Preclinical Evaluation of a Novel MALT1 Inhibitor CTX-177 for Relapse/Refractory Lymphomas

Among various subtypes of malignant lymphomas, activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL), mantle cell lymphoma (MCL), and adult T-cell leukemia/lymphoma (ATL) are clinically intractable as patients with these lymphomas carry a dismal prognosis, with long-term survival rates of 10-30%. Therefore, a novel therapeutic strategy is required to better manage patients with these malignancies. Recently, we and other investigators performed comprehensive genetic studies and revealed frequent genetic alterations in B and T cell antigen receptor signaling and NF-κB pathway, such as CD79A/B and CARD11 mutations in ABC-DLBCL and PLCG1, PRKCB, and CARD11 mutations in ATL, suggesting the biological relevance of this pathway. To exploit a new treatment strategy in these malignant lymphomas, we focused on the protease mucosa-associated lymphoid tissue lymphoma translocation 1 (MALT1) which is a key regulator of the antigen receptor signaling and NF-κB pathway and forms a complex with CARD11 and BCL10, and developed a novel compound CTX-177 to inhibit MALT1 with high potency and specificity. CTX-177 was efficacious against ABC-DLBCL and MCL models in vitro and in vivo. Moreover, CTX-177 exhibited combination synergistic effect with BTK inhibitor. In addition, the MALT1 inhibitor showed an anti-tumor effect against CARD11 mutated ABC-DLBCL model, which is resistant to BTK inhibitor. To further explore efficacy of CTX-177 against malignant lymphomas, we generated animal models such as genetically engineered mice and patient-derived xenograft models recapitulating molecular features of these diseases, and examined the response to the MALT1 inhibitor. In these experiments, target engagement of CTX-177 was confirmed by detecting digested substrates of MALT1, and mode of action was evaluated by downregulation of oncogenic transcriptional factor IRF4 which is critical for lymphoma survival. Importantly, the relationship of susceptibility to MALT1 inhibition and gene mutations was analyzed to identity a patient selection biomarker for CTX-177. In summary, the novel, selective, small-molecule MALT1 inhibitor CTX-177 demonstrated preclinical efficacy along with target engagement in several lymphoma models with activated antigen receptor signaling and NF-κB pathway. Our results underscore the preclinical therapeutic potential of CTX-177 as a single-agent or in combination with other inhibitors like BTK inhibitor for the treatment of malignant lymphomas. Disclosures Morishita: Chordia Therapeutics Inc.: Current Employment, Current equity holder in private company. Mizutani:Chordia Therapeutics Inc.: Current Employment, Current equity holder in private company. Tozaki:Chordia Therapeutics Inc.: Current Employment, Current equity holder in private company. Arikawa:Chordia Therapeutics Inc.: Current Employment, Current equity holder in private company. Kataoka:CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Takeda Pharmaceutical Company: Research Funding; Otsuka Pharmaceutical: Research Funding; Asahi Genomics: Current equity holder in private company. Yoda:Chordia Therapeutics Inc.: Research Funding. Izutsu:Symbio: Research Funding; Solasia: Research Funding; Celgene: Research Funding; Chugai: Research Funding; Novartis: Research Funding; Ono Pharmaceutical: Research Funding; Bayer pharmaceuticals: Research Funding; Daiichi Sankyo: Research Funding; AstraZeneca: Research Funding; Eisai: Research Funding; Incyte: Research Funding; Abbvie pharmaceuticals: Research Funding; HUYA Japan: Research Funding; Sanofi: Research Funding; Janssen: Research Funding; Yakult: Research Funding. Minami:Bristol-Myers Squibb Company: Honoraria; Novartis Pharma KK: Honoraria; Pfizer Japan Inc.: Honoraria; Takeda: Honoraria. Shimoda:Otsuka Pharmaceutical: Research Funding; Pfizer Inc.: Research Funding; Kyowa Hakko Kirin Co., Ltd.: Research Funding; CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Merck & Co.: Research Funding; Astellas Pharma: Research Funding; AbbVie Inc.: Research Funding; PharmaEssentia Japan: Research Funding; Perseus Proteomics: Research Funding; Celgene: Honoraria; Shire plc: Honoraria; Bristol-Myers Squibb: Honoraria; Takeda Pharmaceutical Company: Honoraria; Novartis: Honoraria, Research Funding; Asahi Kasei Medical: Research Funding; Japanese Society of Hematology: Research Funding; The Shinnihon Foundation of Advanced Medical Treatment Research: Research Funding. Miyake:Chordia Therapeutics Inc.: Current Employment, Current equity holder in private company. Ogawa:KAN Research Institute, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Chordia Therapeutics, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Asahi Genomics Co., Ltd.: Current equity holder in private company; Otsuka Pharmaceutical Co., Ltd.: Research Funding; Sumitomo Dainippon Pharma Co., Ltd.: Research Funding; Eisai Co., Ltd.: Research Funding.

Dysregulated CARD11 signaling in the development of diffuse large B cell lymphoma

CARD11 is a crucial scaffold protein that controls antigen-induced activation of lymphocytes. Upon antigen receptor signaling, CARD11 engages several signaling pathways, leading to the activation of NF-κB, mTOR, and JNK. CARD11 mutations are frequently found in patients with non-Hodgkin lymphoma and their ability to induce aberrant lymphocyte proliferation may be enhanced by mutations in regulators of CARD11 signal transduction. Here we describe how dysregulated CARD11 activity can promote lymphomagenesis through branched signaling pathways whose components and intermediates provide targets for novel diagnostic and therapeutic approaches. Statement of novelty: This review discusses how gain-of-function CARD11 mutations promote lymphomagenesis by engaging branching signaling pathways and how these different pathways provide multiple targets for therapies.

Expression of inhibitory receptors by B cells in chronic human infectious diseases restricts responses to membrane-associated antigens

Chronic human infectious diseases, including malaria, are associated with a large expansion of a phenotypically and transcriptionally distinct subpopulation of B cells distinguished by their high expression of a variety of inhibitory receptors including FcγRIIB. Because these B cells, termed atypical memory B cells (MBCs), are unable to respond to soluble antigens, it was suggested that they contributed to the poor acquisition of immunity in chronic infections. Here, we show that the high expression of FcγRIIB restricts atypical MBC responses to membrane-associated antigens that function to actively exclude FcγRIIB from the B cell immune synapse and include the co-receptor CD19, allowing B cell antigen receptor signaling and differentiation toward plasma cells. Thus, chronic infectious diseases result in the expansion of B cells that robustly respond to antigens that associate with cell surfaces, such as antigens in immune complexes, but are unable to respond to fully soluble antigens, such as self-antigens.

Increased yields and biological potency of knob-into-hole-based soluble MHC class II molecules

Assembly of soluble peptide-major histocompatibility complex class II (pMHCII) monomers into multimeric structures enables the detection of antigen-specific CD4+ T cells in biological samples and, in some configurations, their reprogramming in vivo. Unfortunately, current MHCII-αβ chain heterodimerization strategies are typically associated with low production yields and require the use of foreign affinity tags for purification, precluding therapeutic applications in humans. Here, we show that fusion of peptide-tethered or empty MHCII-αβ chains to the IgG1-Fc mutated to form knob-into-hole structures results in the assembly of highly stable pMHCII monomers. This design enables the expression and rapid purification of challenging pMHCII types at high yields without the need for leucine zippers and purification affinity tags. Importantly, this design increases the antigen-receptor signaling potency of multimerized derivatives useful for therapeutic applications and facilitates the detection and amplification of low-avidity T cell specificities in biological samples using flow cytometry.