Abstract 2866: BAY 3375968: An afucosylated anti-CCR8 antibody depleting activated intratumoral regulatory T cells as a cancer immunotherapy

Regulatory T cells (Tregs) play an indispensable role in mediating peripheral tolerance to self-antigens. They can also promote tumor growth by suppressing the function of effector CD8+ and CD4+ T cells in the tumor microenvironment (TME). Furthermore, Tregs are identified as one of the key resistance mechanisms hampering the efficacy of immune checkpoint inhibitors (ICIs) across many tumor types. Therefore, there is a high need for safe and effective agents that would specifically deplete tumor-infiltrating Tregs while sparing both peripheral Tregs and effector T cells.

Chemokine receptor 8 (CCR8) is predominantly expressed on activated tumor-infiltrating Tregs and marks the most suppressive and proliferative Treg population. CCR8+ Tregs are associated with high tumor grade and poor overall survival across many tumor types such as lung, breast, or head-neck cancer. Thus, unlike other approaches directed against Tregs, targeting CCR8 offers the opportunity to specifically deplete intra-tumoral Tregs without impacting peripheral Tregs or other immune cells.

BAY 3375968 is a non-internalizing fully human glycoengineered (afucosylated) monoclonal IgG1 antibody, which in vitro selectively depleted human CCR8+ Tregs via antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP). In vivo efficacy studies using mouse surrogate antibodies showed strong monotherapeutic efficacy across a variety of murine tumor models with clear correlation of intratumoral CCR8+ Treg depletion and CD8+ T cell increase. The monotherapeutic efficacy of CCR8 depleting antibodies was further enhanced by combinations with ICIs. BAY 3375968 also showed a good safety profile in cynomolgus monkeys. In conclusion, CCR8 is a novel Treg depleting immunotherapy target, and due to its highly tumor-restricted expression profile, BAY 3375968 may provide superior clinical safety and efficacy profile comparing to other less specific Treg targeting approaches.

Based on the promising pre-clinical data, preparations for a phase I clinical trial investigating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of BAY 3375968 are underway.

Citation Format: Helge Roider, Su-Yi Tseng, Sabine Hoff, Sandra Berndt, Katharina Filarski, Uwe Gritzan, Beatrix Stelte-Ludwig, Wiebke M. Nadler, Joanna Grudzinska-Goebel, Philipp Ellinger, Mark Trautwein, Matyas Gorjanacz. BAY 3375968: An afucosylated anti-CCR8 antibody depleting activated intratumoral regulatory T cells as a cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2866.

T cell-mediated elimination of cancer cells by blocking CEACAM6–CEACAM1 interaction

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6), a cell surface receptor, is expressed on normal epithelial tissue and highly expressed in cancers of high unmet medical need, such as non-small cell lung, pancreatic, and colorectal cancer. CEACAM receptors undergo homo- and heterophilic interactions thereby regulating normal tissue homeostasis and angiogenesis, and in cancer, tumor invasion and metastasis. CEACAM6 expression on malignant plasma cells inhibits antitumor activity of T cells, and we hypothesize a similar function on epithelial cancer cells.

The interactions between CEACAM6 and its suggested partner CEACAM1 on T cells were studied. A humanized CEACAM6-blocking antibody, BAY 1834942, was developed and characterized for its immunomodulating effects in co-culture experiments with T cells and solid cancer cells and in comparison to antibodies targeting the immune checkpoints programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), and T cell immunoglobulin mucin-3 (TIM-3).

The immunosuppressive activity of CEACAM6 was mediated by binding to CEACAM1 expressed by activated tumor-specific T cells. BAY 1834942 increased cytokine secretion by T cells and T cell-mediated killing of cancer cells. The in vitro efficacy of BAY 1834942 correlated with the degree of CEACAM6 expression on cancer cells, suggesting potential in guiding patient selection. BAY 1834942 was equally or more efficacious compared to blockade of PD-L1, and at least an additive efficacy was observed in combination with anti-PD-1 or anti-TIM-3 antibodies, suggesting an efficacy independent of the PD-1/PD-L1 axis.

In summary, CEACAM6 blockade by BAY 1834942 reactivates the antitumor response of T cells. This warrants clinical evaluation.

Rational Design of Single Copy Expression Cassettes in Defined Chromosomal Sites Overcomes Intraclonal Cell-to-Cell Expression Heterogeneity and Ensures Robust Antibody Production

The expression of endogenous genes as well as transgenes depends on regulatory elements within and surrounding genes as well as their epigenetic modifications. Members of a cloned cell population often show pronounced cell-to-cell heterogeneity with respect to the expression of a certain gene. To investigate the heterogeneity of recombinant protein expression we targeted cassettes into two preselected chromosomal hot-spots in Chinese hamster ovary (CHO) cells. Depending on the gene of interest and the design of the expression cassette, we found strong expression variability that could be reduced by epigenetic modifiers, but not by site-specific recruitment of the modulator dCas9-VPR. In particular, the implementation of ubiquitous chromatin opening elements (UCOEs) reduced cell-to-cell heterogeneity and concomitantly increased expression. The application of this method to recombinant antibody expression confirmed that rational design of cell lines for production of transgenes with predictable and high titers is a promising approach.

Abstract LB-075: Increased T cell- activation resulting from the combination of the anti-CEACAM6 function-blocking antibody BAY 1834942 with checkpoint inhibitors targeting either PD-1/PD-L1 or TIM-3

CEACAM6 (CD66c) is a novel immune checkpoint regulator suppressing the activity of effector T cells against tumors. CEACAM6 is expressed on tumor cells of multiple malignancies e.g.adenocarcinomas of the lung, colon, pancreas and stomach. In these tumor types higher CEACAM6 expression is associated with advanced stages and a poor prognosis. In immunohistochemistry analyses on primary tumor tissue slides and tissue microarrays the tumor cell expression of CEACAM6 was found to be independent from that of programmed death ligand 1 (PD-L1). BAY 1834942 is a humanized monoclonal antibody selectively blocking CEACAM6-mediated suppression of human T cells. Because there is no rodent orthologue of CEACAM6, BAY 1834942 was fully characterized in in vitro studies as reported earlier (AACR 2018, abstract nr. 1771). Benchmarking and combination studies showed that CEACAM6-mediated inhibition of T cell activation is apparently non-redundant with the programmed death-receptor 1 (PD-1)/ PD-L1 axis. Combination experiments were performed in co-cultures of PD-1, T cell immunoglobulin and mucin domain 3 (TIM3) and CEACAM1 (CD66a) positive virus antigen-specific T cells and virus peptide-loaded CEACAM6-expressing tumor cells (HCC2935, HCT116-C6 cells). When BAY 1834942 was combined with antibody inhibitors of either PD-1 or PD-L1, we consistently observed enhanced secretion of proinflammatory cytokines by T cells in the presence of PD-L1 positive tumor cells (HCC2935). Unexpectedly, combination of BAY 1834942 with an anti-TIM3 antibody resulted in an even more pronounced, synergistic increase of cytokine secretion. The combined effect of CEACAM6 and TIM-3 blockade was confirmed using survivin peptide-specific T cells as alternative T cell source. In contrast, combination of BAY 1834942 with an anti-CEACAM1 function blocking antibody was not superior to anti-CEACAM1 treatment alone, which is in line with our hypothesis that CEACAM1 is the main T cell receptor for CEACAM6 in our functional assays. In summary, BAY 1834942 is a novel immune checkpoint inhibitor with monotherapy potential for the treatment of patients with CEACAM6-expressing cancers. The data shown here provide a rationale for examining its combination potential with immune checkpoint inhibitors targeting either PD-1, PD-L1 or TIM-3. BAY 1834942 is currently under investigation in Ph1 clinical trials (NCT03596372).

Citation Format: Joerg Willuda, Hans-Henning Boehm, Jessica Pinkert, Mark Trautwein, Wolf-Dietrich Doecke, Oliver von Ahsen, Karl Ziegelbauer, Rienk Offringa, Bertolt Kreft, Philipp Beckhove. Increased T cell- activation resulting from the combination of the anti-CEACAM6 function-blocking antibody BAY 1834942 with checkpoint inhibitors targeting either PD-1/PD-L1 or TIM-3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-075.

Abstract 1771: BAY 1834942 is an immunotherapeutic antibody blocking the novel immune checkpoint regulator CEACAM6 (CD66c)

CEACAM6 (CD66c) was previously shown to act as a novel immune checkpoint regulator suppressing the activity of effector T cells against tumors (Witzens-Harig et al., Blood 2013). CEACAM6 is a GPI-linked protein that is strongly expressed at the tumor cell surface in multiple cancer indications such as non-small cell lung adenocarcinoma (NSCLC), colorectal carcinoma (CRC), gastric adenocarcinoma and pancreatic cancer. In general, elevated CEACAM6 expression is associated with advanced tumor stages and poor prognosis. In vitro experiments showed that engagement of T-cells with CEACAM6, either expressed on tumor cells or presented on beads, resulted in suppression of TCR-mediated T-cell activation and ZAP70 phosphorylation. Based on these findings, we hypothesized that antibodies targeting CEACAM6 may be employed to enhance T-cell responses against CEACAM6-expressing cancers. Here we report the generation and characterization of BAY 1834942, a humanized monoclonal antibody selectively blocking the inhibitory impact of CEACAM6 on human T cells. There is no rodent ortholog of CEACAM6 precluding in vivo efficacy studies. In tumor cell / T cell co-culture systems, BAY 1834942 increased secretion of T-cell cytokines and effector molecules (e.g. IFNγ, TNFα, IL-2, granzyme B) and resulted in improved tumor cell killing. The effects of BAY 1834942 were dose-dependent, only observed in the context of CEACAM6-expressing tumor cells and could be reproduced in experiments using tumor cell lines and T-cell preparations from different sources, including T cells derived from tumor infiltrating lymphocytes from pancreatic cancer. BAY 1834942 is cross-reactive with the cynomolgus CEACAM6 ortholog and was well-tolerated in monkey toxicology studies. In summary, BAY 1834942 is a novel checkpoint inhibitor with potential for the treatment of patients with CEACAM6 expressing cancers, both as single agent and in combination with other checkpoint inhibitors. First-in-man trials are expected to commence in 2018.

Citation Format: Joerg Willuda, Mark Trautwein, Jessica Pinkert, Wolf-Dietrich Doecke, Hans-Henning Boehm, Florian Wessel, Yingzi Ge, Eva Maria Gutierrez, Joerg Weiske, Christoph Freiberg, Uwe Gritzan, Julian Glueck, Dieter Zopf, Sven Golfier, Oliver von Ahsen, Ruprecht Zierz, Sabine Wittemer-Rump, Heiner Apeler, Ziegelbauer Karl, Rienk Offringa, Bertolt Kreft, Beckhove Philipp. BAY 1834942 is an immunotherapeutic antibody blocking the novel immune checkpoint regulator CEACAM6 (CD66c) [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 1771.

Abstract 2791: Physiologically based pharmacokinetic modeling and simulations to estimate the efficacious dose of the CEACAM6 function-blocking antibody BAY 1834942

BAY 1834942 is an immunostimulatory function-blocking (fb) antibody (Ab) against the target carcinoembryonic antigen related cell adhesion molecule 6 (CEACAM6) expressed on tumor cells in multiple cancer indications. The suggested mode of action of BAY 1834942 is the blockade of the immunosuppressive effect of CEACAM6 on activated T cells which restores the immune response against cancer cells.

Available preclinical pharmacokinetic (PK) and in vitro pharmacodynamic (PD) data, target receptor density information and tumor (patho-)physiology were used to create a model framework taking into account the three most essential ‘pillars' (target exposure, target binding and drug activity) to estimate the human efficacious dosing of BAY 1834942. For this purpose, a physiologically-based pharmacokinetic (PBPK) model considering target binding of BAY 1834942 in tumor tissue and on blood granulocytes has been developed. The aim of the PBPK model was to estimate the dose range and regimen for humans leading to exposure level at the tumor site that allows sufficient target binding. The PBPK simulations were based on 1) an analysis of PD in vitro data in order to estimate the degree of saturation needed for maximum drug activity, 2) the assessment of CEACAM6 receptor numbers on tumor cells and blood granulocytes and 3) in vivo PK data in order to develop and evaluate the PBPK model. For the latter, plasma PK data of BAY 1834942 in monkeys were used as well as known tumor concentration-time profiles of the antibodies MOPC21 (non-targeting Ab) and ZCE025 (anti-CEA Ab) in mice and humans. Uncertainty of parameters which are relevant for CEACAM6 target saturation was considered by stochastic in silico simulations to estimate the CEACAM6 saturation at the tumor vs. dosing. This analysis revealed that the predicted human efficacious dose strongly depends on CEACAM6 density. Thus, a low CEACAM6 density scenario (25,000 CEACAM6/tumor cell) and a high CEACAM6 density scenario (250,000 CEACAM6/tumor cell) were simulated and used to support dose selection for the first-in-man (FIM) study of BAY 1834942. The FIM study is currently under preparation.

Citation Format: Sabine Wittemer-Rump, Christoph Niederalt, Joerg Willuda, Mark Trautwein, Merlin Luetke-Eversloh, Wolf-Dietrich Doecke, Clemens Guenther, Christian Scheerans. Physiologically based pharmacokinetic modeling and simulations to estimate the efficacious dose of the CEACAM6 function-blocking antibody BAY 1834942 [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 2791.

Modular Protein Expression Toolbox (MoPET), a standardized assembly system for defined expression constructs and expression optimization libraries

The design and generation of an optimal expression construct is the first and essential step in in the characterization of a protein of interest. Besides evaluation and optimization of process parameters (e.g. selection of the best expression host or cell line and optimal induction conditions and time points), the design of the expression construct itself has a major impact. However, the path to this final expression construct is often not straight forward and includes multiple learning cycles accompanied by design variations and retesting of construct variants, since multiple, functional DNA sequences of the expression vector backbone, either coding or non-coding, can have a major impact on expression yields. To streamline the generation of defined expression constructs of otherwise difficult to express proteins, the Modular Protein Expression Toolbox (MoPET) has been developed. This cloning platform allows highly efficient DNA assembly of pre-defined, standardized functional DNA modules with a minimal cloning burden. Combining these features with a standardized cloning strategy facilitates the identification of optimized DNA expression constructs in shorter time. The MoPET system currently consists of 53 defined DNA modules divided into eight functional classes and can be flexibly expanded. However, already with the initial set of modules, 792,000 different constructs can be rationally designed and assembled. Furthermore, this starting set was used to generate small and mid-sized combinatorial expression optimization libraries. Applying this screening approach, variants with up to 60-fold expression improvement have been identified by MoPET variant library screening.

The prion-like domain in the exomer-dependent cargo Pin2 serves as a trans-Golgi retention motif

Prion and prion-like domains (PLDs) are found in many proteins throughout the animal kingdom. We found that the PLD in the S. cerevisiae exomer-dependent cargo protein Pin2 is involved in the regulation of protein transport and localization. The domain serves as a Pin2 retention signal in the trans-Golgi network (TGN). Pin2 is localized in a polarized fashion at the plasma membrane of the bud early in the cell cycle and the bud neck at cytokinesis. This polarized localization is dependent on both exo- and endocytosis. Upon environmental stress, Pin2 is rapidly endocytosed, and the PLD aggregates and causes sequestration of Pin2. The aggregation of Pin2 is reversible upon stress removal and Pin2 is rapidly re-exported to the plasma membrane. Altogether, these data uncover a role for PLDs as protein localization elements.

Evaluation of human pancreatic RNase as effector molecule in a therapeutic antibody platform

Human antibody-ribonuclease (RNase) fusion proteins, referred to as immunoRNases, have been proposed as an alternative to heterologous immunotoxins, without their immunogenicity and unspecific toxicity issues. In this study, we investigated if human pancreatic RNase will be suitable as effector component in a therapeutic antibody development platform. We generated several fusion proteins consisting of tumor-specific human immunoglobulins (IgGs) and human pancreatic RNase. Transient mammalian cell production was efficient and IgG-RNases were purified to homogeneity. Antigen binding was comparable to the parental antibodies and RNase catalytic activity was retained even in the presence of 50-fold molar excess of human cytosolic RNase inhibitor (RI). Serum stability, cell binding and internalization of IgG-RNases were comparable to the parental IgGs. Despite these promising properties, none of the IgG-RNases revealed significant inhibition of tumor cell growth in vitro even when targeting different antigens putatively employing different endocytotic pathways. The introduction of different linkers containing endosomal protease cleavage sites into the IgG-RNase did not enhance cytotoxicity. Similarly, RI evasive human pancreatic RNase variants mediated only small inhibiting effects on tumor cell growth at high concentrations, potentially reflecting inefficient cytosolic translocation. Taken together, human pancreatic RNase and variants did not prove to be generally suitable as effector component for a therapeutic antibody drug development platform.

Transport to the plasma membrane is regulated differently early and late in the cell cycle in Saccharomyces cerevisiae

Traffic from the trans-Golgi network to the plasma membrane is thought to occur through at least two different independent pathways. The chitin synthase Chs3p requires the exomer complex and Arf1p to reach the bud neck of yeast cells in a cell-cycle-dependent manner, whereas the hexose transporter Hxt2p localizes over the entire plasma membrane independently of the exomer complex. Here, we conducted a visual screen for communalities and differences between the exomer-dependent and exomer-independent transport to the plasma membrane in Saccharomyces cerevisiae. We found that most of the components that are required for the fusion of transport vesicles with the plasma membrane, are involved in localization of both Chs3p and Hxt2p. However, the lethal giant larva homologue Sro7p is required primarily for the targeting of Chs3p, and not Hxt2p or other cargoes such as Itr1p, Cwp2p and Pma1p. Interestingly, this transport defect was more pronounced in large-budded cells just before cytokinesis than in small-budded cells. In addition, we found that the yeast Rab11 homologue Ypt31p determines the residence time of Chs3p in the bud neck of small-budded, but not large-budded, cells. We propose that transport to and from the bud neck is regulated differently in small- and large-budded cells, and differs early and late in the cell cycle.

Arf1p, Chs5p and the ChAPs are required for export of specialized cargo from the Golgi

In Saccharomyces cerevisiae, the synthesis of chitin is temporally and spatially regulated through the transport of Chs3p (chitin synthase III) to the plasma membrane in the bud neck region. Traffic of Chs3p from the trans-Golgi network (TGN)/early endosome to the plasma membrane requires the function of Chs5p and Chs6p. Chs6p belongs to a family of four proteins that we have named ChAPs for Chs5p-Arf1p-binding Proteins. Here, we show that all ChAPs physically interact not only with Chs5p but also with the small GTPase Arf1p. A short sequence at the C-terminus of the ChAPs is required for protein function and the ability to bind to Chs5p. Simultaneous disruption of two members, Deltabud7 and Deltabch1, phenocopies a Deltachs6 or Deltachs5 deletion with respect to Chs3p transport. Moreover, the ChAPs interact with each other and can form complexes. In addition, they are all at least partially localized to the TGN in a Chs5p-dependent manner. Most importantly, several ChAPs can interact physically with Chs3p. We propose that the ChAPs facilitate export of cargo out of the Golgi.

Policy perspectives on public health for Mexican migrants in California

This analysis focuses on public policies that affect primary HIV prevention and access to HIV care for Mexican migrants residing in California. Policy or structural level interventions, as opposed to behavioral or psychologic interventions, help to shape the environment in which people live. We use a conceptual model for policy analysis in public health to understand better the challenges faced by Mexican migrants. We assess potential policy level interventions that may serve as barriers to or facilitators of primary HIV prevention and care for Mexican migrants. Among potential barriers, we discuss restrictions on public health services based on legal immigration status, limits placed on affirmative action in education, and laws limiting travel and immigration. Under potential facilitators, we discuss community and migrant health centers, language access laws, and the use of community-based groups to provide prevention and treatment outreach. We also report on the limited research evaluating the implications of these public policies and ways to organize for more responsive public policies.

New modules for the repeated internal and N-terminal epitope tagging of genes in Saccharomyces cerevisiae

Epitope tagging is a powerful method for the rapid analysis of protein function. In Saccharomyces cerevisiae epitope tags are introduced easily into chromosomal loci by homologous recombination using a simple PCR-based strategy. Although quite a number of tools exist for C-terminal tagging as well as N-terminal tagging of proteins expressed by heterologous promoters, there are only very limited possibilities to tag proteins at the N-terminus and retain the endogenous expression level. Furthermore, no PCR-templates for internal tagging have been reported. Here we describe new modules that are suitable for both the repeated N-terminal and internal tagging of proteins, leaving their endogenous promoters intact. The tags include 6xHA, 9xMyc, yEGFP, TEV-GST-6xHIS, ProtA, TEV-ProtA and TEV-ProtA-7xHIS in conjunction with different heterologous selection markers.

Arf1p provides an unexpected link between COPI vesicles and mRNA in Saccharomyces cerevisiae

The small GTPase Arf1p is involved in different cellular processes that require its accumulation at specific cellular locations. The recruitment of Arf1p to distinct points of action might be achieved by association of Arf1p with different proteins. To identify new interactors of Arf1p, we performed an affinity chromatography with GTP- or GDP-bound Arf1p proteins. A new interactor of Arf1p-GTP was identified as Pab1p, which binds to the polyA-tail of mRNAs. Pab1p was found to associate with purified COPI-coated vesicles generated from Golgi membranes in vitro. The stability of the Pab1p-Arf1p complex depends on the presence of mRNA. Both symmetrically distributed mRNAs as well as the asymmetrically localized ASH1 mRNA are found in association with Arf1p. Remarkably, Arf1p and Pab1p are both required to restrict ASH1 mRNA to the bud tip. Arf1p and coatomer play an unexpected role in localizing mRNA independent and downstream of the SHE machinery. Hereby acts the SHE machinery in long-range mRNA transport, whereas COPI vesicles could act as short-range and localization vehicles. The endoplasmic reticulum (ER)-Golgi shuttle might be involved in concentrating mRNA at the ER.

Rho transcription factor: symmetry and binding of bicyclomycin

The antibiotic bicyclomycin inhibits rho-dependent termination processes by interfering with RNA translocation by preventing RNA binding at the translocation site or by uncoupling the translocation process from ATP hydrolysis. Previous studies have shown that bicyclomycin binds near the ATP hydrolysis pocket on rho. The hexameric structure of rho indicates that it is in a class of enzymes with strong sequence similarity to F(1)-ATP synthase. The bicyclomycin derivative 5a-formylbicyclomycin, an inhibitor comparable to bicyclomycin, was previously shown to form a stable imine with rho and when reduced to the amine with NaBH(4) to singly label five of the six rho subunits. Lysine-336 was identified by mass spectrometric analysis of trypsin-digested fragments as the site of 5a-formylbicyclomycin adduction. A model of rho was made by threading the rho sequence on the known crystal structure of the alpha and beta subunits of F(1)-ATP synthase. The model, along with information concerning the extent and site of 5a-formylbicyclomycin adduction, indicates an overall C6 symmetry for rho subunit organization. We propose that the sequence similarity between rho and F(1)-ATP synthase extends to a similar quaternary structure and an equivalent enzyme mechanism. The proposed mechanism of RNA translocation coupled with ATP hydrolysis changes the overall symmetry of rho from C6 to C6/C3.