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 MHCII^hi 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).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40164-022-00279-w.

Abstract A088: Selective blockage of the innate immune checkpoint receptor CD47 on mesothelin (MSLN) positive solid tumor cells via dual targeting bispecific antibodies alters the tumor microenvironment to control tumor growth

Up-regulation of CD47 is an immune evasion mechanism used by different cancers to evade immune surveillance. Through its interaction with signal-regulatory protein alpha (SIRPα) on myeloid cells, CD47 delivers a universal “don’t eat me” signal to phagocytes, which prevents immune cells from efficiently eliminating tumor cells. Blockade of the SIRPα–CD47 innate immune checkpoint has therefore emerged as a new way to treat cancer. Several CD47-targeting molecules are in development with encouraging results obtained with monoclonal antibodies (mAb). However, the pharmacologic properties and the safety profile of molecules indiscriminately blocking CD47 can be improved by selectively inhibiting CD47 only on tumor cells. For this purpose, we generated bispecific antibodies (bsAbs) capable of targeting blockade of CD47 specifically to malignanT-cells through the co-engagement of a tumor-associated antigen (TAA). The bsAb NI-1801 specifically targets mesothelin (MSLN)-positive tumors. NI-1801 was shown to bind to MSLN-positive tumor cells, but not to MSLN-negative cells expressing physiologic levels of CD47 (e.g., leukocytes, erythrocytes, platelets). NI-1801 blocks the CD47-SIRPα interaction in a MSLN-dependent manner and thus minimizes the side effects related to a nonspecific blockade of CD47 on healthy cells. Studying antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC) of various MSLN-positive human tumor cell lines revealed that NI-1801 markedly enhanced killing as compared to amatuximab (an anti-MSLN mAb in clinical trials) and to the corresponding anti-MSLN mAb, exemplifying the role of blocking the “don’t eat me” signal to target cancer. NI-1801 also showed efficacy in various xenograft tumor models and analysis of the tumor microenvironment (TME) revealed a significant increase in leukocyte subpopulations (macrophages/monocytes and NK cells) of NI-1801 treated mice, suggesting that NI-1801 mediates the recruitment of monocytes from blood. Additionally, NI-1801 treatment affected the ratio between MHC-II-low and MHC-II-high macrophages in the TME. Finally, nonhuman primate studies with NI-1801 demonstrated a linear elimination profile, minimal target-mediated drug disposition and no hematologic toxicity. Taken together, these results illustrate that this strategy possesses potent anticancer activities both in vitro and in vivo in conjunction with favorable pharmacologic and toxicologic profiles.

Citation Format: Stefano Majocchi, Valéry Moine, Xavier Chauchet, Lucile Broyer, Laura Cons, Laurence Chatel, Eric Hatterer, Vanessa Buatois, Hasnaà Haddouk, Gérard Didelot, Giovanni Magistrelli, Yves Poitevin, Ulla Ravn, Anne Papaioannou, Françoise Richard, Limin Shang, Marie H. Kosco-Vilbois, Nicolas Fischer, Walter G. Ferlin, Krzysztof Masternak. Selective blockage of the innate immune checkpoint receptor CD47 on mesothelin (MSLN) positive solid tumor cells via dual targeting bispecific antibodies alters the tumor microenvironment to control tumor growth [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A088.

Abstract 2770: Dual-targeting mesothelin/CD47 bispecific antibodies for tumor-directed blockade of CD47 in solid cancer

Mesothelin (MSLN) is a lineage restricted cell surface protein with unknown biological function, expressed at low levels on mesothelial cells in healthy tissue. MSLN is also a tumor differentiation antigen as it is highly expressed across a wide range of solid tumors with the highest prevalence in mesothelioma, pancreatic, biliary, ovarian, lung and gastric cancers. Most solid and hematological cancers also upregulate the expression of CD47, a ubiquitous innate immune checkpoint receptor. CD47 interacts with signal-regulatory protein alpha (SIRPα) on myeloid cells, which leads to the inhibition of tumor cell phagocytosis and anti-tumor immune responses. Accordingly, elevated levels of CD47 on tumor cells are associated with cancer's immune evasion capacity and correlate with poor clinical prognosis, all of which makes CD47 a relevant target for therapeutic blockade. We generated a series of dual-targeting bispecific CD47/MSLN antibodies (biAbs) selectively binding to MSLN-positive tumor cells, but not MSLN-negative healthy cells expressing physiological levels of CD47 (e.g., all blood cells). These CD47/MSLN biAbs block CD47-SIRPα interaction in a MSLN-dependent, tumor-specific manner, thus permitting to bypass tolerability and “antigen sink” issues related to ubiquitous CD47 expression in healthy tissues. An array of CD47/MSLN biAbs with anti-MSLN arms targeting different MSLN epitopes was tested in vitro, in antibody dependent cellular phagocytosis (ADCP) and antibody dependent cellular cytotoxicity (ADCC) assays, as well as for anti-tumor activity in vivo using mouse xenograft models. With various MSLN-positive human cancer cell lines, MSLN/CD47 biAbs demonstrate significantly enhanced cancer cell killing by ADCC and ADCP as compared to the corresponding anti-MSLN monoclonal antibody format (mAbs) as well as to amatuximab, a therapeutic anti-MSLN mAb (currently in Phase II clinical trials for mesothelioma). Correspondingly, the MSLN/CD47 biAbs also display superior efficacy in controlling tumor growth in the xenograft models in vivo. Taken together, we conclude that MSLN/CD47 biAbs should allow for efficacious, yet safe, targeting of CD47 in multiple solid tumor indications in the clinic. More generally, our data support the concept of tumor-directed blockade of CD47 with biAbs as a novel way of improving the efficacy of antibody-based cancer therapies.

Citation Format: Valéry Moine, Lucile Broyer, Xavier Chauchet, Eric Hatterer, Stefano Majocchi, Vanessa Buatois, Limin Shang, Gérard Didelot, Giovanni Magistrelli, Yves Poitevin, Ulla Ravn, Marie H. Kosco-Vilbois, Nicolas Fiischer, Walter G. Ferlin, Krzysztof Masternak. Dual-targeting mesothelin/CD47 bispecific antibodies for tumor-directed blockade of CD47 in solid cancer [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 2770.

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.

Abstract 2482: Neutralizing CD47 in cancer cells with dual targeting kappa/lambda bodies

Neutralizing CD47, the ‘don't eat me signal’ hijacked by different tumor types, is a novel generally applicable therapeutic strategy. Because of a distinct mechanism of action and the ability to stimulate the innate anti-tumor immunity, CD47-neutralizing agents are poised as attractive candidates for combination therapies in association with other immunotherapies. However, the development of general CD47 antagonists could be hindered by the ubiquitous and abundant expression of CD47 on virtually all healthy cells. To overcome potential pharmacological and clinical liabilities of a general CD47 antagonist, we have developed bispecific kappa/lambda bodies, which selectively target CD47 in cancer cells. These kappa/lambda bodies:

(i) are full-length bispecific IgGs, (ii) bind with high affinity and neutralize the CD47-SIRP alpha interaction in cancer cells expressing a tumor-associated antigen (TAA), and (iii) mediate efficient cell killing of TAA-positive cancer cells in vitro through Fc-dependent mechanisms such as ADCP (antibody mediated cellular phagocytosis) and ADCC (antibody mediated cellular cytotoxicity).

We are currently developing two molecules of this type, one targeting CD47 and CD19 (for B cell malignancies), the other targeting CD47 and mesothelin (for various mesothelin-positive solid tumors). The efficacy of the CD47/CD19 kappa/lambda body was demonstrated in vivo, using two B-cell lymphoma xenograft models in NOD/SCID mice. We also performed a pharmacokinetics study in non-human primates with the CD47/CD19 lead candidate, with the objective of assessing the potential “antigen sink” effect related to ubiquitous CD47 expression on erythrocytes, platelets and other cells. Encouragingly, the CD47/CD19 kappa/lambda body administered in a single dose to cynomolgus monkeys, at 0.5 and 10 mg/kg, showed an acceptable pharmacokinetic profile and the absence of hematological toxicities. The example of the CD47/CD19 kappa/lambda body illustrates the power of the dual-targeting approach for addressing a ubiquitous cell surface receptor such as CD47.

Citation Format: Krzysztof Masternak, Lucile Broyer, Elie Dheilly, Stefano Majocchi, Valéry Moine, Giovanni Magistrelli, François Rousseau, Ulla Ravn, Franck Gueneau, Pauline Malinge, Sébastien Calloud, Maud Charreton-Galby, Mireille Guerrier, Nessie Costes, Nicolas Bosson, Gérard Didelot, Lucie Bernard, Vanessa Buatois, Laura Cons, Laurence Chatel, Anne Papaioannou, Zoë Johnson, Walter Ferlin, Marie Kosco-Vilbois, Nicolas Fischer. Neutralizing CD47 in cancer cells with dual targeting kappa/lambda bodies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2482. doi:10.1158/1538-7445.AM2015-2482

Robust Antibody-Antigen Complexes Prediction Generated by Combining Sequence Analyses, Mutagenesis, In Vitro Evolution, X-ray Crystallography and In Silico Docking

Hu 15C1 is a potent anti-human Toll-like receptor 4 (TLR4) neutralizing antibody. To better understand the molecular basis of its biological activity, we used a multidisciplinary approach to generate an accurate model of the Hu 15C1-TLR4 complex. By combining site-directed mutagenesis, in vitro antibody evolution, affinity measurements and X-ray crystallography of Fab fragments, we identified key interactions across the Hu 15C1-TLR4 interface. These contact points were used as restraints to predict the structure of the Fab region of Hu 15C1 bound to TLR4 using computational molecular docking. This model was further evaluated and validated by additional site-directed mutagenesis studies. The predicted structure of the Hu 15C1-TLR4 complex indicates that the antibody antagonizes the receptor dimerization necessary for its activation. This study exemplifies how iterative cycles of antibody engineering can facilitate the discovery of components of antibody-target interactions.

Deep sequencing of phage display libraries to support antibody discovery

The use of next generation sequencing (NGS) for the analysis of antibody sequences both in phage display libraries and during in vitro selection processes has become increasingly popular in the last few years. Here, our methods developed for DNA preparation, sequencing and data analysis are presented. A key parameter has also been to develop new software designed for high throughput antibody sequence analysis that is used in combination with publicly available tools. As an example of our methods, we provide data from the extensive analysis of five scFv libraries generated using different heavy chain CDR3 diversification strategies. The results not only confirm that the library designs were correct but also reveal differences in quality not easily identified by standard DNA sequencing approaches. The very large number of reads permits extensive sequence coverage after the selection process. Furthermore, as samples can be multiplexed, costs decrease and more information is gained per NGS run. Using examples of results obtained post phage display selections against two antigens, frequency and clustering analysis identified novel antibody fragments that were then shown to be specific for the target antigen. In summary, the methods described here demonstrate how NGS analysis enhances quality control of complex antibody libraries as well as facilitates the antibody discovery process.

Tequila, a neurotrypsin ortholog, regulates long-term memory formation in Drosophila

Mutations in the human neurotrypsin gene are associated with autosomal recessive mental retardation. To further understand the pathophysiological consequences of the lack of this serine protease, we studied Tequila (Teq), the Drosophila neurotrypsin ortholog, using associative memory as a behavioral readout. We found that teq inactivation resulted in a long-term memory (LTM)-specific defect. After LTM conditioning of wild-type flies, teq expression transiently increased in the mushroom bodies. Moreover, specific inhibition of teq expression in adult mushroom bodies resulted in a reversible LTM defect. Hence, the Teq pathway is essential for information processing in Drosophila.

The β-Thymosin/WH2 Domain

The widespread beta-thymosin/WH2 actin binding domain has versatile regulatory properties in actin dynamics and motility. beta-thymosins (isolated WH2 domain) maintain monomeric actin in a "sequestered" nonpolymerizable form. In contrast, when repeated in tandem or inserted in modular proteins, the beta-thymosin/WH2 domain promotes actin assembly at filament barbed ends, like profilin. The structural basis for these opposite functions is addressed using ciboulot, a three beta-thymosin repeat protein. Only the first repeat binds actin and possesses the function of ciboulot. The region that shows the strongest interaction with actin is an amphipathic N-terminal alpha helix, present in all beta-thymosin/WH2 domains, which recognizes the ATP bound actin structure and uses the shear motion of actin linked to ATP hydrolysis to control polymerization. Crystallographic ((1)H, (15)N), NMR, and mutagenetic data reveal that the weaker interaction of the C-terminal region of beta-thymosin/WH2 domain with actin accounts for the switch in function from inhibition to promotion of actin assembly.