Abstract 952: The bispecific antibody MCLA-129 impairs NSCLC tumor growth by targeting EGFR and c-MET, inhibiting ligand-induced signaling and promoting ADCC and ADCP

MCLA-129 is an ADCC-enhanced common light chain bispecific human IgG1 Biclonics® antibody specifically targeting the receptor tyrosine kinases EGFR and c-MET. It inhibits activation and downstream signaling of EGFR and c-MET induced by their respective ligands EGF and HGF and promotes elimination of tumor cells via Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) and Antibody-Dependent Cell-Mediated Phagocytosis (ADCP).

MCLA-129 was developed to overcome c-MET signaling-dependent EGFR TKI-resistance mechanisms and was identified during an unbiased screening campaign with a focus on inhibition of ligand-induced proliferation and migration of cancer cells. Selectivity of MCLA-129 for tumor cells is achieved by simultaneously targeting both EGFR and c-MET. MCLA-129 blocks EGF and HGF binding to EGFR and c-MET, respectively, and consequently inhibits their ligand-induced phosphorylation. MCLA-129 was shown to bind critical residues on EGFR and c-MET for EGF and HGF ligand binding.

GlymaxX® low fucose glycoengineering technology was used to enhance the mononuclear cell ADCC activity of the bispecific antibody. MCLA-129 demonstrated potent dose-dependent ADCC and ADCP against all NSCLC cell lines tested, which positively correlated with the EGFR and c-MET expression levels on the target cells. Significant inhibition of tumor growth of NCI-H1975EGFR L858R, T790M and HCC827/ER1EGFR del (E746, A750), c-MET amplified NSCLC cell line derived tumors was observed following MCLA-129 treatment.

MCLA-129 can overcome HGF-mediated EGFR-TKI resistance, as demonstrated by testing a non-ADCC enhanced version of this antibody in a panel of NSCLC cell lines in vitro and orthotopic tumors in vivo showing that it inhibits EGFR and c-MET activity. Significant tumor regression was observed following treatment of immunodeficient xenograft NSG-hHGFki mice bearing orthotopic tumors established from HCC827EGFR del (E746, A750) cells. In addition, in an acquired erlotinib EGFR TKI resistance model, treatment of mice harboring tumors as big as >500 mm3 led to significant reduction of tumor size which persisted after the treatment period.

Taken together these data demonstrate that MCLA-129 is a potent inhibitor of tumor growth applying various mechanisms of action, including inhibition of c-MET and EGFR signaling, ADCC and ADCP. MCLA-129 holds promise as a potential treatment for patients with NSCLC and other cancers, and warrants clinical evaluation.

Citation Format: David J. de Gorter, Alexandre Deshiere, Martijn van Rosmalen, Christian Wohn, Berina Eppink, Tristan Gallenne, Rinse Klooster, Li Mao, Wenxin Xu, Liang Deng, Qingyu Shu, Wei Liu, John de Kruif, Mario Di Matteo, Massimiliano Mazzone, Mark Throsby, Cecile A. Geuijen. The bispecific antibody MCLA-129 impairs NSCLC tumor growth by targeting EGFR and c-MET, inhibiting ligand-induced signaling and promoting ADCC and ADCP [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 952.

Absence of MHC class II on cDC1 dendritic cells triggers fatal autoimmunity to a cross-presented self-antigen

Conventional dendritic cells expressing the XCR1 chemokine receptor (cDC1s) excel at cross-presentation. Here, we developed and used a mouse model in which a Cre recombinase is expressed under the control of the Xcr1 gene while preserving XCR1 expression. We used it to generate mice with conditional deletion of MHC class II (MHCII) molecules on cDC1s. By preventing cDC1s to receive suppressive regulatory T cell inputs via MHCII-restricted interactions, the objective of the present study was to gauge whether MHCII-deficient cDC1s lose their capacity of tolerizing autoreactive CD8⁺ T cells. Whereas MHCII⁺ cDC1 readily cross-tolerized strongly autoreactive CD8⁺ T cells specific for a keratinocyte-derived self-antigen, MHCII-deficient cDC1s converted them into potent effectors capable of triggering a fast-onset lethal autoimmunity associated with severe skin histopathological manifestations. Preventing egress of such pathogenic self-reactive CD8⁺ T cell effectors from the cutaneous draining lymph nodes abrogated the autoimmune condition. Therefore, our results revealed that the cross-tolerizing capacity of cDC1s is not a property fully acquired at the time they undergo homeostatic maturation but needs to be enforced via MHCII-restricted, suppressive interactions with regulatory T cells.

A Subset of Type I Conventional Dendritic Cells Controls Cutaneous Bacterial Infections through VEGFα-Mediated Recruitment of Neutrophils

Skin conventional dendritic cells (cDCs) exist as two distinct subsets, cDC1s and cDC2s, which maintain the balance of immunity to pathogens and tolerance to self and microbiota. Here, we examined the roles of dermal cDC1s and cDC2s during bacterial infection, notably Propionibacterium acnes (P. acnes). cDC1s, but not cDC2s, regulated the magnitude of the immune response to P. acnes in the murine dermis by controlling neutrophil recruitment to the inflamed site and survival and function therein. Single-cell mRNA sequencing revealed that this regulation relied on secretion of the cytokine vascular endothelial growth factor α (VEGF-α) by a minor subset of activated EpCAM+CD59+Ly-6D+ cDC1s. Neutrophil recruitment by dermal cDC1s was also observed during S. aureus, bacillus Calmette-Guérin (BCG), or E. coli infection, as well as in a model of bacterial insult in human skin. Thus, skin cDC1s are essential regulators of the innate response in cutaneous immunity and have roles beyond classical antigen presentation.

Novel Cre-Expressing Mouse Strains Permitting to Selectively Track and Edit Type 1 Conventional Dendritic Cells Facilitate Disentangling Their Complexity in vivo

Type 1 conventional DCs (cDC1) excel in the cross-priming of CD8⁺ T cells, which is crucial for orchestrating efficient immune responses against viruses or tumors. However, our understanding of their physiological functions and molecular regulation has been limited by the lack of proper mutant mouse models allowing their conditional genetic targeting. Because the Xcr1 and A530099j19rik (Karma/Gpr141b) genes belong to the core transcriptomic fingerprint of mouse cDC1, we used them to engineer two novel Cre-driver lines, the Xcr1^Cre and Karma^Cre mice, by knocking in an IRES-Cre expression cassette into their 3′-UTR. We used genetic tracing to characterize the specificity and efficiency of these new models in several lymphoid and non-lymphoid tissues, and compared them to the Clec9a^Cre mouse model, which targets the immediate precursors of cDCs. Amongst the three Cre-driver mouse models examined, the Xcr1^Cre model was the most efficient and specific for the fate mapping of all cDC1, regardless of the tissues examined. The Karma^Cre model was rather specific for cDC1 when compared with the Clec9a^Cre mouse, but less efficient than the Xcr1^Cre model. Unexpectedly, the Xcr1^Cre model targeted a small fraction of CD4⁺ T cells, and the Karma^Cre model a significant proportion of mast cells in the skin. Importantly, the targeting specificity of these two mouse models was not changed upon inflammation. A high frequency of germline recombination was observed solely in the Xcr1^Cre mouse model when both the Cre and the floxed alleles were brought by the same gamete irrespective of its gender. Xcr1, Karma, and Clec9a being differentially expressed within the cDC1 population, the three CRE-driver lines examined showed distinct recombination patterns in cDC1 phenotypic subsets. This advances our understanding of cDC1 subset heterogeneity and the differentiation trajectory of these cells. Therefore, to the best of our knowledge, upon informed use, the Xcr1^Cre and Karma^Cre mouse models represent the best tools currently reported to specifically and faithfully target cDC1 in vivo, both at steady state and upon inflammation. Future use of these mutant mouse models will undoubtedly boost our understanding of the biology of cDC1.

Antagonization of IL-17A Attenuates Skin Inflammation and Vascular Dysfunction in Mouse Models of Psoriasis

Besides skin inflammation, patients with severe psoriasis suffer from an increased risk of cardiovascular mortality. IL-17A plays a central role in the development of psoriasis and might connect skin and vascular disease. The aim of this study was to clarify whether anti-IL-17A therapy could also ameliorate the vascular dysfunction associated with severe psoriasis. We analyzed three murine models with varying severities of psoriasis-like skin disease concerning their vascular function and inflammation: (i) K14-IL-17A^ind/+ mice with keratinocyte-specific IL-17A overexpression and an early-onset severe psoriasis-like phenotype; (ii) homozygous CD11c-IL-17A^ind/ind and heterozygous CD11c-IL-17A^ind/+ mice overexpressing IL-17A in CD11c⁺ cells, leading to a delayed onset of moderate psoriasis-like skin disease; and (iii) the acute model of imiquimod-induced psoriasis-like skin inflammation. Similar to the severity of skin disease, vascular dysfunction correlated with peripheral IL-17A levels and neutrophil infiltration into the aortic vessel wall. Successful anti-IL-17A treatment of psoriatic skin lesions diminished peripheral oxidative stress levels, proinflammatory cytokines, and vascular inflammation. These data highlight the pivotal role of IL-17A linking the development of skin lesions and vascular disease in psoriasis. Anti-IL-17A therapy might thus represent a useful approach to attenuate and prevent vascular disease in psoriasis patients.

CD8(+) T-cell priming and boosting: more antigen-presenting DC, or more antigen per DC?

RNA transfection is a standard method to load dendritic cells (DC) with antigen for therapeutic cancer vaccination. While electroporation yields high transfection efficiency and satisfying expression levels, lipofection results in only few cells expressing high amounts of antigen. We compared antigen loading of human monocyte-derived DC by MelanA RNA electroporation and lipofection. No differences in phenotype or migrational capacity were detected, but lipofected DC induced stronger cytokine secretion by antigen-specific T cells and were superior in priming and boosting of MelanA-specific CD8(+) T cells. Interestingly, T cells stimulated with the differently transfected DC did not differ in their functional avidity. To determine whether the amount of antigen per cell is indeed responsible for the superiority of the lipofected DC, we increased the amount of MelanA RNA fivefold and mixed those DC with mock-electroporated ones to mimic the antigen distribution of lipofected cells. This significantly improved the stimulatory capacity, indicating that indeed the amount of antigen per cell seems to be the responsible feature for the observed superiority of lipofected DCs. These data suggest that a few DC that express high amounts of antigen are more immunogenic than many DC expressing lower amounts, although this needs to be tested in a two-armed immunogenicity trial.

Genome-wide expression profiling of five mouse models identifies similarities and differences with human psoriasis

Development of a suitable mouse model would facilitate the investigation of pathomechanisms underlying human psoriasis and would also assist in development of therapeutic treatments.

However, while many psoriasis mouse models have been proposed, no single model recapitulates all features of the human disease, and standardized validation criteria for psoriasis mouse models have not been widely applied. In this study, whole-genome transcriptional profiling is used to compare gene expression patterns manifested by human psoriatic skin lesions with those that occur in five psoriasis mouse models (K5-Tie2, imiquimod, K14-AREG, K5-Stat3C and K5-TGFbeta1). While the cutaneous gene expression profiles associated with each mouse phenotype exhibited statistically significant similarity to the expression profile of psoriasis in humans, each model displayed distinctive sets of similarities and differences in comparison to human psoriasis. For all five models, correspondence to the human disease was strong with respect to genes involved in epidermal development and keratinization. Immune and inflammation-associated gene expression, in contrast, was more variable between models as compared to the human disease. These findings support the value of all five models as research tools, each with identifiable areas of convergence to and divergence from the human disease. Additionally, the approach used in this paper provides an objective and quantitative method for evaluation of proposed mouse models of psoriasis, which can be strategically applied in future studies to score strengths of mouse phenotypes relative to specific aspects of human psoriasis.

IL-1F5, -F6, -F8, and -F9: a novel IL-1 family signaling system that is active in psoriasis and promotes keratinocyte antimicrobial peptide expression

IL-1F6, IL-1F8, and IL-1F9 and the IL-1R6(RP2) receptor antagonist IL-1F5 constitute a novel IL-1 signaling system that is poorly characterized in skin. To further characterize these cytokines in healthy and inflamed skin, we studied their expression in healthy control, uninvolved psoriasis, and psoriasis plaque skin using quantitative RT-PCR and immunohistochemistry. Expression of IL-1F5, -1F6, -1F8, and -1F9 were increased 2 to 3 orders of magnitude in psoriasis plaque versus uninvolved psoriasis skin, which was supported immunohistologically. Moreover, treatment of psoriasis with etanercept led to significantly decreased IL-1F5, -1F6, -1F8, and -1F9 mRNAs, concomitant with clinical improvement. Similarly increased expression of IL-1F5, -1F6, -1F8, and -1F9 was seen in the involved skin of two mouse models of psoriasis. Suggestive of their importance in inflamed epithelia, IL-1α and TNF-α induced IL-1F5, -1F6, -1F8, and -1F9 transcript expression by normal human keratinocytes. Microarray analysis revealed that these cytokines induce the expression of antimicrobial peptides and matrix metalloproteinases by reconstituted human epidermis. In particular, IL-1F8 increased mRNA expression of human β-defensin (HBD)-2, HBD-3, and CAMP and protein secretion of HBD-2 and HBD-3. Collectively, our data suggest important roles for these novel cytokines in inflammatory skin diseases and identify these peptides as potential targets for antipsoriatic therapies.