A Novel B7-H6-Targeted IgG-Like T Cell-Engaging Antibody for the Treatment of Gastrointestinal Tumors.

PURPOSE: Advanced-stage gastrointestinal cancers represent a high unmet need requiring new effective therapies. We investigated the antitumor activity of a novel T cell-engaging antibody (B7-H6/CD3 ITE) targeting B7-H6, a tumor-associated antigen that is expressed in gastrointestinal tumors. EXPERIMENTAL DESIGN: Membrane proteomics and IHC analysis identified B7-H6 as a tumor-associated antigen in gastrointestinal tumor tissues with no to very little expression in normal tissues. The antitumor activity and mode of action of B7-H6/CD3 ITE was evaluated in in vitro coculture assays, in humanized mouse tumor models, and in colorectal cancer precision cut tumor slice cultures. RESULTS: B7-H6 expression was detected in 98% of colorectal cancer, 77% of gastric cancer, and 63% of pancreatic cancer tissue samples. B7-H6/CD3 ITE-mediated redirection of T cells toward B7-H6-positive tumor cells resulted in B7-H6-dependent lysis of tumor cells, activation and proliferation of T cells, and cytokine secretion in in vitro coculture assays, and infiltration of T cells into tumor tissues associated with tumor regression in in vivo colorectal cancer models. In primary patient-derived colorectal cancer precision-cut tumor slice cultures, treatment with B7-H6/CD3 ITE elicited cytokine secretion by endogenous tumor-infiltrating immune cells. Combination with anti-PD-1 further enhanced the activity of the B7-H6/CD3 ITE. CONCLUSION: These data highlight the potential of the B7-H6/CD3 ITE to induce T cell-redirected lysis of tumor cells and recruitment of T cells into noninflamed tumor tissues, leading to antitumor activity in in vitro, in vivo, and human tumor slice cultures, which supports further evaluation in a clinical study.

Analyze impact of tumor-associated kinetics on antibody delivery in solid tumors with a physiologically based pharmacokinetics/pharmacodynamics model.

Monoclonal antibody (mAb)-based drugs are critical anti-cancer therapies. Unfortunately, therapeutic efficacy can be compromised by spatially heterogeneous intratumoral Ab deposition. Binding-site barriers arising from Ab and tumor-associated kinetics often underlie this phenomenon. Quantitative insight into these issues may lead to more efficient drug delivery. Difficulties in addressing this issue include (1) lack of techniques to quantify critical kinetic events, (2) lack of a pharmacokinetic/pharmacodynamic (PK/PD) model to assess important parameters for specific tumor types, and (3) uncertainty or variability of critical kinetic factors even within a single tumor type. This study developed a mechanism-based PK/PD model to profile heterogeneous distribution of Ab within tumors and tested this model using real-life experimental data. Model simulations incorporating several uncertainties were used to determine how mAb and tumor-associated kinetics influence receptor occupancy. Simulations were also used to predict the potential impact of these findings in preclinical tumor models and human tumors. We found significant differences in tumor-associated kinetics between groups in which mAb therapy was effective versus groups in which it was ineffective. These kinetic differences included rates of tumor-associated antigen (TAA) degradation, TAA expression, apparent flow rates of interstitial fluid, and ratios of Ab-TAA complex internalization to TAA degradation. We found less significant differences in mAb kinetics, including rates of clearance or affinity for target antigens. In conclusion, our mechanism-based PK/PD model suggests that TAA-associated kinetic factors participate more significantly than those associated with the Ab in generating barriers to mAb delivery and distribution in tumors.

Allometric scaling of therapeutic monoclonal antibodies in preclinical and clinical settings.

Constant technological advancement enabled the production of therapeutic monoclonal antibodies (mAbs) and will continue to contribute to their rapid expansion. Compared to small-molecule drugs, mAbs have favorable characteristics, but also more complex pharmacokinetics (PK), e.g., target-mediated nonlinear elimination and recycling by neonatal Fc-receptor. This review briefly discusses mAb biology, similarities and differences in PK processes across species and within human, and provides a detailed overview of allometric scaling approaches for translating mAb PK from preclinical species to human and extrapolating from adults to children. The approaches described here will remain vital in mAb drug development, although more data are needed, for example, from very young patients and mAbs with nonlinear PK, to allow for more confident conclusions and contribute to further growth of this field. Improving mAb PK predictions will facilitate better planning of (pediatric) clinical studies and enable progression toward the ultimate goal of expediting drug development.

Quantitative Systems Pharmacology Modeling of PBMC-Humanized Mouse to Facilitate Preclinical Immuno-oncology Drug Development.

Progress in immunotherapy has resulted in explosively increased new therapeutic interventions and they have shown promising results in the treatment of cancer. Animal testing is performed to provide preliminary efficacy and safety data for drugs under development prior to clinical trials. However, translational challenges remain for preclinical studies such as study design and the relevance of animal models to humans. Hence, only a small fraction of cancer patients showed response. The explosion of drug candidates and therapies makes preclinical assessment of every plausible option impossible, but it can be easily tested using Quantitative System Pharmacology (QSP) models. Here, we developed a QSP model for humanized mice. Tumor growth dynamics, T cell dynamics, cytokine release, immune checkpoint expression, and drug administration were modeled and calibrated using experimental data. Tumor growth inhibition data were used for model validation. Pharmacokinetics of T cell engager (TCE), tumor growth profile, T cell expansion in the blood and infiltration into tumor, T cell dissemination from primary tumor, cytokine release profile, and expression of additional PD-L1 induced by IFN-γ were modeled and calibrated using a variety of experimental data and showed good consistency. Mouse-specific response to T cell engager monotherapy also showed the key features of in vivo efficacy of TCE. This novel QSP model, designed for human peripheral blood mononuclear cells (PBMC) engrafted xenograft mice, incorporating the most critical components of the mouse model with key cancer and immune cells, can become an integral part of preclinical drug development.

Selective Tumor Cell Apoptosis and Tumor Regression in CDH17-Positive Colorectal Cancer Models using BI 905711, a Novel Liver-Sparing TRAILR2 Agonist.

Activation of TRAILR2 has emerged as an important therapeutic concept in cancer treatment. TRAILR2 agonistic molecules have only had limited clinical success, to date, due either to lack of efficacy or hepatotoxicity. BI 905711 is a novel tetravalent bispecific antibody targeting both TRAILR2 and CDH17 and represents a novel liver-sparing TRAILR2 agonist specifically designed to overcome the disadvantages of previous strategies. Here, we show that BI 905711 effectively triggered apoptosis in a broad panel of CDH17-positive colorectal cancer tumor cells in vitro. Efficient induction of apoptosis was dependent on the presence of CDH17, as exemplified by the greater than 1,000-fold drop in potency in CDH17-negative cells. BI 905711 demonstrated single-agent tumor regressions in CDH17-positive colorectal cancer xenografts, an effect that was further enhanced upon combination with irinotecan. Antitumor efficacy correlated with induction of caspase activation, as measured in both the tumor and plasma. Effective tumor growth inhibition was further demonstrated across a series of different colorectal cancer PDX models. BI 905711 induced apoptosis in both a cis (same cell) as well as trans (adjacent cell) fashion, translating into significant antitumor activity even in xenograft models with heterogeneous CDH17 expression. In summary, we demonstrate that BI 905711 has potent and selective antitumor activity in CDH17-positive colorectal cancer models both in vitro and in vivo. The high prevalence of over 95% CDH17-positive tumors in patients with colorectal cancer, the molecule preclinical efficacy together with its potential for a favorable safety profile, support the ongoing BI 905711 phase I trial in colorectal cancer and additional CDH17-positive cancer types (NCT04137289).

Combination therapy with T cell engager and PD-L1 blockade enhances the antitumor potency of T cells as predicted by a QSP model.

BACKGROUND: T cells have been recognized as core effectors for cancer immunotherapy. How to restore the anti-tumor ability of suppressed T cells or improve the lethality of cytotoxic T cells has become the main focus in immunotherapy. Bispecific antibodies, especially bispecific T cell engagers (TCEs), have shown their unique ability to enhance the patient's immune response to tumors by stimulating T cell activation and cytokine production in an MHC-independent manner. Antibodies targeting the checkpoint inhibitory molecules such as programmed cell death protein 1 (PD-1), PD-ligand 1 (PD-L1) and cytotoxic lymphocyte activated antigen 4 are able to restore the cytotoxic effect of immune suppressed T cells and have also shown durable responses in patients with malignancies. However, both types have their own limitations in treating certain cancers. Preclinical and clinical results have emphasized the potential of combining these two antibodies to improve tumor response and patients' survival. However, the selection and evaluation of combination partners clinically is a costly endeavor. In addition, despite advances made in immunotherapy, there are subsets of patients who are non-responders, and reliable biomarkers for different immunotherapies are urgently needed to improve the ability to prospectively predict patients' response and improve clinical study design. Therefore, mathematical and computational models are essential to optimize patient benefit, and guide combination approaches with lower cost and in a faster manner. METHOD: In this study, we continued to extend the quantitative systems pharmacology (QSP) model we developed for a bispecific TCE to explore efficacy of combination therapy with an anti-PD-L1 monoclonal antibody in patients with colorectal cancer. RESULTS: Patient-specific response to TCE monotherapy, anti-PD-L1 monotherapy and the combination therapy were predicted using this model according to each patient's individual characteristics. CONCLUSIONS: Individual biomarkers for TCE monotherapy, anti-PD-L1 monotherapy and their combination have been determined based on the QSP model. Best treatment options for specific patients could be suggested based on their own characteristics to improve clinical trial efficiency. The model can be further used to assess plausible combination strategies for different TCEs and immune checkpoint inhibitors in different types of cancer.

A Bispecific DLL3/CD3 IgG-Like T-Cell Engaging Antibody Induces Antitumor Responses in Small Cell Lung Cancer.

PURPOSE: Small cell lung cancer (SCLC) is the most lethal and aggressive subtype of lung carcinoma characterized by highly chemotherapy-resistant recurrence in the majority of patients. To effectively treat SCLC, we have developed a unique and novel IgG-like T-cell engaging bispecific antibody (ITE) that potently redirects T-cells to specifically lyse SCLC cells expressing Delta-like ligand 3 (DLL3), an antigen that is frequently expressed on the cell surface of SCLC cells, with no to very little detectable expression in normal tissues. EXPERIMENTAL DESIGN: The antitumor activity and mode of action of DLL3/CD3 ITE was evaluated in vitro using SCLC cell lines and primary human effector cells and in vivo in an SCLC xenograft model reconstituted with human CD3+ T-cells. RESULTS: Selective binding of DLL3/CD3 ITE to DLL3-positive tumor cells and T-cells induces formation of an immunological synapse resulting in tumor cell lysis and activation of T-cells. In a human T-cell engrafted xenograft model, the DLL3/CD3 ITE leads to an increase in infiltration of T-cells into the tumor tissue resulting in apoptosis of the tumor cells and tumor regression. Consistent with the mode of action, the DLL3/CD3 ITE treatment led to upregulation of PD-1, PD-L1, and LAG-3. CONCLUSIONS: This study highlights the ability of the DLL3/CD3 ITE to induce strictly DLL3-dependent T-cell redirected lysis of tumor cells and recruitment of T-cells into noninflamed tumor tissues leading to tumor regression in a preclinical in vivo model. These data support clinical testing of the DLL3/CD3 ITE in patients with SCLC.

A Quantitative Systems Pharmacology Model of T Cell Engager Applied to Solid Tumor.

Cancer immunotherapy has recently drawn remarkable attention as promising results in the clinic have shown its ability to improve the overall survival, and T cells are considered to be one of the primary effectors for cancer immunotherapy. Enhanced and restored T cell tumoricidal activity has shown great potential for killing cancer cells. Bispecific T cell engagers (TCEs) are a growing class of molecules that are designed to bind two different antigens on the surface of T cells and cancer cells to bring them in close proximity and selectively activate effector T cells to kill target cancer cells. New T cell engagers are being investigated for the treatment of solid tumors. The activity of newly developed T cell engagers showed a strong correlation with tumor target antigen expression. However, the correlation between tumor-associated antigen expression and overall response of cancer patients is poorly understood. In this study, we used a well-calibrated quantitative systems pharmacology (QSP) model extended to bispecific T cell engagers to explore their efficacy and identify potential biomarkers. In principle, patient-specific response can be predicted through this model according to each patient's individual characteristics. This extended QSP model has been calibrated with available experimental data and provides predictions of patients' response to TCE treatment.

Neonatal Fc receptor and its role in the absorption, distribution, metabolism and excretion of immunoglobulin G-based biotherapeutics.

The neonatal Fc receptor (FcRn) is a heterodimeric membrane associated protein expressed in a variety of endothelial, epithelial and hematopoietic cells. FcRn regulates pH dependent intracellular trafficking of immunoglobulin G (IgG) and albumin, resulting in enhanced serum persistence and transcellular permeability of these proteins compared to other proteins of similar size. FcRn confers passive immunity during the early stages of life by facilitating maternal transmission of antibodies during gestation, and in some species during the neonatal period. The receptor continues to contribute to immunity beyond the perinatal period and throughout life by providing immunosurveillance in intestinal, pulmonary and genitourinary mucosa. In this capacity, FcRn facilitates bidirectional transport of IgG across mucosa and intracellular trafficking of antigen-antibody complexes in antigen presenting cells. Based on the functional roles of FcRn in regulating serum persistence and transcellular permeability, protein engineers have sought to exploit this receptor as a means of enhancing the absorption, distribution, metabolism and excretion (ADME) of IgG-based therapeutics. In this review, the current state of knowledge regarding the structural, mechanistic and functional properties of FcRn, as they relate to the ADME of IgG-based therapeutics, are discussed.

Ni-to-Ni+ 3-ethylene-bridged partially modified retro-inverso tetrapeptide beta-turn mimetic: design, synthesis, and structural characterization.

A 10-membered heterocyclic ring system 1,3,8-trisubstituted 2,5,7-trioxo-1,4,8-triazadecane that represents a Ni-to-Ni+ 3-ethylene-bridged partially modified retro-inverso tetrapeptide beta-turn mimetic (EBRIT-BTM) has been designed, synthesized, and structurally analyzed. These compounds utilize an ethylene bridge to replace the COi...HNi + 3 10-membered hydrogen bond of standard beta-turns. The N,N'-ethylene-bridged dimer was obtained in 90% yield by reductive alkylation of phenylalanylamide with a tert-butyl N-(9-fluorenylmethyloxycarbonyl),N-(2-formylmethyl)-glycinate. An orthogonal protection strategy and HATU-mediated couplings allowed efficient stepwise additions of monomeric building blocks leading to a N(i)-to-N(i+3)-ethylene-bridged linear precursor: Further elaboration of the linear precursor generated the ethylene-bridged model compounds (16) and (18) (g, gem-diaminoalkyl; m, malonyl; and r, direction-reversed amino acid residue) in 44 and 39% yields, respectively. The structural features of the two EBRIT-BTM compounds were determined using 1H NMR and extensive computer simulations. The results indicate that the 10-membered rings are conformationally constrained with well-defined structural features and that the three amide bonds in the ring are in the trans orientation. The topological arrangement of the residues in the ring system closely resembles a type II' beta-turn. Transformation of CONH(2) in the N-terminal amino acid residue of 16 into NHCOCH3 in 18 resulted in the formation of a hydrogen bond between the NH of gPhe-COCH3 and the C-terminal carboxyl of Gly, initiating an antiparallel beta-sheet. The formulation of the concept applying a minimalistic structural elaboration approach and the synthetic exploration, together with the conformational analysis, offer a new molecular scaffolding system and a true tetrapeptide secondary structure mimetic that can be used to generate peptidomimetics of biological interest.