Targeting B-cell non Hodgkin lymphoma: New and old tricks

The management of B-cell malignancies continues to pose a clinical challenge. In the past years, rituximab (anti-CD20) emerged as the standard of care in the induction treatment of follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), and mantle cell lymphoma (MCL), as well as in other subsets. Since the benefits of immuno-chemotherapy have been clearly demonstrated in a whole range of lymphomas, several innovative approaches are being explored to achieve significant responses, particularly in refractory B-cell non-Hodgkin lymphoma (NHL) cases. Studies of the comparative effectiveness and structure/function relationship of therapeutic monoclonal antibodies, together with an increased understanding of the molecular features of NHLs, have led to the development of a range of novel therapies, many of which target the tumor in a tailored fashion. Although several molecules can help clinicians to dissect the pathological mechanisms acting in the natural history of the disease, the main purpose of this review emphasize the recent developments in targeting the B-cell NHLs surface. These novel approaches are illustrated, and the new intriguing opportunities offered by bispecific antibodies and antibody-associated immune modulation are addressed.

Epstein-Barr virus and multiple sclerosis. From evidence to therapeutic strategies

Multiple sclerosis is caused by a complex interaction between genetic predisposition and environmental factors. Epstein-Barr virus (EBV) is an environmental risk factor that is strongly related to multiple sclerosis (MS), since EBV seropositivity is linked to a significant risk of developing MS. EBV may be involved in the pathogenesis of the disease and it is possibly a prerequisite for the development of MS. EBV infection persists in B-cells during the lifetime of the host and can modulate their function. In addition, MS patients might have a deficient capacity to eliminate latent EBV infection in the central nervous system and this would promote the accumulation of infected B cells. Several mechanisms of pathogenesis, including a direct and indirect function of infected B cells, have been postulated in inflammation and neurodegeneration. A relationship between EBV and human endogenous retroviruses in the pathogenesis of MS has also been reported. If EBV is important in the pathogenesis of MS, different therapeutic strategies seem possible for MS treatment.

Immunophenotypic markers in adult acute lymphoblastic leukemia: the prognostic significance of CD20 and TdT expression

BACKGROUND

Efforts to overcome poor outcomes in patients with adult acute lymphoblastic leukemia (ALL) have focused on combining new therapeutic agents targeting immunophenotypic markers (IPMs) with classical cytotoxic agents; therefore, it is important to evaluate the clinical significance of IPMs.

METHODS

Baseline characteristics and clinical outcomes of patients with adult ALL were retrospectively analyzed. The percentage of blasts expressing IPMs at diagnosis was measured by multicolor flow cytometry analysis. Samples in which ≥20% of blasts expressed an IPM were considered positive.

RESULTS

Among the total patient population (N=230), almost all (92%) were in first or second hematological complete remission (HCR) and 54% received allogeneic hematopoietic cell transplant (allo-HCT). Five-year hematologic relapse-free survival (HRFS) and overall survival (OS) rates were 36% and 39%, respectively, and 45.6% and 80.5% of patients were positive for the IPMs CD20 and terminal deoxynucleotidyl transferase (TdT), respectively. Expression of CD20, CD13, CD34, and TdT was associated with HRFS rate, and expression of CD20 and CD13 was associated with OS rate, as was the performance of allo-HCT. In multivariate analysis, positivity for CD20 (HRFS: hazard ratio [HR], 2.21, P<0.001; OS: HR, 1.63, P=0.015) and negativity for TdT (HRFS: HR, 2.30, P=0.001) were both significantly associated with outcomes. When patients were categorized into three subgroups according to positivity for CD20 and TdT, there were significant differences in HRFS and OS among the subgroups.

CONCLUSION

Positivity for CD20 and TdT expression and clinical risk group were prognostic factors in adult ALL.

Development of Novel Anti-Cd20 Monoclonal Antibodies and Modulation in Cd20 Levels on Cell Surface: Looking to Improve Immunotherapy Response

Rituximab has been revolutionized and validated CD20 targeting monoclonal antibody. Although, it is widely used for lymphoma therapy and many patients have been benefited. However significant numbers of patients are refractory or developed resistance to current therapies due to low level of CD20 expression and/or availability on cells surface. Thus development of novel anti-CD20 mAbs with great cell killing ability and enhance CD20 levels on cell surface can potentially exploit lymphoma therapy. In this scenario, we are summarizing the recently developed mAbs against CD20 and compounds that have ability to induce CD20 expression at significant level. We also are providing information regarding combination strategy for use of radiation and anti-CD20 mAbs in vitro. However, it will need to be determined by rigorous at pre-clinical and clinic testing. We hope this review will be beneficial for current research in the area of immunotherapy or radio-immunotherapy.

Subcutaneous injections of low doses of humanized anti-CD20 veltuzumab: a phase I study in chronic lymphocytic leukemia

To evaluate the potential of subcutaneous (SC) injections with anti-CD20 antibody veltuzumab in chronic lymphocytic leukemia (CLL), 21 patients received 80, 160, or 320 mg injections every 2 weeks × 4 doses (n = 11) or 160 or 320 mg twice-weekly × 16 doses (n = 10). Treatment was well tolerated with only occasional, mild-moderate, transient injection reactions. Lymphocytosis decreased in all patients (maximum decrease, 5-91%), with 12 patients obtaining >50% decreases. Of 14 patients with lymphadenopathy on CT imaging, 5 (36%) achieved 14-61% reductions (sum of perpendicular diameters). By NCI-WG criteria, two patients achieved partial responses (10%). SC veltuzumab appeared active in all dose groups, with no obvious exposure-response relationship, despite cumulative doses ranging from 320-5120 mg. Overall median progression-free survival was 7.7 months; three patients remained progression-free >1 year (2 ongoing at 2-year study completion). These data suggest further studies of SC veltuzumab in CLL are warranted.

Production and Characterization of New Anti-Human CD20 Monoclonal Antibody

The B-cell CD20 antigen is one of the most reliable surface targets in immunotherapy of B lymphoma. In this project, we studied the production and characterization of a new monoclonal antibody against chimeric human CD20 extra loops (hCD20 exl). The results showed that clone C12H, IgG2/k isotype reacted with the antigen in ELISA and immunoblot. The Kd value was found to be 2×10(-9)M and flow cytometry results showed that 99.9% and 99.7% of the Daudi and Raji cells respectively were stained with C12H monoclonal antibody (mab) but not with Jurkat cell lines. It also effectively competed with Rituximab, thus, the staining of the Daudi and Raji cell lines was reduced to 55.9% and 40.5% of cells respectively. Based on the high affinity reaction of C12H mab and appropriate reactivity of C12H mab with the native antigen on the surface of Raji and Daudi cells in flow cytometry, it was concluded that development and evaluation of C12H mab could be a beneficial candidate for further application in genetically engineered monoclonal antibody.

Rapid activation and hepatic recruitment of innate-like regulatory B cells after invariant NKT cell stimulation in mice

BACKGROUND & AIMS

Invariant natural killer T (iNKT) cells are present within the liver and have been implicated in the development of many liver diseases. Upon activation by glycolipid ligands (including α-galactosylceramide; αGalCer), hepatic iNKT cells produce numerous cytokines and recruit both pro-inflammatory and regulatory immune cells. However, the involvement of B cells in this process is poorly defined.

METHODS

Wild-type (male, C57BL/6), B cell deficient, or B cell depleted mice were injected with αGalCer or vehicle, hepatic B cell phenotype and liver injury was subsequently determined.

RESULTS

iNKT cell activation resulted in liver injury and the rapid activation and hepatic recruitment of B cells (mainly innate-like B1 and MZ-like B cells) from the spleen and peritoneal cavity. B cells recruited to the liver produce IL-10 and TGFβ, and express cell surface CD73 (ectoenzyme which generates adenosine). B cell deficient mice developed augmented αGalCer-induced hepatitis, enhanced neutrophil recruitment and striking alterations in the hepatic cytokine milieu. αGalCer-induced hepatitis was unaltered in IL-10(-/-) mice, or after TGFβ neutralization, but was significantly worsened in mice treated with a CD73 inhibitor.

CONCLUSIONS

iNKT cell stimulation recruits innate-like regulatory B cells to the liver which suppress hepatic inflammation through IL-10 and TGFβ1 independent mechanisms, but involve CD73 activity. These findings highlight an important inflammation suppressing role for B cells at early time points during the development of an innate immune response within the liver, and represent a potential therapeutic target for the treatment of liver disease.

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.

Relationship of thymic changes and complications after congenital heart surgery

BACKGROUND

The true role of thymic function in children with congenital heart defects is largely unknown.

AIM

To study the possible role of thymic CD3 (T-lymphocyte marker) and CD20 (B-lymphocyte marker) expression and thymic histopathological changes in complications after surgery for congenital heart defects.

METHODS

Between January and July 2014, thymic tissue samples were obtained from 13 (69% male, 31% female, mean age 10.9 ± 2 years) of 25 Iraqi patients who underwent open heart surgery with partial thymectomy for correction of congenital heart defects. The samples were evaluated for thymic expression of CD markers (CD3 and CD20) and histopathological changes. For up to 6 months after surgery, data on complications were collected from each patient, including wound infection, cardiac arrhythmias, heart failure, rehospitalization, chest infection, and death.

RESULTS

The prevalence of thymic hypoplasia was 15% and it occurred more frequently in patients with absent thymic CD3 expression (p = 0.005). Only wound infection (n = 2) and atrial fibrillation (n = 1) comprised the postoperative complications in our patients. Absence of thymic CD20 expression correlated significantly with postoperative complications and obstructive cardiac defects (p = 0.04), whereas no significant correlations were found between thymic hypoplasia with CD3 expression and postoperative complications (p > 0.05).

CONCLUSION

Patients with absent thymic CD20 expression had significantly more postoperative complications and cardiac obstructive defects than those with positive CD20 expression.

CD20 Over-Expression in Hodgkin-Reed-Sternberg Cells of Classical Hodgkin Lymphoma: the Neglected Quest

We have scrutinized a previously analyzed cohort of classical Hodgkin lymphoma patients for evidence of a CD20 over-expression. This was pursued in order to determine whether all the 24 (12.6%) CD20+++ patients had clinical and/or biological profiles which would warrant a separate consideration and treatment or would carry a different outcome from our 166 CD20 (-) classical Hodgkin lymphoma patients. Except for an older age and a significantly lower expression of non-sialyl-CD15 antigen, both previously described in classical Hodgkin lymphoma, no justification to exclude these CD20+++ patients from the cohort at large is apparent. We suggest that the generally accepted view to the contrary be revised. In addition, we propose alternative interpretations for the low expression of CD20 found in a majority of Hodgkin-Reed-Sternberg cells in classical Hodgkin lymphoma.

An open-label, single-arm, phase 1 study to assess biomarker effects, efficacy and safety of ofatumumab in patients with refractory chronic lymphocytic leukemia

This open-label, phase 1 study evaluated the effects of ofatumumab on QTc intervals, safety, efficacy, B-cell and neutrophil counts, complement levels, and cytokine and chemokine concentrations. Fourteen patients with fludarabine-refractory chronic lymphocytic leukemia received 12 ofatumumab infusions. A higher maximum infusion rate of 400 mL/h was tested at the first two doses and was well tolerated. The 43% overall response rate was similar to previous data (42-51%). B-cell depletion was observed along with complement consumption; median C2 and CH50 levels appeared lower during monthly dosing in patients who responded. Responding patients appeared to have higher median levels of certain pro-inflammatory cytokines and lower median levels of certain immunotolerant cytokines than patients who did not respond. Ofatumumab-induced complement-dependent cytotoxicity activity can be detected clinically by measuring complement and may be associated with clinical activity. The potential relationship between changes in complement or cytokines and clinical response to ofatumumab warrants further study.

CD20-positive multiple myeloma: can conventional chemotherapy still be used to achieve ideal outcome for these patients?

In order to ascertain clinical characteristics and outcomes of CD20 + multiple myeloma (MM) patients, we retrospectively analyzed 331 newly diagnosed patients with multiple myeloma in our center. The clinical characteristics, cell morphology, immunophenotype, and cytogenetic were different between the CD20 + and CD20 - group. The median course of treatment to < nCR (near complete recovery) were 4.5 in the CD20+ group and 2 in the CD20 - group. Excluding the IgD type, overall survival (OS) and progression-free survival (PFS) in the CD20 + group were higher than that in the CD20 - group. There were no statistically significant differences in PFS and OS in CD20+ patients after treatment with conventional regimens, novel drugs ± transplant, nor statistical significance between those with the response < nCR and < nCR after treatment. In conclusion, CD20-positive myeloma cells are a cluster with heterogenous clinical characteristics, cell morphology, immunophenotype and cytogenetics. For these non-IgD CD20 + MM patients, conventional therapy might be a choice to achieve an ideal outcome.

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.

CAR-T Cell Therapy for Lymphoma

Lymphomas arise from clonal expansions of B, T, or NK cells at different stages of differentiation. Because they occur in the immunocyte-rich lymphoid tissues, they are easily accessible to antibodies and cell-based immunotherapy. Expressing chimeric antigen receptors (CARs) on T cells is a means of combining the antigen-binding site of a monoclonal antibody with the activating machinery of a T cell, enabling antigen recognition independent of major histocompatibility complex restriction, while retaining the desirable antitumor properties of a T cell. Here, we discuss the basic design of CARs and their potential advantages and disadvantages over other immune therapies for lymphomas. We review current clinical trials in the field and consider strategies to improve the in vivo function and safety of immune cells expressing CARs. The ultimate driver of CAR development and implementation for lymphoma will be the demonstration of their ability to safely and cost-effectively cure these malignancies.

Obinutuzumab for the treatment of patients with previously untreated chronic lymphocytic leukemia: overview and perspective

Chronic lymphocytic leukemia (CLL) is the most common lymphoproliferative disorder in the Western world and predominantly affects older people. Until recently, most studies in CLL focused on younger patients in whom intensive therapy with the addition of rituximab to fludarabine and cyclophosphamide was shown to improve survival. Obinutuzumab is a novel type II anti-CD20 monoclonal antibody (mAb) that recently demonstrated an overall survival advantage when combined with chemotherapy in previously untreated older patients with CLL and comorbidities. Obinutuzumab was superior to rituximab in this same study in terms of response rates and progression-free survival. Several preclinical and early phase clinical studies also support the efficacy of obinutuzumab. The most frequent adverse event noted with obinutuzumab is infusion-related reactions, which occur more frequently than with rituximab and are typically restricted to the first cycle of therapy. Based on these results, obinutuzumab should be considered the gold standard mAb for combination with chemotherapy in previously untreated patients with CLL and comorbidities. The marked efficacy of obinutuzumab with a weak chemotherapy backbone implies significant potency of this mAb, making it the ideal partner for combination studies with other agents in CLL.

CD20-positive primary gastric T-cell lymphoma poorly responding to initial treatment with rituximab plus CHOP, and a literature review

There have been rare reported cases of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) that co-expressed CD20. A 44-year-old Japanese male was initially misdiagnosed as CD20-positive diffuse large B-cell lymphoma with a background of reactive CD3-positive T-cells in the stomach. After four cycles of R-CHOP [rituximab plus cyclophosphamide (CY), doxorubicin, vincristine, and prednisolone (PSL)], total gastrectomy with regional lymph node dissection was performed due to the poor response to R-CHOP. A final diagnosis of CD20-positive primary gastric PTCL-NOS was made based on the immunohistochemical, flow cytometric, and molecular genetic findings. In the present case, CD20 immunostaining for T-cell lymphoma cells in tumor tissue varied; in a large part, these were strong to weak-positive, and in some parts, absent. We additionally reviewed the literature focusing on CD20-positive PTCL-NOS treated with rituximab. The administration of rituximab has been performed as an initial treatment in 11 cases, including the case reported here. The response was good in cases with high expression of CD20, while it was poor in cases with variable intensity in CD20 staining, which is consistent with our experience in the present case. The efficacy of rituximab may be associated with intensity of CD20 expression in T cells and its homogeneity in the tumor tissue.

Bone marrow infiltration of CD20-negative follicular lymphoma after rituximab therapy: a histological mimicker of hematogones and B-cell acute lymphoblastic leukemia/lymphoma

Rituximab is a monoclonal antibody against CD20. Rituximab combined with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy, termed R-CHOP, have improved the overall survival of patients with B-cell lymphoma in comparison with that of CHOP therapy. However, as with other molecularly-targeted therapies, resistance to rituximab could emerge sooner or later after rituximab administration. A number of mechanisms for rituximab resistance have been proposed, including downregulation of CD20 protein expression. Differential diagnosis of B-cell proliferation with reduced or lost CD20 expression includes not only B-cell lymphomas with CD20 downregulation, but also other tumorous and non-tumorous lesions. These include precursor B-cell neoplasms such as B acute lymphoblastic leukemia/lymphoblastic lymphoma (B-ALL/LBL) and hematogones, a normal precursor B-cell proliferation during regeneration of hematopoiesis, typically observed following bone marrow suppression by chemotherapy. It is important to distinguish these possibilities because distinct therapies are required for each. In this paper, we report a case where bone marrow infiltration of follicular lymphoma histopathologically mimicked hematogones or B-ALL/LBL when CD20 expression was downregulated in follicular lymphoma after R-CHOP therapy.

Construction and characterization of an anti-CD20 mAb nanocomb with exceptionally excellent lymphoma-suppressing activity

The CD20-directed monoclonal antibody rituximab (RTX) established a new era in the treatment of non-Hodgkin lymphoma (NHL); however, suboptimal response and/or resistance to RTX still limit its clinical merits. Although four effector mechanisms are validated to participate in CD20-based immunotherapy, including complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, caspase-dependent apoptosis, and lysosome-mediated programmed cell death (PCD), they could hardly be synchronously activated by any anti-CD20 mAb or mAb derivative until now. Herein, a novel mAb nanocomb (polyethylenimine polymer–RTX–tositumomab [PPRT nanocomb]) was firstly constructed through mass arming two different anti-CD20 mAbs (RTX and tositumomab) to one polymer by nanotechnology. Comparing with free mAbs, PPRT nanocomb possesses a comparable binding ability and reduced “off-rate” to surface CD20 of NHL cells. When treated by PPRT nanocomb, the caspase-dependent apoptosis was remarkably enhanced except for concurrently eliciting complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, and lysosome-mediated PCD. Besides, “cross-cell link”-assisted homotypic adhesion by PPRT nanocomb further enhanced the susceptibility to PCD of lymphoma cells. Pharmacokinetic assays revealed that PPRT nanocomb experienced a relatively reduced clearance from peripheral blood compared with free antibodies. With the cooperation of all the abovementioned superiorities, PPRT nanocomb exhibits exceptionally excellent in vivo antitumor activities in both disseminated and localized human NHL xenotransplant models.

Antibody modulation: Limiting the efficacy of therapeutic antibodies

Monoclonal antibodies (mAb) have revolutionised the way in which we treat disease. From cancer to autoimmunity, antibody therapy has been responsible for some of the most impressive clinical responses observed in the last 2 decades. A key component of this success has been their generally low levels of toxicity, and unique mechanisms of action. These two facets have allowed them to (a) be integrated rapidly into clinical practice in combination with conventional radio- and chemo-therapies and (b) to avoid the resistance mechanisms typically observed with classical small molecule drugs, such as upregulation of drug efflux transporters, dysregulation of apoptosis and mutations in key target enzymes/pathways. Although success with mAb therapies has been impressive, they are also subject to their own resistance mechanisms. In this perspective we discuss the various ways in which mAb therapeutics can be inhibited, concentrating mainly on the ways in which they can be removed from the target cell surface-a process called modulation. This can be achieved either in a cis-fashion on a single cell or in trans, precipitated by engagement with a second phagocytic cell. The evidence for each of these processes will be discussed, in addition to possible therapeutic strategies that might be employed to inhibit or reverse them.

Association between polymorphism of CD20 gene and chronic lymphocytic leukemia in Chinese population

Rituximab was widely used in clinical practice. Some chronic lymphocytic leukemia (CLL) patients were primary or secondary resistance to rituximab, but the mechanism has not been yet clear. CD20 gene coding region was amplified by PCR in 92 cases of newly diagnosed CLL patients and 200 healthy donors. The expression of CD20 was conducted in peripheral blood specimens of CLL patients. Proportions of CD20 expression and fluorescence intensity were detected by flow cytometry. Exon-3 c.246C>T (rs17155019) and Exon-4 c.632C>T (rs2070770) were present in 4.35% (4/92) and 9.78% (9/92) of newly diagnosed CLL patients. The mutations were not found in remaining exons. The frequency of C/C genotype and C allele of rs2070770 were significantly higher than the normal control population (90.22% vs 81.00%, P=0.04; 95.11% vs 90%, P=0.04). There was no significant relationship between genotypes with CLL development (P>0.05), however, C allele of rs2070770 may be associated with CLL (P=0.04, OR=0.46, 95% CI=0.22-0.98). The expression CD20 mRNA, proportion and intensity of CD20 were no significant different between genotypes of two polymorphic loci (P>0.05). Low expression of CD20 for CLL was not associated with mutation of CD20 gene coding region. Other mechanisms, such as promoter methylation, may result in low expression of CD20.

Obinutuzumab in hematologic malignancies: lessons learned to date

The routine use of anti-CD20 monoclonal antibodies (mAbs) has improved patient outcomes in CD20-positive non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL). Despite the clinical success achieved with rituximab, relapses are still common with further improvements in anti-CD20 mAb efficacy required. Many novel anti-CD20 antibodies are in development, but obinutuzumab is currently the only type II glycoengineered anti-CD20 mAb in clinical testing. Obinutuzumab has increased antibody-dependent cell-mediated cytotoxicity, reduced complement-dependent cytotoxicity and enhanced direct non-apoptotic cell death. In preclinical models, obinutuzumab induced superior tumor remission compared with rituximab at the equivalent dose levels, and was active in rituximab-refractory tumors. Obinutuzumab exhibits encouraging efficacy as monotherapy in NHL, and combined with chemotherapy in relapsed/refractory NHL and treatment-naïve symptomatic CLL. In a recent randomized, phase III trial in patients with untreated comorbid CLL, overall response rate was significantly greater (78% vs. 65%, P<0.0001) and median progression-free survival was significantly prolonged (26.7 vs. 15.2months, P<0.0001) for obinutuzumab plus chlorambucil vs. rituximab plus chlorambucil. Obinutuzumab is a type II anti-CD20 antibody that utilizes distinct mechanisms of action relative to type I antibodies like rituximab and has led to significant clinical improvement over rituximab in a phase III trial in CLL. Further trials are ongoing to determine whether such improvements in outcome will be seen in CD20-positive B-cell malignancies.

Disseminated Infections with Talaromyces marneffei in Non-AIDS Patients Given Monoclonal Antibodies against CD20 and Kinase Inhibitors

Infections with the fungus Talaromyces (formerly Penicillium) marneffei are rare in patients who do not have AIDS. We report disseminated T. marneffei infection in 4 hematology patients without AIDS who received targeted therapy with monoclonal antibodies against CD20 or kinase inhibitors during the past 2 years. Clinicians should be aware of this emerging complication, especially in patients from disease-endemic regions.

Enhancing natural killer cell-mediated lysis of lymphoma cells by combining therapeutic antibodies with CD20-specific immunoligands engaging NKG2D or NKp30

Antibody-dependent cell-mediated cytotoxicity (ADCC) mediated through the IgG Fc receptor FcγRIIIa represents a major effector function of many therapeutic antibodies. In an attempt to further enhance natural killer (NK) cell-mediated ADCC, we combined therapeutic antibodies against CD20 and CD38 with recombinant immunoligands against the stimulatory NK cell receptors NKG2D or NKp30. These immunoligands, respectively designated as ULBP2:7D8 and B7-H6:7D8, contained the CD20 scFv 7D8 as a targeting moiety and a cognate ligand for either NKG2D or NKp30 (i.e. ULBP2 and B7-H6, respectively). Both the immunoligands synergistically augmented ADCC in combination with the CD20 antibody rituximab and the CD38 antibody daratumumab. Combinations with ULBP2:7D8 resulted in higher cytotoxicity compared to combinations with B7-H6:7D8, suggesting that coligation of FcγRIIIa with NKG2D triggered NK cells more efficiently than with NKp30. Addition of B7-H6:7D8 to ULBP2:7D8 and rituximab in a triple combination did not further increase the extent of tumor cell lysis. Importantly, immunoligand-mediated enhancement of ADCC was also observed for tumor cells and autologous NK cells from patients with hematologic malignancies, in which, again, ULBP2:7D8 was particularly active. In summary, co-targeting of NKG2D was more effective in promoting rituximab or daratumumab-mediated ADCC by NK cells than co-ligation of NKp30. The observed increase in the ADCC activity of these therapeutic antibodies suggests promise for a 'dual-dual-targeting' approach in which tumor cell surface antigens are targeted in concert with two distinct activating NK cell receptors (i.e. FcγRIIIa and NKG2D or B7-H6).

Clear cell variant of diffuse large B-cell lymphoma: a case report and review of the literature

Diffuse large B cell lymphoma (DLBCL) is a diffuse proliferation of large neoplastic B lymphoid cells with nuclear size equal to or exceeding that of normal macrophage nuclei. The DLBCL morphological variants are centroblastic, immunoblastic, T-cell- and histiocyte-rich, anaplastic, plasmablastic, anaplastic lymphoma kinase-positive, and primary mediastinal large B-cell lymphoma (PMBCL). These histopathologically-recognized morphological variants respond differently to treatment and have distinct prognoses. We report a case of a 43-year-old patient who presented pain in the lower abdomen that had begun four months prior. Ultrasound-guided biopsy revealed epithelial cell features and a partial alveolar growth pattern. We discovered large diffuse areas comprising large cells with slightly irregular nuclei and very clear cytoplasm. These features were similar to those of clear cell carcinoma in renal tissue, suggesting the possibility of an epithelial neoplasm. To test this possibility, immunohistochemistry for cluster designation markers was performed, but the diffuse areas were found to be positive only for CD45. Additional immunohistochemistry was performed, and the diffuse areas were found to be positive for CD20, CD79a, P53, and Mum-1. Based on these characteristics, a diagnosis of a clear cell variant of DLBCL was made, and the patient was treated with chemotherapy. Precise histological diagnosis is crucial for clinical management and ultimately for patient survival. There has been one additional report of a case of clear cell DLBCL, in outside the mediastinum. The features we identified can be used to define a new subtype of DLBCL. The expression of P53 and Mum-1 suggest a poor prognosis.

Characterization of the B cell response to Leishmania infection after anti-CD20 B cell depletion

Anti-CD20 depletion therapies targeting B cells are commonly used in malignant B cell disease and autoimmune diseases. There are concerns about the ability of B cells to respond to infectious diseases acquired either before or after B cell depletion. There is evidence that the B cell response to existing or acquired viral infections is compromised during treatment, as well as the antibody response to vaccination. Our laboratory has an experimental system using co-infection of C3H mice with both Leishmania major and Leishmania amazonensis that suggests that the B cell response is important to healing infected mice. We tested if anti-CD20 treatment would completely restrict the B cell response to these intracellular pathogens. Infected mice that received anti-CD20 B cell depletion therapy had a significant decrease in CD19(+) cells within their lymph nodes and spleens. However, splenic B cells were detected in depleted mice and an antigen-specific antibody response was produced. These results indicate that an antigen-specific B cell response towards intracellular pathogens can be generated during anti-CD20 depletion therapy.

Prognostic significance of CD20 expression and Epstein-Barr virus (EBV) association in classical Hodgkin lymphoma in Japan: a clinicopathologic study

To investigate the clinicopathological significance of CD20 expression and Epstein-Barr virus (EBV) association in Hodgkin and Reed-Sterberg cells of classical Hodgkin lymphoma (CHL), CD20 expression and EBV positivity (by EBER in situ hybridization) were investigated in 389 CHL patients in Japan. They included 74 CD20-positive cases (19%) and 315 CD20-negative cases (81%). CD20-positive cases showed significantly older age at onset (P = 0.018) and higher association with EBV (P = 0.002). Multivariate analysis identified EBV-positivity (but not CD20-positivity), presence of B symptoms, thrombocytopenia, elevated serum lactate dehydrogenase and performance status >1 as poor prognostic factors for overall survival (OS). We constructed a new prognostic model with these five factors classifying patients into three groups: low risk, 0-1 adverse factor; intermediate risk, 2-3 factors; high risk, 4-5 factors. This prognostic model could stratify the prognosis of CHL patients (P < 0.0001). For 144 patients (58%) classified into the low-risk group, the 5-year OS was 91%. For 92 patients (37%) in the intermediate group, the 5-year OS was 66%; for 11 patients (5%) in the high-risk group, the 5-year OS was 36%. In conclusion, EBV is identified as an independent poor prognostic factor for CHL patients. Therefore, examination of EBV association in CHL is recommended as routine pathologic practice especially in countries where EBV infection prevails.

Action and resistance of monoclonal CD20 antibodies therapy in B-cell Non-Hodgkin Lymphomas

Anti-CD20 monoclonal antibodies (mAbs) have improved patient's survival with Non-Hodgkin Lymphoma, when combined with chemotherapy. Several mechanisms of action have been reported, including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity and induction of apoptosis. Despite the large amount of studies and published data, the role each mechanism played in vivo is not fully understood. Furthermore, the reason why a significant percentage of patients are refractory or resistant remains unknown. Several activated intracellular signaling pathways have been implicated in the mechanisms of resistance of rituximab. In the present manuscript, we review those mechanisms and new anti-CD20 mAbs, as well as the efforts being accomplished to overcome it, focusing on new drugs targeting pathways implicated in resistance to rituximab.

Drug-free macromolecular therapeutics induce apoptosis of patient chronic lymphocytic leukemia cells

A new drug-free nanotherapeutic approach for B-cell malignancies was developed. Exposure of B-cells to an anti-CD20 Fab'-morpholino oligonucleotide1 (MORF1) conjugate decorated the cell surface with MORF1; further exposure of the decorated cells to multivalent polymer-oligonucleotide2 conjugates (P-MORF2) resulted in CD20 clustering at the cell surface with induction of apoptosis. We evaluated this concept in chronic lymphocytic leukemia (CLL) cells isolated from 10 patients. Apoptosis and cytotoxicity were observed in eight samples, including 2 samples with the 17p13 deletion, which suggested a p53-independent mechanism of apoptosis induction. When compared to an anti-CD20 monoclonal antibody (mAb), the nanotherapeutic showed significantly more potent apoptosis-inducing activity and cytotoxicity. This was due to the multivalency effect (8 binding sites per polymer chain) of our design in comparison to the divalent mAb. In conclusion, we have developed a novel and potent therapeutic system against CLL and other B-cell malignancies with significant advantages over conventional chemo-immunotherapy.

A Two-Step Pretargeted Nanotherapy for CD20 Crosslinking May Achieve Superior Anti-Lymphoma Efficacy to Rituximab

The use of rituximab, an anti-CD20 mAb, in combination with chemotherapy is the current standard for the treatment of B-cell lymphomas. However, because of a significant number of treatment failures, there is a demand for new, improved therapeutics. Here, we designed a nanomedicine that crosslinks CD20 and directly induces apoptosis of B-cells without the need for toxins or immune effector functions. The therapeutic system comprises a pretargeting component (anti-CD20 Fab' conjugated with an oligonucleotide1) and a crosslinking component (N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer grafted with multiple complementary oligonucleotide2). Consecutive treatment with the two components resulted in CD20 clustering on the cell surface and effectively killed malignant B-cells in vivo. To enhance therapeutic efficacy, a two-step pretargeting approach was employed. We showed that the time lag between the two doses can be optimized based on pharmacokinetics and biodistribution of the Fab'-oligonucleotide1 conjugate. In a mouse model of human non-Hodgkin lymphoma (NHL), increasing the time lag from 1 h to 5 h resulted in dramatically improved tumor growth inhibition and animal survival. When the 5 h interval was used, the nanotherapy was more efficacious than rituximab and led to complete eradication of lymphoma cells with no signs of metastasis or disease recurrence. We further evaluated the nanomedicine using patient mantle cell lymphoma cells; the treatment demonstrated more potent apoptosis-inducing activity than rituximab hyper-crosslinked with secondary antibodies. In summary, our approach may constitute a novel treatment for NHL and other B-cell malignancies with significant advantages over conventional chemo-immunotherapy.

Investigational therapies targeting lymphocyte antigens for the treatment of non-Hodgkin's lymphoma

INTRODUCTION

The advent of the anti-CD20 mAb rituximab has opened a new era in the treatment of non-Hodgkin's lymphomas (NHL), markedly altering standard treatment strategies. Moreover, the proof-of-concept that targeting a specific lymphocyte surface antigen may induce a highly effective and safe targeted killing of malignant cells has opened the door to the development of a plethora of novel mAbs directed towards different B- and T-cell-specific antigens.

AREAS COVERED

This review discusses the recent available clinical data about new-generation anti-CD20 mAbs characterized by increased antibody- (obinutuzumab) or complement-dependent cyotoxicity (ofatumumab) as well as novel investigational agents targeting other lymphocyte antigens (e.g., CD19, CD22, CD30, CD40, CD52, CCR4), which are currently under investigation for B- and T-cell NHL treatment. In addition, antibody-drug conjugates (inotuzumab ozogamicin, brentuximab vedotin, polatuzumab vedotin), bispecific T-cell engagers (blinatumomab) and a new class of antibodies targeting cytotoxic T-lymphocyte-associated antigen 4, programmed death 1 or programmed death ligand 1 (immune checkpoint inhibitors) are specifically considered.

EXPERT OPINION

Among the novel mAbs challenging rituximab, obinutuzumab seems to be in the most advanced phase, with the results of randomized trials awaited shortly. Brentuximab vedotin is increasing its role in T-cell NHL. Furthermore, immune checkpoint inhibitors have the potential to acquire a great relevance in NHL therapy.

Anti-CD20 single chain variable antibody fragment-apolipoprotein A-I chimera containing nanodisks promote targeted bioactive agent delivery to CD20-positive lymphomas

A fusion protein comprising an α-CD20 single chain variable fragment (scFv) antibody, a spacer peptide, and human apolipoprotein (apo) A-I was constructed and expressed in Escherichia coli. The lipid interaction properties intrinsic to apoA-I as well as the antigen recognition properties of the scFv were retained by the chimera. scFv•apoA-I was formulated into nanoscale reconstituted high-density lipoprotein particles (termed nanodisks; ND) and incubated with cultured cells. α-CD20 scFv•apoA-I ND bound to CD20-positive non-Hodgkins lymphoma (NHL) cells (Ramos and Granta) but not to CD20-negative T lymphocytes (i.e., Jurkat). Binding to NHL cells was partially inhibited by pre-incubation with rituximab, a monoclonal antibody directed against CD20. Confocal fluorescence microscopy analysis of Granta cells following incubation with α-CD20 scFv•apoA-I ND formulated with the intrinsically fluorescent hydrophobic polyphenol, curcumin, revealed α-CD20 scFv•apoA-I localizes to the cell surface, while curcumin off-loads and gains entry to the cell. Compared to control incubations, viability of cultured NHL cells was decreased upon incubation with α-CD20 scFv•apoA-I ND harboring curcumin. Thus, formulation of curcumin ND with α-CD20 scFv•apoA-I as the scaffold component confers cell targeting and enhanced bioactive agent delivery, providing a strategy to minimize toxicity associated with chemotherapeutic agents.

How to outsmart NK cell tolerance

Immune tolerance induced by regulatory mechanisms is an integral and fundamental part of immunity. In therapeutic settings, however, tolerance may significantly limit efficacy. Here, we summarize possible strategies to enhance therapeutic antibody dependent cellular cytotoxicity by overcoming NK cell tolerance.

CD20+ T cells have a predominantly Tc1 effector memory phenotype and are expanded in the ascites of patients with ovarian cancer

Recently, a small subset of T cells that expresses the B cell marker CD20 has been identified in healthy volunteers and in patients with rheumatoid arthritis and multiple sclerosis. The origin of these CD20-positive T cells as well as their relevance in human disease remains unclear. Here, we identified that after functional B cell/T cell interaction CD20 molecules are transferred to the cell surface of T cells by trogocytosis together with the established trogocytosis marker HLA-DR. Further, the presence of CD20 on isolated CD20⁺ T cells remained stable for up to 48h of ex vivo culture. These CD20⁺ T cells almost exclusively produced IFNγ (∼70% vs. ∼20% in the CD20^- T cell population) and were predominantly (CD8⁺) effector memory T cells (∼60-70%). This IFNγ producing and effector memory phenotype was also determined for CD20⁺ T cells as detected in the peripheral blood and ascitic fluids of ovarian cancer (OC) patients. In the latter, the percentage of CD20⁺ T cells was further strongly increased (from ∼6% in peripheral blood to 23% in ascitic fluid). Taken together, the data presented here indicate that CD20 is transferred to T cells upon intimate T cell/B cell interaction. Further, CD20⁺ T cells are of memory and IFNγ producing phenotype and are present in increased amounts in ascitic fluid of OC patients.

Optimization of anti-CD20 humanized antibody hu8E4 by site-directed mutation based on epitope analysis

Despite the effectiveness of the anti-CD20 chimeric antibody (mAb), rituximab, in treating B-cell lymphomas, its efficacy remains variable and often modest. Hu8E4 is an anti-CD20 humanized antibody which exhibits markedly higher antitumor activity compared with rituximab. Previous studies have indicated that rituximab and almost all known anti-CD20 murine mAbs recognize the A170/P172 motif within the large extracellular loop of CD20. In this study, we demonstrated that hu8E4 also recognized the A170/P172 motif, suggesting that the epitopes recognized by rituximab and hu8E4 are very similar. Based on this, three single mutations (D57E, Y102K and Y102T) at the heavy chain variable region that can improve the affinity of rituximab were transferred to hu8E4. The results showed that D57E and Y102T but not Y102K successfully enhanced the binding of hu8E4 to CD20. Out of these hu8E4 mutants, hu8E4D57E exhibited the highest affinity. The in vitro and in vivo antitumor activity of hu8E4D57E was further investigated. Our data indicated that hu8E4D57E was as effective as hu8E4 in mediating CDC and inducing apoptosis in B-lymphoma cells, but it was more potent in ADCC than hu8E4. Importantly, hu8E4D57E was shown to be significantly more effective than Hu8E4 in prolonging the survival of SCID mice bearing disseminated B-lymphoma cells, suggesting that it might be a promising therapeutic agent for B-cell lymphomas. Moreover, this study also suggests that the mutations that can improve the affinity of rituximab may be transferred to other anti-CD20 murine mAbs to enhance their binding to CD20.

Clinical role of obinutuzumab in the treatment of naive patients with chronic lymphocytic leukemia

The introduction of targeted therapy against CD20⁺ with the monoclonal antibody rituximab has dramatically improved the survival of B-cell non-Hodgkin lymphoma including chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma. Unfortunately, CLL remains incurable with chemoimmunotherapy, with many patients having refractory or relapsing disease after rituximab-containing therapy. Obinutuzumab (GA101) is a novel humanized Type II anti-CD20 monoclonal antibody that has been investigated and compared to rituximab. Here, we provide an overview of obinutuzumab, including its mechanisms of action, preclinical data, and Phase I to III clinical studies. Preclinical data illustrate obinutuzumab’s higher potency compared to rituximab through antibody-dependent cellular cytotoxicity and direct cell death. Recently, the CLL11 study presented a significant benefit from obinutuzumab chemoimmunotherapy and supports its use for treatment-naive unfit CLL patients. Herein, we review that obinutuzumab is both a safe and effective alternative to rituximab.

Incidence and risk of xerosis with targeted anticancer therapies

BACKGROUND

Many targeted therapies used in the treatment of cancer can lead to the development of xerosis, but the incidence and relative risk of xerosis have not been ascertained.

OBJECTIVE

We conducted a systematic review and metaanalysis of clinical trials, to ascertain the incidence and risk of developing xerosis after taking anticancer drugs.

METHODS

The PubMed (1966-October 2013), Web of Science (January 1998-October 2013), and American Society of Clinical Oncology abstracts (2004-2013) databases were searched for clinical trials of 58 targeted agents. Results were calculated using random or fixed effects models.

RESULTS

The incidences of all- and high-grade xerosis were 17.9% (95% confidence interval [CI]: 15.6-20.4%) and 1.0% (95% CI: 0.9-1.5%), respectively. The risk of developing all-grade xerosis was 2.99 (95% CI: 2.0-4.3), and it varied across different drugs (P < .001).

LIMITATIONS

The reporting of xerosis may vary among clinicians and institutions, and the incidence may be affected by age, concomitant medications, comorbidities, and underlying malignancies or skin conditions.

CONCLUSION

Patients receiving targeted therapies have a significant risk of developing xerosis. Patients should be counseled and treated early for this symptom to prevent suboptimal dosing and quality of life impairment.

Pharmacologically relevant doses of valproate upregulate CD20 expression in three diffuse large B-cell lymphoma patients in vivo

Background

Epigenetic code modifications by histone deacetylase inhibitors (HDACi) have been proposed as potential new therapies for lymphoid malignancies. Diffuse large B-cell lymphoma (DLBCL) is the most common type of aggressive lymphoma for which standard first line treatment is the chemotherapy regimen CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) combined with the monoclonal anti-CD20 antibody rituximab (R-CHOP). The HDACi valproate, which has for long been utilized in anti-convulsive therapy, has been shown to sensitize to chemotherapy in vitro. Valproate upregulates expression of CD20 in lymphoma cell lines; therefore, 48 hour pre-treatment with valproate before first line R-CHOP in DLBCL stages II-IV is evaluated in the phase I clinical trial VALFRID; Valproate as First line therapy in combination with Rituximab and CHOP in Diffuse large B-cell lymphoma.

Findings

Pretreatment with valproate at oral doses comparable to anti-convulsive therapy, resulted in upregulation of CD20 mRNA and CD20 protein on the cell surface as measured by qPCR and FACS analysis in lymphoma biopsies from three evaluated patients from the VALFRID study. Valproate-treatment corresponded to increased acetylation of Histone3Lysine9 (H3K9ac) in peripheral blood mononuclear cells (PBMCs), which were employed as surrogate tissue for valproate-related epigenetic modifications.

Conclusions

Valproate treatment at pharmacologically relevant doses resulted in upregulation of CD20 in vivo, and also in expected epigenetic modifications. This suggests that pre-treatment with valproate or other HDACis before anti-CD20 therapy could be advantageous in CD20-low B-cell lymphomas. Further studies are warranted to evaluate this conclusion.

Bone marrow stromal mesenchymal cells induce down regulation of CD20 expression on B-CLL: implications for rituximab resistance in CLL

Although the majority of B cells express surface CD20 in chronic lymphocytic leukaemia (B-CLL), only ∼50% of patients respond to treatment with rituximab. Decreased CD20 expression on these tumour B cells could be responsible for the lack of response observed in some patients treated with rituximab. Despite the potential critical role of CD20 in the biology of B cell malignancies, the mechanisms controlling its expression are poorly understood. At the bone marrow level, mesenchymal stromal cells (MSC) may regulate and support the survival of malignant cells, such as B-CLL cells. In this study, we investigated whether MSC may regulate the CD20 expression on B-CLL. For this purpose, B cells from CLL patients were isolated and co-cultured on MSC. B-CLL cells were collected from B-CLL/MSC co-cultures and examined for their expression of CD20. We demonstrate decreased CD20 expression in B-CLL cells after 2 weeks of co-culture with MSC, under contact and non-contact conditions, which was associated with a decreased susceptibility to rituximab. Additionally, B cells co-cultured with MSCs show an increase in CD59 expression. Our findings strongly suggest that the interaction between B-CLL cells and MSC may play a major role in the resistance to rituximab-induced apoptosis of B-CLL cells.

Type II anti-CD20 mAb-induced lysosome mediated cell death is mediated through a ceramide-dependent pathway

In the past decade, monoclonal antibodies (mAbs) have revolutionized the treatment of non-Hodgkin lymphomas (NHLs). Although Fc-dependent mechanisms of mAb-mediated tumor clearance have been extensively studied, the ability of mAbs to directly evoke programmed cell death (PCD) and the underlying mechanisms involved remain unclear. It is well established that type II anti-CD20 mAb (Tositumomab) potently evoked PCD through a caspases-independent, lysosome-mediated process, which is related to homotypic adhesion (HA) in NHL cell lines. Herein, we reveal that the induction of ceramide generation by anti-CD20 mAbs directly correlates with their ability to induce PCD. The inhibition of ceramide abrogated Tositumomab-induced PCD indicating that ceramide is required for the execution of cell death. Further experimental results revealed that ceramide was generated downstream of mAb-induced HA and upstream of lysosome leakage. These findings provide further insights into a previously unrecognized role for ceramide generation in mediating PCD evoked by type II anti-CD20 mAbs in Burkitt's lymphoma cells. This newly characterized cell death pathway may potentially be exploited to eliminate malignant cells.

Activatory and inhibitory Fcγ receptors augment rituximab-mediated internalization of CD20 independent of signaling via the cytoplasmic domain

Type I anti-CD20 mAb such as rituximab and ofatumumab engage with the inhibitory FcγR, FcγRIIb on the surface of B cells, resulting in immunoreceptor tyrosine-based inhibitory motif (ITIM) phosphorylation. Internalization of the CD20·mAb·FcγRIIb complex follows, the rate of which correlates with FcγRIIb expression. In contrast, although type II anti-CD20 mAb such as tositumomab and obinutuzumab also interact with and activate FcγRIIb, this interaction fails to augment the rate of CD20·mAb internalization, raising the question of whether ITIM phosphorylation plays any role in this process. We have assessed the molecular requirements for the internalization process and demonstrate that in contrast to internalization of IgG immune complexes, FcγRIIb-augmented internalization of rituximab-ligated CD20 occurs independently of the FcγRIIb ITIM, indicating that signaling downstream of FcγRIIb is not required. In transfected cells, activatory FcγRI, FcγRIIa, and FcγRIIIa augmented internalization of rituximab-ligated CD20 in a similar manner. However, FcγRIIa mediated a slower rate of internalization than cells expressing equivalent levels of the highly homologous FcγRIIb. The difference was maintained in cells expressing FcγRIIa and FcγRIIb lacking cytoplasmic domains and in which the transmembrane domains had been exchanged. This difference may be due to increased degradation of FcγRIIa, which traffics to lysosomes independently of rituximab. We conclude that the cytoplasmic domain of FcγR is not required for promoting internalization of rituximab-ligated CD20. Instead, we propose that FcγR provides a structural role in augmenting endocytosis that differs from that employed during the endocytosis of immune complexes.

CD8-positive peripheral T-cell lymphoma with aberrant expression of CD20 and concurrent in situ follicular lymphoma

A case of a 78-year-old woman with a CD8-positive peripheral T-cell lymphoma with aberrant expression of CD20 associated with follicular lymphoma in situ (FLIS) is reported. The neoplasm presented initially as cutaneous macules, papules, plaques and nodules. A skin biopsy was performed and the diagnosis of peripheral T-cell lymphoma (PTCl) with aberrant expression of CD20 was made. The staging procedures included an excisional inguinal lymph node biopsy that showed findings similar to those of the previous diagnosis. In addition, FLIS was identified. The clinicopathologic features of PTCLs with aberrant CD20 expression involving the skin as well as this uncommon association are reviewed.

Ceramide participates in lysosome-mediated cell death induced by type II anti-CD20 monoclonal antibodies

Considering the variable and often modest therapeutic efficacy of rituximab for a substantial proportion of patients suffering from non-Hodgkin lymphomas (NHLs), various type II anti-CD20 monoclonal antibodies (mAbs) with excellent ability in inducing programmed cell death (PCD) are currently being developed for their enhanced therapeutic index. Although homotypic adhesion (HA) and lysosome leakage are proven to be of vital importance in type II mAb-induced PCD in NHL cells, the detailed relationship between them remains unclear. Herein, for the first time we discovered that improved intracellular ceramide level is an important mediator between HA and lysosome leakage in tositumomab-induced cell death. Further experimental results revealed that the generation of intracellular ceramide acts as the outcome of HA and major cause of lysosome leakage. The clarification of ceramide involvement in type II anti-CD20 mAb-induced PCD may provide new ideas on CD20-based immunotherapy against NHLs.

Inhibitors of SRC kinases impair antitumor activity of anti-CD20 monoclonal antibodies

Clinical trials with SRC family kinases (SFKs) inhibitors used alone or in a combination with anti-CD20 monoclonal antibodies (mAbs) are currently underway in the treatment of B-cell tumors. However, molecular interactions between these therapeutics have not been studied so far. A transcriptional profiling of tumor cells incubated with SFKs inhibitors revealed strong downregulation of MS4A1 gene encoding CD20 antigen. In a panel of primary and established B-cell tumors we observed that SFKs inhibitors strongly affect CD20 expression at the transcriptional level, leading to inhibition of anti-CD20 mAbs binding and increased resistance of tumor cells to complement-dependent cytotoxicity. Activation of the AKT signaling pathway significantly protected cells from dasatinib-triggered CD20 downregulation. Additionally, SFKs inhibitors suppressed antibody-dependent cell-mediated cytotoxicity by direct inhibition of natural killer cells. Abrogation of antitumor activity of rituximab was also observed in vivo in a mouse model. Noteworthy, the effects of SFKs inhibitors on NK cell function are largely reversible. The results of our studies indicate that development of optimal combinations of novel treatment modalities with anti-CD20 mAbs should be preceded by detailed preclinical evaluation of their effects on target cells.

Current and emerging monoclonal antibody treatments for chronic lymphocytic leukemia: state of the art

Anti-CD20 monoclonal antibodies (mAbs), rituximab, ofatumumab and obinutuzumab, have a significant impact in the treatment of chronic lymphocytic leukemia (CLL), particularly in combination with chemotherapy. Over the last few years, several new mAbs have been developed and investigated in CLL. The most promising newer mAbs are directed against CD20, CD19, CD37 and CD40. Combinations of antibodies with targeted drugs like ibrutinib, idelalisib or lenalidomide will probably replace chemotherapy-based combinations in the near future. This review gives a critical overview of established mAbs as well as new antibodies potentially useful in CLL.

Update on obinutuzumab in the treatment of B-cell malignancies

INTRODUCTION

The anti-CD20 mAb rituximab has revolutionized the treatment of B-cell malignancies, improving outcome for patients. Despite these improvements, the majority of patients still relapse and become refractory to rituximab. Further efforts to improve anti-CD20 mAb efficacy have recently focused on obinutuzumab /GA101, a novel anti-CD20 mAb glycoengineered to display enhanced Fc-mediated effector mechanisms and induce direct cell death.

AREAS COVERED

We provide an overview of the current insights into the mechanisms of action of obinutuzumab focusing on how structural modifications and differences to rituximab led to designation of obinutuzumab as a type II antibody. We summarize data from preclinical studies and recent clinical trials including the Phase III trial in chronic lymphocytic leukemia (CLL), which led to FDA approval in November 2013.

EXPERT OPINION

Clinical data are now emerging confirming the promise of the initial preclinical data that demonstrated superior efficacy of obinutuzumab over rituximab at similar dosing. The emerging randomized Phase III data from older comorbid patients with previously untreated CLL demonstrated significant improvements in molecular remission rates and median progression-free survival of obinutuzumab plus chlorambucil versus rituximab plus chlorambucil. This emerging data provide reasons to be optimistic that outcomes for patients with B-cell malignancies can be further improved with obinutuzumab.

Peripheral B cell depletion and central proinflammatory cytokine reduction following repeated intrathecal administration of rituximab in progressive Multiple Sclerosis

B cells and/or the enhanced inflammatory milieu in the subarachnoid space are supposed to have a role in cortical pathology of progressive multiple sclerosis (PMS). The efficacy of intravenous rituximab to deplete circulating B cells is remarkable in MS, and its intrathecal delivery could target compartmentalized inflammation in PMS. We describe the central and peripheral effects of repeated intrathecal rituximab administrations in a patient with severe PMS. Peripheral CD20+ B cells were reduced, while oligoclonal bands were unaffected. Several central proinflammatory cytokines, and markers of neurodegeneration were markedly reduced. Central B cells modulation should be investigated in PMS.

Assessment of the effect of ofatumumab on cardiac repolarization

Ofatumumab is a human monoclonal antibody that binds to a unique CD20 epitope on the surface of B lymphocytes, resulting in efficient lysis of CD20-expressing cells via complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity. The potential effect of ofatumumab on cardiac repolarization and the relationship between ofatumumab concentration and change in corrected QT interval (ΔQTcF) were evaluated in data from three clinical trials in 82 patients with chronic lymphocytic leukemia receiving ofatumumab alone (n = 14), ofatumumab with chemotherapy (n = 33), and chemotherapy alone (n = 35). Because of ofatumumab accumulation, baseline QTcF interval was recorded prior to the first infusion for each patient. No patient had a post-baseline QTcF interval >480 milliseconds or a ΔQTcF >60 milliseconds; five patients (four on ofatumumab) had a ΔQTcF between 30 and 60 milliseconds. At cycle 6 (week 21; 308 μg/mL), there was an increase in QTcF in patients on ofatumumab treatment, with an estimated between-treatment difference (90% CI) of 12.5 (4.5, 20.5) milliseconds. However, at the visit with the highest median concentration (week 8; 1386 μg/mL), median ΔQTcF was 4.8 milliseconds. There was no significant relationship between ofatumumab plasma concentration and ΔQTcF. Ofatumumab did not have a clinically significant effect on cardiac repolarization.

Ofatumumab in refractory chronic lymphocytic leukemia: experience through the French early access program

BACKGROUND

The Autorisation Temporaire d'Utilisation (ATU) is an early access program available in France for drugs aimed at treating severe diseases not yet covered by a marketing authorization, for patients without any other therapeutic option and who cannot be included in a clinical trial.

PATIENTS AND METHODS

This report presents the use of single-agent ofatumumab in 30 patients with advanced chronic lymphocytic leukemia (CLL) in the French ATU program.

RESULTS

These very-high-risk patients had received multiple previous treatments (median = 6), and most had disease that was fludarabine-refractory or alemtuzumab-refractory (or both) or was unsuitable for alemtuzumab treatment. In the intent-to-treat analysis, the overall response rate was 47% (4 of 30, complete response; 10 of 30, partial response). Of 13 patients with 17p deletion, 6 displayed response to ofatumumab, including 2 complete responses. Treatment was well tolerated, with 17 grade 3 or 4 adverse events; 4 cases of grade 3 or 4 infusion reactions were reported, with favorable immediate outcome. Among nonhematologic complications, infections were the most frequent.

CONCLUSION

The results confirm the efficacy and acceptable tolerability profile of ofatumumab as a single agent in severely ill patients with CLL. Attention should be paid to possible early infusion reactions to ofatumumab, as well as to the risk of infection.

The Expression and Prognostic Impact of CD95 Death Receptor and CD20, CD34 and CD44 Differentiation Markers in Pediatric Acute Lymphoblastic Leukemia

OBJECTIVE

This study investigated the expression and prognostic significance of the CD95 death receptor and CD20, a B cell-lineage associated marker, along with CD34 and CD44 non-lineage associated molecules in Iranian children with acute lymphoblastic leukemia (ALL).

METHODS

We performed immunophenotyping for expressions of the molecules in blood samples from children diagnosed with ALL by using a panel of monoclonal antibodies for flow cytometry analysis. The expression of markers was evaluated in relation to clinical and paraclinical features as well as response to treatment in the patients. Findings : CD95 showed a higher expression in T-ALL compared to B-ALL (P<0.001). Analysis of the clinical and laboratory findings at diagnosis in the group of B-ALL patients revealed an association between CD95 expression with lower white blood cell (WBC) numbers and bone marrow blasts (P<0.05). We detected a positive correlation between the expressions of CD95 and CD44 (r=0.445, P<0.01) in B-ALL patients. There was an association between CD20 expression and several poor prognostic factors that included increased extramedullary involvement (EMI) and decreased platelet numbers (P<0.008). The mean expression of CD34 in B-ALL was higher than T-ALL (P=0.004). At follow-up, complete remission duration (CRD) and survival duration did not significantly differ between patients who were positive or negative for each marker.

CONCLUSION

Association of the studied molecules with several prognostic factors implies the significance of CD95 molecule as favorable and CD20 as unfavorable prognostic markers for childhood ALL.

Residual cancer lymphocytes in patients with chronic lymphocytic leukemia after therapy show increased expression of surface antigen CD52 detected using quantitative fluorescence cytometry

BACKGROUND

Rituximab and alemtuzumab, mAbs used in recent years to treat CLL, are directed against antigens CD20 and CD52. CD20 is not highly expressed by CLL tumor cells, and rituximab does not have significant effectiveness in CLL unless combined with chemotherapy. Alemtuzumab targets CD52, which is much more highly expressed, and is currently the most effective agent used alone for CLL. Variability in expression of both antigens among these patients might be related to different individual therapeutic responses to mAb therapy.

PATIENTS AND METHODS

A total 95 patients diagnosed with CLL and/or SLL were divided into 4 groups: (1) untreated; (2) in complete or partial remission; (3) disease in progression; and (4) diagnosed with SLL. Flow cytometry of peripheral blood cells included gating of the CD5(+)CD19(+) tumor population, within which mean fluorescence intensity of fluorescein isothiocyanate (FITC) conjugated with anti-CD20 or anti-CD52 antibody was measured. The resulting expression of the 2 antigens was deduced from the calibration curve using Quantum FITC particles.

RESULTS

Expression of CD20 showed no significant differences among the 4 groups of patients. However, significantly greater expression of surface antigen CD52 was recorded in patient group 2 in complete or partial remission (P < .001).

CONCLUSION

The residual population of CLL cells after therapy is characterized by increased surface detection of CD52. Although the exact cause of this phenomenon is unknown, our results provide a basis to consider the potential for CLL consolidation therapy using alemtuzumab.