Discovery and optimization of a series of small-molecule allosteric inhibitors of MALT1 protease.

We describe a series of potent and highly selective small-molecule MALT1 inhibitors, optimized from a High-Throughput Screening hit. Advanced analogues such as compound 40 show high potency (IC50: 0.01 µM) in a biochemical assay measuring MALT1 enzymatic activity, as well as in cellular assays: Jurkat T cell activation (0.05 µM) and IL6/10 secretion (IC50: 0.10/0.06 µM) in the TMD8 B-cell lymphoma line. Compound 40 also inhibited cleavage of the MALT1 substrate RelB (IC50: 0.10 µM). Mechanistic enzymology results suggest that these compounds bind to the known allosteric site of the protease.

Anti-tumor necrosis factor α prevents bowel fibrosis assessed by messenger RNA, histology, and magnetization transfer MRI in rats with Crohn's disease.

OBJECTIVE: Treatment of Crohn's disease (CD) with anti-tumor necrosis factor α (TNFα) decreases intestinal inflammation, but the effect on fibrosis remains unclear. We hypothesized that treatment with rat-specific anti-TNFα will decrease the development of intestinal fibrosis in a rat model of CD. We further hypothesized that magnetization transfer magnetic resonance imaging (MT-MRI) will be sensitive in detecting these differences in collagen content. METHODS: Rats were injected in the distal ileum and cecum with peptidoglycan-polysaccharide (PG-PS) or human serum albumin (control) at laparotomy and then received intraperitoneal injections of rat-specific anti-TNFα or vehicle daily for 21 days after laparotomy. Rats underwent MT-MRI abdominal imaging on day 19 or 20. MT ratio was calculated in the cecal wall. Cecal tissue histologic inflammation was scored. Cecal tissue procollagen, cytokine, and growth factor messenger RNAs were measured by quantitative real-time PCR. RESULTS: PG-PS-injected rats treated with anti-TNFα had less histologic inflammation, and cecal tissue expressed lower levels of proinflammatory cytokine messenger RNAs than vehicle-treated PG-PS-injected rats (IL-1ß: 5.59 ± 1.53 versus 10.41 ± 1.78, P = 0.02; IL-6: 23.23 ± 9.33 versus 45.89 ± 11.79, P = 0.07). PG-PS-injected rats treated with anti-TNFα developed less intestinal fibrosis than vehicle-treated PG-PS-injected rats by tissue procollagen I (2.87 ± 0.66 versus 9.28 ± 1.11; P = 0.00002), procollagen III (2.25 ± 0.35 versus 7.28 ± 0.76; P = 0.0000009), and MT-MRI (MT ratio: 17.79 ± 1.61 versus 27.95 ± 1.75; P = 0.0001). Insulin-like growth factor I (2.52 ± 0.44 versus 5.14 ± 0.60; P = 0.0007) and transforming growth factor ß1 (2.34 ± 0.29 versus 3.45 ± 0.29; P = 0.006) were also decreased in anti-TNFα-treated PG-PS-injected rats. CONCLUSIONS: Anti-TNFα prevents the development of bowel wall inflammation and fibrosis in the PG-PS rat model of CD. MT-MRI measurably demonstrates this decrease in intestinal fibrosis.

Mutated BCR-ABL generates immunogenic T-cell epitopes in CML patients.

PURPOSE: Characterization of an approach to identify leukemia neoantigens arising in the context of drug resistance. EXPERIMENTAL DESIGN: We assessed whether leukemia neoantigens could be generated from drug-resistant mutations in BCR-ABL after imatinib relapse in patients with chronic myelogenous leukemia (CML). RESULTS: We computationally predicted that approximately 70 peptides derived from 26 BCR-ABL mutations would bind eight common alleles of MHC class I (IC(50) < 1,000 nmol/L). Seven of nine imatinib-resistant CML patients were predicted to generate at least 1 peptide that binds autologous HLA alleles. We predicted and confirmed that an E255K mutation-derived peptide would bind HLA-A3 with high affinity (IC(50) = 28 nmol/L), and showed that this peptide is endogenously processed and presented. Polyfunctional E255K-specific CD8+ T cells were detected in two imatinib-resistant HLA-A3+ CML patients concurrent with an effective anti-CML response to further therapy. CONCLUSIONS: Our in vitro studies support the hypothesis that leukemia-driven genetic alterations are targeted by the immune system in association with a clinical response, and suggest the possibility of immunizing relapsed patients with CML against newly acquired tumor neoantigens.

Effective posttransplant antitumor immunity is associated with TLR-stimulating nucleic acid-immunoglobulin complexes in humans.

Donor lymphocyte infusion (DLI), whereby donor mononuclear cells are infused into patients, is one of the few effective immunotherapeutic strategies that generate long-lasting tumor remissions. We previously demonstrated that chronic myelogenous leukemia (CML) patients treated with DLI develop high-titer plasma antibodies specific for CML-associated antigens, the majority of which have been reported to bind nucleic acids These observations led us to predict that circulating antibody-antigen complexes in DLI-responsive patients carry nucleic acids that can engage innate immune sensors. Consistent with this, we report here that post-DLI plasma from 5 CML patients that responded to DLI treatment induced massive upregulation of MIP-1α, IP-10, and IFN-α in normal blood mononuclear cells. Importantly, this was not observed with plasma obtained before DLI and from DLI nonresponders and imatinib-treated patients. This endogenous immunostimulatory activity required nucleic acid and protein for its adjuvant effect and activated antigen-presenting cells through the RNA and DNA sensors TLR8 and TLR9. Presence of the immunoglobulin Fc receptor CD32 enhanced cellular responses, suggesting that immunoglobulins associate with this activity. Finally, a TLR-induced expression signature was detectable in post-DLI but not pre-DLI blood, consistent with an active circulating TLR8/9-stimulating factor. We have therefore demonstrated that effective tumor immunity correlates with the presence of endogenous nucleic acid-immunoglobulin complexes in patient plasma, thus providing a putative mechanism for the induction of potent antigen-specific immunity against malignant cells.

Characterization of golimumab, a human monoclonal antibody specific for human tumor necrosis factor α.

We prepared and characterized golimumab (CNTO148), a human IgG1 tumor necrosis factor alpha (TNFα) antagonist monoclonal antibody chosen for clinical development based on its molecular properties. Golimumab was compared with infliximab, adalimumab and etanercept for affinity and in vitro TNFα neutralization. The affinity of golimumab for soluble human TNFα, as determined by surface plasmon resonance, was similar to that of etanercept (18 pM versus 11 pM), greater than that of infliximab (44 pM) and significantly greater than that of adalimumab (127 pM, p=0.018).  The concentration of golimumab necessary to neutralize TNFα-induced E-selectin expression on human endothelial cells by 50% was significantly less than those for infliximab (3.2 fold; p=0.017) and adalimumab (3.3-fold; p=0.008) and comparable to that for etanercept. The conformational stability of golimumab was greater than that of infliximab (primary melting temperature [Tm] 74.8 °C vs. 69.5 °C) as assessed by differential scanning calorimetry.  In addition, golimumab showed minimal aggregation over the intended shelf life when formulated as a high concentration liquid product (100 mg/mL) for subcutaneous administration.  In vivo, golimumab at doses of 1 and 10 mg/kg significantly delayed disease progression in a mouse model of human TNFα-induced arthritis when compared with untreated mice, while infliximab was effective only at 10 mg/kg. Golimumab also significantly reduced histological scores for arthritis severity and cartilage damage, as well as serum levels of pro-inflammatory cytokines and chemokines associated with arthritis. Thus, we have demonstrated that golimumab is a highly stable human monoclonal antibody with high affinity and capacity to neutralize human TNFα in vitro and in vivo.

Serologic markers of effective tumor immunity against chronic lymphocytic leukemia include nonmutated B-cell antigens.

Patients with chronic lymphocytic leukemia (CLL) who relapse after allogeneic transplant may achieve durable remission following donor lymphocyte infusion (DLI), showing the potency of donor-derived immunity in eradicating tumors. We sought to elucidate the antigenic basis of the effective graft-versus-leukemia (GvL) responses associated with DLI for the treatment of CLL by analyzing the specificity of plasma antibody responses developing in two DLI-treated patients who achieved long-term remission without graft-versus-host disease. By probing high-density protein microarrays with patient plasma, we discovered 35 predominantly intracellular antigens that elicited high-titer antibody reactivity greater in post-DLI than in pre-DLI plasma. Three antigens-C6orf130, MDS032, and ZFYVE19-were identified by both patients. Along with additional candidate antigens DAPK3, SERBP1, and OGFOD1, these proteins showed higher transcript and protein expression in B cells and CLL cells compared with normal peripheral blood mononuclear cells. DAPK3 and the shared antigens do not represent minor histocompatibility antigens, as their sequences are identical in both donor and tumor. Although ZFYVE19, DAPK3, and OGFOD1 elicited minimal antibody reactivity in 12 normal subjects and 12 chemotherapy-treated CLL patients, 5 of 12 CLL patients with clinical GvL responses were serologically reactive to these antigens. Moreover, antibody reactivity against these antigens was temporally correlated with clinical disease regression. These B-cell antigens represent promising biomarkers of effective anti-CLL immunity.

Efficacious immune therapy in chronic myelogenous leukemia (CML) recognizes antigens that are expressed on CML progenitor cells.

Curative effects of graft-versus-leukemia-based therapies such as donor lymphocyte infusion (DLI) for chronic myelogenous leukemia (CML) may result from immunologic ablation of self-renewing CML progenitor cells. Patients who achieved durable remissions after DLI developed a significant B-cell lymphocytosis after treatment, which did not occur in patients who were unresponsive to DLI. In this study, we identified antigen targets of this B-cell response by probing two immunoproteomic platforms with plasma immunoglobulins from seven CML patients with clinically apparent graft-versus-leukemia responses after DLI. In total, 62 antigens elicited greater reactivity from post-DLI versus pre-DLI plasma. Microarray analysis revealed that >70% of the antigens were expressed in CML CD34(+) cells, suggesting that expression in malignant progenitor cells is a feature common to antibody targets of DLI. We confirmed elevated expression of three target antigens (RAB38, TBCE, and DUSP12) in CML that together consistently elicited antibody responses in 18 of 21 of an additional cohort of CML patients with therapeutic responses, but not in normal donors and rarely in non-CML patients. In summary, immunologic targets of curative DLI responses include multiple antigens on CML progenitor cells, identifying them as potential immunogens for vaccination and/or monitoring of immunotherapeutics designed to eliminate myeloid leukemia stem cells.

Quantitative in vivo comparisons of the Fc gamma receptor-dependent agonist activities of different fucosylation variants of an immunoglobulin G antibody.

Although it has been shown that functions of immunoglobulin G (IgG) antibodies (Abs) that depend on binding to certain Fc gamma receptors (Fc gamma R) can be influenced by Fc glycan fucosylation, quantitative in vivo analyses comparing the effects of different levels of fucose are still lacking. We used a simple mouse model to compare Fc gamma R-dependent T cell activation induced by different fucosylation variants of a hamster/human IgG1 chimeric version of anti-mouse CD3 monoclonal Ab, 145-2C11 (2C11). Initial studies supported the expectation that this agonist activity by 2C11 was a reflection of Fc gamma R binding, including comparisons of human IgG1 and IgG4 variants of 2C11 that showed the IgG4 to be dramatically less active at inducing T cell activation. Dose-response analyses in mice then showed that a sample of the human IgG1 version of 2C11 Ab in which 40% of the Fc glycans in the population of Ab molecules were fucosylated was 3-5 times more potent than a sample with 90% of its Fc glycans fucosylated. A sample with 10% fucosylation showed the same activity as the 40% fucosylated sample, revealing that complete absence of fucose was not necessary to achieve maximal Fc function in this model. In vitro binding to recombinant mouse Fc gamma Rs by the 2C11 variants revealed interesting relationships between fucose content and receptor affinity, and suggested the involvement of Fc gamma RIV in mediating 2C11 activity in vivo. These analyses showed that low-fucose human IgG1 Abs indeed show greater Fc gamma R-dependent activities in mice, but that Abs with moderate levels of fucose may be just as potent as Abs with very low or no fucose.

Higher levels of sialylated Fc glycans in immunoglobulin G molecules can adversely impact functionality.

Although it is now clear that certain Fc glycan structures on immunoglobulin G (IgG) antibodies (Abs) can have a dramatic influence on binding to selected Fcgamma receptors (FcgammaR) and on Fc-mediated immune functions, the effects of all known Fc glycan structures still have not been exhaustively studied. We report that in vitro analyses of pairs of monoclonal human IgG Abs that differ in the amount of sialic acid in their Fc glycans revealed that, for each of the three Ab pairs we examined, higher levels of sialylation were associated with reduced activity in Ab-dependent cellular cytotoxicity (ADCC) assays. This relationship between sialylation and ADCC activity was observed regardless of whether the differences in the extent of sialylation were derived by different Ab production processes, use of a lectin column to separate monoclonal Ab preparations into differentially sialylated fractions, or use of direct in vitro glycoengineering methods to convert a lesser sialylated Ab into a highly sialylated Ab. Subsequent investigations revealed that, depending on the individual Ab and how the differences in sialylation were derived, the lower ADCC potency of the more sialylated variants was apparently due to lower-affinity binding to FcgammaRIIIa on natural killer (NK) cells and/or, more interestingly, lower-affinity binding to cell-surface antigen. Our data provide the first example of an Fc glycan structure impacting antigen binding and suggest that avoiding Fc glycan sialylation can offer another means of optimizing ADCC activity of Abs.

Expression and regulation of murine macrophage angiopoietin-2.

Our understanding of angiogenesis has increased significantly in the past few years with the discovery of angiopoietins (Ang). Specifically, Ang2 has been associated with pathologic as well as normal vascularization. While previous studies have shown that a major source of Ang2 has been endothelial cells and tumor cells, we reasoned that macrophages would also have the ability to express angiopoietins, specifically Ang2, due to that cell's role in wound healing, tumor angiogenesis, and a number of non-oncological diseases, such as rheumatoid arthritis and psoriasis. In this study, murine macrophages constitutively expressed both transcripts and protein for Ang2 but not Ang1 or Ang3. The secretion of Ang2 was enhanced by treatment with lipopolysaccharide, interferon-gamma, prostaglandin E2 and other cyclic AMP-elevating agents, as well as vascular endothelial growth factor (VEGF). Cyclic AMP-dependent protein kinase (PKA) played a major role in this enhancement since the PKA inhibitor, H89, blocked secretion of Ang2. Since stimulation of the PKA pathway can lead to macrophage production of VEGF, it is possible that enhancement of Ang2 production by macrophages may be due to autocrine responsiveness to VEGF. Adding anti-VEGF antibodies to the supernatants of stimulated macrophages blocked secretion of Ang2. This study is the first to show murine macrophage production of Ang2 and to provide evidence that it can be regulated. Understanding the regulation of macrophage Ang2 production is especially important in an effort to target the pathologic role of macrophages while preserving their role in immunity and homeostasis.

Addition of an extra immunoglobulin domain to two anti-rodent TNF monoclonal antibodies substantially increased their potency.

The functional valency of a monoclonal antibody (mAb) has important influences on such things as antigen avidity, Fc-mediated immune effector functions, and clearance of immune complexes. cV1q, a neutralizing rat/mouse chimeric anti-mouse tumor necrosis factor (TNF) monoclonal antibody (mAb), and Rt108, a neutralizing mouse anti-rat TNF (anti-raTNF) mAb, appear to be functionally monovalent for TNF-binding despite containing two antigen binding sites. The functional monovalency of these two independent anti-rodent TNF mAbs is presumably a result of steric hindrance from one TNF molecule binding to one Fab arm that prevents binding of a second TNF molecule to the other Fab arm. To test whether this steric hindrance could be overcome by introducing extra space and flexibility between the Fab arms, these mAbs were engineered to contain an extra CH1 immunoglobulin domain between the CH1 and hinge domains of their heavy chains. In vitro binding data showed that, compared to the original mAbs, the modified mAbs (S-mAbs) had greater capability of binding two TNF molecules simultaneously. In vitro activity assays showed that, compared to the original mAbs, the S-mAbs had significantly greater TNF-neutralization potency, with the S-mAb version of cV1q (S-cV1q) being 200-fold more effective at blocking mouse TNF (muTNF) and the S-mAb version of Rt108 (S-Rt108) being 20-fold more effective at blocking raTNF. Similar results were observed in vivo, where S-cV1q was between 100- and 500-fold more protective than cV1q in mice challenged with endotoxin. These data reveal that introduction of another constant region immunoglobulin domain into two unrelated mAbs dramatically enhanced their neutralization potency. Other mAbs may also show more potent activity using this engineering approach, particularly mAbs that recognize homopolymeric antigens.

Binding and functional comparisons of two types of tumor necrosis factor antagonists.

Two tumor necrosis factor (TNF) antagonists infliximab (a chimeric monoclonal antibody) and etanercept (a p75 TNF receptor/Fc fusion protein) have been approved for treatment of rheumatoid arthritis. However, these agents have shown different degrees of clinical benefit in controlled clinical trials in other TNF-mediated diseases such as Crohn's disease (CD) and psoriasis. We investigated whether structural differences between these two antagonists translate into different binding and functional characteristics. To study the binding of infliximab and etanercept to both the soluble and cell-surface transmembrane forms of TNF, a variety of in vitro binding and cell-based assays were performed. Binding assays using (125)I-labeled TNF showed that infliximab binds to both monomer and trimer forms of soluble TNF (sTNF), whereas etanercept binding is restricted to the trimer form. Infliximab formed stable complexes with sTNF, whereas etanercept formed relatively unstable complexes, resulting in release of dissociated TNF. KYM-1D4 cell killing assays and human umbilical vein endothelial cell activation assays demonstrated that TNF that had dissociated from etanercept was bioactive. Infliximab also formed more stable complexes with the transmembrane form of TNF expressed on transfected cells relative to analogous complexes formed with etanercept. Additionally, more infliximab molecules bound to the transmembrane TNF with higher avidity than etanercept. Although both infliximab and etanercept inhibited transmembrane TNF-mediated activation of human endothelial cells, infliximab was significantly more effective. The differences between infliximab and etanercept in their TNF binding characteristics may help explain their differential efficacy in CD and psoriasis clinical trials.