Direct Cell Death Research Articles

Encouraging Activity of Obinutuzumab (GA101) Monotherapy in Relapsed/Refractory Aggressive Non-Hodgkin's Lymphoma: Results From a Phase II Study (BO20999),

Abstract 3655▪▪This icon denotes a clinically relevant abstractObinutuzumab (GA101) is a type II glycoengineered, humanized anti-CD20 monoclonal antibody that has increased antibody-dependent cellular cytotoxicity and direct cell death activity but lower complement-dependent cytotoxicity compared with type I anti-CD20 antibodies such as rituximab and ofatumumab. GA101 is in clinical development for the treatment of lymphoma and chronic lymphocytic leukemia. The Phase I/II study BO20999 has evaluated the efficacy and safety of GA101 monotherapy in patients with relapsed/refractory aggressive non-Hodgkin's lymphoma (aNHL). Here, we report updated Phase II results including progression-free survival (PFS) and best overall response (BOR).Patients (n = 40) were randomized to receive GA101 (D1, D8 and D22, then 3-weekly for total of 9 infusions) at either a high dose (1,600 mg on D1 and D8, then 800 mg thereafter; 1,600/800 mg cohort; n = 19), or a flat low dose of 400 mg (400/400 mg cohort; n = 21).Baseline patient characteristics were similar for both cohorts (Table 1). The median observation time for all patients was 9.5 months (0.3–26.1 months). BOR rates are given in Table 2, with 8/25 diffuse large B-cell lymphoma (DLBCL) patients (32%) and 4/15 mantle cell lymphoma (MCL) patients (27%) responding to GA101. Among the patients with rituximab-refractory disease, a response was observed in 1/13 patients (7.7%) and 4/12 patients (33.3%) treated in the 400/400 mg and 1,600/800 mg cohorts, respectively. Of these, 4 patients (1,600/800 mg cohort) had a response duration > 6 months, with 2 patients having an ongoing response (response duration: 9.8, 16.5+, 19.5 and 20.0+ months). Median PFS for patients with DLBCL (Figure 1) was 1.9 months (range: 0.3–15.7 months) for the 400/400 mg cohort and 2.7 months (range: 0.2–22.3) months) for the 1,600/800 mg cohort (hazard ratio: 0.70; 95% CI: 0.30–1.66). For the DLBCL subgroup, response duration was 3.1, 3.1+, 5.8, 16.5+ and 19.5 months for the 5 responders in the 1,600/800 mg cohort, compared with 6.3, 8.6 and 9.8 months for the 3 responders in the 400/400 mg cohort. Individual response data indicated that 2 MCL patients had an ongoing response for ≥ 20 months (20.0 and 20.4 months). GA101 was well tolerated in both cohorts. Infusion-related reactions (IRRs; all grades) were the most common adverse event (AE), occurring in 81% of patients in the 400/400 mg cohort and 68% of patients in the 1600/800 mg cohort. Grade 3/4 AEs occurring in >5% of patients across both cohorts included IRRs (10%), tumor lysis syndrome (10%), cardiac failure (not treatment-related; 10%), anemia (14%) and thrombocytopenia (14%) in the 400/400 mg cohort and IRRs (5%) and anemia (5%) in the 1,600/800 mg cohort.Table 1Baseline patient characteristicsCharacteristic400/400 mg (n = 21)1,600/800 mg (n = 19)All (n = 40)Median age, years (range)70 (43–80)72 (22–85)71 (22–85)Histology, nDLBCL101525MCL11415Median number of prior treatments, n (range)4 (1–17)3 (1–6)3 (1–17)Previous rituximab, n211940Rituximab refractory*, n131225Prior stem cell transplant, n268DLBCL, diffuse large B-cell lymphoma; MCL, mantle cell lymphoma.*Rituximab refractory defined as patients who had a response of < 6 months or who failed to respond to a rituximab-containing regimen (rituximab monotherapy or in combination with chemotherapy) at any point during their treatment history.Table 2Best overall response according to diagnosis and cohortDLBCLMCLResponse, n (%)400/400 mg (n = 10)1,600/800 mg (n = 15)400/400 mg (n = 11)1,600/800 mg (n = 4)Complete response (CR)0 (0.0)3 (20.0)2 (18.2)0 (0.0)CR unconfirmed1 (10.0)0 (0.0)0 (0.0)0 (0.0)Partial response2 (20.0)2 (13.3)0 (0.0)2 (50.0)Stable disease1 (10.0)1 (6.7)3 (27.3)0 (0.0)Progressive disease5 (50.0)9 (60.0)6 (54.5)2 (50.0)No response assessment1 (10.0)0 (0.0)0 (0.0)0 (0.0)DLBCL, diffuse large B-cell lymphoma; MCL, mantle cell lymphoma. [Display omitted] In conclusion, GA101 shows encouraging single-agent efficacy in these heavily pretreated patients with relapsed/refractory aNHL (DLBCL or MCL). A Phase III trial of rituximab plus CHOP vs GA101 plus CHOP in first-line DLBCL has recently started. Disclosures:Morschhauser:Roche: Honoraria; Celgene: Consultancy, Honoraria. Cartron:Roche: Consultancy, Honoraria; GSK: Honoraria; LFB: Honoraria. Milpied:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Wenger:Roche: Employment. Wassner-Fritsch:Roche: Employment. Asikanius:Roche: Employment. Salles:Roche: Consultancy, Honoraria.

Adenoviruses-mediated transduction of human oesophageal carcinoma cells with the interferon-λ genes produced anti-tumour effects

Background:Interferon-λs (IFN-λs) are novel cytokines with multiple functions, like IFN-α and -β. We examined possible anti-tumour effects produced by adenoviruses bearing the IFN-λ1 or -λ2 gene (Ad/IFN-λ) with the type-35 fibre-knob structure.Methods:Proliferation of oesophageal carcinoma cells transduced with Ad/IFN-λ and mechanisms of the inhibited growth were investigated.Results:Transduction with Ad/IFN-λ upregulated the expression of the class I antigens of the major histocompatibility complexes and induced the growth suppression. Increased sub-G1 populations and the cleavage of caspase-3 and poly (ADP-ribose) polymerase were detected in IFN-λ-sensitive YES-2 and T.Tn cells. The cell death was accompanied by cytoplasmic cytochrome C and increased cleaved caspase-9 and Bax expression, suggesting mitochondria-mediated apoptosis. Adenovirus/IFN-λ-infected YES-2 cells subsequently reduced the tumourigenicity. Adenovirus/IFN-λ-infected fibroblasts, negative for the IFN-λ receptors, induced death of YES-2 or T.Tn cells that were co-cultured. Inoculation of YES-2 cells in nude mice, when mixed with the Ad/IFN-λ-infected fibroblasts, resulted in retardation of the tumour growth. The growth suppression was not linked with upregulated CD69 expression on natural killer cells or increased numbers of CD31-positive cells.Conclusion:Adenovirus/IFN-λ induced apoptosis, and fibroblast-mediated delivery of IFN-λs is a potential cancer treatment by inducing direct cell death of the target carcinoma.

Perspectives on the Role of Photodynamic Therapy in the Treatment of Pancreatic Cancer

Photodynamic therapy (PDT) is a noninvasive procedure involving a photosensitizing agent that is activated by light to produce reactive oxygen species (ROS) that selectively destroy tumor cells. In recent years, PDT has been used in the treatment of pancreatic cancer (PC). The antitumor effects of PDT include three main mechanisms: direct tumor cell death (necrosis, apoptosis, and autophagy), vascular destruction, and immune system activation. The present paper systematically summarizes the effects of PDT in the treatment of PC from the experimental studies to the clinical studies and discusses the mechanisms of PDT-induced PC destruction.

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

CD20 monoclonal antibodies are widely used in clinical practice. Antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity and direct cell death have been suggested to be important effector functions for CD20 antibodies. However, their specific contributions to the in vivo mechanism of action of CD20 immunotherapy have not been well defined. Here we studied the in vivo mechanism of action of type I (rituximab and ofatumumab) and type II (HuMab-11B8) CD20 antibodies in a peritoneal, syngeneic, mouse model with EL4-CD20 cells using low and high tumor burden. Interestingly, we observed striking differences in the in vivo mechanism of action of CD20 antibodies dependent on tumor load. In conditions of low tumor burden, complement was sufficient for tumor killing both for type I and type II CD20 antibodies. In contrast, in conditions of high tumor burden, activating FcγR (specifically FcγRIII), active complement and complement receptor 3 were all essential for tumor killing. Our data suggest that complement-enhanced antibody-dependent cellular cytotoxicity may critically affect tumor killing by CD20 antibodies in vivo. The type II CD20 antibody 11B8, which is a poor inducer of complement activation, was ineffective against high tumor burden. Tumor burden affects the in vivo mechanism of action of CD20 antibodies. Low tumor load can be eliminated by complement alone, whereas elimination of high tumor load requires multiple effector mechanisms.

Topical aminolaevulinic acid-photodynamic therapy produces an inflammatory infiltrate but reduces Langerhans cells in healthy human skin in vivo

Topical photodynamic therapy (PDT) elicits a therapeutic response in both skin cancer and immune-mediated skin disorders. While PDT induces direct cell death, host inflammatory and immune responses to PDT may contribute to the therapeutic effects. To examine the impact of topical PDT on leucocyte trafficking and mediators of chemotaxis in healthy human skin. Aminolaevulinic acid (ALA)-PDT was performed on the buttock skin of seven healthy volunteers. Biopsies for immunohistochemical assessment were taken 1, 4 and 24 h post-PDT and from untreated contralateral buttock skin (baseline). A significant dermal neutrophilic infiltrate appeared early, peaking at 4 h (P < 0·01) and returning to near baseline by 24 h. Expression of E-selectin was significantly higher at 4 h (P < 0·05) and correlated strongly with neutrophil numbers (r = 0·93). Expression of intercellular adhesion molecule 1 was significantly elevated after 24 h (P < 0·05) with an apparent gradual increase in CD4+ T cells up to this time point. Notably, epidermal Langerhans cells were significantly reduced 24 h post-PDT compared with baseline (P < 0·01) and comprised a significantly larger proportion of cells with migratory rather than dendritic morphology (P < 0·05). The number of epidermal cells expressing tumour necrosis factor-α significantly increased at 4 h (P < 0·05) and remained elevated 24 h post-PDT, whereas no significant change in expression of interleukin (IL)-1β or IL-8 was seen. Reduction of Langerhans cells by topical PDT of human skin may play a significant role in PDT-induced local immunosuppression, potentially benefiting the treatment of immune-mediated skin disorders but negatively impacting on antitumour responses. Further exploration according to disease indication/treatment protocol is warranted.

Herceptin conjugates linked by EDC boost direct tumor cell death via programmed tumor cell necrosis.

Tumor-targeted antibody therapy is one of the safest biological therapeutics for cancer patients, but it is often ineffective at inducing direct tumor cell death and is ineffective against resistant tumor cells. Currently, the antitumor efficacy of antibody therapy is primarily achieved by inducing indirect tumor cell death, such as antibody-dependent cell cytotoxicity. Our study reveals that Herceptin conjugates, if generated via the crosslinker EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride), are capable of engendering human epidermal growth factor receptor 2 (Her2) positive tumor cells death. Using a high-performance liquid chromatography (HPLC) system, three peaks with estimated molecular weights of antibody monomer, dimer, and trimer were isolated. Both Herceptin trimer and dimer separated by HPLC induced significant levels of necrotic tumor cell death, although the trimer was more effective than the dimer. Notably, the Herceptin trimer also induced Herceptin-resistant tumor cell death. Surprisingly different from the known cell death mechanism that often results from antibody treatment, the Herceptin trimer elicited effective and direct tumor cell death via a novel mechanism: programmed cell necrosis. In Her2-positive cells, inhibition of necrosis pathways significantly reversed Herceptin trimer-induced cell death. In summary, the Herceptin trimer reported herein harbors great potential for overcoming tumor cell resistance to Herceptin treatment.

Oral mucositis

Oral mucositis remains one of the most common and troubling side effects of standard chemoradiation regimens used for the treatment of head and neck cancer. Virtually all patients who receive cumulative radiation doses of more than 30 Gy that includes oral mucosal fields will develop the condition. Not only does mucositis cause extreme discomfort, often necessitating opioid analgesia, but it is also associated with increased use of health resources and cost of treatment. The incremental cost of mucositis in patients with head and neck cancer is more than $17 000 (US). Much has been learned about the pathobiology that underlies the condition. The departure from the historical paradigm of direct cell death as being the primary cause for mucosal injury in favor of a more comprehensive view of the impact of chemoradiation on all the cells of the mucosa, has resulted in a picture of mucositis pathogenesis, which is biologically broad based. Although there are currently few treatment options for oral mucositis at the moment, the recognition that its underlying biology is complex has provided a range of treatment options that are currently being developed.

Neutrons do not produce a bystander effect in zebrafish irradiated in vivo

Purpose: Neutron irradiations at the McMaster Tandetron Accelerator were performed to study direct and bystander effects of neutrons in a live organism.Methods: The neutrons were produced through 7Li(p,n)7Be reaction. Although the gamma contamination of the neutron beam cannot be completely eliminated, it was designed to be as low as possible and remain below a threshold already established for bystander effects. Microdosimetric methods using a tissue-equivalent proportional counter have been used to measure the neutron and gamma doses for the cell irradiation. Previous data for a cell line exposed in vitro suggested that neutrons did not produce bystander effects at doses below 300 mGy. The current experiments sought to confirm this using a live whole organism (zebrafish) where tissue samples harvested 2 h after exposure were examined for direct evidence of apoptosis and tested for secretion of bystander factors using an established bioassay. Fish were either exposed directly to the beam or were allowed to swim with or in water previously occupied by irradiated fish.Results: Using the zebrafish model it was found that there was significant direct cell death seen both by apoptosis scores and clonogenic assay when the neutron dose was approximately 100 mGy. An equivalent dose of gamma rays produced a more toxic effect. It was further found that neutrons did not induce a bystander effect in fish receiving signals from irradiated fish.Conclusion: The results confirm in vitro experiments which suggest neutrons do not induce bystander signaling. In fact they may suppress gamma induced signaling suggesting a possible intriguing new and as yet unclear mechanism.

Direct cytotoxicity produced by adenoviral-mediated interferon α gene transfer in interferon-resistant cancer cells involves ER stress and caspase 4 activation

Over the past several years we have obtained considerable evidence indicating that adenoviruses-expressing interferon α (Ad-IFNα) can overcome resistance to the IFNα protein itself. Since cancer cells infected with Ad-IFNα also show high perinuclear cytoplasmic IFNα expression, we were interested in whether endoplasmic reticulum (ER) stress and cleavage of caspase 4 could have a major role in Ad-IFNα-produced cancer cell death. Indeed, procaspase 4 was upregulated and cleaved as early as 12 h after Ad-IFNα infection of the cancer cells, which co-localized with IFNα staining and ER tracker. In contrast, immortalized normal human urothelial cells, although exhibiting similar perinuclear IFNα staining, showed no cleaved caspase 4. Caspase 4 cleavage was not blocked by the caspase 8 specific inhibitor zIETD, indicating that caspase 4 activation was independent of caspase 8 activation. Blocking caspase 4 also inhibited activation of caspase 3 in Ad-IFNα containing cells. Finally, the cleaved form of caspase 4 (p10) was detected in Ad-IFNα-positive cancer cells from the urine of a patient following intravesical Ad-IFNα/Syn3 treatment. Therefore, ER stress and activation of caspase 4 appears to be an important mechanism involved in the direct cancer cell death produced by Ad-IFNα and also occurs in the clinical setting.

The role of vacuole in plant cell death

Almost all plant cells have large vacuoles that contain both hydrolytic enzymes and a variety of defense proteins. Plants use vacuoles and vacuolar contents for programmed cell death (PCD) in two different ways: for a destructive way and for a non-destructive way. Destruction is caused by vacuolar membrane collapse, followed by the release of vacuolar hydrolytic enzymes into the cytosol, resulting in rapid and direct cell death. The destructive way is effective in the digestion of viruses proliferating in the cytosol, in susceptible cell death induced by fungal toxins, and in developmental cell death to generate integuments (seed coats) and tracheary elements. On the other hand, the non-destructive way involves fusion of the vacuolar and the plasma membrane, which allows vacuolar defense proteins to be discharged into the extracellular space where the bacteria proliferate. Membrane fusion, which is normally suppressed, was triggered in a proteasome-dependent manner. Intriguingly, both ways use enzymes with caspase-like activity; the membrane-fusion system uses proteasome subunit PBA1 with caspase-3-like activity, and the vacuolar-collapse system uses vacuolar processing enzyme (VPE) with caspase-1-like activity. This review summarizes two different ways of vacuole-mediated PCD and discusses how plants use them to attack pathogens that invade unexpectedly.

Abstract 4559: Herceptin trimers linked by EDC could boost direct tumor cell death and overcome resistance to trastuzumab treatment via programmed tumor cell necrosis

Abstract The human epidermal growth factor receptor 2 (Her2) is overexpressed in multiple types of tumors, including breast tumors and osteosarcoma. Tumor-targeted antibody therapy is one of the safest therapeutics available, but it is often ineffective in treating primary and acquired antibody-resistant tumor cells via indirect tumor cell death and inducing direct tumor cell death. This study reveals that Herceptin conjugates, if generated via the crosslinker EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodimide hydrochloride), is capable of causing Her2 positive tumor cell death. Using an HPLC system, two peaks with estimated molecular weights of antibody dimers and trimers were isolated. The Herceptin dimer and trimer separated by HPLC, especially the trimer, induces significant levels of necrotic tumor cell death. Unlike SMCC conjugated Herceptin, this study indicates that the EDC-conjugated Herceptin overcomes the acquired resistance. The Herceptin trimer is more effective than the dimer in enhancing Herceptin-resistant tumor cell death. Surprisingly different from the known cell death mechanism often resulting from antibody treatment, the Herceptin trimer causes effective and direct tumor cell death via a novel cell death mechanism: programmed cell necrosis. Inhibition of RIP, a critical regulator of programmed necrotic cell death, reversed the Herceptin trimer-induced cell death. In summary, the Herceptin conjugate especially trimer linked by EDC could overcome Her2 positive breast cancer or osteosarcoma cells as well as the resistant cell lines via program cell necrosis cell death. This conjugate has great potential for overcoming the tumor cell resistance to the Herceptin treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4559. doi:10.1158/1538-7445.AM2011-4559

Mechanism of Action of Type II, Glycoengineered, Anti-CD20 Monoclonal Antibody GA101 in B-Chronic Lymphocytic Leukemia Whole Blood Assays in Comparison with Rituximab and Alemtuzumab

We analyzed in B-chronic lymphocytic leukemia (B-CLL) whole blood assays the activity of therapeutic mAbs alemtuzumab, rituximab, and type II glycoengineered anti-CD20 mAb GA101. Whole blood samples were treated with Abs, and death of CD19(+) B-CLL was measured by flow cytometry. Alemtuzumab efficiently lysed B-CLL targets with maximal lysis at 1-4 h (62%). In contrast, rituximab induced a more limited cell death (21%) that was maximal only at 24 h. GA101 killed B-CLL targets to a similar extent but more rapidly than rituximab, with 19.2 and 23.5% cell death at 4 and 24 h, respectively, compared with 7.9 and 21.4% for rituximab. Lysis by both rituximab and GA101 correlated directly with CD20 expression levels (r(2) = 0.88 and 0.85, respectively). Interestingly, lysis by all three Abs at high concentrations was mostly complement dependent, because it was blocked by the anti-C5 Ab eculizumab by 90% in the case of alemtuzumab and rituximab and by 64% in the case of GA101. Although GA101 caused homotypic adhesion, it induced only limited (3%) direct cell death of purified B-CLL cells. Both rituximab and GA101 showed the same efficiency in phagocytosis assays, but phagocytosis was not significant in whole blood due to excess Igs. Finally, GA101 at 1-100 μg/ml induced 2- to 3-fold more efficient NK cell degranulation than rituximab in isolated B-CLL or normal PBMCs. GA101, but not rituximab, also mediated significant NK cell degranulation in whole blood samples. Thus, complement and Ab-dependent cellular cytotoxicity are believed to be the major effector mechanisms of GA101 in whole blood assays.

Oligodendroglial pathology in the development of myelin breakdown in the dmy mutant rat

The dmy rat is an autosomal recessive mutant that exhibits severe myelin destruction throughout the white matter of the central nervous system. Recently, a point mutation in intron 3 of the Mrs2 has been found in the dmy rat. Mrs2 encodes an essential component of the major electrophoretic Mg 2+ influx system in mitochondria of yeast as well as human cells. In this study, we examined the morphological and numerical changes of oligodendroctyes in the development of myelin destruction in the spinal cord of the dmy rat. The number of oligodendrocytes decreases rapidly from 7 weeks of age in the dmy rat in accordance with myelin breakdown. Hypertrophic oligodendrocytes were frequently observed, and the cytoplasm was found to be intensely positive for prohibitin and cytochrome oxidase, mitochondrial markers. These data suggest that mitochondrial dysfunction causes a work/compensatory hypertrophy of oligodendrocytes, resulting in direct cell death and leading to myelin destruction.

Direct gene transfer of adenoviral-mediated interferon α into human bladder cancer cells but not the bystander factors produced induces endoplasmic reticulum stress-related cytotoxicity

We have previously shown that adenoviral-mediated interferon α (Ad-IFNα) is cytotoxic both to cells that are sensitive to recombinant interferon α (IFNα) and to cells which are resistant to IFNα. The cancer cell-specific cytotoxic effects of Ad-IFNα involve three different mechanisms: 1. The direct effect of IFNα production causing cancer cell death in IFNα sensitive cells (1); 2. The direct effect of Ad-IFNα infection and high levels of IFNα expression in IFNα resistant cancer cells (2); and 3. The indirect effect of the Ad-IFNα bystander factors produced (2-4). After Ad-IFNα infection, the cells produce a large amount of perinuclear localized IFN protein. This protein over-load could be a major factor in the direct cancer cell death of those cells infected with Ad-IFNα compared with the indirect cytotoxic effects of the bystander factors produced. Here, we investigated whether a component of Ad-IFN-induced cell death involves protein overload-induced endoplasmic reticulum (ER) stress, using an IFNα-resistant human bladder cancer cell line (KU7), and the normal human urothelial cell line, TERT-NHUC, as preclinical models. We found that the two ER stress response pathways examined were activated in KU7 cells. In contrast, following treatment of the normal TERT-NHUC cells with Ad-IFNα, no ER stress signals were observed. In addition, no ER stress related changes were seen, when KU7 cells were exposed to conditioned medium from Ad-IFNα-treated KU7 cells, indicating that bystander produced cytotoxicity did not involve ER stress. After 24 h of Ad-IFNα infection, the KU7 cancer cells produced spliced X-box binding protein 1 and activating transcription factor 6 protein (ATF6), evoking an ER stress response that could contribute to Ad-IFNα induced apoptosis in these cancer cells. In addition, GADD153/CHOP, GADD34 and BAX were also subsequently modified following activation of the ER stress pathways, thereby signaling downstream effectors in a pro-apoptotic manner.

Comparison of the in vitro effects of the anti‐CD20 antibodies rituximab and GA101 on chronic lymphocytic leukaemia cells

The effects of two CD20 antibodies, namely rituximab, the current standard for treatment of chronic lymphocytic leukaemia (CLL) in combination with chemotherapy, and GA101, a glyco-engineered type II antibody were compared on CLL cells ex vivo. Antibody-induced phosphatidylserine exposure was examined in isolated CLL cells. For a more comprehensive assessment of antibody-mediated cell killing including Fc-mediated mechanisms, B cell depletion from whole blood samples was monitored. Treatment with rituximab or GA101 reduced the average viability of isolated CLL cells by 6% or 11%, and the ratio of B to T cells in whole blood samples by 12% or 33%, respectively. Combination with GA101 enhanced the cytotoxicity of the chemotherapeutic agent chlorambucil on isolated CLL cells. CD20 surface expression on CLL cells correlated with GA101-induced B cell depletion, but not with direct cell death induction. Treatment of whole blood samples from CLL patients with a CpG-containing oligonucleotide increased CD20 expression on CLL cells and GA101-dependent B cell depletion. Despite the variable responses of individual CLL samples, the CLL cell depletion from whole blood by GA101 was consistently much stronger than by rituximab, which argues for clinical investigation of GA101 in CLL patients.

The Anti-CD20 Monoclonal Antibody GA101 Displays More Robust Anti-Tumor Activity Versus Rituximab In Waldenstrom's Macroglobulinemia (WM)

AbstractAbstract 4904 Background:Rituximab is an IgG class CD20-directed monoclonal antibody used in the treatment of B-cell malignancies, including WM. We and others have previously demonstrated dependence for IgG class therapeutic antibodies on polymorphisms at FcγRIIIA-158. Approximately half of WM patients express V/V or V/F, and the remainder half express F/F at this polymorphic locus. Patients with WM expressing FcγRIIIA-158 V/V or V/F show improved rituximab single agent activity, as well as attainment of deeper responses (VGPR or CR) with combination Rituximab therapy. GA101 is a novel humanized anti-CD20 antibody with a glyco-engineered Fc domain that exhibits increased Fcg receptor binding and ADCC activity. Methods:In this study, we examined the in vitro activity of GA101 and Rituximab against WM cells, and also examined the activity of these antibodies in context of FcγRIIIA-158 polymorphisms. ADCC activity for GA101 and Rituximab was assessed using genotyped healthy donor derived NK cells against BCWM.1 WM cells, as well autologous NK cells against the patient's own lymphoplasmacytic cells. In vitro B-cell depletion and direct cell death induction assays were also performed. Results:We observed significantly greater ADCC activity against WM cells for GA101 versus Rituximab in both healthy donor, as well as autologous NK cell assays. GA101 mediated ADCC activity was particularly more robust versus Rituximab in patients expressing FcγRIIIA-158 F/F versus V/V or V/F (Figure 1). In addition, GA101 induced significant direct cell death against WM lymphoplasmacytic cells, as well as in vitro B-cell depletion assays in comparison to Rituximab, which exhibited little direct cell death induction activity. Nuclear translocation of apoptosis inducing factor (AIF) was observed following GA101 by immunofluorescence microscopy. Conclusions:GA101 is associated with enhanced ADCC activity relative to Rituximab by NK cells, particularly for those subjects expressing FcγRIIIA-158 F/F. In addition, GA101 demonstrated direct cell death in WM lymphoplasmacytic cells through an AIF mediated caspase-independent pathway. These studies provide the framework for the investigation of GA101 in WM, and suggest particular benefit for those patients who express FcγRIIIA-158 F/F. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Superior Efficacy of the Novel Type II, Glycoengineered CD20 Antibody GA101vs. the Type I CD20 Antibodies Rituximab and Ofatumumab

AbstractAbstract 3925GA101 is Type II, glycoengineered CD20 monoclonal antibody currently in PhII/III clinical trials. We have previously shown that GA101 mediates superior in vitro and in vivo activity compared to the Type I CD20 antibody rituximab. By epitope mapping and crystallography we have shown that GA101 recognizes CD20 in a unique way that is different from Type I CD20 antibodies and have proposed that this may be the basis for the Type II character of GA101.Here we compare for the first time GA101 with rituximab, the standard of care in various clinical settings in NHL and B-CLL in combination with chemotherapy, as well as with the Type I CD20 antibody ofatumumab, which was recently approved for treatment of B-CLL patients refractory to fludarabine and alemtuzumab. The following assays were used to compare the three anti-CD20 antibodies: i) Binding to NHL cell lines Z138 (MCL, ca. 60.000 CD20 binding sites per cell) and SU-DHL4 (DLBCL, ca. 1 Mio CD20 binding sites per cell) assessed by FACS, ii) Cell death induction, detected by AxV/PI staining and FACS, on a panel of NHL cell lines, iii) Antibody dependent cellular cytotoxicity mediated by PBMNCs as effector and Z138, SU-DHL4 as target cells (ADCC, LDH release assay); iv) Complement dependent cytotoxicity with Z138, SU-DHL4 as target cells (CDC, LDH release assay) and v) B-cell depletion (assessed by FACS) in whole blood from healthy donors. Dose-dependent anti-tumoral activity was assessed in a s.c. SU-DHL4 NHL xenograft model in Scid beige mice. Survival experiments in a disseminated Z138 MCL model are ongoing and an update on the results will be included as part of the poster presentation. Ofatumumab (“Arzerra”) was purchased from a local pharmacy, GA101 and rituximab were obtained from Hoffmann La Roche AG, Basel.First, binding studies confirmed that GA101 shows half-maximal binding to NHL cells relative to rituximab and ofatumumab, a known property of Type II CD20 antibodies. EC50 values of binding were comparable indicating that GA101, rituximab and ofatumumab have apparent binding affinities in the low nanomolar range on NHL cells independent of the level of CD20 expression.Second, the three CD20 antibodies were compared for their induction of direct cell death as measured by AxV/PI staining. Overall, GA101 mediated superior direct cell death induction compared to rituximab and ofatumumab utilizing a panel of NHL cell lines of different origins.Immune effector-related mechanisms of action were subsequently compared by ADCC and CDC assays. GA101, a glycoengineered antibody with enhanced affinity for FcgRIIIa, was found to exhibit up to 100-fold higher ADCC potency than rituximab and ofatumumab on Z138 and SU-DHL4 cells. CDC, as expected for a Type II CD20 antibody was ca. 10 to 1,000 less potent compared to the Type I antibodies rituximab and ofatumumab. In order to integrate the different mechanisms of action (direct cell death, ADCC, CDC), autologous ex vivo B-cell depletion assays with whole blood from healthy donors containing natural immune effector cells, human complement and physiological concentrations of human immunoglobulins were performed. These studies showed that GA101 was more potent in terms of EC50 values and more efficacious in terms of absolute B-cell depletion when compared to rituximab and ofatumumab.Finally, the dose-dependent effects of the three CD20 antibodies was studied on the growth of s.c. SU-DHL4 DLBCL xenografts in SCID beige mice. GA101 induced a dose-dependent anti-tumoral effect including complete tumor remission and was superior to the Type I antibodies rituximab and ofatumumab at saturating antibody doses.In summary, the preclinical data presented herein demonstrate that the Type II, glycoengineered CD20 antibody GA101 is differentiated from the Type I CD20 antibodies rituximab and ofatumumab by its superior overall activity supporting its further clinical investigation. Of note, in contrast to previous publications, in this series of assays no superior preclinical activity of ofatumumab was observed when compared to rituximab. Disclosures:Herter:Roche: Employment, Patents & Royalties. Waldhauer:Roche: Employment. Otz:Roche: Employment. Herting:Roche: Employment, Patents & Royalties. Lang:Roche: Employment. Nicolini:Roche: Employment. Römmele:Roche: Employment. Friess:Roche: Employment, Patents & Royalties. Van Puijenbroek:Roche: Employment. Bacac:Roche: Employment. Weidner:Roche: Employment, Equity Ownership. Gerdes:Roche: Employment, Equity Ownership, Patents & Royalties. Umana:Roche: Employment, Equity Ownership, Patents & Royalties. Klein:Roche: Employment, Equity Ownership, Patents & Royalties.

Daratumumab Directly Induces Human Multiple Myeloma Cell Death and Acts Synergistically with Conventional and Novel Anti-Myeloma Drugs

AbstractAbstract 3013Daratumumab is a novel fully human therapeutic CD38-specific monoclonal antibody (mAb) that is currently in phase I/II safety and dose finding clinical studies in MM. We recently demonstrated that daratumumab induces antibody dependent cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC) against multiple myeloma (MM) cells (ASH Abstract #608, 2009). Significantly, daratumumab induces ADCC-mediated autologous lysis against MM patient cells. In addition, when cross-linked, daratumumab directly induces Ramos lymphoma cell death. We here studied whether daratumumab directly kills MM cells and whether daratumumab could be combined with other anti-MM drugs to further enhance its direct cytotoxicity. Direct daratumumab-induced MM cell death was determined using CellTiter-Glo luminescent cell viability assay and Annexin V/PI flow cytometry analysis, with or without goat anti-human IgG crosslinking. Following 48h incubation, daratumumab (0.1-10 μg/ml), when cross-linked, directly induced cytoxicity against dexamethasone (dex)-sensitive MM1S and dex-resistant MM1R cells, as evidenced by decreased cell viability in a dose-dependent manner. Importantly, cross-linked daratumumab increased caspase 3/7 activities in a dose-dependent fashion, as assessed by the Caspase-Glo® 3/7 luminescence assay. Furthermore, daratumumab upregulated Annexin V+ and Annexin V+/PI+ cells in freshly isolated CD138+ MM patient cells, from 7.7% to 20.6% and 10.9% to 15.4 %. Therefore, cross-linked daratumumab can directly trigger apoptosis of patient myeloma cells. Cell viability assay was further performed on MM1S cells when daratumumab (0.1, 1, 10 μg/ml) was combined with dex (0.5 and 1 μM) or bortezomib (2.5, 5, and 10 nM). Following 48–72h incubation with daratumumab, both dex and bortezomib synergistically inhibited MM cell viability, as determined by combination index (CI) < 0.5 at given combined concentrations of these drugs. Enhanced caspase 3/7 activation was also seen when daratumumab was combined with dex. To evaluate combination cytotoxicity induced by lenalidomide with daratumumab, peripheral blood mononuclear effector cells (PBMCs) from normal donors (n=2) were pretreated with lenalidomide (2 μM) for 3 days followed by daratumumab-mediated ADCC assays against MM1S cells. Using calcein-AM release measurements, lenalidomide-pretreated PBMCs further augmented daratumumab-induced MM1S cell lysis, whereas daratumumab-pretreated PBMCs did not alter ADCC. Taken together, our studies show that daratumumab directly induces MM cell death via activation of caspase 3/7 and daratumumab induced synergistic cytotoxicity with dex or bortezomib. Moreover, lenalidomide augments daratumumab-induced ADCC against MM cells. These results further support combination clinical trials of conventional and novel anti-MM drugs with daratumumab in MM. Disclosures:Weers:Genmab: Employment. Parren:Genmab: Employment. Richardson:Keryx Biopharmaceuticals: Honoraria. Munshi:Millennium Pharmaceuticals: Honoraria, Speakers Bureau. Anderson:Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

Differential Regulation Patterns of Anti-CD20 Antibodies GA101 and Rituximab in Mantle Cell Lymphoma

AbstractAbstract 1839 Background:Mantle cell lymphoma (MCL) is a distinct lymphoma subtype characterized by a poor long-term prognosis. Rituximab, a chimeric type I anti-CD20 antibody has shown an anti-proliferative effect in MCL cell lines and is meanwhile widely clinically applied in combination with chemotherapy. GA101, a type II, glycoengineered CD20 IgG1 antibody has been shown to result in higher direct cell death induction and increased ADCC in comparison to rituximab. In previous experiments GA101 displayed a significant higher cytotoxicity in comparison to rituximab. Aim of this study was the elucidation of the involved downstream signal pathways of the two antibodies. Methods:In two sensitive MCL cell lines (Rec-1, Granta-519) we determined the effect of GA101, rituximab and the combination of both antibodies on cell viability and proliferation. Granta 519 and Rec-1 were treated at a cell density of 5×105 cells/ml with GA101 or rituximab at a previously defined dose of 10 μg/ml. After 4h of exposure samples of 3×106 cells were harvested and processed for 2D-PAGE (polyacrylamide gel electrophoresis) analysis. Protein spots with altered expression after antibody treatment from untreated controls were identified and analyzed by mass spectrometry (MALDI-TOF). In parallel, Affymetrix micro-array analysis of MCL cell lines (Granta-519, HBL-2, Jeko-1, Rec-1 and Z-138) was performed after 4h exposure with either rituximab or GA101. To determine downstream pathways, Ingenuity Pathway Analysis of the identified genes was performed. Results:After mono-exposure with GA101 70% and 40 % cell reduction was achieved in Granta-519 and Rec-1, respectively. In contrast, rituximab led to 25% and 5% in Granta-519 and Rec-1. Interestingly, combination of both antibodies resulted in a cytotoxicity comparable to rituximab monotherapy. Computer-based analysis of the respective 2D-PAGE protein maps revealed 40 and 39 distinct differently expressed protein spots after GA101 and rituximab treatment, respectively. 23 of these protein spots were commonly altered after both antibodies (e.g. CCDC158, MACF1, RAB39, RAD23B) whereas after GA101 treatment 17 proteins (e.g. ENO1, MKI67, NPM1, HSPA5) and after rituximab 16 proteins (e.g. DST, G3BP2, LMO7, PSMD13) were uniquely altered.Micro-array analysis resulted in 2–3 (Granta 519) to 14–78 (HBL; GA101 and rituximab respectively) modulated genes after antibody exposure in all five distinct MCL cell lines. Again, applying a fold-change cut-off of 2, unique candidate genes after GA101 (EGR2, EGR3, NFATC1, SPRY2, ZBTB24 (includes EG: 9841)) and rituximab exposure (BCL2A1, CHL1, LILRA4, LPL, LY9, RHEBL1, SOX11, WNT3) were affected in multiple cell lines. Interestingly, transcriptome and proteome-based analysis characterized different sets of candidate molecules, which were however were mapped to common cellular functions including e.g. “cellular growth and proliferation”, “cell death” and “cell cycle”. Combination of both antibodies resulted in a rituximab-like expression pattern, both on RNA and protein level. Conclusions:Our analyses identified different and antibody-specific downstream expression patterns of GA101 and rituximab, which may represent the molecular basis of the superior effect of GA101 in comparison to rituximab. The simultaneous application of both antibodies resulted in a rituximab-like expression pattern of affected cellular functions and canonical pathways. These data will help to identify a molecular-based rationale for future combined therapeutic approaches and avoid potential antagonist effects. Disclosures:Dreyling:Roche: Support of in vitro studies in MCL.

Enhanced Activity of GA101, a Novel Type II, Glycoengineered CD20 Antibody, In Combination with Bendamustine or Fludarabine, and with the Bcl-2 Family Inhibitors ABT-737 or ABT-263

AbstractAbstract 3915GA101 is type II, glycoengineered CD20 antibody currently in PhII/III clinical trials. GA101 mediates enhanced direct cell death with a concomitant reduction of CDC; and high ADCC induction due to increased affinity for FcgRIIIa. We have shown that GA101 compared to rituximab mediates superior efficacy in NHL xenograft models including the induction of complete tumor remission.In clinical practice the combination of rituximab with chemotherapy e.g. CHOP, CVP, bendamustine, fludarabine or FC results in a substantial clinical benefit. To assess the potential of GA101 for combination with bendamustine or fludarabine, in vivo combination studies in s.c. Z138 (MCL) xenografts in Scid beige mice were devised. GA101 and rituximab at sub-optimal doses of 1 mg/kg (once weekly) were combined with 3 mg/kg bendamustine (days 19, 20, 21, 22); or with 40 mg/kg fludarabine (days 22, 23, 24) and compared to the corresponding monotherapy arms. GA101 in combination with bendamustine mediated statistically superior efficacy in terms of tumor growth inhibition (TGI) compared to the combination of rituximab and bendamustine: TGI values on day 33 were 29% for rituximab, 42% for rituximab + bendamustine, 47% for GA101 and 72% for GA101 + bendamustine. Treatment with bendamustine did not show significant antitumor activity. Statistical evaluation based on sAUC showed a more than additive and significant effect on tumor growth for the combination of GA101 with bendamustine compared to the corresponding monotherapy arms. GA101 in combination with fludarabine demonstrated statistically superior efficacy in terms of TGI and yielded a significant difference compared to the combination of rituximab and fludarabine or GA101 as monotherpy. TGI values on day 36 were 50% for fludarabine, 60% for rituximab, 85% for rituximab + fludarabine, 86% for GA101 and >100% for GA101 + fludarabine. Furthermore, the superiority of the GA101-fludarabine combination was demonstrated by the observation of 3 tumor-free animals at the end of the study.ABT-263 (navitoclax) is a Bcl-2 family inhibitor that is currently in Phase I/II clinical trials for lymphoid malignancies. To provide evidence that GA101 can be combined with ABT-263 and the experimental Bcl-2 family inhibitor ABT-737, in vivo combination studies in s.c. SU-DHL4 (DLBCL) xenografts in Scid beige mice were devised. 10 mg/kg GA101 and rituximab (once weekly) were combined with 50 mg/kg ABT-737 (i.p., days 19, 22, 24, 26, 29, 31, 33). In a second study, 3 mg/kg GA101 or 10 mg/kg rituximab (once weekly) were combined with 100 mg/kg ABT-263 (orally, once daily). GA101 at a sub-optimal dose of 10 mg/kg demonstrated statistically superior efficacy in combination with ABT-737 in terms of tumor growth inhibition compared to GA101 alone or the combination of 10 mg/kg rituximab and ABT-737. Both combination treatments were statistically significant compared to the corresponding monotherapy arms. TGI values based on means on day 36 were 20% for ABT-737, 45% for rituximab, 92% for rituximab + ABT-737, 96% for GA101 and >100% for GA101 + ABT-737. The superiority of the combination of GA101 and ABT-737 was supported by complete tumor regression in all animals whereas none was observed with the combination of rituximab and ABT-737. GA101 at a sub-optimal dose of 3 mg/kg or rituximab at a dose of 10 mg/kg mediated statistically superior efficacy in terms of tumor growth inhibition in combination with ABT-263 compared to the respective monotherapy arms. TGI values based on means on day 43 were 15% for ABT-263, 89% for rituximab, >100% for rituximab + ABT-263, 80% for GA101 (at the sub-optimal dose) and >100% for GA101 (sub-optimal dose) + ABT-263.Taken together i) GA101 as single agent was at least as efficacious as the combination of rituximab with bendamustine, fludarabine or ABT-737; ii) the combination of GA101 with bendamustine or fludarabine was superior to the respective monotherapy arms and resulted in an enhanced, at least additive effect of the combination; iii) the combination of GA101 with Bcl-2 family inhibitors ABT-737 and ABT-263 was superior to the respective monotherapy arms and resulted in an enhanced effect of the combination including the induction of tumor remission. These data strongly support the further clinical investigation of GA101 in combination with Fludarabine, Bendamustine or Bcl-2 family inhibitors. Disclosures:Herting:Roche: Employment. Bader:Roche: Employment. Umana:Roche: Employment, Equity Ownership. Klein:Roche: Employment, Equity Ownership.