pretreated patients with indolent lymphoproliferative disorders.

Murine model of immune-mediated rejection of the acute lymphoblastic leukemia 70Z/3

70Z/3 is a murine pre-B cell leukemia line derived from BDF(1) mice and has been used in the study of signaling pathways in B cells. 70Z/3 cells were initially found to cause widespread disease upon injections in animals. We have isolated 70Z/3 variants divergent in their capacity to lead to morbidity after injections. One variant, 70Z/3-NL, elicits an immune response protecting the animal from tumor growth. Another variant, 70Z/3-L, does not induce an effective immune response and causes morbidity. We demonstrated that both CD4(+) and CD8(+) T cells are required for the rejection of 70Z/3-NL cells. Interestingly, the immune response generated against 70Z/3-NL cells was found to protect against a challenge with the lethal variant, 70Z/3-L. This indicates that although both lines can be recognized and killed by the immune system, only 70Z/3-NL is capable of inducing a protective response. Further observations, using subclones isolated from 70Z/3-NL, demonstrated that immune recognition of a portion of the cells was sufficient for protection. Depletion of CD4(+) and CD8(+) T cells in animals injected previously with 70Z/3-NL cells showed that T cells, and not Abs, were required for the maintenance of the protection initiated by 70Z/3-NL. We tested the capacity of 70Z/3-NL cells to treat mice challenged with 70Z/3-L. We can delay injections of 70Z/3-NL and still provide protection for the animals. We have a model of immune-mediated rejection which will allow us to dissect the requirements for the initiation of immune responses against an ALL tumor cell line.

Pharmacokinetic behavior of rituximab: a study of different schedules of administration for heterogeneous clinical settings

This study was designed to report the pharmacokinetic behavior of Rituximab in patients affected with different diseases and treated with different schedules of administration. A low tumor burden was a common feature of all patients (N=48) included in our study, whereas the timing of Rituximab administration varied from weekly (groups 1, 2, 3) to monthly (group 4). Group 1 included patients with follicular lymphoma treated with 4 weekly doses of Rituximab after first-line chemotherapy with CHOP. At the start of Rituximab, patients were in partial or complete clinical response but showed persistence of disease at molecular level (bcl-2-positive) in bone marrow and/or peripheral blood. Patients in group 2 had autoimmune disorders and Rituximab was given to act on B-cells, interfering with their production of autoantibodies. In patients with amyloidosis (group 3), Rituximab was given to kill progenitor B-cells of the small clone terminating in amyloid-producing plasma cells. In groups 2 and 3, the target of monoclonal antibody was a population of small B cells, which make an intrinsic feature of the diseases. Group 4 included patients with relapsed or refractory follicular and mantle cell lymphoma who underwent a salvage program of immunochemotherapy, purging in vivo and autotransplant: the first of the six planned doses of Rituximab was administered after a debulking phase with a third-generation regimen, such as VACOP-B. An enzyme-linked immunoassay (ELISA) developed and validated in our laboratory was used for the pharmacokinetic study. Rituximab disposition was characterized by a 2-exponential decay, with a long elimination half-life of approximately 3 weeks (range, 248-859 hours). The total systemic clearance ranged between 3.1 and 11.9 mL/hr/m. After 4 weekly infusions, Rituximab concentration was approximately 2.5 microg/mL, which is approximately 85% of the steady-state level. Steady-state plasma concentrations of Rituximab were reached after 6 to 8 weekly infusions. The adopted pharmacokinetic model (2-compartment open model) seems to provide the best fit of Rituximab disposition both during and after treatment, even when different schedules of drug administration are used. Because several studies reported an association between response and serum Rituximab concentrations, a treatment based on a pharmacokinetic model may be useful for predicting the desired drug concentration.

B cells in health and disease

B cells play a key role in regulating the immune system by producing antibodies, acting as antigen-presenting cells, providing support to other mononuclear cells, and contributing directly to Inflammatory pathways. Accumulating evidence points to disruption of these tightly regulated processes in the pathogenesis of autoimmune disorders. Although the exact mechanisms involved remain to be elucidated, a fundamental feature of many autoimmune disorders is a loss of B-cell tolerance and the inappropriate production of autoantibodies. Dysfunctional immune responses resulting from genetic mutations that cause intrinsic B-cell abnormalities and induction of autoimmunity in the T-cell compartment by B cells that have broken tolerance may also contribute to these disorders. These findings provide the rationale for B-cell depletion as a potential therapeutic strategy in autoimmune disorders and other disease states characterized by inappropriate immune responses. Preliminary results with the CD20-targeted monoclonal antibody rituximab indicate that rituximab can improve symptoms in a number of autoimmune and neurologic disorders (including rheumatoid arthritis, systemic lupus erythematosus, and paraneoplastic neurologic syndromes). Additional studies are warranted to further characterize the role of B cells in autoimmune diseases and the therapeutic utility of B-cell depletion.

Depletion of B Cells by a Humanized Anti-CD20 Antibody PRO70769 in Macaca Fascicularis

PRO70769 is a humanized IgG1 monoclonal antibody against the CD20 molecule that is present on normal and malignant B cells. PRO70769 is being evaluated for treatment of B-cell-mediated diseases and is in a phase 1 trial for rheumatoid arthritis. As part of the preclinical toxicology evaluation, B-cell depletion profiles and safety of PRO70769 were assessed in cynomolgus monkeys. Animals were administered drug (IV) on days 1 and 15 with 10, 50, or 100 mg/kg PRO70769 and killed 2 weeks after the second dose and after a 3-month recovery period. In a parallel study, animals were not necropsied but instead were retreated with a second cycle of PRO70769 administered under an identical regimen. PRO70769 suppressed B cells in the blood to undetectable levels and significantly reduced B cells in lymphoid tissues. Splenic B cells were depleted to a greater extent compared with lymph node B cells. A second cycle of treatment resulted in a greater extent of depletion in lymphoid tissues compared with the depletion observed after one cycle of treatment; however, residual B cells in lymphoid tissues were still detectable, even at the highest dose. The rate of B-cell recovery in peripheral blood appeared similar between one and two cycles of treatment. Upon depletion there was a change in the profile of lymph node B-cell subsets. After recovery, B-cell subsets were reconstituted to normal levels. Depletion of CD20-expressing cells and lymphoid follicular atrophy were the only treatment-related effects.

Immunohistochemistry of the B-Cell Component in Lower Lip Salivary Glands of Sjogren's Syndrome and Healthy Subjects

Serial sections of lower lip salivary gland (LSG) biopsies were examined by immunohistochemistry, using a battery of B- and partly T-related antibodies (CD5, CD20, CD21, CD27, CD38, CD45RO, CD79a, Bcl-2 and Bcl-6) in different groups of subjects: healthy controls and clinically verified smoking or nonsmoking cases of primary Sjögren's syndrome (SS). The purpose was to characterize the B-cell pattern of the lymphocytic foci and of the tiny perivascular infiltrates preceding the development of foci. Hyperplastic tonsil was used as stain control. In normal LSG, widely dispersed CD38+ and CD79a+ as well as some CD5+ cells are a normal constituent, with lack of staining with the other antibodies. In SS/LSG, the lymphocytic foci showed staining with all the antibodies, with variable degrees of overlapping or nonoverlapping. In SS/LSG of nonsmokers, CD20+ B cells make up a prominent part of the fully developed periductal lymphocytic foci, not overlapping with CD45RO. Also, CD20+ B cells did not overlap in the infiltrates with colocalized CD27+/CD38+ cells. CD20+ B cells and CD45RO+ T cells also occur as minute infiltrates perivascularly in areas of no foci in SS/LSG as well as in SS smokers lacking the typical foci. Smokers lack foci, but tiny infiltrates express CD20 as well CD45R0. Our findings suggest that CD20+ B cells and CD45RO+ T cells are early immigrants in the LSG of SS of smokers as well as nonsmokers and that another subgroup of CD27+/CD38+ B cells gradually mix with the first two to form the characteristic foci in SS/LSG. The simultaneous demonstration of CD20+ and CD27+ B cells in SS/LSG may constitute a significant diagnostic tool. Further, the findings suggest that the early immigrating lymphocytes may have been primed at a site remote from the glands before arriving via the blood to the gland tissue.

Antibody-targeted therapy: a paradigm of innovative treatment strategies in indolent and aggressive B-cell non-Hodgkin lymphoma

PURPOSE OF REVIEW

This review outlines the principles of treatment of indolent and aggressive B-cell lymphoma based on current knowledge on the classification of hematologic malignancies and the rationale to implement new antibody-targeted immunotherapeutic approaches.

RECENT FINDINGS

An update is provided on the use of antibody-targeted therapies in clinical trials, with emphasis on new, emerging strategies of immunotherapy in B-cell non-Hodgkin lymphoma.

SUMMARY

The success of immune-mediated therapies has encouraged studies on antibody-targeted therapy in B-cell non-Hodgkin lymphoma. Promising new approaches combine classical dose-intense chemotherapy with "tumor-specific" antibody targeting during several phases of the disease. The safety and efficacy of anti-CD20 in the treatment of indolent and aggressive B-cell non-Hodgkin lymphoma at any stage of disease, either as a single agent or as part of multimodality regimes, as an unconjugated antibody or as radioimmunoconjugate have changed dramatically our treatment strategies. Increasing insights into basic molecular biology and immunology of B-cell non-Hodgkin lymphoma may identify subgroups of patients categorized in current classification systems who may benefit from tailored approaches with new modality antibody-targeted therapy in near future.

Rituximab-mediated depletion of cynomolgus monkey B cells in vitro in different matrices: possible inhibitory effect of IgG

The mechanism of rituximab-mediated depletion of nonmalignant CD20+B cells remains to be clarified. In this report, we examine contributions of complement- and cell-dependent killing to the rituximab-mediated depletion of cynomolgus monkey B cells in the in vitro assay. B cell depletion was assessed in whole blood, buffer, autologus plasma (plasma), heat-inactivated plasma (H/I plasma), and cobra venom factor (CVF)-treated plasma matrices in cynomolgus monkey and human samples. Rituximab-mediated B cell depletion in buffer appeared to be greater than that in whole blood or in autologus plasma. Heat inactivation of plasma resulted in the degree of B cell depletion closer to that seen in buffer, whereas CVF treatment of plasma had no effect on B cell depletion. Addition of IgG to the buffer decreased the degree of B cell depletion. The results of these studies imply that (i) plasma components (including complement) are not the mediators of the rituximab-triggered B cell depletion in the in vitro assay, suggesting that cell-mediated mechanisms are likely to be responsible for in vitro killing of normal B cells, and that (ii) some plasma components appear to inhibit rituximab-mediated B cell depletion in the in vitro assay, with IgG identified as a possible inhibitor component.

Emerging antibody-targeted therapy in leukemia and lymphoma: current concepts and clinical implications

The success of immune-mediated therapies has encouraged studies on passive and active immunotherapy in leukemia and lymphoma. This review outlines the impact of increasing insights from basic immunology studies on the potentiation of effective immune responses and the identification of new antigens as targets for antibody (Ab)-targeted therapies. The principles of treatment in leukemia and lymphoma based on current knowledge on the classification of hematologic malignancies are reviewed, and discussed in the context of a rationale to implement new Ab-targeted immunotherapeutic approaches. An update is provided on the use of Ab-targeted therapies in clinical trials with emphasis on new emerging strategies to further expand the successful field of immunotherapy in leukemia and lymphoma.

Defective class II transactivator expression in a B lymphoma cell line

Loss of MHC class II expression in B-cell lymphoma has been associated with a higher tumorigenicity resulting from lower titers of tumor-infiltrating lymphocytes. This report aims towards the identification of the molecular mechanism leading to defective MHC class II expression in a B-cell lymphoma cell line, Rec-1. We evidenced a coordinated alteration of HLA-D gene transcription, reminiscent of B lymphoblastoid cell lines from patients with MHC class II deficiency. Genetic complementation performed between these cell lines and the lymphoma cells indicated that Rec-1 is altered in the MHC2TA gene. MHC2TA encodes the class II transactivator (CIITA), the master regulator of HLA-D gene expression. However, the coding sequence of the Rec-1 CIITA transcript did not reveal any mutation that could hamper the activity of the encoded protein. In agreement with the genetic complementation analysis, we evidenced a highly residual CIITA protein expression in the Rec-1 cell line resulting from a transcriptional defect affecting MHC2TA expression. Anti-HLA-DR monoclonal antibody treatment has proved efficient in the destruction of B lymphoma cells. Our data indicate that the appearance of variants losing CIITA, and thereby HLA-DR, expression will require a thorough monitoring during such immunotherapy protocols.

The role of monoclonal antibodies in stem cell transplantation

Monoclonal antibodies directed at the lymphoid antigens have become established treatments for hematological malignancies either alone or in combination with chemotherapy. However, their incorporation in the transplant setting remains investigational. This review focuses on the currently available data for in vitro and in vivo purging with these antibodies as well as their role in modulating graft-versus-host disease (GVHD).

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.

Chlorambucil in combination with induction and maintenance rituximab is feasible and active in indolent non-Hodgkin's lymphoma

We investigated the toxicity and efficacy of the chimaeric anti-CD20 antibody rituximab in combination with standard-dose chlorambucil in newly diagnosed and relapsed/refractory indolent B-cell lymphoma patients. A total of 29 patients (15 newly diagnosed and 14 relapsed/refractory) with low-grade or follicular B-cell non-Hodgkin's lymphoma (NHL) were included in this phase II study. Therapy consisted of chlorambucil 6 mg/m2/d for 6 consecutive weeks in combination with a standard 4-weekly rituximab administration schedule in the induction phase. Patients responding to the induction therapy received four additional cycles with chlorambucil (6 mg/m2/d for 2 weeks/month) plus rituximab (once a month). Twenty-six patients (89%) completed the treatment; only one patient discontinued treatment because of haematological toxicity. At the end of the study, the dose of chlorambucil had to be reduced in seven patients (27%) and six patients (23%) required a delay in further treatment, as a result of toxicity during consolidation therapy. Only one patient was withdrawn from the study because of progressive disease; the 27 patients evaluable for response at the end of consolidation achieved a clinical response (63% complete response and 26% partial response). A significant CD4+ and CD56+ depletion was observed after induction and during consolidation therapy; two herpes zoster virus infections and one perianal abscess represented major infectious morbidities registered during the study. Based on our preliminary data, the combination of chlorambucil with rituximab seemed to be well tolerated and active. Its definitive role in the treatment of low-grade NHL should be further evaluated in randomized trials.

Innovative strategies in lymphoma therapy

Treatment of malignant non-Hodgkin lymphomas (NHL) in the 21st century has been revolutionized by novel biological agents offering targeted approaches in addition to radio-chemotherapy. Monoclonal antibodies (MoAbs) against lymphatic surface antigens have been effective as monotherapeutic agents, and have already shown their superiority to conventional strategies when combined with chemotherapy. Radioimmunoconjugates are more effective than unlabelled antibodies. Specific inhibitors of neoangiogenesis as well as intracellular signal transduction pathways and antiapoptotic mechanisms have shown their efficacy in phase II studies. Long-term improvement in the setting of minimal residual disease has been observed after vaccination against surface antigens and non-myeloablative allogeneic stem cell transplantation is effective in controlling lymphoma growth. Novel specific antigens are currently identified using expression profiling of lymphomas. In the near future, combinations of biological agents will challenge conventional therapy. These exciting new strategies will improve the success rate in aggressive NHLs and may even challenge the paradigm of incurability of indolent lymphomas.

Mechanism of action and resistance to monoclonal antibody therapy

Monoclonal antibodies (MoAbs) are increasingly used in the treatment of patients with hematological malignancies and autoimmune diseases. The most commonly employed humanized and chimeric MoAbs are rituximab, alemtuzumab (Campath-1H, Ilex Pharmaceuticals, San Antonio, TX), and gemtuzumab-ozogamicin (Mylotarg, Wyeth-Ayerst Laboratories, St Davids, PA). The mechanism of action of these antibodies, and host and cellular factors influencing the response, are not completely known. Induction of apoptosis, antibody-dependent cell cytotoxicity (ADCC), and complement-mediated cell death (CDC) is the proposed mechanism of action of these antibodies. We review the current understanding of the mechanism of action of and resistance to these MoAbs.

The power of the third dimension: tissue architecture and autoimmunity in rheumatoid arthritis

Lymphoid organs are the anatomic solution to the challenge of responding to minute amounts of antigen with powerful effector mechanisms. By arranging interacting cells in complex three-dimensional topographies lymphoid organs provide an optimal match between form and function. This principle is exploited in ectopic lymphoid structures that characteristically appear in rheumatoid synovitis. Synovial tissue T cells and B cells cooperate in different types of lymphoid organizations. Dendritic cell networks in the inflamed synovial membrane optimize antigen collection, storage, processing, and presentation. Synovial tissue cells participate in lymphocyte recruitment and the formation of tissue architectures that amplify immune responses. Recent data support the concept that the tissue organization in the rheumatoid joint fosters a breakdown in self-tolerance by promoting a phase transition from self-limited immune responses to self-perpetuating autoimmune responses.

T cell costimulus-independent and very efficacious inhibition of tumor growth in mice bearing subcutaneous or leukemic human B cell lymphoma xenografts by a CD19-/CD3- bispecific single-chain antibody construct

We have recently demonstrated that a recombinant single-chain bispecific Ab construct, bscCD19xCD3, in vitro induces rapid B lymphoma-directed cytotoxicity at picomolar concentrations with unstimulated peripheral T cells. In this study, we show that treatment of nonobese diabetic SCID mice with submicrogram doses of bscCD19xCD3 could prevent growth of s.c. human B lymphoma xenografts and essentially cured animals when given at an early tumor stage. The effect was dose dependent, dependent on E:T ratio and the time between tumor inoculation and administration of bscCD19xCD3. No therapeutic effect was seen in the presence of human lymphocytes alone, a vehicle control, or with a bispecific single-chain construct of identical T cell-binding activity but different target specificity. In a leukemic nonobese diabetic SCID mouse model, treatment with bscCD19xCD3 prolonged survival of mice in a dose-dependent fashion. The human lymphocytes used as effector cells in both animal models did not express detectable T cell activation markers at the time of coinoculation with tumor cells. The bispecific Ab therefore showed an in vivo activity comparable to that observed in cell culture with respect to high potency and T cell costimulus independence. These properties make bscCD19xCD3 superior to previously investigated CD19 bispecific Ab-based therapies.