MALT1 small molecule inhibitors specifically suppress ABC-DLBCL in vitro and in vivo

MALT1 cleavage activity is linked to the pathogenesis of activated B cell-like diffuse large B cell lymphoma (ABC-DLBCL), a chemoresistant form of DLBCL. We developed a MALT1 activity assay and identified chemically diverse MALT1 inhibitors. A selected lead compound, MI-2, featured direct binding to MALT1 and suppression of its protease function. MI-2 concentrated within human ABC-DLBCL cells and irreversibly inhibited cleavage of MALT1 substrates. This was accompanied by NF-κB reporter activity suppression, c-REL nuclear localization inhibition, and NF-κB target gene downregulation. Most notably, MI-2 was nontoxic to mice, and displayed selective activity against ABC-DLBCL cell lines in vitro and xenotransplanted ABC-DLBCL tumors in vivo. The compound was also effective against primary human non-germinal center B cell-like DLBCLs ex vivo.

Selective Inhibition of HDAC3 Targets Synthetic Vulnerabilities and Activates Immune Surveillance in Lymphoma

CREBBP mutations are highly recurrent in B-cell lymphomas and either inactivate its histone acetyltransferase (HAT) domain or truncate the protein. Herein, we show that these two classes of mutations yield different degrees of disruption of the epigenome, with HAT mutations being more severe and associated with inferior clinical outcome. Genes perturbed by CREBBP mutation are direct targets of the BCL6-HDAC3 onco-repressor complex. Accordingly, we show that HDAC3-selective inhibitors reverse CREBBP-mutant aberrant epigenetic programming, resulting in: (i) growth inhibition of lymphoma cells through induction of BCL6 target genes such as CDKN1A and (ii) restoration of immune surveillance due to induction of BCL6-repressed IFN pathway and antigen-presenting genes. By reactivating these genes, exposure to HDAC3 inhibitors restored the ability of tumor-infiltrating lymphocytes to kill DLBCL cells in an MHC class I and II-dependent manner, and synergized with PD-L1 blockade in a syngeneic model in vivo. Hence, HDAC3 inhibition represents a novel mechanism-based immune epigenetic therapy for CREBBP-mutant lymphomas. SIGNIFICANCE: We have leveraged the molecular characterization of different types of CREBBP mutations to define a rational approach for targeting these mutations through selective inhibition of HDAC3. This represents an attractive therapeutic avenue for targeting synthetic vulnerabilities in CREBBP-mutant cells in tandem with promoting antitumor immunity.This article is highlighted in the In This Issue feature, p. 327.

Lymphoma stem cells: enough evidence to support their existence?

While leukemia-originating stem cells are critical in the initiation and maintenance of leukemias, the existence of similar cell populations that may generate B-cell lymphoma upon mutation remains uncertain. Here we propose that committed lymphoid progenitor/precursor cells with an active V-D-J recombination program are the initiating cells of follicular lymphoma and mantle cell lymphoma when targeted by immunoglobulin (IG)- gene translocations in the bone marrow. However, these pre-malignant lymphoma-initiating cells cannot drive complete malignant transformation, requiring additional cooperating mutations in specific stem-cell programs to be converted into the lymphoma-originating cells able to generate and sustain lymphoma development. Conversely, diffuse large B-cell lymphoma and sporadic Burkitt's lymphoma derive from B lymphocytes that acquire translocations through IG-hyper-mutation or class-switching errors within the germinal center. Although secondary reprogramming mutations are generally required, some cells such as centroblasts or memory B cells that have certain stem cell-like features, or lymphocytes with MYC rearrangements that deregulate self-renewal pathways, may bypass this need and directly function as the lymphoma-originating cells. An alternative model supports an aberrant epigenetic modification of gene sets as the first occurring hit, which either leads to retaining stem-cell features in hematopoietic stem or progenitor cells, or reprograms stemness into more committed lymphocytes, followed by secondary chromosomal translocations that eventually drive lymphoma development. Isolation and characterization of the cells that are at the origin of the different B-cell non-Hodgkin's lymphomas will provide critical insights into the disease pathogenesis and will represent a step towards the development of more effective therapies.

MALT1 Inhibition Is Efficacious in Both Naïve and Ibrutinib-Resistant Chronic Lymphocytic Leukemia

The clinical efficacy displayed by ibrutinib in chronic lymphocytic leukemia (CLL) has been challenged by the frequent emergence of resistant clones. The ibrutinib target, Bruton's tyrosine kinase (BTK), is essential for B-cell receptor signaling, and most resistant cases carry mutations in BTK or PLCG2, a downstream effector target of BTK. Recent findings show that MI-2, a small molecule inhibitor of the para-caspase MALT1, is effective in preclinical models of another type of BCR pathway-dependent lymphoma. We therefore studied the activity of MI-2 against CLL and ibrutinib-resistant CLL. Treatment of CLL cells in vitro with MI-2 inhibited MALT1 proteolytic activity reduced BCR and NF-κB signaling, inhibited nuclear translocation of RelB and p50, and decreased Bcl-xL levels. MI-2 selectively induced dose and time-dependent apoptosis in CLL cells, sparing normal B lymphocytes. Furthermore, MI-2 abrogated survival signals provided by stromal cells and BCR cross-linking and was effective against CLL cells harboring features associated with poor outcomes, including 17p deletion and unmutated IGHV Notably, MI-2 was effective against CLL cells collected from patients harboring mutations conferring resistance to ibrutinib. Overall, our findings provide a preclinical rationale for the clinical development of MALT1 inhibitors in CLL, in particular for ibrutinib-resistant forms of this disease. Cancer Res; 77(24); 7038-48. ©2017 AACR.

Circulating L-Arginine predicts the survival of cancer patients treated with immune checkpoint inhibitors

BACKGROUND

The discovery of immune checkpoint inhibitors (ICIs) has revolutionized the systemic approach to cancer treatment. However, most patients receiving ICIs do not derive benefits. Therefore, it is crucial to identify reliable predictive biomarkers of response to ICIs. One important pathway in regulating immune cell reactivity is L-arginine (ARG) metabolism, essential to T-cell activation. We therefore aimed to evaluate the association between baseline plasma ARG levels and the clinical benefit of ICIs.

PATIENTS AND METHODS

The correlation between ARG levels and clinical ICI activity was assessed by analyzing plasma samples obtained before treatment onset in two independent cohorts of patients with advanced cancer included in two institutional molecular profiling programs (BIP, NCT02534649, n = 77; PREMIS, NCT03984318, n = 296) and from patients in a phase 1 first-in-human study of budigalimab monotherapy (NCT03000257). Additionally, the correlation between ARG levels and ICI efficacy in preclinical settings was evaluated using a syngeneic mouse model of colorectal cancer responsive to ICIs. Using matched PBMC plasma samples, we analyzed the correlation between ARG levels and PBMC features through multiplexed flow cytometry analysis.

RESULTS

In both discovery and validation cohorts, low ARG levels at baseline (<42 μM) were significantly and independently associated with a worse clinical benefit rate, progression-free survival, and overall survival. Moreover, at the preclinical level, the tumor rejection rate was significantly higher in mice with high baseline ARG levels than in those with low ARG levels (85.7% versus 23.8%; P = 0.004). Finally, PBMC immunophenotyping showed that low ARG levels were significantly associated with increased PD-L1 expression in several immune cell subsets from the myeloid lineage.

CONCLUSION

We demonstrate that baseline ARG levels predict ICI response. Plasma ARG quantification may therefore represent an attractive biomarker to tailor novel therapeutic regimens targeting the ARG pathway in combination with ICIs.

Combinatorial treatment rescues tumour-microenvironment-mediated attenuation of MALT1 inhibitors in B-cell lymphomas

Activated B-cell-like diffuse large B-cell lymphomas (ABC-DLBCLs) are characterized by constitutive activation of nuclear factor κB driven by the B-cell receptor (BCR) and Toll-like receptor (TLR) pathways. However, BCR-pathway-targeted therapies have limited impact on DLBCLs. Here we used >1,100 DLBCL patient samples to determine immune and extracellular matrix cues in the lymphoid tumour microenvironment (Ly-TME) and built representative synthetic-hydrogel-based B-cell-lymphoma organoids accordingly. We demonstrate that Ly-TME cellular and biophysical factors amplify the BCR-MYD88-TLR9 multiprotein supercomplex and induce cooperative signalling pathways in ABC-DLBCL cells, which reduce the efficacy of compounds targeting the BCR pathway members Bruton tyrosine kinase and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1). Combinatorial inhibition of multiple aberrant signalling pathways induced higher antitumour efficacy in lymphoid organoids and implanted ABC-DLBCL patient tumours in vivo. Our studies define the complex crosstalk between malignant ABC-DLBCL cells and Ly-TME, and provide rational combinatorial therapies that rescue Ly-TME-mediated attenuation of treatment response to MALT1 inhibitors.

Identification of MALT1 feedback mechanisms enables rational design of potent antilymphoma regimens for ABC-DLBCL

MALT1 inhibitors are promising therapeutic agents for B-cell lymphomas that are dependent on constitutive or aberrant signaling pathways. However, a potential limitation for signal transduction-targeted therapies is the occurrence of feedback mechanisms that enable escape from the full impact of such drugs. Here, we used a functional genomics screen in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) cells treated with a small molecule irreversible inhibitor of MALT1 to identify genes that might confer resistance or enhance the activity of MALT1 inhibition (MALT1i). We find that loss of B-cell receptor (BCR)- and phosphatidylinositol 3-kinase (PI3K)-activating proteins enhanced sensitivity, whereas loss of negative regulators of these pathways (eg, TRAF2, TNFAIP3) promoted resistance. These findings were validated by knockdown of individual genes and a combinatorial drug screen focused on BCR and PI3K pathway-targeting drugs. Among these, the most potent combinatorial effect was observed with PI3Kδ inhibitors against ABC-DLBCLs in vitro and in vivo, but that led to an adaptive increase in phosphorylated S6 and eventual disease progression. Along these lines, MALT1i promoted increased MTORC1 activity and phosphorylation of S6K1-T389 and S6-S235/6, an effect that was only partially blocked by PI3Kδ inhibition in vitro and in vivo. In contrast, simultaneous inhibition of MALT1 and MTORC1 prevented S6 phosphorylation, yielded potent activity against DLBCL cell lines and primary patient specimens, and resulted in more profound tumor regression and significantly improved survival of ABC-DLBCLs in vivo compared with PI3K inhibitors. These findings provide a basis for maximal therapeutic impact of MALT1 inhibitors in the clinic, by disrupting feedback mechanisms that might otherwise limit their efficacy.

BCL10 Mutations Define Distinct Dependencies Guiding Precision Therapy for DLBCL

Activated B cell-like diffuse large B-cell lymphomas (ABC-DLBCL) have unfavorable outcomes and chronic activation of CARD11-BCL10-MALT1 (CBM) signal amplification complexes that form due to polymerization of BCL10 subunits, which is affected by recurrent somatic mutations in ABC-DLBCLs. Herein, we show that BCL10 mutants fall into at least two functionally distinct classes: missense mutations of the BCL10 CARD domain and truncation of its C-terminal tail. Truncating mutations abrogated a motif through which MALT1 inhibits BCL10 polymerization, trapping MALT1 in its activated filament-bound state. CARD missense mutations enhanced BCL10 filament formation, forming glutamine network structures that stabilize BCL10 filaments. Mutant forms of BCL10 were less dependent on upstream CARD11 activation and thus manifested resistance to BTK inhibitors, whereas BCL10 truncating but not CARD mutants were hypersensitive to MALT1 inhibitors. Therefore, BCL10 mutations are potential biomarkers for BTK inhibitor resistance in ABC-DLBCL, and further precision can be achieved by selecting therapy based on specific biochemical effects of distinct mutation classes.

SIGNIFICANCE

ABC-DLBCLs feature frequent mutations of signaling mediators that converge on the CBM complex. We use structure-function approaches to reveal that BCL10 mutations fall into two distinct biochemical classes. Both classes confer resistance to BTK inhibitors, whereas BCL10 truncations confer hyperresponsiveness to MALT1 inhibitors, providing a road map for precision therapies in ABC-DLBCLs. See related commentary by Phelan and Oellerich, p. 1844. This article is highlighted in the In This Issue feature, p. 1825.

Integrative oncogenomic analysis of microarray data in hematologic malignancies

During the last decade, gene expression microarrays and array-based comparative genomic hybridization (array-CGH) have unraveled the complexity of human tumor genomes more precisely and comprehensively than ever before. More recently, the simultaneous assessment of global changes in messenger RNA (mRNA) expression and in DNA copy number through "integrative oncogenomic" analyses has allowed researchers the access to results uncovered through the analysis of one-dimensional data sets, thus accelerating cancer gene discovery. In this chapter, we discuss the major contributions of DNA microarrays to the study of hematological malignancies, focusing on the integrative oncogenomic approaches that correlate genomic and transcriptomic data. We also present the basic aspects of these methodologies and their present and future application in clinical oncology.

Generation of a new monoclonal antibody against MALT1 by genetic immunization

Genetic immunization (GI), which is primarily used for vaccine purposes, is a method for producing antibodies to a protein by delivering the gene encoding the protein as a eukaryotic expression vector instead of the protein itself. The mucosa-associated lymphoid tissue lymphoma translocation gene 1 (MALT1) is one of the most likely candidates for involvement in pathogenesis of MALT lymphoma and probably of multiple myelomas. In the present work we describe the production and characterization of a mouse monoclonal antibody (mAb) directed against MALT1 and the study of MALT1 protein expression in a large series of lymphomas and myeloma cell lines. The full-length coding sequence of human MALT1 was inserted into pcDNA3 vector and delivered into mouse skin using a helium gene gun. Six new mAbs against the MALT1 molecule were produced. In order to characterize and confirm the specificity of these mAbs, Western blot (WB) and immunoprecipitation (IP) analyses were performed. A new anti-MALT1 mAb was selected and tested in a large series of cell lines. These results confirm that GI is a reliable and effective alternative method for production of mAbs, allowing accurate and sensitive detection and screening of proteins by WB.

Discovering what makes STAT signaling TYK in T-ALL

SUMMARY

RNA interference screening establishes TYK2 dependence in T-cell acute lymphoblastic leukemia (T-ALL), leading to identification of TYK2-activating mutations and increased IL-10 receptor signaling in T-ALL cell lines. Cancer Discov; 3(5); 494-6. ©2013 AACR.

Abstract PO-49: Discovery of JNJ-67856633: A novel, first-in-class MALT1 protease inhibitor for the treatment of B-cell lymphomas

Introduction: Constitutive activation of the classical nuclear factor kappa-light-chain-enhancer of activated B cells (NF κB) pathway is a clear driver of B-cell lymphomas, especially the aggressive activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL). Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a key mediator of the classical NF-κB signaling pathway downstream of B-cell receptor and T-cell receptor. MALT1 possesses two functions: a scaffolding function to recruit NF-κB signaling proteins and a protease function to cleave and inactivate inhibitors of the NF-κB signaling pathway.

Methods: Using a high-throughput screen followed by iterative structure-activity relationship (SAR) analyses, the MALT1 inhibitor JNJ-67856633 was identified. JNJ-67856633 was evaluated using biochemical, cellular in vitro, in vivo tumor efficacy and safety models.

Results: JNJ-67856633 is a potent, selective, allosteric inhibitor of MALT1 protease activity as measured by biochemical assays or downstream cellular cytokine readouts (IL6/10) or direct MALT1 substrate cleavage (RelB, BCL10). The compound inhibits proliferation of activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) cell lines bearing CD79b or CARD11 mutations as well as models mimicking resistance to covalent Bruton's tyrosine kinase (BTK) inhibitors. Furthermore, combination effects were observed in CD79b cellular ABC-DLBCL models when JNJ-67856633 was combined with a BTK inhibitor. JNJ-67856633 showed activity in organoid cultures derived from ABC-DLBCL patients. JNJ-67856633 leads to potent in vivo pharmacodynamic shutdown in CD79b- as well as CARD11-mutant ABC-DLBCL models as measured by serum IL10 or uncleaved BCL10 levels in tumors. JNJ-67856633 exhibits potent tumor growth inhibition in two human DLBCL xenograft models, OCI Ly3 and OCI Ly10. In addition, &gt;5 patient-derived DLBCL xenografts were evaluated and activity in mutation selected models was observed. To address the role of MALT1 inhibition in T cells, primary human T cells derived from normal healthy volunteers were treated with JNJ-67856633 in vitro. Dose-dependent inhibition of the generation of Tregs (CD4+CD25+FoxP3+) following CD3/28 stimulation was observed upon treatment with JNJ-67856633, suggesting a potential immune-modulatory role of MALT1 inhibition.

Conclusions: Phase 1 clinical trials assessing the safety and efficacy of JNJ-67856633 initiated in 2019. JNJ-67856633 is a combination partner for BTK inhibitors and a promising treatment option for BTKi-resistant tumors, with demonstrated preclinical activity in CARD11 mutant tumors. In addition to ABC-DLBCL, a MALT1 inhibitor is a promising treatment option for patients with CLL, MCL, WM, and FL whose tumors have been shown to be sensitive to inhibition of BTK. MALT lymphomas, characterized by MALT1 and BCL10 translocation, represent another attractive target for MALT1 inhibition.

Citation Format: Ulrike Philippar, Tianbao Lu, Lorena Fontan, Nele Vloemans, Mariette Bekkers, Luc van Nuffel, Marcello Gaudiano, Katarzyna Wnuk-Lipinska, Bas-Jan Van Der Leede, Katie Amssoms, Kristof Kimpe, Bart Medaer, Tony Greway, Yann Abraham, Max Cummings, Emanuele Trella, Greet Vanhoof, Weimei Sun, Jan Willem Thuring, Peter Connolly, Haopeng Rui, Sriram Balasubramanian, John Gerecitano, Ari Melnick, Ricardo Attar. Discovery of JNJ-67856633: A novel, first-in-class MALT1 protease inhibitor for the treatment of B-cell lymphomas [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-49.

Abstract 797: Targeting HDAC3 reactivates immunosurveillance and enhances immunocheckpoint activity in B-cell lymphoma

Somatic mutation of the histone acetyltransferase CREBBP occurs in ~40% of diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) patients. CREBBP mutation leads to transcriptional repression of genes involved in B-cell differentiation, antigen presentation and cell growth, and this repressive effect is mediated specifically through HDAC3. Hence CREBBP mutant DLBCL cells are biologically dependent on HDAC3 for both cell autonomous effects on cell proliferation and evasion of immune surveillance. Because of this we hypothesize that CREBBP mutant DLBCL would be highly responsive to HDAC3 specific inhibition.Therefore we treated a panel of DLBCL cell lines with increasing dose of the clinically relevant HDAC3 selective inhibitor (HDAC3i) KDAC0001 (from 0.1 to 20 μM), which resulted in a dose- and time-dependent growth inhibition and cell death. HDAC3i treatment demonstrated a stronger efficacy in cells carrying CREBBP mutation compared to the wild type with an IC50 20-30 fold lower at 72 Hrs. Knockdown by shRNA or loss of function mutations introduced via CRISPR in CREBBP wt cell lines (MD901, OCI-LY18 and RL) led to increased sensitivity to KDAC0001 compared to the parental lines. Along these lines we placed six primary DLBCL specimens (3 GCB and 3 ABC) in our 3D organoid culture system and observed potent growth suppression by KDAC001 vs vehicle after 6 days. To identify the genes through which HDAC3 drives the lymphoma phenotype we performed RNA Seq analysis using 3 DLBCL cell lines (OCI-LY1 CREBBP wt, OCI-LY19 and OZ CREBBP m) treated with either DMSO or KDAC0001 at 10 μM for 24 Hrs (a timepoint prior to cells manifesting any response to drug). We observed induction of over 1100 genes whereas 74 genes were downregulated. Gene pathway analysis showed that HDAC3 induced genes corresponded to those that are repressed in CREBBP mutant lymphomas, and regulated by BCL6-HDAC3 complexes linked to gene enhancers, including their known downstream p53 and NFKB target genes. On the other hand KDAC0001 treatment also broadly induced MHC class II and antigen presentation genes. We confirmed the increase in MHC class II genes, CIITA, PD-1 and PD-L1 not only at the transcriptional level, as determined by qPCR, but also at the protein level, as determined by flow cytometry. Co-culturing OCI-LY18 DLBCL cells and human lymphocytes with increasing amounts of HDAC3i was associated with increased cytotoxicity in a time-dependent manner. We engrafted three CREBBP wild type primary human PDX in NSG mice and treated with either vehicle or KDAC0001 at 25 or 50 mh/kg daily for 21 days. Even thought these PDX were not CREBBP mutant, there was still cell autonomous activity against all these tumors. In conclusion, HDAC3 inhibitor KDAC0001 has both cell autonomous and immune related activities.Therefore, it can be used as a novel form of “epigenetic immunotherapy” to restore immune clearance of resistant DLBCL and FL.

Citation Format: Patrizia Mondello, Matt Teater, Lorena Fontan, Matthew Durant, Elisa de Stanchina, Giorgio Inghirami, Michael Green, Ari Melnick. Targeting HDAC3 reactivates immunosurveillance and enhances immunocheckpoint activity in B-cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 797.

Abstract LB-303: Substrate-mimetic covalent inhibitor of MALT1 is most effective against CARD11 mutant ABC-DLBCL

Diffuse Large B-cell lymphoma is the most common subtype of B-cell non Hodgkin Lymphoma (B-NHL) representing 30% of all B-NHL. There are three molecular subtypes: germinal center B cell-like (GCB) DLBCL, activated B cell-like (ABC) DLBCL, and primary mediastinal B cell lymphoma (PMBL). Of those, Activated B-cell like Diffuse Large B-cell Lymphoma (ABC-DLBCL) represents a third of the patients and is characterized by constitutive NF-κB activity due to mutations in various proteins of the B-cell receptor (BCR) as well as Toll-like receptor (TLR) pathways. Mutations in the BCR pathway include: activating mutations of CD79A/B (20% of ABC-DLBCLs) and CARD11 (10%) and deletion or inactivating mutation of A20 (20-30%). In the TLR pathway, MYD88 is mutated in 37% of ABC-DLBCL patients. Given this scenario, numerous therapeutic strategies targeting proteins signaling downstream of the BCR pathway have been proposed for ABC-DLBCL -including inhibitors targeting kinases SYK, BTK, PI3K, PKC, MAPKs and AKT or the protease MALT1. MALT1 inhibition provides advantages to other targets because it is downstream of most of the BCR pathway mutations present in patients, including CARD11. Patients with CARD11 mutations do not respond to BTK inhibitors. However, none of the MALT1 inhibitors reported to date are good candidates for clinical use.

Here we report a new class of substrate mimetic MALT1 inhibitors based on Z-VRPR-fmk. Our lead compound, SCM-02-138 displayed nanomolar potency in biochemical and cellular MALT1 protease reporter assays. Crystallography shows covalent binding of the compound to MALT1 active site Cys residue. SCM-02-138 was highly selective for MALT1 and showed over 100-fold differential killing in sensitive vs resistant cell lines. MALT1 inhibition was most effective in CARD11 mutant cells. SCM-02-138 was active in vivo, as assessed by hIL10 inhibition in xenografted models of ABC-DLBCL cell lines. Moreover it was effective against ABC-DLBCL xenografts and PDX DLBCL ex vivo. Combination of SCM-02-138 with other BCR inhibitors revealed PI3K delta inhibition as the most synergistic combination. Combination of SCM-02-138 and CAL-101 potentiated both proliferation inhibition and apoptosis.

In summary, we have developed a new class of MALT1 peptidic inhibitor characterized by nanomolar potency, irreversibility and high specificity. This inhibitor will be particularly useful against CARD11 mutant ABC-DLBCL, which are resistant to BTK inhibitors.

Citation Format: Lorena Fontan, David Scott, John Hatcher, Qi Qiao, Ilkay Us, Gabriella Casalena, Mariette Bekkers, Ulrike Philippar, Matthew Durant, Spandan Chennamadhavuni, Hao Wu, Nathaniel Gray, Ari Melnick. Substrate-mimetic covalent inhibitor of MALT1 is most effective against CARD11 mutant ABC-DLBCL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-303. doi:10.1158/1538-7445.AM2017-LB-303

Abstract 1267: Combination therapy of JNJ-67856633, a novel, first-in-class MALT1 protease inhibitor, and JNJ-64264681, a novel BTK inhibitor, for the treatment of B-cell lymphomas

Background: Constitutive activation of the classical nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) pathway is a clear driver of B-cell non-Hodgkin lymphomas (NHL). Bruton's Tyrosine Kinase (BTK) and Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), which lies downstream of BTK, are key mediators of the classical NF-κB signaling pathway activated by BCR and TCR receptors. JNJ-67856633 is a first-in-class MALT1 protease inhibitor. JNJ-64264681 is a BTK inhibitor with improved selectivity against BTK. Blocking the BCR pathway at multiple points using these two orally bioavailable compounds could enhance clinical activity in B-cell lymphoma patients.

Methods: JNJ-67856633 and JNJ-64264681 are currently being evaluated in phase 1 clinical trials designed to establish safety, PK, PD and the Recommended Phase 2 Dose (RP2D) of each agent.

Results: JNJ-67856633 is a potent, selective, orally bioavailable, allosteric inhibitor of MALT1 protease activity. The compound inhibits proliferation of activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) cell lines bearing CD79b or CARD11 mutations as well as models mimicking resistance to covalent BTK inhibitors. JNJ-67856633 exhibits potent tumor growth inhibition in two human DLBCL xenograft models, OCI-Ly3 and OCI-Ly10, and mutation selected patient derived DLBCL xenografts. Furthermore, treatment with JNJ-67856633 leads to dose dependent inhibition of the generation of Tregs (CD4+CD25+FoxP3+) following CD3/28 stimulation in vitro, suggesting a potential immune modulatory role of MALT1 inhibition. JNJ-64264681 is an orally active small molecule that is a potent, selective, and irreversible covalent BTK inhibitor. JNJ-64264681 inhibits the growth of CD79b-mutant DLBCL cell lines in vitro and potently inhibits tumor growth in xenograft- or patient-derived DLBCL models in vivo. Treatment with JNJ-64264681 and JNJ-67856633 administered together demonstrated statistically significant tumor growth inhibition compared with vehicle control in two CD79b mutant mouse lymphoma models, one based on a DLBCL cell line (OCI-Ly10) and one based on a patient-derived DLBCL model (LY2298). In both models, the combination showed increased growth inhibition compared with single agents and tumor regression in the combination arm. Synergistic anti-proliferative activity was observed in three DLBCL cell lines carrying CD79b mutations and one MCL cell line.

Conclusions: Taken together, the in vitro and in vivo data for JNJ-67856633 and JNJ-64264681 suggest that combination therapy can increase the anti-tumor effect of the monotherapies and provide a more sustained response, offering strong support for clinical investigation of the combination of these two novel agents. A phase 1b combination study is scheduled to initiate.

Citation Format: Ulrike Philippar, Lorena Fontan, Ivo Cornelissen, Haopeng Rui, Sriram Balasubramanian, Marcello Gaudiano, Mariette Bekkers, Luc Van Nuffel, Tianbao Lu, Tianbao Lu, John Wiener, Mark Tichenor, Tony Greway, Kathryn Packman, Bie Verbist, Yusri Elsayed, Ricardo Attar, Jacqueline Bussolari, John Gerecitano. Combination therapy of JNJ-67856633, a novel, first-in-class MALT1 protease inhibitor, and JNJ-64264681, a novel BTK inhibitor, for the treatment of B-cell lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1267.

Abstract IA49: MALT1 targeting for B-cell lymphomas

MALT1 biology and function MALT1 is an oncogene frequently translocated to API2 t(11;18)(q21;q21) or IgH t(14;18)(q32;q21) in MALT lymphomas. MALT1 forms part of the CBM complex along with CARD11 and BCL10. This is a high-order complex where MALT1 acts as a scaffolding protein to recruit TRAF6 and the IKK complex and leads to NF-kappaB activation. MALT1 is also a cysteine protease. We now know 10 substrates of MALT1 (including itself) and 2 neosubstrates for the API2-MALT1 fusion protein. MALT1 substrates include several regulators of NF-kappaB and MAPK activation (A20, CYLD, RELB, and HOIL1), and their cleavage amplifies and/or prolongs activation of these pathways. HOIL1 cleavage by MALT1 might also contribute to negative feedback at late stages of signal transduction. Moreover, MALT1 cleaves at least three RNases that modulate the expression of proinflammatory genes and play an important role in T-cell differentiation. Less is known about their role in B-cell biology. Interestingly, CARD11 and MALT1 have been implicated in glutamine transport and its metabolism and, although their role has not been fully elucidated, they may contribute to the metabolic switch from oxidative phosphorylation to aerobic glycolysis that accompanies T- and B-cell activation. MALT1 knockout mice are immunosuppressed and fail to activate T-cell and B-cell receptors but are generally healthy and fertile. However, older mice tend to develop atopic dermatitis. On the other hand, in MALT1 C472A mice where protease activity is lost while scaffolding activity is intact, T and B cells can activate NF-kappaB signaling downstream of TCR/BCR. However, signaling is reduced, likely due to increased activity of MALT1 targets A20, CYLD, RELB, and HOIL1. These mice develop severe autoimmunity that leads to death and that has been attributed to loss of T-regulatory cells, which are very dependent on MALT1 protease activity for differentiation and maintenance. Loss of T-regulatory cells allows unrestricted T-effector cell function leading to the autoimmune syndrome, which is likely antigen driven because independently generated models showed symptoms in different organ systems. Therapeutic targeting of MALT1 A genome-wide shRNA screen uncovered MALT1 as an essential gene for ABC-DLBCL, and subsequent studies using a substrate mimetic inhibitor of MALT1 determined that ABC-DLBCLs were dependent on its protease activity. These findings arouse great interest in targeting MALT1's protease activity and, in the last 8 years, there have been numerous small molecules developed that target MALT1 through different mechanisms. Active site and allosteric inhibitors have been developed that show activity and efficacy in vivo in ABC-DLBCL xenograft models, serving as proof of concept of the therapeutic value of MALT1 inhibition. The first clinical trial for a MALT1 inhibitor was launched in April 2019 (NCT03900598) and is now open in 32 centers. All efficacy studies published to date are based on xenograft studies in immunodeficient mice. Studies in genetically engineered ABC-DLBCL models will shed light on what will be the effects of MALT1 inhibition in the antitumoral immune response. Recent studies using syngeneic solid tumor models in immunocompetent mice showed decreased engraftment of tumors in mice lacking MALT1 protease activity. Moreover, use of a MALT1 inhibitor in combination with PD1 blockage greatly enhanced each other's activity, particularly in highly immunogenic tumors. This effect was attributed to the effects of MALT1 on T-regulatory cells, but deeper mechanistic studies are needed to fully understand the mechanisms at play. Nonetheless, these results suggest that MALT1 inhibition could have both tumor-intrinsic and -extrinsic effects that could cooperate to kill ABC-DLBCL. If general effects over the antitumoral immune response are confirmed, MALT1 inhibition could have a broader application as adjuvant for other immune-oncology approaches in cancer. Little is known to date on what mechanisms of resistance could be deployed by tumor cells to escape MALT1 inhibition. However, based on what is known for BTK and other signaling mediators, resistance will likely arise and combinatorial regimens will be needed to attain durable responses and maximal effectiveness. Our recent work on combinations anchored in MALT1 inhibition showed that BCR, PI3K, and TLR directed inhibitors were either additive or synergistic with MALT1 inhibition. MALT1/PI3Kdelta-i combinations showed enhanced but not durable responses in vivo. Tumors in mice treated with this combinatorial regime resumed growth while in treatment and displayed active NF-kappaB and MTORC1 signaling. This study revealed that MTORC1 activation could constitute a critical feedback mechanism limiting the effect of MALT1 inhibitors. In concordance, a MALT1/MTORC1 combinatorial regime suppressed MTORC1 activation and was highly effective in vivo, leading to tumor regression and significant enhanced survival after only one cycle of treatment. Future studies using clinical candidates and patient samples will further our understanding of this mechanism and elucidate other mechanisms that can be deployed by cells to overcome MALT1 inhibition and will help shape the future of MALT1 inhibition-centered oncologic regimens.

Citation Format: Lorena Fontan. MALT1 targeting for B-cell lymphomas [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr IA49.

Abstract A28: BCL10 mutations define distinct dependencies guiding precision therapy for DLBCL

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoid malignancy and the activated B cell-like subtype (ABC-DLBCL) is the most aggressive form and harbors frequent mutations of immune signaling pathways that culminate in constitutive activation of CARD11-MALT1-BCL10 (CBM) complex and downstream NF-κB pathway. CBM complexes form large macromolecular structures due to signal-induced polymerization of the BCL10 subunit, which is affected by recurrent somatic mutations in ABC-DLBCLs. Through biochemical, structural and functional dissection of these mutations, we find that BCL10 mutations fall into two functionally distinct classes: missense mutations of the BCL10 CARD domain (hotspot R58Q) and truncation of its C-terminal tail (hotspot E140X). To explore the functional consequences of BCL10 mutations, we established reporter systems to evaluate their impact on MALT1 and NF-𝜅B activities which are BCL10 downstream signaling cascades. We found that almost all mutants induced aberrantly strong NF-𝜅B and MALT1 activities in lymphoma cells as compared to WT BCL10, indicating the gain-of-function effect of BCL10 mutations. By performing immunohistochemistry staining of p65 in a set of tumor tissue microarray from DLBCL patients (n=298), we revealed that BCL10 mutant tumors have significantly (Mann-Whitney p&lt;0.0001) increased p65 nuclear staining score compared to BCL10 WT tumors, suggesting enhanced NF-𝜅B activity. To investigate the biochemical impact of BCL10 mutants on CBM complex formation, we performed fluorescence polarization and filamentation formation assays with purified WT and mutant BCL10 proteins and found that both BCL10R58Q and BCL10E140X manifested faster and more spontaneous polarization compared to BCL10WT. Surprisingly, through mapping the BCL10-MALT1 interaction, we found that truncating mutation (E140X) abrogated a novel protein interaction motif through which MALT1 inhibits BCL10 polymerization, thus unleashing spontaneous CBM filament formation and inducing addiction to MALT1 activity. In marked contrast, the CARD missense mutation (R58Q) on BCL10 filament interface not only does not disrupt but enhances filament formation and it also alters CBM complex kinetics forming glutamine network structures that stabilize BCL10 filaments, but this still may require the upstream signal to activate MALT1. Importantly, we found that BCL10 mutant cells were less dependent on upstream CARD11 activation in MALT1 activation, NF-𝜅B signaling and cell growth assays performed in ABC-DLBCL lines. Furthermore, in vitro and in vivo xenograft studies revealed that BCL10 mutant lymphomas are resistant to BTK inhibitors, whereas BCL10 truncating (E140X) but not missense CARD (R58Q) mutants were hypersensitive to MALT1 protease inhibitors. Therefore, BCL10 mutations are potential biomarkers for BTK inhibitor resistance in ABC-DLBCL and further precision can be achieved by tailoring therapy (e.g. MALT1 inhibitors that are currently being tested in clinical trials) according to specific biochemical effects of distinct mutation classes.

Citation Format: Min Xia, Liron David, Matthew R Teater, Johana Gutierrez, Xiang Wang, Cem Meydan, Andrew Lytle, Graham Slack, David Scott, Ozlem Onder, Kojo Elenitoba-Johnson, Nahuel Zamponi, Leandro Cerchietti, Tianbao Lu, Ulrike Philippar, Lorena Fontan, Hao Wu, Ari Melnick. BCL10 mutations define distinct dependencies guiding precision therapy for DLBCL [abstract]. In: Proceedings of the Third AACR International Meeting: Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2022 Jun 23-26; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2022;3(5_Suppl):Abstract nr A28.

[Multitest evaluation of the immune status of patients with bronchogenic carcinoma before and after radiotherapy]

Sixty-two patients with lung cancer underwent the multitest before and after radiotherapy so as to assess the initial immune state and modifications induced by radiation therapy. In cancer patients, a significantly smaller number of positive skin reactions were encountered than in the controls. No statistically significant differences emerged between patients grouped on the basis of histotype, clinical stage and performance or otherwise of surgery. In living patients, higher values were observed than in patients who died. After radiotherapy, multitest values underwent a very slight decrease.

Abstract A19: MALT1 inhibition as an anchor for combinatorial therapy of ABC-DLBCL

MALT1 (Mucossa Associated Lymphoid tissue Lymphoma Translocated protein 1) is critical for the proliferation and survival of Activated B-cell like Diffuse Large B-cell Lymphoma (ABC-DLBCL), the most chemo-resistant form of DLBCL. MALT1 mediates activation of the B-cell receptor pathway (BCR) downstream of characteristic somatic mutations in CD79, CARD11 or MYD88 that lead to chronically activated NF-κB. MALT1 is a paracaspase and the effector enzyme of the CARD11/Bcl10/MALT1 signalosome, a high order assembly that functions as an amplifier of BCR signaling to NF-κB. MALT1 constitutes a compelling therapeutic target because: i) it is the only paracaspase in humans, ii) MALT1 knockout mice are viable, and iii) ABC-DLBCLs are biologically dependent on MALT1 paracaspase activity.

MALT1 is only active when forming multimeric complexes. In order to identify potential MALT1 inhibitors we engineered a leucine zipper-MALT1, obliged and enzymatically active dimer, and established a paracaspase enzymatic assay for high throughput screening. Screening a ~50,000 compound chemical diversity library allowed us the identification and validation of 19 distinct chemical scaffolds that inhibited MALT1 with an IC50&lt;20 μM. Three compounds significantly induced selective dose-dependent suppression of MALT1-dependent ABC-DLBCL cells (MI-2, p&lt;0.0001; MI-4, p=0.006; MI-11, p&lt;0.0001). The most potent compound in cell-based assays was MI-2 with a GI25 in the low nanomolar range. MI-2 analogs also displayed nanomolar activity. In depth analysis using NMR and LC-MS revealed that MI-2 binds covalently to the active site of MALT1. In DLBCL cells, MI-2 inhibited MALT1 cleavage of its targets TNFAIP3, BCL10 and RelB, as well as nuclear translocation of c-REL and overall NF-κB activation. MI-2 inhibited proliferation by inducing G1 arrest and ultimately promoted apoptosis in ABC-DLBCLs including those with mutations that bypass BTK inhibitors, like CARD11 activating mutation. MI-2 was non toxic in vivo and potently and specifically inhibited the growth of xenotransplanted ABC-DLBCLs (p=0.014, t-test) but not GCB-DLBCLs. Moreover, MI-2 selectively killed primary human ABC-DLBCL specimens ex vivo.

Given that multiple pathways contribute to ABC-DLBCL pathogenesis, we hypothesized that MALT1 inhibitors would be most effective within combinatorial therapy regimens. Along these lines MI-2 strongly enhanced the activity of CHOP chemotherapy drugs against ABC-DLBCL cells. The addition of MI-2 to doxorubicin allowed for 2.5 to 13-fold reduction in the doxorubicin dose as determined by the dose-reduction index that was specific for the doxorubicin resistant cell lines (GI50 &gt; 200 nM). Because the BCR pathway constitutes a complex network of signaling molecules beyond NF-κB activation, we tested combination of MI-2 with inhibitors of other proteins in this pathway affecting other branches of this pathway. Combination of MI-2 with the pan PI3K inhibitor BKM120, that was in our hands the most effective against a broad group of ABC-DLBCL cell lines, resulted in synergistic cell killing of OCI-Ly10 and Rc-K8 and had an additive effect in HBL-1 while it was less than additive for OCI-Ly3 and TMD8. These cell lines harbor mutations in different proteins of the pathway, which may contribute to the differences in response to the combination. Finally MI-2 strongly synergized with BH3 mimetics (most notably ABT-737) that target fundamental complementary survival pathways to BCR signaling in ABC-DLBCLs. Synergistic killing was at least partially due to induction of apoptosis, as concurrent administration of the two drugs induced increased apoptosis assessed by Caspase-7/3 activity and Annexin V+ DAPI- flow cytometry.

In summary, we identified the first specific MALT1 inhibitor drug and demonstrated a promising role for MALT1 targeted therapy as an anchor of rational combinatorial therapy against ABC-DLBCL.

Citation Format: Lorena Fontan, Chenghua Yang, Himaly Shinglot, Venkataraman Kabaleeswaran, Volpon Laurent, Michael Osborne, Elena Beltran, Monica Rosen, Rita Shaknovich, Shao N. Yang, Randy D. Gascoyne, Leandro Cerchietti, Jose A. MArtinez-Climent, J Fraser Glickman, KAtherine Borden, Hao Wu, Ari Melnick. MALT1 inhibition as an anchor for combinatorial therapy of ABC-DLBCL. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A19.

[Screening for mild cognitive impairment: usefulness of the 7-Minute Screen Test]

INTRODUCTION

The <<7- Minute Screen>> is a neurocognitive screening test for the detection of Alzheimer's disease (AD) patients in primary care settings. It consists of 4 brief subtests (orientation, memory, visuoconstruction and verbal fluency) and provides a broader neuropsychological profile than other widely used screening tests, The aim of the present study was to study the usefulness of this screening test for the detection of Mild Cognitive Impairment (MCI).

METHODS

Thirty-two patients with probable AD (NINCDS-ADRDA criteria), 25 patients with MCI, and 35 healthy control subjects, matched for age and education, underwent a comprehensive neuropsychological battery and the Rio-de-la-Plata version of the 7-Minute Screen. RESULTS. This test showed 93 % sensitivity and 97% specificity in detecting mild-moderate Alzheimer's disease MMSE<24), but it exhibited a substantially decreased sensitivity (28 %) in its ability to detect MCI in AD (MMSE >2 4 ).

CONCLUSION

The screening batteries do not replace a m o re compre h e n s i ve neuro psychological assessment. Th ey are useful in detecting patients with mild dementia, but caution must be the rule when considering a diagnosis of MCI.

[High-dose-rate brachytherapy in esophageal carcinoma: the Italian experience]

The results are reported of HDR intracavitary brachytherapy in 134 esophageal carcinoma patients (110 men and 24 women) treated in 10 Italian centers. Forty-one patients received radical treatment and brachytherapy was often combined with external irradiation and/or chemotherapy. Clinical response rates follow: 56% complete remissions, 34% partial remissions, 10% no response/disease progression and not assessed. Ninety-three patients underwent palliative treatment: dysphagia was reduced in 80% of them and pain was reduced in 71% of them. Treatment-induced esophageal damage consisted in G3-G4 esophagitis (5% of patients), strictures (10%) and fistulas (3%). Complication rates were correlated with fraction dose (9.5% complications for fraction doses < 500 cGy, 20% with doses ranging 500-800 cGy and 38% with fraction doses > 800 cGy). Moreover, the esophagus was more severely injured when small tubes were used (24% with tubes phi < 2 mm, 19% with tubes phi 2-6 mm and 5% with tubes phi > 6 mm). When external irradiation was combined with brachytherapy, dysphagia was more relieved than with brachytherapy alone (89% vs. 71%), with no increase in complication rates. Also the chemotherapy-brachytherapy combination improved swallowing more than brachytherapy alone (88% vs. 79%) and once again complication rates did not increase. To conclude, in the radical treatment of esophageal carcinoma, HDR brachytherapy permits higher radiation doses to be delivered, with fair complication rates. As for palliative treatment, HDR brachytherapy is safe, has low morbidity and provides adequate relief of dysphagia in 80% of patients. We suggest the use of tubes phi > 6 mm and fraction doses ranging 5-6 Gy.

Profiling the activity of the para-caspase MALT1 in B-cell acute lymphoblastic leukemia for potential targeted therapeutic application

B-cell acute lymphoblastic leukemia (B-ALL) remains a hard-to-treat disease with a poor prognosis in adults. Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a para-caspase required for B-cell receptor (BCR)-mediated NF-κB activation. Inhibition of MALT1 in preclinical models has proven efficacious in many B-cell malignancies including chronic lymphocytic leukemia, mantle cell lymphoma and diffuse large B-cell lymphoma. We sought to examine the role of MALT1 in B-ALL and determine the biological consequences of its inhibition. Targeting MALT1 with both Z-VRPR-fmk and MI-2 efficiently kills B-ALL cells independent of the cell-of-origin (pro, pre, mature) or the presence of the Philadelphia chromosome, and spares normal B cells. The mechanism of cell death was through apoptotic induction, mostly in cycling cells. The proteolytic activity of MALT1 can be studied by measuring its ability to cleave its substrates. Surprisingly, with the exception of mature B-ALL, we did not detect cleavage of MALT1 substrates at baseline, nor after proteasomal inhibition or following activation of pre-BCR. To explore the possibility of a distinct role for MALT1 in B-ALL, independent of signaling through BCR, we studied the changes in gene expression profiling following a 24-hour treatment with MI-2 in 12 B-ALL cell lines. Our transcriptome analysis revealed a strong inhibitory effect on MYC-regulated gene signatures, further confirmed by Myc protein downregulation, concomitant with an increase in the Myc degrader FBXW7. In conclusion, our evidence suggests a novel role for MALT1 in B-ALL through Myc regulation and provides support for clinical testing of MALT1 inhibitors in B-ALL.