Development and characterization of NILK-2301, a novel CEACAM5xCD3 κλ bispecific antibody for immunotherapy of CEACAM5-expressing cancers.

BACKGROUND: T-cell retargeting to eliminate CEACAM5-expressing cancer cells via CEACAM5xCD3 bispecific antibodies (BsAbs) showed limited clinical activity so far, mostly due to insufficient T-cell activation, dose-limiting toxicities, and formation of anti-drug antibodies (ADA). METHODS: We present here the generation and preclinical development of NILK-2301, a BsAb composed of a common heavy chain and two different light chains, one kappa and one lambda, determining specificity (so-called κλ body format). RESULTS: NILK-2301 binds CD3ɛ on T-cells with its lambda light chain arm with an affinity of ≈100 nM, and the CEACAM5 A2 domain on tumor cells by its kappa light chain arm with an affinity of ≈5 nM. FcγR-binding is abrogated by the "LALAPA" mutation (Leu234Ala, Leu235Ala, Pro329Ala). NILK-2301 induced T-cell activation, proliferation, cytokine release, and T-cell dependent cellular cytotoxicity of CEACAM5-positive tumor cell lines (5/5 colorectal, 2/2 gastric, 2/2 lung), e.g., SK-CO-1 (Emax = 89%), MKN-45 (Emax = 84%), and H2122 (Emax = 97%), with EC50 ranging from 0.02 to 0.14 nM. NILK-2301 binds neither to CEACAM5-negative or primary colon epithelial cells nor to other CEACAM family members. NILK-2301 alone or in combination with checkpoint inhibition showed activity in organotypic tumor tissue slices and colorectal cancer organoid models. In vivo, NILK-2301 at 10 mg/kg significantly delayed tumor progression in colon- and a pancreatic adenocarcinoma model. Single-dose pharmacokinetics (PK) and tolerability in cynomolgus monkeys at 0.5 or 10 mg/kg intravenously or 20 mg subcutaneously showed dose-proportional PK, bioavailability ≈100%, and a projected half-life in humans of 13.1 days. NILK-2301 was well-tolerated. Data were confirmed in human FcRn TG32 mice. CONCLUSIONS: In summary, NILK-2301 combines promising preclinical activity and safety with lower probability of ADA-generation due to its format compared to other molecules and is scheduled to enter clinical testing at the end of 2023.

Extracellular nicotinamide phosphoribosyltransferase: role in disease pathophysiology and as a biomarker.

Nicotinamide phosphoribosyltransferase (NAMPT) plays a central role in mammalian cell metabolism by contributing to nicotinamide adenine dinucleotide biosynthesis. However, NAMPT activity is not limited to the intracellular compartment, as once secreted, the protein accomplishes diverse functions in the extracellular space. Extracellular NAMPT (eNAMPT, also called visfatin or pre-B-cell colony enhancing factor) has been shown to possess adipocytokine, pro-inflammatory, and pro-angiogenic activities. Numerous studies have reported the association between elevated levels of circulating eNAMPT and various inflammatory and metabolic disorders such as obesity, diabetes, atherosclerosis, arthritis, inflammatory bowel disease, lung injury and cancer. In this review, we summarize the current state of knowledge on eNAMPT biology, proposed roles in disease pathogenesis, and its potential as a disease biomarker. We also briefly discuss the emerging therapeutic approaches for eNAMPT inhibition.

CD47xCD19 bispecific antibody triggers recruitment and activation of innate immune effector cells in a B-cell lymphoma xenograft model.

BACKGROUND: CD47/SIRPα axis is recognized as an innate immune checkpoint and emerging clinical data validate the interest of interrupting this pathway in cancer, particularly in hematological malignancies. In preclinical models, CD47/SIRPα blocking agents have been shown to mobilize phagocytic cells and trigger adaptive immune responses to eliminate tumors. Here, we describe the mechanisms afforded by a CD47xCD19 bispecific antibody (NI-1701) at controlling tumor growth in a mouse xenograft B-cell lymphoma model. METHODS: The contribution of immune effector cell subsets behind the antitumor activity of NI-1701 was investigated using flow cytometry, transcriptomic analysis, and in vivo immune-cell depletion experiments. RESULTS: We showed that NI-1701 treatment transformed the tumor microenvironment (TME) into a more anti-tumorigenic state with increased NK cells, monocytes, dendritic cells (DC) and MHCIIhi tumor-associated macrophages (TAMs) and decreased granulocytic myeloid-derived suppressor cells. Notably, molecular analysis of isolated tumor-infiltrating leukocytes following NI-1701 administration revealed an upregulation of genes linked to immune activation, including IFNγ and IL-12b. Moreover, TAM-mediated phagocytosis of lymphoma tumor cells was enhanced in the TME in the presence of NI-1701, highlighting the role of macrophages in tumor control. In vivo cell depletion experiments demonstrated that both macrophages and NK cells contribute to the antitumor activity. In addition, NI-1701 enhanced dendritic cell-mediated phagocytosis of tumor cells in vitro, resulting in an increased cross-priming of tumor-specific CD8 T cells. CONCLUSIONS: The study described the mechanisms afforded by the CD47xCD19 bispecific antibody, NI-1701, at controlling tumor growth in lymphoma mouse model. NI-1701 is currently being evaluated in a Phase I clinical trial for the treatment of refractory or relapsed B-cell lymphoma (NCT04806035).

Targeting a membrane-proximal epitope on mesothelin increases the tumoricidal activity of a bispecific antibody blocking CD47 on mesothelin-positive tumors.

Mesothelin (MSLN) is a cell surface glycoprotein overexpressed in several solid malignancies, including gastric, lung, mesothelioma, pancreatic and ovarian cancers. While several MSLN-targeting therapeutic approaches are in development, only limited efficacy has been achieved in patients. A potential shortcoming of several described antibody-based approaches is that they target the membrane distal region of MSLN and, additionally, are known to be handicapped by the high levels of circulating soluble MSLN in patients. We show here, using monoclonal antibodies (mAbs) targeting different MSLN-spanning epitopes, that the membrane-proximal region resulted in more efficient killing of MSLN-positive tumor cells in antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Surprisingly, no augmented killing was observed in antibody-dependent cellular phagocytosis (ADCP) by mAbs targeting this membrane-proximal region. To further increase the ADCP potential, we, therefore, generated bispecific antibodies (bsAbs) coupling a high-affinity MSLN binding arm to a blocking CD47 arm. Here, targeting the membrane-proximal domain of MSLN demonstrated enhanced ADCP activity compared to membrane-distal domains when the bsAbs were used in in vitro phagocytosis killing assays. Importantly, the superior anti-tumor activity was also translated in xenograft tumor models. Furthermore, we show that the bsAb approach targeting the membrane-proximal epitope of MSLN optimized ADCC activity by augmenting FcγR-IIIA activation and enhanced ADCP via a more efficient blockade of the CD47/SIRPα axis.

Preclinical Development of a Bispecific Antibody that Safely and Effectively Targets CD19 and CD47 for the Treatment of B-Cell Lymphoma and Leukemia.

CD47, an ubiquitously expressed innate immune checkpoint receptor that serves as a universal "don't eat me" signal of phagocytosis, is often upregulated by hematologic and solid cancers to evade immune surveillance. Development of CD47-targeted modalities is hindered by the ubiquitous expression of the target, often leading to rapid drug elimination and hemotoxicity including anemia. To overcome such liabilities, we have developed a fully human bispecific antibody, NI-1701, designed to coengage CD47 and CD19 selectively on B cells. NI-1701 demonstrates favorable elimination kinetics with no deleterious effects seen on hematologic parameters following single or multiple administrations to nonhuman primates. Potent in vitro and in vivo activity is induced by NI-1701 to kill cancer cells across a plethora of B-cell malignancies and control tumor growth in xenograft mouse models. The mechanism affording maximal tumor growth inhibition by NI-1701 is dependent on the coengagement of CD47/CD19 on B cells inducing potent antibody-dependent cellular phagocytosis of the targeted cells. NI-1701-induced control of tumor growth in immunodeficient NOD/SCID mice was more effective than that achieved with the anti-CD20 targeted antibody, rituximab. Interestingly, a synergistic effect was seen when tumor-implanted mice were coadministered NI-1701 and rituximab leading to significantly improved tumor growth inhibition and regression in some animals. We describe herein, a novel bispecific antibody approach aimed at sensitizing B cells to become more readily phagocytosed and eliminated thus offering an alternative or adjunct therapeutic option to patients with B-cell malignancies refractory/resistant to anti-CD20-targeted therapy. Mol Cancer Ther; 17(8); 1739-51. ©2018 AACR.

Tumor-Directed Blockade of CD47 with Bispecific Antibodies Induces Adaptive Antitumor Immunity.

CD47 serves as an anti-phagocytic receptor that is upregulated by cancer to promote immune escape. As such, CD47 is the focus of intense immuno-oncology drug development efforts. However, as CD47 is expressed ubiquitously, clinical development of conventional drugs, e.g., monoclonal antibodies, is confronted with patient safety issues and poor pharmacology due to the widespread CD47 "antigen sink". A potential solution is tumor-directed blockade of CD47, which can be achieved with bispecific antibodies (biAbs). Using mouse CD47-blocking biAbs in a syngeneic tumor model allowed us to evaluate the efficacy of tumor-directed blockade of CD47 in the presence of the CD47 antigen sink and a functional adaptive immune system. We show here that CD47-targeting biAbs inhibited tumor growth in vivo, promoting durable antitumor responses and stimulating CD8+ T cell activation in vitro. In vivo efficacy of the biAbs could be further enhanced when combined with chemotherapy or PD-1/PD-L1 immune checkpoint blockade. We also show that selectivity and pharmacological properties of the biAb are dependent on the affinity of the anti-CD47 arm. Taken together, our study validates the approach to use CD47-blocking biAbs either as a monotherapy or part of a multi-drug approach to enhance antitumor immunity.

Selective Blockade of the Ubiquitous Checkpoint Receptor CD47 Is Enabled by Dual-Targeting Bispecific Antibodies.

CD47 is a ubiquitously expressed immune checkpoint receptor that is often upregulated in cancer. CD47 interacts with its counter-receptor SIRPα on macrophages and other myeloid cells to inhibit cancer cell phagocytosis and drive immune evasion. To overcome tolerability and "antigen sink" issues arising from widespread CD47 expression, we generated dual-targeting bispecific antibodies that selectively block the CD47-SIRPα interaction on malignant cells expressing a specific tumor-associated antigen; e.g., CD19 or mesothelin. These bispecific κλ bodies are fully human, native IgG1 molecules, combining tumor targeting and selective CD47 blockade with immune activating mechanisms mediated by the Fc portion of the antibody. CD47-neutralizing κλ bodies efficiently kill cancer cells in vitro and in vivo but interact only weakly with healthy cells expressing physiological levels of CD47. Accordingly, a κλ body administered to non-human primates showed a typical IgG pharmacokinetic profile and was well tolerated. Importantly, κλ bodies preserve their tumoricidal capabilities in the presence of a CD47 antigen sink. Thus, dual-targeting κλ bodies allow for efficacious yet safe targeting of CD47 in cancer. Such a bispecific design could be applied to limit the extent of neutralization of other ubiquitously expressed therapeutic targets.

Exploiting light chains for the scalable generation and platform purification of native human bispecific IgG.

Bispecific antibodies enable unique therapeutic approaches but it remains a challenge to produce them at the industrial scale, and the modifications introduced to achieve bispecificity often have an impact on stability and risk of immunogenicity. Here we describe a fully human bispecific IgG devoid of any modification, which can be produced at the industrial scale, using a platform process. This format, referred to as a κλ-body, is assembled by co-expressing one heavy chain and two different light chains, one κ and one λ. Using ten different targets, we demonstrate that light chains can play a dominant role in mediating specificity and high affinity. The κλ-bodies support multiple modes of action, and their stability and pharmacokinetic properties are indistinguishable from therapeutic antibodies. Thus, the κλ-body represents a unique, fully human format that exploits light-chain variable domains for antigen binding and light-chain constant domains for robust downstream processing, to realize the potential of bispecific antibodies.

CCR7 is involved in the migration of neutrophils to lymph nodes.

Increasing evidence suggests that neutrophils may participate in the regulation of adaptive immune responses, and can reach draining lymph nodes and cross-prime naive T cells. The aim of this study was to identify the mechanism(s) involved in the migration of neutrophils to the draining lymph nodes. We demonstrate that a subpopulation of human and mouse neutrophils express CCR7. CCR7 is rapidly expressed at the membrane upon stimulation. In vitro, stimulated human neutrophils migrate in response to the CCR7 ligands CCL19 and CCL21. In vivo, injection of complete Freund adjuvant induces a rapid recruitment of neutrophils to the lymph nodes in wild-type mice but not in Ccr7(-/-) mice. Moreover, intradermally injected interleukin-17-and granulocyte-macrophage colony-stimulating factor-stimulated neutrophils from wild-type mice, but not from Ccr7(-/-) mice, migrate to the draining lymph nodes. These results identify CCR7 as a chemokine receptor involved in the migration of neutrophils to the lymph nodes.

New functions of the major histocompatibility complex class II-specific transcription factor RFXANK revealed by a high-resolution mutagenesis study.

The transcription factors RFX and CIITA are major players in regulation of the expression of all classical and nonclassical major histocompatibility complex class II (MHC-II) genes. RFX nucleates the formation of a multiprotein complex, called the MHC-II enhanceosome, on MHC-II promoters. Assembly of this enhanceosome is an obligatory step for recruitment of the coactivator CIITA and thus for activation of MHC-II gene transcription. We have analyzed the function of the ankyrin repeat-containing protein RFXANK, which forms the heterotrimeric RFX complex together with RFX5 and RFXAP. We discovered that ANKRA2, the closest paralogue of RFXANK, can substitute for RFXANK in the activation of MHC-II genes and that this ability is mediated by its ankyrin repeat domain (ARD). This finding provided the basis for a high-resolution structure-function analysis of the ARD of RFXANK, which allowed us to map the RFX5 interaction domain and residues critical for assembly of the RFX complex. We also found that mutations in the fourth ankyrin repeat of RFXANK abolish assembly of the enhanceosome on MHC-II promoters in vivo but not in vitro, suggesting a new role of RFXANK in facilitating promoter occupation in the context of chromatin.

Long distance control of MHC class II expression by multiple distal enhancers regulated by regulatory factor X complex and CIITA.

MHC class II (MHC-II) genes are regulated by an enhanceosome complex containing two gene-specific transcription factors, regulatory factor X complex (RFX) and CIITA. These factors assemble on a strictly conserved regulatory module (S-X-X2-Y) found immediately upstream of the promoters of all classical and nonclassical MHC-II genes as well as the invariant chain (Ii) gene. To identify new targets of RFX and CIITA, we developed a computational approach based on the unique and highly constrained architecture of the composite S-Y motif. We identified six novel S'-Y' modules situated far away from the promoters of known human RFX- and CIITA-controlled genes. Four are situated at strategic positions within the MHC-II locus, and two are found within the Ii gene. These S'-Y' modules function as transcriptional enhancers, are bona fide targets of RFX and CIITA in B cells and IFN-gamma-induced cells, and induce broad domains of histone hyperacetylation. These results reveal a hitherto unexpected level of complexity involving long distance control of MHC-II expression by multiple distal regulatory elements.

The S box of major histocompatibility complex class II promoters is a key determinant for recruitment of the transcriptional co-activator CIITA.

Tightly regulated expression of major histocompatibility complex (MHC) class II genes is critical for the immune system. A conserved regulatory module consisting of four cis-acting elements, the W, X, X2 and Y boxes, controls transcription of MHC class II genes. The X, X2, and Y boxes are bound, respectively, by RFX, CREB, and NF-Y to form a MHC class II-specific enhanceosome complex. The latter constitutes a landing pad for recruitment of the transcriptional co-activator CIITA. In contrast to the well defined roles of the X, X2, and Y boxes, the role of the W region has remained controversial. In vitro binding studies have suggested that it might contain a second RFX-binding site. We demonstrate here by means of promoter pull-down assays that the most conserved subsequence within the W region, called the S box, is a critical determinant for tethering of CIITA to the enhanceosome complex. Binding of CIITA to the enhanceosome requires both integrity of the S box and a remarkably stringent spacing between the S and X boxes. Even a 1-2-base pair change in the native S-X distance is detrimental for CIITA recruitment and promoter function. In contrast to current models, binding of RFX to a putative duplicated binding site in the W box is thus not required for either CIITA recruitment or promoter activity. This paves the way for the identification of novel factors mediating the contribution of the S box to the activation of MHC class II promoters.

In vivo, RFX5 binds differently to the human leucocyte antigen-E, -F, and -G gene promoters and participates in HLA class I protein expression in a cell type-dependent manner.

We analysed the regulation of human leucocyte antigen (HLA)-E, -F and -G genes, focusing on the SXY module, a promoter region that controls major histocompatibility complex (MHC) class II expression and participates in the expression of classical HLA class I molecules. It comprises the X1, X2 and Y boxes, bound by RFX, X2-BP/ATF/CREB and NFY factors, respectively. The complex recruits the master control factor CIITA. The SXY module is conserved in HLA-E and HLA-F gene promoters, whereas in the HLA-G promoter, the only conserved boxes are S and X1. Chromatin immunoprecipitation assays, performed on HLA-G positive and negative cell lines, demonstrated the in situ binding of RFX5 and CIITA to HLA-E and HLA-F, but not to HLA-G, promoters. In B cells from bare lymphocyte syndrome patients lacking RFX5 or CIITA, we observed lower steady-state levels of HLA-E and HLA-F transcripts but did not find any significant decrease in the cell-surface expression of HLA-E/classical HLA class I. In RFX5-deficient fibroblasts, the cell-surface expression of HLA molecules was decreased. RFX5 and CIITA are thus not involved in HLA-G expression and their importance for the surface expression of HLA-E/classical HLA class I molecules may vary depending on the cell type.

Chromatin remodeling and extragenic transcription at the MHC class II locus control region.

In vivo, a wild-type pattern of major histocompatibility complex (MHC) class II expression requires a locus control region (LCR). Whereas the role of promoter-proximal MHC class II regulatory sequences is well established, the function of the distal LCR remained obscure. We show here that this LCR is bound by the MHC class II-specific transactivators regulatory factor X (RFX) and class II transactivator (CIITA). Binding of these factors induces long-range histone acetylation, RNA polymerase II recruitment and the synthesis of extragenic transcripts within the LCR. The finding that RFX and CIITA regulate the function of the MHC class II LCR reveals an unexpected degree of complexity in the mechanisms controlling MHC class II gene expression.

Promoter-specific functions of CIITA and the MHC class II enhanceosome in transcriptional activation.

Transcription of the major histocompatibility complex class II family of genes is regulated by conserved promoter elements and two gene-specific trans-activators, RFX and CIITA. RFX binds DNA and nucleates the assembly of an enhanceosome, which recruits CIITA through protein--protein interactions. Transcriptional activation is a complex, multi-step process involving chromatin modification and recruitment of the transcription apparatus. To examine the roles of the enhanceosome and CIITA in these processes, we analysed the level of promoter-associated hyperacetylated histones H3 and H4, TBP, TFIIB and RNA poly merase II in cells lacking RFX or CIITA. We compared four genes co-regulated by RFX and CIITA (HLA-DRA, HLA-DPB, HLA-DMB and Ii) and found that the enhanceosome and CIITA make variable, promoter-dependent contributions to histone acetylation and transcription apparatus recruitment. CIITA is generally implicated at multiple levels of the activation process, while the enhanceosome contributes in a CIITA-independent manner only at certain promoters. Our results support the general notion that the impact of a particular activator on transcription in vivo may vary depending on the promoter and the chromatin context.