Chimeric anti-CD20 Antibody Research Articles

Monitoring Disease Progression and Therapeutic Response in a Disseminated Tumor Model for Non-Hodgkin Lymphoma by Bioluminescence Imaging

Xenograft tumor models are widely studied in cancer research. Our aim was to establish and apply a model for aggressive CD20-positive B-cell non-Hodgkin lymphomas, enabling us to monitor tumor growth and shrinkage in a noninvasive manner. By stably transfecting a luciferase expression vector, we created two bioluminescent human non-Hodgkin lymphoma cell lines, Jeko1(luci) and OCI-Ly3(luci), that are CD20 positive, a prerequisite to studying rituximab, a chimeric anti-CD20 antibody. To investigate the therapy response in vivo, we established a disseminated xenograft tumor model injecting these cell lines in NOD/SCID mice. We observed a close correlation of bioluminescence intensity and tumor burden, allowing us to monitor therapy response in the living animal. Cyclophosphamide reduced tumor burden in mice injected with either cell line in a dose-dependent manner. Rituximab alone was effective in OCI-Ly3(luci)-injected mice and acted additively in combination with cyclophosphamide. In contrast, it improved the therapeutic outcome of Jeko1(luci)-injected mice only in combination with cyclophosphamide. We conclude that well-established bioluminescence imaging is a valuable tool in disseminated xenograft tumor models. Our model can be translated to other cell lines and used to examine new therapeutic agents and schedules.

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.

Systemic Rituximab for Conjunctival Marginal Zone (Malt) Lymphoma is not Protective for Subsequent Disease Development in the Contralateral Eye

Purpose: We report a case of a 35-year old male who presented with unilateral conjunctival extranodal marginal zone (MALT) lymphoma and underwent systemic Rituximab immunotherapy as primary treatment. After an excellent initial response and four years of complete remission he presents with MALT lymphoma to the contralateral conjunctiva. Methods: MALT lymphoma is the most common lymphoid neoplasm of the conjunctiva, and has an indolent clinical course. Rare cases of spontaneous remission, bilateral involvement, systemic dissemination, and common local and contralateral relapses have been reported. Rituximab is a chimeric anti-CD20 antibody, currently used as first-line treatment of CD20 positive non-Hodgkin’s lymphoma. Several mechanisms can be responsible for rituximab resistance. Transformation of CD20 positive indolent to aggressive CD20 negative form is one of them. Results: In this case, the patient did not demonstrate any systemic or orbital involvement. Both histological reports of the incisional biopsies revealed CD20 positive immunohistochemistry. Conclusion: This is a highly unusual case of new primary conjunctival MALT lymphoma to the contralateral eye after systemic Rituximab treatment. This further supports the assumption that rituximab does not suppress MALT lymphoma formation in the long term in the other eye, suggesting that the predisposing immune factors are not annihilated by the course of rituximab. Long term review of these patients is therefore warranted.

Anti-JC virus antibodies in rituximab-treated patients with neuromyelitis optica spectrum disorder.

Rituximab, a chimeric monoclonal anti-CD20 antibody, has been proposed to be effective for neuromyelitis optica spectrum disorder (NMOSD). A concern for developing progressive multifocal leukoencephalopathy (PML), which is caused by John Cunningham virus (JCV), has been suggested particularly in patients treated long term with rituximab. In this study, using a modified enzyme-linked immunosorbent assay with glutathione S-transferase-tagged VP1 as the antigen, we investigated the seroprevalence of anti-JCV antibodies among 78 Korean patients with NMOSD and the change in anti-JCV antibody serostatus following long-term rituximab treatment. The overall seroprevalence of anti-JCV antibodies was 69 % prior to rituximab administration. Over a mean of 4 years of repeated treatment with rituximab, no patient developed PML. Of 24 initially seronegative patients, none converted into seropositive, whereas six (11 %) of 54 initially seropositive patients converted into seronegative. Our results might support the safety of long-term rituximab treatment in patients with NMOSD with regard to the risk of developing PML.

Solid phase-based cross-matching as solution for kidney allograft recipients pretreated with therapeutic antibodies.

In order to select recipients without donor-specific anti-HLA antibodies, the complement-dependent cytotoxicity crossmatch (CDC-CM) was established as the standard procedure about 40 years ago. However, the interpretability of this functional assay strongly depends on the vitality of isolated donors' lymphocytes. Since the application of therapeutic antibodies for the immunosuppressive regimen falsifies the outcome of the CDC-crossmatch as a result of these antibodies' complement-activating capacity in the recipients' sera, we looked for an alternative methodical approach. We here present 27 examples of AB0 blood group-incompatible living kidney allograft recipients who, due to their treatment with the humanized chimeric monoclonal anti-CD20 antibody Rituximab, did not present valid outcomes of CDC-based pretransplant cross-matching. Additionally, four cases of posttransplant cross-matching after living kidney allografting and consequent treatment with the therapeutic anti-CD25 antibody Basiliximab (Simulect) due to acute biopsy-proven rejection episodes are presented and compared regarding CDC- and ELISA-based crossmatch outcomes. In all cases, it became evident that the classical CDC-based crossmatch was completely unfeasible for the detection of donor-specific anti-HLA antibodies, whereas ELISA-based cross-matching not requiring vital cells was not artificially affected. We conclude that ELISA-based cross-matching is a valuable tool to methodically circumvent false positive CDC-based crossmatch results in the presence of therapeutically applied antibodies.

Efficacy and safety of rituximab in rheumatic diseases.

B-cell depleting therapy is now in clinical use for more than 10 years in rheumatology. In 2001, a first report was published on five rheumatoid arthritis patients responding to the chimeric anti-CD20 antibody rituximab. Since then, numerous clinical trials, prospective and retrospective studies, registry data as well as case reports on the use of rituximab in autoimmune rheumatic diseases have been published. This review gives a short overview on clinical data of rituximab in rheumatic diseases currently available.

Targeted treatment for chronic lymphocytic leukemia: clinical potential of obinutuzumab.

Introduction of targeted agents revolutionized the treatment of chronic lymphocytic leukemia (CLL) in the past decade. Addition of chimeric monoclonal anti-CD20 antibody rituximab to chemotherapy significantly improved efficacy including overall survival (OS) in untreated fit patients; humanized anti-CD52 antibody alemtuzumab and fully human anti-CD20 antibody ofatumumab lead to improvement in refractory disease. Novel small molecule inhibitors such as ibrutinib and idelalisib demonstrated excellent activity and were very recently licensed in relapsed/refractory CLL. Obinutuzumab (GA101) is the newest monoclonal antibody approved for the treatment of CLL. This novel, glycoengineered, type II humanized anti-CD20 antibody is characterized by enhanced antibody-dependent cellular cytotoxicity and direct induction of cell death compared to type I antibodies. Combination of obinutuzumab and chlorambucil yielded significantly better OS in comparison to chlorambucil monotherapy in untreated comorbid patients. These results led to approval of obinuzutumab for the treatment of CLL. Numerous clinical trials combining obinutuzumab with other cytotoxic drugs and novel small molecules are currently under way. This review focuses on the role of obinutuzumab in the treatment of CLL.

Design of a Phase 2 STudy of Brentuximab Vedotin (SGN-35) as Salvage Therapy for Males with Chemoresistant Germ-Cell Tumors (GCT)

ABSTRACT Background Complete responses with third-line or later salvage chemotherapy (CT) for GCT range from 5% to 10%, and nearly all patients (pts) progressing after high-dose CT will ultimately die. CD30 is expressed by embryonal carcinoma (ECA) thus lending support to a rationale for a targeted approach. SGN-35 is an antibody-drug conjugate consisting of the chimeric anti-CD30 antibody SGN-30 chemically conjugated to an antitubulin synthetic analog. The primary objective of the study will be the activity of SGN35 in refractory GCT. Trial design 24 pts with biopsy-proven CD30+ GCT will receive intravenous SGN35 at the dose of 1.8 mg/Kg every 3 weeks until disease progression or onset of unacceptable toxicity. Further eligibility requirements will include failure of 2 or 3 platinum-based CT (including HDCT). All pts will undergo measurement of serum tumor markers, a computed tomography and a PET scan q6 weeks. An optimal Simon's 2-stage design will be applied. The primary endpoint is the objective response-rate (ORR). An ORR of 5% is not promising, while a 25% rate will be promising. In stage 1, 9 evaluable patients will be accrued. If ≥1 patient will be responding, enrollment will be extended to the 2nd stage for further 15. If, over the total of 24 stage 1 plus stage 2 pts, 3 at least will be responding, treatment will be declared worthy for further investigations. The type I and II error are set both at 0.1 (power = 90%). We will test the hypothesis that brentuximab can promote anti-tumor immunity, which might contribute to the clinical efficacy. We will use multiparametric flow cytometry to assess whether SGN-35 can: a) impact on frequency and absolute counts of all main cellular subsets; b) shift the TH1/TH2 balance, in favor of a TH1-type of response; c) reduce the frequency of circulating CD30+ regulatory T cells and CD30+ TH2 memory T cells; d) promote an increase in circulating CD161+TH17 T cells; d) reverse the condition of immune dysfunction, by assessing the expression of negative co-signaling molecules (PD-1, CTLA-4, CD160, CD244, CD57, TIM-3, LAG-3) and of activation/proliferation markers (Ki67, GranzymeB, CD69) on main T cell subsets. As of July 2014, 6 pts have been enrolled (NCT01851200). Disclosure All authors have declared no conflicts of interest.

SAT0247 Safety of RAPID Rituximab Infusion in Rheumatoid Arthritis in A Single Community Practice

BackgroundRituximab, a chimeric monoclonal anti-CD20 antibody, is approved to be infused over 4hours and 15minutes, due to the potential for infusion reactions. The risk of infusion reactions has been shown...

Outcome Comparison of ABO-Incompatible Kidney Transplantation With Low-Dose Rituximab and ABO-Compatible Kidney Transplantation: A Single-Center Experience

BackgroundThe development of immunosuppressive techniques has helped overcome the ABO incompatibility barrier. However, the outcomes of ABO-incompatible (ABOi) kidney transplantation remain a controversial issue with the advent of the anti-CD20 chimeric antibody rituximab. Herein, we report the outcomes of ABOi kidney transplantation with low-dose rituximab. Patients and MethodsBetween June 2006 and April 2013, 42 patients underwent living-related kidney transplantation at our hospital. The patients were divided into 2 groups: ABO-compatible (ABOc; n = 29) and ABOi kidney transplants using low-dose rituximab (100 mg/m2) without splenectomy (n = 13). The basic immunosuppression regimen (calcineurin inhibitor [CNI], mycophenolate mofetil [MMF], and steroids) was the same for both groups, except for the use of rituximab and therapeutic apheresis in the ABOi group. We compared post-transplantation renal function, incidents of virus infection, episodes of rejection, and graft survival between the 2 groups. ResultsIn our hospital, 30% of recipients received ABOi kidney transplants. The estimated glomerular filtration rate (eGFR) did not differ between the groups. Rejection episodes confirmed by biopsy in the ABOc and ABOi groups were 8 (28%) and 4 (31%) patients (P = .833), acute antibody-mediated rejection was observed in 1 (3.5%) and 2 (15%) patients (P = .165), and virus infection was observed in 14 (48%) and 3 (23%) patients (P = .252), respectively. The 5-year patient survival rate was 100% in both groups, and the 5-year graft survival rates were 95% for ABOc and 100% for ABOi transplants (P = .527). ConclusionsThese results suggest that the outcomes of ABOi kidney transplantation with low-dose rituximab are similar to those of ABOc kidney transplantation. Further study is necessary to address the efficacy and safety of ABOi kidney transplantation.

The CD37-targeted antibody–drug conjugate IMGN529 is highly active against human CLL and in a novel CD37 transgenic murine leukemia model

Therapeutic regimens for chronic lymphocytic leukemia (CLL) have increasingly utilized monoclonal antibodies since the chimeric anti-CD20 antibody rituximab was introduced. Despite improved clinical outcomes, current CLL therapies are not curative. Therefore, antibodies with greater efficacy and novel targets are desirable. One promising target is CD37, a tetraspanin protein highly expressed on malignant B-cells in CLL and non-Hodgkin lymphoma. While several novel CD37-directed therapeutics are emerging, detailed preclinical evaluation of these agents is limited by lack of appropriate animal models with spontaneous leukemia expressing the human CD37 (hCD37) target. To address this, we generated a murine CLL model that develops transplantable hCD37+ leukemia. Subsequently, we engrafted healthy mice with this leukemia to evaluate IMGN529, a novel hCD37-targeting antibody-drug conjugate. IMGN529 rapidly eliminated peripheral blood leukemia and improved overall survival. In contrast, the antibody component of IMGN529 could not alter disease course despite exhibiting substantial in vitro cytotoxicity. Furthermore, IMGN529 is directly cytotoxic to human CLL in vitro, depletes B-cells in patient whole blood, and promotes killing by macrophages and NK cells. Our results demonstrate the utility of a novel mouse model for evaluating anti-human CD37 therapeutics and highlight the potential of IMGN529 for treatment of CLL and other CD37-positive B-cell malignancies.

Accelerated therapeutic progress in diffuse large B cell lymphoma.

Diffuse large B cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma in the world. Clinically, biologically, and pathologically, DLBCL is a heterogeneous entity with a range of potential outcomes. Immunochemotherapy regimens, consisting of the chimeric monoclonal anti-CD20 antibody rituximab in combination with chemotherapy, have improved the outcomes. Relapsed DLBCL is generally treated with salvage immunochemotherapy followed by high-dose therapy and autologous stem cell transplantation; however, DLBCL is not yet curable in up to a third of patients. The real promise for cure lies in novel agents and their rational combinations. The improved understanding of DLBCL subtypes and gene expression profiling has led to the identification of targeted drugs that may allow for subtype specific therapy. We have summarized the existing data on the prognostic factors and the treatment of DLBCL, including the use of novel agents such as lenalidomide, carfilzomib, and ibrutinib. We also share our thoughts on the direction of future clinical trials.

Brentuximab Vedotin for Hodgkin Lymphoma and Systemic Anaplastic Large Cell Lymphoma: A Review of Clinical Experience and Future Directions

SUMMARY Brentuximab vedotin is a novel agent indicated for the treatment of relapsed and refractory Hodgkin lymphoma and systemic anaplastic large cell lymphoma. Brentuximab vedotin is an antibody–drug conjugate consisting of chimeric anti-CD30 antibody cAC10, linked to four molecules of monomethylauristatin E, a tubulin destabilizer. It was granted US FDA approval in 2011 following two pivotal Phase II studies showing objective responses of 75 and 86% in heavily pretreated relapsed and refractory Hodgkin lymphoma and systemic anaplastic large cell lymphoma, respectively. Brentuximab vedotin can be used as a bridge to more definitive stem cell transplant. There are currently over 30 open clinical studies involving the use of brentuximab vedotin used as single agent or combined with chemotherapy in both front-line and salvage settings. These studies include use in other CD30-positive B- and T-cell lymphomas, as well as in CD30-positive germ cell tumors. In clinical practice brentuximab vedotin has been associated with significant sensory and motor neuropathies and clinicians should be alert to the potential for significant neuropathy and the need for dose reduction. However, the potential for significant neuropathy must be balanced against the remarkable clinical benefit of brentuximab vedotin in patients with heavily pretreated relapsed and refractory lymphomas.

Rituximab as therapy for the recurrence of bile salt export pump deficiency after liver transplantation

Progressive familial intrahepatic cholestasis type 2 (PFIC2) results from recessive mutations in the adenosine triphosphate-binding cassette B11 gene, which encodes for bile salt export pump (BSEP). Liver transplantation (LT) is offered to PFIC2 patients with end-stage liver disease. Reports have described recurrent cholestasis in PFIC2 patients after transplantation, and this has been associated with immunoglobulin G antibodies to BSEP. High-titer anti-BSEP antibodies appear to correlate with episodes of cholestatic graft dysfunction. There is no established paradigm for treating antibody-mediated posttransplant BSEP disease. It appears to be refractory to changes in immunosuppressant medications that would typically be effective in treating allograft rejection. Taking what is known about its pathophysiology, we designed a treatment consisting of rituximab, a chimeric monoclonal anti-CD20 antibody, in combination with intravenous immunoglobulin and plasmapheresis. Using this approach, we report the successful management of 2 patients with antibody-mediated recurrence of PFIC2 after LT.

Identification Of The Ki-1 Antigen (CD30) As a Novel Marker and Potential Therapeutic Target In Neoplastic Mast Cells In Advanced Systemic Mastocytosis

Systemic mastocytosis (SM) is a hematologic neoplasm characterized by abnormal expansion and accumulation of neoplastic mast cells (MC) in various organs, including the bone marrow, skin, liver, spleen and gastrointestinal tract. In a majority of all patients, the transforming KIT mutation D816V is detectable. The clinical picture and prognosis in SM vary, depending on the variant of SM and the presence of an associated hematologic non-MC-lineage disease (AHNMD). The WHO classification discriminates between indolent SM (ISM), SM-AHNMD, aggressive SM (ASM) and MC leukemia (MCL). Recent data suggest that neoplastic MC in ASM and MCL express substantial amounts of cytoplasmic Ki-1 (CD30), a lymphoid antigen otherwise expressed in neoplastic cells in anaplastic large cell lymphoma and Hodgkin lymphoma, where CD30 serves as a therapy target. In the present study, we examined the expression of CD30 in various human MC-lines (HMC-1, MCPV) and primary neoplastic MC in patients with ISM (n=20) and advanced SM (ASM/MCL; n=10) and asked whether CD30 may serve as potential therapeutic target in SM. We found that CD30 is expressed abundantly in the cytoplasm of neoplastic MC in ASM and MCL in almost all patients, whereas in a majority of patients with ISM, MC expressed only low amounts or did not express cytoplasmic CD30. As assessed by flow cytometry, neoplastic MC in SM were also found to express cell surface CD30. In contrast to cytoplasmic expression, no clear correlation was found between the type of SM and CD30 surface expression on MC. Notably, MC expressed surface CD30 in 8/9 ISM patients and in 2/6 ASM/MCL patients. The immature human RAS-transformed MCL line MCPV (KIT D816V negative) also expressed cell surface CD30, whereas the MCL line HMC-1.1 (lacking KIT D816V) expressed only low levels, and the HMC-1.2 subclone (KIT D816V+) was found to stain CD30 negative. To examine whether CD30 may serve as a therapy target in SM, we applied brentuximab vedotin (provided by Millennium: The Takeda Oncology Company, Cambridge, MA, USA), which is an antibody-drug conjugate consisting of a chimeric anti-CD30 antibody and the microtuble inhibitor monomethyl auristatin E (MMAE). Brentuximab vedotin has recently been described to induce dose-dependent growth arrest in human CD30+ lymphoblastic cell lines. In the present study, brentuximab vedotin was found to inhibit the proliferation of MCPV and HMC-1 cells in a dose-dependent manner, with lower IC50 values found in CD30+ MCPV and HMC-1.1 cells (5 µg/ml) than in CD30− HMC-1.2 cells (10 µg/ml). As assessed by AnnexinV/PI staining and staining for active-caspase-3, brentuximab vedotin also induced dose-dependent apoptosis in CD30+ MCPV and HMC-1.1 cells, but did not induce substantial apoptosis in CD30− HMC-1.2 cells. Brentuximab vedotin was also found to induce growth inhibition and apoptosis in the CD30+ canine-mastocytoma cell line C2. We next examined the effects of brentuximab vedotin on in vitro survival (apoptosis) of primary neoplastic MC in patients with CD30− SM (n=3) and in patients with CD30+ SM (n=3). In these experiments, brentuximab vedotin was found to induce dose-dependent apoptosis at pharmacologically relevant concentrations in neoplastic MC in patients with CD30+ SM, whereas no effects were seen in patients with CD30− SM (Figure). Finally, we examined the effects of a drug combination consisting of brentuximab vedotin and the KIT D816V targeting drug PKC412 (midostaurin). We found that both drugs synergize with each other in inhibiting the in vitro proliferation of CD30+ MCPV cells. In conclusion, our data provide evidence that the target-antigen CD30 is expressed on the surface of neoplastic MC in patients with indolent and advanced SM. In addition, our data show that the CD30-targeting antibody brentuximab vedotin induces growth arrest and apoptosis in neoplastic MC and synergizes with midostaurin in inhibiting the growth of CD30+ neoplastic MC. Whether these effects also occur in vivo in patients with advanced mastocytosis remains to be determined in clinical trials. [Display omitted] Neoplastic MC from patients with CD30− SM (n=3, grey bars) and CD30+ SM (n=3, black bars) were incubated in control medium (Co) or in various concentrations of brentuximab vedotin (37°C). After 96 hours, the percentage of AnnexinV+ viable DAPI-negative MC was determined by flow cytometry. Results represent the mean±S.D. of 3 independent experiments. Asterisk: p<0.05 compared to control. Disclosures:Sotlar:Nanostring: Honoraria; Novartis: Consultancy. Reiter:Novartis: Consultancy, Honoraria. Horny:Novartis: Consultancy, Honoraria. Valent:Novartis: Consultancy, Honoraria, Research Funding.

Adjuvant rituximab therapy in pemphigus: a single-center experience of 18 cases

Background: Pemphigus vulgaris (PV) follows a chronic relapsing course where the mainstay of therapy has been oral corticosteroids and second-line immunosuppressive and immunomodulating therapies. Successful responses have been reported with rituximab, a chimeric monoclonal anti-CD20 antibody targeting B lymphocytes, although its use in recalcitrant pemphigus is still being studied. Methods: A retrospective analysis is presented of 18 patients with cutaneous and mucous membrane involvement after disease relapse following steroid and other adjuvant therapies who were treated with rituximab (4 intravenous infusions of 375 mg/m2 once weekly for 4 consecutive weeks). Results: At 3 months follow-up, 44% (8/18) of cases achieved complete disease remission with a further 44% (8/18) showing partial remission. Further follow-up showed 5/8 partial responders achieving a complete response with 4 cases experiencing disease relapse (72% response at 9 months). There were no adverse drug-related events and its use resulted in a significant reduction in steroid dosage during follow-up. Conclusion: Rituximab is beneficial in the management of refractory PV, resulting in clinical remission and a steroid-sparing effect. Further study needs to examine rituximab dosage and scheduling as well as its place within the treatment algorithm.

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Rheumatoid arthritis (RA) is a chronic polyarthritis driven by autoimmune inflammatory processes involving various factors and molecules. Not only humoral factors but cellular surface antigens can be promising targets for regulation of the disease. Rituximab (RTX) and abatacept (ABT) are drugs targeting cellular surface antigens that are now available for the treatment of RA. RTX is partially humanized chimeric anti-CD20 antibody, which was developed for the treatment of B cell lymphoma. The efficacy of RTX when added on methotrexate (MTX) for the treatment of RA was confirmed by the DANCER trial. RTX is now established as a second-line biologic drug in RA treatment guidelines in EU and US because of the effectiveness proven by the REFLEX trial. Unfortunately, RTX is not approved in Japan, and clinical trials of ocrelizumab and ofatumumab, newly developed anti-CD20 antibodies, had failed because of safety issues. ABT is a chimeric protein that combines the extracellular domain of CTLA-4 and the Fc portion of IgG1. CTLA-4 is a surface molecule expressed on T cell and is a negative regulator of the interaction between T cells and antigen presenting cells. CTLA-4 or ABT competitively inhibits CD28-CD80/86 interaction, which is an essential co-stimulatory pathway of T cell activation, and induces an anergic state in T cells. The effectiveness of ABT for biologics-naïve RA and tumor necrosis factor (TNF) antagonist-refractory RA were confirmed by the AIM trial and the ATTAIN trial, respectively. ABT is now available globally and is established as a therapeutic option for RA treatment also in Japan. (Jpn J Clin Pharmacol Ther 2013; 44(1): 15-21)

Acanthamoeba encephalitis in a patient with systemic lupus treated with rituximab

Acanthamoeba species are free-living protozoa that can infect humans and animals. Acanthamoeba can cause serious central nervous system infections in immunocompromised hosts. Here we report a case of Acanthamoeba encephalitis in a patient with lupus nephritis, 1 month after completing a course of rituximab, an anti-CD20 chimeric antibody.

Rituximab: rescue therapy in life-threatening complications or refractory autoimmune diseases: a single center experience

Rituximab (RTX) is a chimeric anti-CD20 antibody, approved for rheumatoid arthritis (RA) patients who failed anti-Tumor Necrosis Factor therapy. It has been used occasionally for life-threatening autoimmune diseases (AID). We report our center experience in the use of RTX in life-threatening complications or refractory AID. Clinical charts of patients treated with RTX at our center were reviewed, cases treated for life-threatening complications or refractory AID were analyzed. Acute damage to vital organs such as lung, heart, kidney, nervous system with severe functional impairment were defined as life-threatening complications; treatment failure with high-dose corticosteroids, cyclophosphamide, IVIG, plasmapheresis was defined as refractory autoimmune disease. During the years 2003-2009, 117 patients were treated with RTX, most of them for RA. Nine patients (6 females, mean age 51.5 years, mean disease duration 6.3 years) answered the criteria. The indications were as follows: pulmonary hemorrhage (1 patient with cryoglobulinemic vasculitis, 1 with systemic sclerosis, 1 with ANCA-associated vasculitis), catastrophic anti-phospholipid syndrome (2 SLE patients), non-bacterial endocarditis and pulmonary hypertension (1 patient with mixed connective tissue disease), vasculitis and feet necrosis (1 patient with systemic lupus erythematosus), severe lupus demyelinative neuropathy and acute renal failure (1 patient), and severe rheumatoid lung disease with recurrent empyema and pneumothorax (1 patient). B cell depletion was achieved in all patients. The median time since starting of complications to RTX administration was 3 weeks (range 2-15 weeks). Complete remission (suppression of the hazardous situation and return to previous stable state) was seen in 7 out of 9 patients. Partial remission (significant improvement) was achieved in the remained. The median time to response was 3 weeks (range 1-8 weeks), mean follow-up 47.2 months (range 6-60 months). A rapid tapering off of steroids was achieved in all patients. Two patients relapsed and were successfully retreated with RTX: the patient with severe RA lung relapsed after 3 years, one of the patients with ANCA-associated pulmonary alveolar hemorrhage relapsed after 10 months. There were no side effects during RTX infusion. Two episodes of serious infections were registered: fatal Gram-negative sepsis 6 months after RTX treatment, and septic discitis 4 months after receiving RTX. RTX serves as a safe, efficient, and prompt rescue therapy in certain life-threatening conditions and resistant to aggressive immunosuppression AID. RTX when administrated at an earlier stage, prevented irreversible vital organ damage, and allowed rapid steroid tapering off in already severe immunodepressed patients.

Generation of a Potent Recombinant Homophilic Chimeric Anti-CD20 Antibody

Previously we increased the potency of therapeutic antibodies in targeting, induction of apoptosis, and growth inhibition in vitro and in vivo by chemically conjugating a homophilic peptide to the antibody. Here, we describe the construction of a chimeric fusion gene derived from the murine anti-CD20 antibody (1F5) variable region, with an engineered homophilic domain at the C-terminus of the human IgG1 sequence. The construct was expressed in CHO suspension cells and purified. The potency of the homophilic anti-CD20 antibody was compared to a chimeric antibody without the engineered homophilic domain. In this comparison, the homophilic anti-CD20 antibody showed increased binding to a human CD20 cell line, and significantly more ADCC, CDC, and induction of apoptosis in three cell lines. In addition, the homophilic anti-CD20 antibody demonstrated increased inhibition of proliferation of two cell lines. These data show that homophilic fusion protein antibodies with enhanced therapeutic potency can be produced with industry-standard fermentation protocols.