Raludotatug Deruxtecan, a CDH6-Targeting Antibody-Drug Conjugate with a DNA Topoisomerase I Inhibitor DXd, Is Efficacious in Human Ovarian and Kidney Cancer Models

Cadherin-6 (CDH6) is expressed in several cancer types, but no CDH6-targeted therapy is currently clinically available. Here, we generated raludotatug deruxtecan (R-DXd; DS-6000), a novel CDH6-targeting antibody-drug conjugate with a potent DNA topoisomerase I inhibitor, and evaluated its properties, pharmacologic activities, and safety profile. In vitro pharmacologic activities and the mechanisms of action of R-DXd were assessed in serous-type ovarian cancer and renal cell carcinoma cell lines. In vivo pharmacologic activities were evaluated with several human cancer cell lines and patient-derived xenograft mouse models. The safety profile in cynomolgus monkeys was also assessed. R-DXd exhibited CDH6 expression-dependent cell growth-inhibitory activity and induced tumor regression in xenograft models. In this process, R-DXd specifically bound to CDH6, was internalized into cancer cells, and then translocated to the lysosome. The DXd released from R-DXd induced the phosphorylation of Chk1, a DNA damage marker, and cleaved caspase-3, an apoptosis marker, in cancer cells. It was also confirmed that the DXd payload had a bystander effect, passing through the cell membrane and impacting surrounding cells. The safety profile of R-DXd was favorable and the highest non-severely toxic dose was 30 mg/kg in cynomolgus monkeys. R-DXd demonstrated potent antitumor activity against CDH6-expressing tumors in mice and an acceptable safety profile in monkeys. These findings indicate the potential of R-DXd as a new treatment option for patients with CDH6-expressing serous-type ovarian cancer and renal cell carcinoma in a clinical setting.

A novel T cell-redirecting anti-GPRC5D × CD3 bispecific antibody with potent antitumor activity in multiple myeloma preclinical models

G-protein-coupled receptor class 5 member D (GPRC5D) is detected in malignant plasma cells in approximately 90% of patients diagnosed with multiple myeloma (MM). Here, we constructed BsAb5003, a novel humanized bispecific monoclonal antibody targeting CD3 and GPRC5D, and evaluated its therapeutic impact on MM. BsAb5003 induced specific cytotoxicity of GPRC5D-positive MM cells with concomitant T cell activation and cytokine release. The efficacy of BsAb5003 was associated with GPRC5D expression levels in MM cell lines. Flow cytometry analysis of bone marrow mononuclear cells (BMMNCs) from 49 MM patients revealed that GPRC5D was expressed in a wide population of MM patients, including heavily treated and high-risk patients. In ex vivo assays using BMMNCs, BsAb5003 induced potent efficacy against CD138 + MM cells in both newly diagnosed and relapsed/refractory patient samples in a GPRC5D expression-dependent manner. BsAb5003 significantly enhanced T cell activation and cytokine production in combination with immunomodulatory drugs (IMiDs) against MM cell lines. BsAb5003 also demonstrated significant inhibition of in vivo tumor growth by recruiting T cells. Taken together, these results suggest that T cell-redirecting bispecific antibody targeting GPRC5D as monotherapy and combination therapy with IMiDs could be a highly potent and effective treatment approach for a wide population of MM patients.

Abstract 2932: Datopotamab deruxtecan (Dato-DXd) enhances antitumor response to PD-1/PD-L1 inhibitors in TROP2-expressing tumors in mice

Background: Trophoblast cell surface antigen 2 (TROP2) is highly expressed in various epithelial tumors, including non-small cell lung cancer (NSCLC) and triple negative breast cancer (TNBC), and correlates with poor prognosis. Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate (ADC) consisting of a humanized anti-TROP2 IgG1 monoclonal antibody covalently linked to a highly potent topoisomerase I (Topo I) inhibitor payload via a stable, tumor-selective, tetrapeptide-based cleavable linker. Dato-DXd has shown encouraging antitumor activity and a manageable safety profile in patients with NSCLC and TNBC as part of the first-in-human, Phase 1 study (NCT03401385). To enhance clinical responses, clinical trials evaluating combination therapy of Dato-DXd with PD-1/PD-L1 inhibitors in NSCLC and TNBC are currently ongoing (e.g. NCT04526691 and NCT03742102). Here we report preclinical evidence for supporting increased antitumor activity of Dato-DXd in combination with PD-1/PD-L1 inhibitors using a syngeneic mouse tumor model and its impact on tumor immunity.

Methods: MC38 mouse colon adenocarcinoma cells stably transfected with human TROP2 (hTROP2_MC38) were inoculated subcutaneously in immunocompetent C57BL6 mice or immunodeficient nude mice and the antitumor activity of Dato-DXd with or without mouse PD-1/PD-L1 inhibitors was evaluated. The tumor infiltrating immune cells in hTROP2_MC38 tumors were analyzed by flow cytometry at 3 days and 10 days after dosing. In addition, the impact of CD8+ T cell depletion on the antitumor activity of Dato-DXd against hTROP2_MC38 tumors in C57BL6 mice was evaluated.

Results: Dato-DXd showed stronger antitumor activity against hTROP2_MC38 tumors in immunocompetent C57BL6 mice than in immunodeficient nude mice, which suggests that immune cells play an important role in the mechanism of action (MoA) of Dato-DXd. The combination of Dato-DXd and mouse PD-1/PD-L1 inhibitors enhanced antitumor activity compared to monotherapy against hTROP2_MC38 tumors in C57BL6 mice. Activation of the dendritic cells in hTROP2_MC38 tumors in C57BL6 mice was observed after Dato-DXd monotherapy or combination therapy with mouse PD-1/PD-L1 inhibitors, which led to the increase of tumor infiltrating CD8+ T cells. Involvement of CD8+ T cells in the MoA of Dato-DXd was also supported by the result that CD8+ T cell depletion in C57BL6 mice decreased the antitumor activity of Dato-DXd against hTROP2_MC38 tumors. In addition, activation of tumor infiltrating NK cells and macrophages was observed after Dato-DXd monotherapy or combination therapy, suggesting the potential effect on innate immunity.

Conclusion: These results suggest that Dato-DXd may stimulate tumor immunity and sensitize tumors to PD-1/PD-L1 inhibitors. The combination of Dato-DXd and PD-1/PD-L1 blockers could be a valuable therapy for patients with TROP2-positive tumors.

Citation Format: Daisuke Okajima, Satoru Yasuda, Takami Suzuki, Michiko Kitamura, Junko Yamaguchi, Takanori Maejima, Tsuyoshi Karibe, Tadashi Toki, Penny Phillips, Toshinori Agatsuma. Datopotamab deruxtecan (Dato-DXd) enhances antitumor response to PD-1/PD-L1 inhibitors in TROP2-expressing tumors in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2932.

DS-7300a, a DNA Topoisomerase I Inhibitor, DXd-Based Antibody-Drug Conjugate Targeting B7-H3, Exerts Potent Antitumor Activities in Preclinical Models

B7-H3 is overexpressed in various solid tumors and has been considered as an attractive target for cancer therapy. Here, we report the development of DS-7300a, a novel B7-H3-targeting antibody-drug conjugate with a potent DNA topoisomerase I inhibitor, and its in vitro profile, pharmacokinetic profiles, safety profiles, and in vivo antitumor activities in nonclinical species. The target specificity and species cross-reactivity of DS-7300a were assessed. Its pharmacologic activities were evaluated in several human cancer cell lines in vitro and xenograft mouse models, including patient-derived xenograft (PDX) mouse models in vivo. Pharmacokinetics was investigated in cynomolgus monkeys. Safety profiles in rats and cynomolgus monkeys were also assessed. DS-7300a specifically bound to B7-H3 and inhibited the growth of B7-H3-expressing cancer cells, but not that of B7-H3-negative cancer cells, in vitro. Additionally, treatment with DS-7300a and DXd induced phosphorylated checkpoint kinase 1, a DNA damage marker, and cleaved PARP, an apoptosis marker, in cancer cells. Moreover, DS-7300a demonstrated potent in vivo antitumor activities in high-B7-H3 tumor xenograft models, including various tumor types of high-B7-H3 PDX models. Furthermore, DS-7300a was stable in circulation with acceptable pharmacokinetic profiles in monkeys, and well tolerated in rats and monkeys. DS-7300a exerted potent antitumor activities against B7-H3-expressing tumors in in vitro and in vivo models, including PDX mouse models, and showed acceptable pharmacokinetic and safety profiles in nonclinical species. Therefore, DS-7300a may be effective in treating patients with B7-H3-expressing solid tumors in a clinical setting.

Datopotamab Deruxtecan, a Novel TROP2-directed Antibody-drug Conjugate, Demonstrates Potent Antitumor Activity by Efficient Drug Delivery to Tumor Cells

Trophoblast cell surface antigen 2 (TROP2) is highly expressed on various epithelial tumors and correlates with poor prognosis. We developed the novel TROP2-directed antibody-drug conjugate (ADC), datopotamab deruxtecan (Dato-DXd, DS-1062a), with a potent DNA topoisomerase I inhibitor (DXd), and evaluated its antitumor activity and safety profiles in preclinical models.The pharmacologic activity and mechanism of action of Dato-DXd were investigated in several human cancer cell lines and xenograft mouse models including patient-derived xenograft (PDX) models. Safety profiles were also assessed in rats and cynomolgus monkeys.Dato-DXd bound specifically to TROP2 and was internalized into tumor cells followed by intracellular trafficking to lysosome and DXd release, which induced DNA damage and apoptosis in TROP2-expressing tumor cells in vitro. Dato-DXd exhibited in vivo antitumor activity with DNA damage induced by the accumulated DXd in TROP2-expressing xenograft tumors, but neither isotype control IgG-ADC nor anti-TROP2 antibody had this effect. Dato-DXd also showed potent antitumor activity with tumor regression in several TROP2-expressing xenograft tumors including NSCLC PDX models. Safety profiles of Dato-DXd in rats and cynomolgus monkeys were acceptable.Dato-DXd demonstrated potent antitumor activity against TROP2-expressing tumors by efficient payload delivery into tumors and acceptable safety profiles in preclinical models. These results suggest Dato-DXd could be a valuable treatment option for patients with TROP2-expressing tumors in the clinical setting.

Abstract 1847: Anti-GARP antibody DS-1055a augments antitumor immunity by depleting highly suppressive GARP+ regulatory T cells

Immune checkpoint blockers (ICBs) have drastically changed the clinical care of cancer; however, the population of patients who can benefit is relatively small because of intrinsic or acquired resistance to immune therapy. To evade immune destruction, tumors exploit several distinct strategies including immunosuppressive cells such as regulatory T (Treg) cells. Treg cells, an essential component for maintaining self-tolerance, inhibit antitumor immunity, consequently hindering protective cancer immunosurveillance and hampering effective antitumor immune responses in tumor-bearing hosts. It is often reported that a high ratio of Treg cells to effector CD8+ T cells is associated with poor prognosis in patients with cancer, and Treg cells represent one of the most important factors associated with resistance to ICBs, suggesting that Treg cells represent a new promising target for anti-cancer therapy. In this study, we performed a comprehensive screening to identify a tumor-infiltrating Treg cell-specific molecule among immune cell subsets in humans. Glycoprotein A repetitions predominant (GARP) was identified as a suitable target for selective Treg cell depletion in the tumor microenvironment (TME) of multiple caner types. In the periphery, GARP was selectively induced in Treg cells, but not in effector T cells, by polyclonal stimulation in humans. DS-1055a, a novel afucosylated anti-human GARP antibody, effectively depleted GARP+ Treg cells, leading to the activation of effector T cells. Moreover, DS-1055a decreased FOXP3+CD4+ T cell counts in the TME and exhibited remarkable antitumor activity in a human peripheral blood mononuclear cell-transplanted humanized mouse model bearing HT-29 tumors. From these results, we propose that DS-1055a can be a new Treg cell-targeted regent that augments antitumor T cell immunity by depleting GARP+ Treg cells. Currently, a Phase I study of DS-1055a is on-going (NCT04419532).

Citation Format: Kazuki Satoh, Yoichi Kobayashi, Kaori Fujimaki, Masato Hata, Shinko Hayashi, Saori Ishida, Daisuke Sugiyama, Takahiko Sato, Lim Kyungtaek, Megumi Miyamoto, Shiho Kozuma, Michinori Kadokura, Kenichi Wakita, Kazuki Hirahara, Masato Amano, Ichiro Watanabe, Atsushi Okamoto, Andrea Tuettenberg, Helmut Jonuleit, Atsushi Tanemura, Shoichi Maruyama, Toshinori Agatsuma, Teiji Wada, Hiroyoshi Nishikawa. Anti-GARP antibody DS-1055a augments antitumor immunity by depleting highly suppressive GARP+ regulatory T cells [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 1847.

Novel anti-GARP antibody DS-1055a augments anti-tumor immunity by depleting highly suppressive GARP+ regulatory T cells

Regulatory T (Treg) cells, which are essential for maintaining self-tolerance, inhibit anti-tumor immunity, consequently hindering protective cancer immunosurveillance, and hampering effective anti-tumor immune responses in tumor-bearing hosts. Here, we show that depletion of Treg cells via targeting glycoprotein A repetitions predominant (GARP) induces effective anti-tumor immune responses. GARP was specifically expressed by highly suppressive Treg cells in the tumor microenvironment (TME) of multiple cancer types in humans. In the periphery, GARP was selectively induced in Treg cells, but not in effector T cells, by polyclonal stimulation. DS-1055a, a novel afucosylated anti-human GARP monoclonal antibody, efficiently depleted GARP+ Treg cells, leading to the activation of effector T cells. Moreover, DS-1055a decreased FoxP3+CD4+ T cells in the TME and exhibited remarkable anti-tumor activity in humanized mice bearing HT-29 tumors. We propose that DS-1055a is a new Treg-cell-targeted cancer immunotherapy agent with augmentation of anti-tumor immunity.

Identification and Therapeutic Targeting of GPR20, Selectively Expressed in Gastrointestinal Stromal Tumors, with DS-6157a, a First-in-Class Antibody-Drug Conjugate

Currently, the only approved treatments for gastrointestinal stromal tumor (GIST) are tyrosine kinase inhibitors (TKI), which eventually lead to the development of secondary resistance mutations in KIT or PDGFRA and disease progression. Herein, we identified G protein-coupled receptor 20 (GPR20) as a novel non-tyrosine kinase target in GIST, developed new GPR20 IHC, and assessed GPR20 expression in cell lines, patient-derived xenografts, and clinical samples from two institutes (United States and Japan). We studied GPR20 expression stratified by treatment line, KIT expression, GIST molecular subtype, and primary tumor location. We produced DS-6157a, an anti-GPR20 antibody-drug conjugate with a novel tetrapeptide-based linker and DNA topoisomerase I inhibitor exatecan derivative (DXd). DS-6157a exhibited GPR20 expression-dependent antitumor activity in GIST xenograft models including a GIST model resistant to imatinib, sunitinib, and regorafenib. Preclinical pharmacokinetics and safety profile of DS-6157a support its clinical development as a potential novel GIST therapy in patients who are refractory or have resistance or intolerance to approved TKIs. SIGNIFICANCE: GPR20 is selectively expressed in GIST across all treatment lines, regardless of KIT/PDGFRA genotypes. We generated DS-6157a, a DXd-based antibody-drug conjugate that exhibited antitumor activity in GIST models by a different mode of action than currently approved TKIs, showing favorable pharmacokinetics and safety profiles.This article is highlighted in the In This Issue feature, p. 1307.

DS-7080a, a Selective Anti-ROBO4 Antibody, Shows Anti-Angiogenic Efficacy with Distinctly Different Profiles from Anti-VEGF Agents

Purpose

Neovascular age-related macular degeneration (nAMD) results from choroidal neovascularization (CNV) and causes severe vision loss. Intravitreal anti-vascular endothelial growth factor (VEGF) therapies have significantly improved therapeutic outcomes; however, a substantial number of patients experience disease progression. Roundabout 4 (ROBO4) has been reported to be a vascular-specific protein that stabilizes vasculature in ocular pathological angiogenesis. To explore ROBO4 targeting as a novel treatment against neovascularization, we generated a humanized anti-human ROBO4 antibody, DS-7080a, and evaluated its efficacy.

Methods

ROBO4 mRNA in human whole eye cross-sections was examined by in situ hybridization. Human umbilical vein endothelial cell (HUVEC) migration was measured in the presence of VEGF, basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), or conditioned medium of primary human retinal pigment epithelial (HRPE) cells. CNV was induced in cynomolgus monkeys by laser irradiation. Vascular leakage was measured by fluorescein angiography, and pathological changes were determined by histology.

Results

ROBO4 mRNA was detected in choroidal vessels of nAMD patients. DS-7080a suppressed HGF- or bFGF-induced HUVEC migration in addition to that induced by VEGF. Further, HUVEC migration induced by HRPE-conditioned medium was inhibited by either DS-7080a or ranibizumab in a similar manner, and the combination of these showed further inhibition. In a laser-induced CNV monkey model, single intravitreous administration of 1.1 mg/eye of DS-7080a reduced the incidence of grade 4 leakage from 44.45% in control eyes to 1.85% (P < 0.05 by Dunnett's test).

Conclusions

Anti-ROBO4 antibody DS-7080a suppressed HUVEC migration in a distinctly different fashion from anti-VEGF agents and improved laser-induced CNV in non-human primates.

Translational Relevance

DS-7080a may be a novel treatment option for nAMD.

Abstract 5181: Therapeutic targeting of GPR20, selectively expressed in gastrointestinal stromal tumor (GIST), with DS-6157a, an antibody-drug conjugate (ADC)

More than 85% of GISTs are driven by activating mutations in KIT proto-oncogene receptor tyrosine kinase (KIT) or platelet-derived growth factor receptor alpha (PDGFRA). Currently, the only approved treatments for GIST are KIT directed tyrosine kinase inhibitors (TKIs). However, treatment with approved TKIs eventually results in disease progression most often due to the development of secondary resistance mutations in KIT. In addition, these agents have limited activity in PDGFRA mutant GIST and KIT/PDGFRA wild type (WT) GIST as primary therapy. Therefore, it is essential to develop novel therapeutic strategies with different modes of action in advanced GIST. G protein-coupled receptor 20 (GPR20) is an orphan GPCR selectively and abundantly expressed in GIST. GPR20 expression is regulated by FOXF1 and ETV1, transcription factors that play critical roles in KIT-driven GIST initiation, proliferation, and survival. We hypothesize that GPR20 is a potential therapeutic target for ADC development for the treatment of GIST. In this study, 1) GPR20 and KIT protein expression was assessed by IHC staining on GIST samples from DFCI (n=144) and NCCHE (n=100) as well as on normal and malignant tissue microarrays obtained commercially, and 2) an anti-GPR20 ADC (DS-6157a) was generated to evaluate antitumor activity in GIST models and to assess safety. GPR20 was expressed in more than 88% of the GIST samples analyzed, with higher expression levels in samples that: (I) received multiple treatment lines compared to naïve/early treated samples, (II) expressed higher KIT levels, (III) were small intestinal GIST, and/or (IV) had no KIT mutation, including succinate dehydrogenase (SDH) deficient GIST and neurofibromatosis type 1 (NF1)-associated GIST. The interstitial cells of Cajal were the only normal cells positive for GPR20. Normal mast cells expressed KIT but not GPR20. DS-6157a is an ADC composed of a humanized anti-GPR20 antibody, a Gly-Gly-Phe-Gly tetra-peptide-based linker, and a DNA topoisomerase I (TOP1) inhibitor Dxd. DS-6157a exhibited GPR20 expression-dependent cell growth-inhibitory activity and induced tumor regression with dosing at 3 to 10 mg/kg in multiple GIST xenograft models. In addition, DS-6157a showed antitumor activity in a GIST patient-derived xenograft model that was resistant to imatinib, sunitinib, and regorafenib. In vitro, DS-6157a induced TOP1 inhibitor-associated markers of DNA damage (phosphorylation of Chk1) and apoptosis (cleaved PARP) in GPR20 expressing cells. In preclinical toxicology studies using rats and cynomolgus monkeys, the pharmacokinetics and safety profile of DS-6157a were favorable at up to 200 mg/kg and 30 mg/kg, respectively. These data support the clinical development of DS-6157a as a potential novel GIST therapy with activity in patients that are resistant, refractory, or intolerant to approved TKIs.

Citation Format: Kenji Iida, Amr H. Abdelhamid, Akiko Kawano Nagatsuma, Tomoko Shibutani, Satoru Yasuda, Michiko Kitamura, Chiharu Hattori, Manabu Abe, Jun Hasegawa, Takuma Iguchi, Tsuyoshi Karibe, Takashi Nakada, Koichiro Inaki, Reiko Kamei, Yuki Abe, Jessica L. Andersen, Sandro Santagata, Matthew L. Hemming, Suzanne George, Toshihiko Doi, Atsushi Ochiai, George D. Demetri, Toshinori Agatsuma. Therapeutic targeting of GPR20, selectively expressed in gastrointestinal stromal tumor (GIST), with DS-6157a, an antibody-drug conjugate (ADC) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5181.

Anti-ORAI1 antibody DS-2741a, a specific CRAC channel blocker, shows ideal therapeutic profiles for allergic disease via suppression of aberrant T-cell and mast cell activation

ORAI1 constitutes the pore-forming subunit of the calcium release-activated calcium (CRAC) channel, which is responsible for store-operated calcium entry into lymphocytes. It is known that ORAI1 is essential for the activation of T cells and mast cells and is considered to be a potent therapeutic target for autoimmune and allergic diseases. Here, we obtained a new humanized antibody, DS-2741a, that inhibits ORAI1 function. DS-2741a bound to human-ORAI1 with high affinity and without cross-reactivity to rodent Orai1. DS-2741a demonstrated suppression of CRAC-mediated human and mouse T-cell activation and mast cell degranulation in human ORAI1 knock-in mice. Furthermore, DS-2741a ameliorated house dust mite antigen-induced dermatitis in the human ORAI1 knock-in mouse. Taken together, DS-2741a inhibited T-cell and mast cell functions, thus improving skin inflammation in animal models of atopic dermatitis and reinforcing the need for investigation of DS-2741a for the treatment of allergic diseases in a clinical setting.

Abstract C026: DS-1062a, a novel TROP2-targeting antibody-drug conjugate with a novel DNA topoisomerase I inhibitor DXd, demonstrates potent antitumor activity in preclinical models

Background: A trophoblast cell surface antigen 2 (TROP2) is a 36-kDa single-pass transmembrane protein overexpressed in various epithelial tumors including non-small cell lung cancer (NSCLC) with relatively low and restricted expression in normal tissues, and is associated with aggressive tumor behavior. Therefore, TROP2 could be an attractive target for cancer therapy. We created DS-1062a, TROP2-targeting antibody-drug conjugate (ADC) with Daiichi Sankyo DXd technology using a novel DNA topoisomerase I inhibitor DXd. In this study, the pharmacological activity and the mechanism of action of DS-1062a were evaluated in preclinical in vitro and in vivo models. Methods: In vitro cell growth inhibitory and in vivo antitumor activities of DS-1062a were evaluated using TROP2-high and -low tumor cell lines and xenograft mouse models. Internalization and intracellular trafficking of DS-1062a in tumor cells were analyzed by immunofluorescence microscopy. Induction of DNA damage and apoptosis to tumor cells by DXd payload released from DS-1062a were assessed by western blot and immunohistochemistry. Pharmacokinetic profiles of DS-1062a were also analyzed in xenograft mouse model. Results: DS-1062a showed in vitro cell growth inhibitory activity to TROP2-high tumor cells, but not to TROP2-low tumor cells. It was observed with confocal microscopy that DS-1062a was co-localized with a lysosomal marker LAMP-2 after internalizing into TROP2-high tumor cells. The amount of DXd payload released from TROP2-high tumor cells after the in vitro treatment with DS-1062a was higher than that of TROP2-low tumor cells. DNA damage and apoptosis were induced in TROP2-high tumor cells after the in vitro treatment with DXd and DS-1062a, but not with isotype control IgG ADC. Similarly, DS-1062a exhibited strong antitumor activity with tumor regression in several TROP2-high tumors including NSCLC and DXd accumulation and DNA damage in TROP2-high tumors were observed in DS-1062a-treated tumors, but not in isotype control IgG ADC-treated tumors. Pharmacokinetic profiles of DS-1062a in xenograft mouse model were preferable. Conclusion: Based on these preclinical results, DS-1062a could provide a valuable therapy with a potential benefit in TROP2-expressing cancers in the clinical setting. A first-in-human phase 1 study in patients with advanced solid tumors is in progress (NCT03401385).

Citation Format: Daisuke Okajima, Junko Yamaguchi, Michiko Kitamura, Reiko Kamei, Takanori Maejima, Tomoko Shibutani, Satoru Yasuda, Tadashi Toki, Tsuyoshi Karibe, Tomomichi Fujitani, Takashi Nakada, Riki Goto, Yutaka Noguchi, Yuki Abe, Toshinori Agatsuma. DS-1062a, a novel TROP2-targeting antibody-drug conjugate with a novel DNA topoisomerase I inhibitor DXd, demonstrates potent antitumor activity in preclinical models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C026. doi:10.1158/1535-7163.TARG-19-C026

Genetic diversity and DNA barcoding of the black fly (Diptera: Simuliidae) vectors of parasites causing human onchocerciasis in Guatemala

Genetic variation based on mitochondrial cytochrome c oxidase I (COI) and II (COII) sequences was investigated for three black fly nominal species, Simulium metallicum Bellardi complex, S. callidum Dyar and Shannon, and S. ochraceum Walker complex, which are vectors of human onchocerciasis from Guatemala. High levels of genetic diversity were found in S. metallicum complex and S. ochraceum complex with maximum intraspecific genetic divergences of 11.39% and 4.25%, respectively. Levels of genetic diversity of these nominal species are consistent with species status for both of them as they are cytologically complexes of species. Phylogenetic analyses revealed that the S. metallicum complex from Guatemala divided into three distinct clades, two with members of this species from several Central and South American countries and another exclusively from Mexico. The Simulium ochraceum complex from Guatemala formed a clade with members of this species from Mexico and Costa Rica while those from Ecuador and Colombia formed another distinct clade. Very low diversity in S. callidum was found for both genes with maximum intraspecific genetic divergence of 0.68% for COI and 0.88% for COII. Low genetic diversity in S. callidum might be a consequence of the result being informative of only recent population history of the species.

Abstract B095: Novel anti-CD147 antibodies inducing activation of SMAD signaling and tumor shrinkage in intractable cancer models

CD147, a type I membrane protein, is highly expressed in various cancers and is involved in the growth, metastasis, and activation of inflammatory signals in cancer cells via interaction with various molecules, such as integrins, CD44, and monocarboxylate transporters. Additionally, the expression of CD147 in tumors positively correlates with poor prognosis in various cancers. Therefore, CD147 is an attractive target for cancer therapy. However, there have been no successful drugs targeting CD147 so far, possibly because it is a multifunctional protein interacting with multiple molecules, making it challenging to discover a relevant CD147-targeting drug candidate by general in vitro screening methodologies. In this study, we developed novel anti-CD147 antibodies, which showed significant antitumor efficacy in immune-deficient mice bearing human pancreatic cancer cell lines, PANC-1 or MIA PaCa-2. Six anti-CD147 antibodies showing in vivo anti-tumor efficacy were obtained; one mouse IgG3, two rat IgG2b, two rat IgG1, and one rat IgG2a antibodies. Analysis of antibody dependent cellular toxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity of chimeric and humanized antibodies with human IgG2 or IgG4P derived from the obtained 6 anti-CD147 antibodies, #147A/B/C/D/E/F, suggested no significant immune-effector function for these antibodies. Despite lacking effector function, these antibodies exhibited significant in vivo antitumor activity, suggesting that the mechanism underlying their anti-tumor efficacy did not involve their effector function. We also found that the anti-tumor efficacy of antibodies #147A and #147B positively correlated with SMAD4 protein expression rather than CD147 protein expression in 10 pancreatic cancer xenograft models (correlation coefficient of #147B: anti-tumor efficacy vs. CD147, 0.245; vs. SMAD4, 0.9328). Moreover, the administration of anti-CD147 antibodies upregulated rhoB expression in an anti-CD147 antibody-sensitive SMAD4-positive MIA PaCa-2 graft mouse model. The stable expression of SMAD4 increased the sensitivity to the anti-CD147 antibody, ch4#147A (chimeric IgG4P derived from #147A) in xenograft mice inoculated with the BxPC-3 pancreatic cancer cell line, which is originally negative for SMAD4 and has low sensitivity to anti-CD147 antibodies. These data suggest that the expression of SMAD4 and activation of SMAD signaling are functionally important for susceptibility to anti-CD147 antibody treatment. The humanized anti-CD147 IgG4P antibody, h4#147D, derived from #147D with cross reactivity to monkey CD147, showed superior anti-tumor efficacy with complete tumor reduction, compared to standard anticancer drugs, including gemcitabine, imatinib, and sorafenib, in xenograft mice bearing corresponding cancer cell lines, MIA PaCa-2, KU812 chronic myeloid leukemia, and HepG2 liver cancer cell lines, respectively. No toxicity of h4#147D was observed in cynomolgus monkeys at a single dose of 100 mg/kg. These data suggest that h4#147D might be a novel anti-CD147 antibody, which could induce SMAD activation and tumor shrinkage in multiple xenograft models. Therefore, it has potential as a promising antitumor therapeutic antibody with superior anti-tumor efficacy to existing therapy.

Citation Format: Keisuke Fukuchi, Kayoko Nanai, Shoji Yamamoto, Jun Tsukada, Yusuke Totoki, Koichiro Inaki, Masato Ishigami, Naoyuki Makita, Yoko Nakano, Chigusa Yoshimura, Kozo Yoneda, Masato Amano, Kensuke Nakamura, Yoshiyuki Kanari, Yoko Oda, Haruyuki Nishigohri, Rika Nakano, Atsuko Nishida, Kenji Murakami, Yumi Matsui, Naomi Kasanuki, Shoji Midori, Satoko Funo, Sayako Takahashi, Hironobu Komori, Toshiaki Ohtsuka, Toshinori Agatsuma. Novel anti-CD147 antibodies inducing activation of SMAD signaling and tumor shrinkage in intractable cancer models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B095. doi:10.1158/1535-7163.TARG-19-B095

[Fam-] trastuzumab deruxtecan (DS-8201a)-induced antitumor immunity is facilitated by the anti-CTLA-4 antibody in a mouse model

[Fam-] trastuzumab deruxtecan (DS-8201a) is a HER2 (ERBB2)-targeting antibody-drug conjugate, composed of a HER2-targeting antibody and a topoisomerase I inhibitor, exatecan derivative, that has antitumor effects in preclinical xenograft models and clinical trials. Recently, [fam-] trastuzumab deruxtecan was reported to enhance antitumor immunity and was beneficial in combination with an anti-PD-1 antibody in a mouse model. In this study, the antitumor effect of [fam-] trastuzumab deruxtecan in combination with an anti-CTLA-4 antibody was evaluated. [Fam-] trastuzumab deruxtecan monotherapy had antitumor activity in an immunocompetent mouse model with EMT6 human HER2-expressing mouse breast cancer cells (EMT6-hHER2). [Fam-] trastuzumab deruxtecan in combination with the anti-CTLA-4 antibody induced more potent antitumor activity than that by monotherapy with either agent. The combination therapy increased tumor-infiltrating CD4+ and CD8+ T cells in vivo. Mechanistically, cured mice with treatment of [fam-] trastuzumab deruxtecan and an anti-CTLA-4 antibody completely rejected EMT6-mock cells similar to EMT6-hHER2 cells, and splenocytes from the cured mice responded to both EMT6-hHER2 and EMT6-mock cells as measured by interferon-gamma release. Taken together, these results indicate that antitumor immunity is induced by [fam-] trastuzumab deruxtecan and is facilitated in combination with anti-CTLA-4 antibody.

A Novel HER3-Targeting Antibody-Drug Conjugate, U3-1402, Exhibits Potent Therapeutic Efficacy through the Delivery of Cytotoxic Payload by Efficient Internalization

PURPOSE

HER3 is a compelling target for cancer treatment; however, no HER3-targeted therapy is currently clinically available. Here, we produced U3-1402, an anti-HER3 antibody-drug conjugate with a topoisomerase I inhibitor exatecan derivative (DXd), and systematically investigated its targeted drug delivery potential and antitumor activity in preclinical models.

EXPERIMENTAL DESIGN

In vitro pharmacologic activities and the mechanisms of action of U3-1402 were assessed in several human cancer cell lines. Antitumor activity of U3-1402 was evaluated in xenograft mouse models, including patient-derived xenograft (PDX) models. Safety assessments were also conducted in rats and monkeys.

RESULTS

U3-1402 showed HER3-specific binding followed by highly efficient cancer cell internalization. Subsequently, U3-1402 was translocated to the lysosome and released its payload DXd. While U3-1402 was able to inhibit HER3-activated signaling similar to its naked antibody patritumab, the cytotoxic activity of U3-1402 in HER3-expressing cells was predominantly mediated by released DXd through DNA damage and apoptosis induction. In xenograft mouse models, U3-1402 exhibited dose-dependent and HER3-dependent antitumor activity. Furthermore, U3-1402 exerted potent antitumor activity against PDX tumors with HER3 expression. Acceptable toxicity was noted in both rats and monkeys.

CONCLUSIONS

U3-1402 demonstrated promising antitumor activity against HER3-expressing tumors with tolerable safety profiles. The activity of U3-1402 was driven by HER3-mediated payload delivery via high internalization into tumor cells.

Preclinical Development of U3-1784, a Novel FGFR4 Antibody Against Cancer, and Avoidance of Its On-target Toxicity

The FGFR4/FGF19 signaling axis is overactivated in 20% of liver tumors and currently represents a promising targetable signaling mechanism in this cancer type. However, blocking FGFR4 or FGF19 has proven challenging due to its physiological role in suppressing bile acid synthesis which leads to increased toxic bile acid plasma levels upon FGFR4 inhibition. An FGFR4-targeting antibody, U3-1784, was generated in order to investigate its suitability as a cancer treatment without major side effects.U3-1784 is a high-affinity fully human antibody that was obtained by phage display technology and specifically binds to FGFR4. The antibody inhibits cell signaling by competing with various FGFs for their FGFR4 binding site thereby inhibiting receptor activation and downstream signaling via FRS2 and Erk. The inhibitory effect on tumor growth was investigated in 10 different liver cancer models in vivo The antibody specifically slowed tumor growth of models overexpressing FGF19 by up to 90% whereas tumor growth of models not expressing FGF19 was unaffected. In cynomolgus monkeys, intravenous injection of U3-1784 caused elevated serum bile acid and liver enzyme levels indicating potential liver damage. These effects could be completely prevented by the concomitant oral treatment with the bile acid sequestrant colestyramine, which binds and eliminates bile acids in the gut. These results offer a new biomarker-driven treatment modality in liver cancer without toxicity and they suggest a general strategy for avoiding adverse events with FGFR4 inhibitors.

Abstract LB-275: U3-1402, a novel HER3-targeting antibody-drug conjugate, exhibits its antitumor activity through increased payload intracellular delivery via highly efficient drug internalization

Background: Human epidermal growth factor receptor 3 (HER3), a member of the ErbB receptor tyrosine kinase family, is overexpressed in a variety of human cancers and plays an important role in cell proliferation and survival. U3-1402 is a novel HER3-targeting antibody-drug conjugate (ADC) consisting of a fully human anti-HER3 antibody (patritumab), a tetrapeptide-based linker, and a topoisomerase I inhibitor payload. It is currently being investigated in clinical trials for HER3-positive breast cancer (phase 1/2) and NSCLC (phase 1). In principle, effective action of ADCs depends on multiple dynamic factors including antigen-specific binding, internalization, trafficking to lysosomes, and payload release, as well as other inherent characteristics such as payload potency and linker stability.

Methods: To assess the targeted delivery potential of U3-1402, the HER3-mediated molecular dynamics of U3-1402 (cell surface binding, internalization, trafficking, and payload release) were investigated in 8 cancer cell lines with various HER3 expression levels, along with cell growth inhibition activity. In vitro molecular dynamics were compared between U3-1402 and trastuzumab (anti-HER2 antibody) using the MDA-MB-453 cell line, which expresses both HER2 and HER3. The activity of patritumab (naked antibody of U3-1402) was tested. In vivo efficacy of U3-1402 was also evaluated and immunostaining of HER3 and γH2AX (marker of DNA double-stranded breaks) as well as drug concentration assessment were performed.

Results: U3-1402 bound to the cell surface of HER3-positive cell lines in HER3 expression level-dependent manner, and was then internalized into cells. Interestingly, the internalization rate of U3-1402 in MDA-MB-453 cells at 1 h was 64%, which was higher than that observed with trastuzumab (2%). Subsequently, U3-1402 was translocated to the lysosome, followed by payload release, leading to an improved cell growth inhibition compared to that noted with patritumab. In vivo antitumor efficacy was also demonstrated in a HER3-dependent manner in MDA-MB-453 xenograft model. In the study, internalization of HER3 from cell membrane into the intracellular compartment by U3-1402 treatment was observed, followed by increased free payload and γH2AX levels in tumor tissue.

Conclusion: U3-1402 has a high internalization property for effective payload delivery to HER3-expressing cancer cells, resulting in a favorable ADC-driven efficacy.

Citation Format: Kumiko Koyama, Yuuri Hashimoto, Yasuki Kamai, Yoshinobu Shiose, Manabu Abe, Yuki Kaneda, Naoyuki Maeda, Kenji Hirotani, Yusuke Ogitani, Tsuyoshi Karibe, Takashi Kagari, Kenichi Wakita, Suguru Ueno, Toshinori Agatsuma, Masato Murakami. U3-1402, a novel HER3-targeting antibody-drug conjugate, exhibits its antitumor activity through increased payload intracellular delivery via highly efficient drug internalization [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-275.

The Latest Research and Development into the Antibody-Drug Conjugate, [fam-] Trastuzumab Deruxtecan (DS-8201a), for HER2 Cancer Therapy

A major limitation of traditional chemotherapy for cancer is dose-limiting toxicity, caused by the exposure of non-tumor cells to cytotoxic agents. Use of molecular targeted drugs, such as specific kinase inhibitors and monoclonal antibodies, is a possible solution to overcome this limitation and has achieved clinical success so far. Use of an antibody-drug conjugate (ADC) is a rational strategy for improving efficacy and reducing systemic adverse events. ADCs use antibodies selectively to deliver a potent cytotoxic agent to tumor cells, thus drastically improving the therapeutic index of chemotherapeutic agents. Lessons learned from clinical failure of early ADCs during the 1980s to 90s have recently led to improvements in ADC technology, and resulted in the approval of four novel ADCs. Nonetheless, further advances in ADC technology are still required to streamline their clinical efficacy and reduce toxicity. [fam-] Trastuzumab deruxtecan (DS-8201a) is a next-generation ADC that satisfies these requirements based on currently available evidence. DS-8201a has several innovative features; a highly potent novel payload with a high drug-to-antibody ratio, good homogeneity, a tumor-selective cleavable linker, stable linker-payload in circulation, and a short systemic half-life cytotoxic agent in vivo; the released cytotoxic payload could exert a bystander effect. With respect to its preclinical profiles, DS-8201a could provide a valuable therapy with a great potential against HER2-expressing cancers in clinical settings. In a phase I trial, DS-8201a showed acceptable safety profiles with potential therapeutic efficacy, with the wide therapeutic index.

Anti-tumor effects of mAb against L-type amino acid transporter 1 (LAT1) bound to human and monkey LAT1 with dual avidity modes

l‐Type amino acid transporter 1 (LAT1) disulfide linked to CD98 heavy chain (hc) is highly expressed in most cancer cells, but weakly expressed in normal cells. In the present study, we developed novel anti‐LAT1 mAbs and showed internalization activity, inhibitory effects of amino acid uptake and cell growth and antibody‐dependent cellular cytotoxicity, as well as in vivo antitumor effects in athymic mice. Furthermore, we examined the reactivity of mAbs with LAT1 of Macaca fascicularis to evaluate possible side‐effects of antihuman LAT1 mAbs in clinical trials. Antihuman LAT1 mAbs reacted with ACHN human and MK.P3 macaca kidney‐derived cells, and this reactivity was significantly decreased by siRNAs against LAT1. Macaca LAT1 cDNA was cloned from MK.P3, and only two amino acid differences between human and macaca LAT1 were seen. RH7777 rat hepatoma and HEK293 human embryonic kidney cells expressing macaca LAT1 were established as stable transfectants, and antihuman LAT1 mAbs were equivalently reactive against transfectants expressing human or macaca LAT1. Dual (high and low) avidity modes were detected in transfectants expressing macaca LAT1, MK.P3, ACHN and HCT116 human colon cancer cells, and K_A values were increased by anti‐CD98hc mAb, suggesting anti‐LAT1 mAbs detect an epitope on LAT1‐CD98hc complexes on the cell surface. Based on these results, LAT1 may be a promising anticancer target and Macaca fascicularis can be used in preclinical studies with antihuman LAT1 mAbs.

Development of New ADC Technology with Topoisomerase I Inhibitor

Antibody-drug conjugates (ADCs) selectively deliver large amounts of antitumor drugs to tumor tissue and show significant antitumor effects with a wide therapeutic window. We developed a new linker-drug technology platform with an exatecan derivative, which is a highly potent topoisomerase I inhibitor. The major advantages of the technology are: 1) high and homogeneous drug-to-antibody ratio (DAR) availability; 2) potent antitumor activity in conjunction with bystander killing; 3) few safety concerns because of the stable linker limiting release of free drug; and 4) a wide application to therapeutic antibodies. Using this linker-drug technology, we generated an anti-HER2 ADC, namely DS-8201a. DS-8201a, in which almost all eight cysteine residues of the antibody are bound to drug, was effective against trastuzumab DM1 (T-DM1)-insensitive patient-derived xenograft (PDX) models with high HER2 expression and also demonstrated antitumor efficacy against several breast cancer PDX models with low HER2 expression. DS-8201a was well tolerated in rats and monkeys following repeated administration. These results suggest that DS-8201a may be efficacious in a broader population of HER2-positive cancer patients and also confirm the importance of this new class of novel topoisomerase I inhibitor-based ADC technology.

Abstract 3092: U3-1402a, a novel HER3-targeting ADC with a novel DNA topoisomerase I inhibitor, demonstrates a potent antitumor efficacy

Background HER3 (human epidermal growth factor receptor 3) is a member of HER family, and overexpressed in breast cancer, NSCLC, melanoma, gastric cancer and pancreatic cancer patients` tissues. U3-1402a is an antibody-drug conjugate (ADC) comprised of a fully human anti-HER3 monoclonal immunoglobulin G1 (IgG1) antibody (U3-1287) covalently conjugated via a cleavable peptide linker to exatecan derivative (DXd). The DXd is released after internalization of U3-1402a and leads to apoptosis of the target tumor cells by the inhibition of topoisomerase I. This ADC achieves a high drug-to-antibody-ratio (DAR 7 to 8) with homogeneous conjugation with the topoisomerase I inhibitor. The aim of this study was to preclinically evaluate the efficacy of U3-1402a in breast cancer models.

Materials and methods In order to evaluate the pharmacological potential of U3-1402a, in vitro and in vivo studies were performed. In vitro growth inhibition assay evaluated the sensitivity of U3-1402a in HER3-positive human breast cancer cell line (HCC1569) and HER3-negative human cervical carcinoma cell line (C33A). Cells were treated with U3-1402a or MAAA-1181 (payload of U3-1402a) depending on its concentration (U3-1402a: 0.153 to 10 000 ng/mL, MAAA-1181: 2.44 to 160,000 pg/mL). In vivo growth inhibition study evaluated the dose-dependent sensitivity of U3-1402a in HER3-positive breast cancer xenograft model, MDA-MB-453. In addition, several xenograft models with different HER3 expression were tested with its sensitivity to U3-1402a. These models were HCC1569 (human breast cancer cell line, HER3 IHC score 3+), MDA-MB-453 (human breast cancer cell line, HER3 IHC score 2+), NIBIO-G016 (human gastric cancer patient-derived xenograft, HER3 IHC score 1+) and MDA-MB-231 (human breast cancer cell line, HER3 IHC score 0). R

esults In vitro study, U3-1402a exhibited anti-tumor killing activity in HER3-positive human breast cancer cell line, HCC1569. C-33A human cervical carcinoma cell line was not sensitive to U3-1402a even MAAA-1181 itself exhibited anti-tumor killing activity to this cell line. In vivo study, U3-1402a showed dose-dependent anti-tumor killing activity in a HER3-positive breast cancer MDA-MB-453 xenograft model. Finally, in vivo tumor regression was only observed in HER3 2+ and 3+ models.

Conclusions U3-1402a preclinically exhibited its efficacy in breast cancer model in vitro and in vivo. In vivo efficacy was correlated with HER3 expression. These studies suggest that U3-1402a, a novel HER3-targeting ADC, would be efficacious in a broader patient population with HER3 expression like breast cancer, melanoma, NSCLC, gastric cancer and pancreatic cancer.

Citation Format: Suguru Ueno, Kenji Hirotani, Reimar Abraham, Sabine Blum, Birgit Frankenberger, Mauricio Redondo-Muller, Johannes Bange, Yusuke Ogitani, Akiko Zembutsu, Koji Morita, Takashi Nakada, Shuji Majima, Yuki Abe, Toshinori Agatsuma. U3-1402a, a novel HER3-targeting ADC with a novel DNA topoisomerase I inhibitor, demonstrates a potent antitumor efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3092. doi:10.1158/1538-7445.AM2017-3092

DS-8201a, a HER2-targeting antibody-drug conjugate, to elicit immune responses and benefits in combination with an anti-PD-1 antibody

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Background: DS-8201a, a HER2-targeting antibody–drug conjugate (ADC), with a topoisomerase I inhibitor, exatecan drivative (DX-8951 derivative, DXd) has been shown to have antitumor effects in preclinical xenograft models and clinical trials, but the involvement of the immune system in the antitumor efficacy of DS-8201a has not been elucidated yet. Methods: The antitumor efficacy of DS-8201a individually and in combination with an anti-PD-1 antibody was determined in a syngeneic mouse model with human HER2-expressing CT26.WT (CT26.WT-hHER2) cells. Mice whose tumors had been cured by DS-8201a treatment were rechallenged with CT26.WT-hHER2 cells; their splenocytes were co-cultured with CT26.WT-hHER2 or CT26.WT-mock cells, and IFN-g secretion by these cells was determined. To investigate effects of DXd and DS-8201a on dendritic cells (DCs), the expression of DC markers on bone marrow derived DCs (BMDCs) and intratumoral DCs was analyzed by flow cytometry. Furthermore, MHC class I and PD-L1 expression on tumor cells was analyzed. Results: At a weekly dosage of 10 mg/kg, DS-8201a showed significant antitumor effects in the mouse model. Mice whose tumors had been cured by DS-8201a treatment rejected the rechallenge with CT26.WT-hHER2 cells, and splenocytes from these mice were activated by both CT26.WT-hHER2 and CT26.WT-mock cells. In the mouse model, DS-8201a treatment raised a population of intratumoral DCs (CD45+CD11c+MHC class II+) and increased DC expression of CD86, a DC activation marker; DXd also up-regulated CD86 expression on BMDCs in vitro. Furthermore, DS-8201a up-regulated PD-L1 and MHC class I expression on tumor cells. Notably, antitumor effects of the combination of DS-8201a with an anti-PD-1 antibody were better than those of monotherapy. Conclusions: DS-8201a elicits immune responses via mechanisms other than cytotoxic effects on tumor cells. This finding suggests additional benefits of combining DS-8201a with an immune checkpoint inhibitor (ICI). The combination of DS-8201a and an anti-PD-1 antibody was effective in tumor suppression, indicating that DS-8201a may be successfully combined with an ICI in human clinical applications.

Helminths in rodents from Wet Markets in Thailand

Only a few surveys have ever been carried out of the helminths of the commensal rodents found in the traditional wet markets that play such an important part of daily life in South-east Asia. The potential of rodents as reservoirs of zoonoses including helminths is of great interest since in these markets humans and rodents come into closer contact than in other environments and food may be indirectly contaminated via rodent faeces. Helminths in a total of 98 rats belonging to two species (Rattus norvegicus and Rattus exulans) were surveyed in eight traditional wet markets in Udon Thani, Thailand. Thirteen species of helminths were recovered, seven of which are potentially zoo-notic, with an overall prevalence of 89.8 %. Our results show that rodents in wet markets could pose a threat to human health as potential reservoirs of zoonotic helminthiases.

Novel anti-EPHA2 antibody, DS-8895a for cancer treatment

Overexpression of EPHA2 has been observed in multiple cancers and reported to be associated with poor prognosis. Here, we produced an afucosylated humanized anti-EPHA2 monoclonal antibody (mAb), DS-8895a for cancer treatment. The antibody recognizes the extracellular juxtamembrane region of EPHA2 and therefore can bind to both full-length and truncated forms of EPHA2, which are anchored to cell membranes and recently reported to be produced by post-translational cleavage in tumors. DS-8895a exhibited markedly increased antibody dependent cellular cytotoxicity (ADCC) in vitro and also inhibited tumor growth in EPHA2-positive human breast cancer MDA-MB-231 and human gastric cancer SNU-16 xenograft mouse models. Moreover, DS-8895a in combination with cisplatin (CDDP) showed better efficacy than each of the monotherapies did in the human gastric cancer model. These results suggest that a novel antibody, DS-8895a has therapeutic potential against EPHA2-expressing tumors.

Wide application of a novel topoisomerase I inhibitor-based drug conjugation technology

To establish a novel and widely applicable payload-linker technology for antibody-drug conjugates (ADCs), we have focused our research on applying exatecan mesylate (DX-8951f), a potent topoisomerase I inhibitor, which exhibits extensive antitumor activity as well as significant myelotoxicity, as the payload part. Through this study, we discovered a promising exatecan derivative (DX-8951 derivative, DXd), that has the characteristics of low membrane permeability and shows considerably less myelotoxicity than that shown by exatecan mesylate in an in vitro human colony forming unit-granulocyte macrophage assay. DXd was further used for drug conjugation by using commercially or clinically useful monoclonal antibodies to evaluate the potency of the ADC. The result revealed that the DXd-ADCs targeting CD30, CD33, and CD70 were effective against each of their respective target-expressing tumor cell lines. Moreover, a novel DXd-ADC targeting B7-H3, which is a new target for ADCs, also showed potent antitumor efficacy both in vitro and in vivo. In conclusion, this study showed that this novel topoisomerase I inhibitor-based ADC technology is widely applicable to a diverse number of antibodies and is expected to mitigate myelotoxicity, thereby possibly resulting in better safety profiles than that of existing ADC technologies.

Abstract 3852: U3-1784, a human anti-FGFR4 antibody for the treatment of cancer

Fibroblast Growth Factor Receptor 4 (FGFR4) is the fourth member of the Fibroblast Growth Factor Receptor (FGFR) family of receptor tyrosine kinases. All of the FGFR's have been implicated in cancer development due to increased activation of their enzymatic activity either by gene mutation, over-expression or inadvertent ligand-mediated stimulation. One important alteration that may lead to FGFR4 activation in cancer is the overexpression of its ligand FGF19 in 20-40% of primary liver cancer.

Here, we report the development of U3-1784, a phage display-derived fully human antibody that specifically binds to FGFR4 but not to isoforms of FGFR1-3. The antibody binds to an epitope in the putative ligand binding domain of the receptor and consequently inhibits ligand binding and downstream signaling. In a panel of 10 tumor models derived from hepatocellular carcinoma, U3-1784 significantly inhibits the growth of FGF19-expressing models up to 90% whereas models without FGF19 expression are insensitive. These results strongly suggest that the FGFR4/FGF19 axis is an oncogenic driver in hepatocellular carcinoma. U3-1784 is currently in phase I clinical trials.

Citation Format: Rene Bartz, Keisuke Fukuchi, Tanja Lange, Katrin Gruner, Toshiaki Ohtsuka, Ichiro Watanabe, Shinko Hayashi, Mauricio Redondo-Müller, Mizuki Takahashi, Toshinori Agatsuma, Johannes Bange, Reimar Abraham. U3-1784, a human anti-FGFR4 antibody for the treatment of cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3852.

Bystander killing effect of DS-8201a, a novel anti-human epidermal growth factor receptor 2 antibody-drug conjugate, in tumors with human epidermal growth factor receptor 2 heterogeneity

Antibody–drug conjugates deliver anticancer agents selectively and efficiently to tumor tissue and have significant antitumor efficacy with a wide therapeutic window. DS‐8201a is a human epidermal growth factor receptor 2 (HER2)‐targeting antibody–drug conjugate prepared using a novel linker‐payload system with a potent topoisomerase I inhibitor, exatecan derivative (DX‐8951 derivative, DXd). It was effective against trastuzumab emtansine (T‐DM1)‐insensitive patient‐derived xenograft models with both high and low HER2 expression. In this study, the bystander killing effect of DS‐8201a was evaluated and compared with that of T‐DM1. We confirmed that the payload of DS‐8201a, DXd (1), was highly membrane‐permeable whereas that of T‐DM1, Lys‐SMCC‐DM1, had a low level of permeability. Under a coculture condition of HER2‐positive KPL‐4 cells and negative MDA‐MB‐468 cells in vitro, DS‐8201a killed both cells, whereas T‐DM1 and an antibody–drug conjugate with a low permeable payload, anti‐HER2‐DXd (2), did not. In vivo evaluation was carried out using mice inoculated with a mixture of HER2‐positive NCI‐N87 cells and HER2‐negative MDA‐MB‐468‐Luc cells by using an in vivo imaging system. In vivo, DS‐8201a reduced the luciferase signal of the mice, indicating suppression of the MDA‐MB‐468‐Luc population; however, T‐DM1 and anti‐HER2‐DXd (2) did not. Furthermore, it was confirmed that DS‐8201a was not effective against MDA‐MB‐468‐Luc tumors inoculated at the opposite side of the NCI‐N87 tumor, suggesting that the bystander killing effect of DS‐8201a is observed only in cells neighboring HER2‐positive cells, indicating low concern in terms of systemic toxicity. These results indicated that DS‐8201a has a potent bystander effect due to a highly membrane‐permeable payload and is beneficial in treating tumors with HER2 heterogeneity that are unresponsive to T‐DM1.

Anti-Human Immunodeficiency Virus Type 1 Activity of R-95288, a Phosphodiester Hexadeoxyribonucleotide Modified by Dibenzyloxybenzyl and Hydroxyethyl Residues at the 5′- and 3′-Ends

The phosphodiester hexadeoxyribonucleotide R-95288 is a potent anti-human immunodeficiency virus type 1 (HIV-1) agent in vitro which consists or a TGGGAG nucleoside sequence with dibenzyloxybenzyl and hydroxyethyl substituents at the 5′- and 3′-ends, respectively. In this study, the antiviral activity of R-95288 against various strains of HIV-1 in vitro was assessed and its mechanism of action was analysed. R-95288 inhibited replication of all strains of HIV-1 used including laboratory strains with the syncytium-inducing (SI) phenotype and clinical isolates with both SI and non-SI (NSI) phenotypes. The 50% inhibitory concentrations (IC50s) were 0.62–18 μg mL−1 (0.21–6.2 μM). R-95288 inhibited the binding and fusion of HIV-1-infected T cells with CD4+ cells. In addition, R-95288 specifically blocked the binding of monoclonal antibodies, recognizing the anti-V3 loop or the CD4-binding site of the virus envelope glycoprotein gp120. Furthermore, the target site of R-95288 within the V3 loop was found in the putative heparin-binding region by binding inhibition assays using various anti-V3 loop antibodies. These results suggest that R-95288 can inhibit various strains of HIV-1, possibly by specific interaction with gp120.

Development of DS-5573a: A novel afucosylated mAb directed at B7-H3 with potent antitumor activity

B7‐H3 is highly overexpressed in a variety of human clinical tumors, and its expression is significantly associated with poor outcomes. In our study, we aimed to develop new antitumor mAbs by employing cancer cell immunization, and succeeded in generating a mouse anti‐human B7‐H3 antibody (M30) that shows antitumor activity. M30 was humanized (Hu‐M30), and an afucosylated Hu‐M30 (DS‐5573a) was also generated. To assess the potency of DS‐5573a as a therapeutic mAb, we characterized this mAb and evaluated its antitumor activity in vitro and in vivo. Flow cytometry analysis showed that B7‐H3 proteins were expressed on various types of cancer cell lines broadly, and DS‐5573a binds to IgC1 and IgC2 domains of human B7‐H3. Antibody‐dependent cellular cytotoxicity activity of DS‐5573a was drastically enhanced against medium to high B7‐H3‐expressing cancer cell lines MDA‐MB‐231 and NCI‐H322. DS‐5573a also induced high antibody‐dependent cellular cytotoxicity activity against low B7‐H3‐expressing cancer cell line COLO205, whereas Hu‐M30 induced little activity against it. In addition, DS‐5573a was found to be a novel anti‐B7‐H3 antibody which showed antibody‐dependent cellular phagocytosis activity. Furthermore, DS‐5573a showed dose‐dependent and significant antitumor efficacy (0.03–3 mg/kg) in MDA‐MB‐231‐bearing SCID mice (which have functional natural killer cells and macrophages), but little antitumor efficacy in NOG mice (which lack natural killer cells and have reduced macrophage function). These results suggest that antitumor activity of DS‐5573a is mediated by effector cells, and this mAb could be a promising antitumor therapy for patients with a wide range of B7‐H3‐expressing tumors.

MRGD, a MAS-related G-protein coupled receptor, promotes tumorigenisis and is highly expressed in lung cancer

To elucidate the function of MAS-related GPCR, member D (MRGD) in cancers, we investigated the in vitro and in vivo oncogenic function of MRGD using murine fibroblast cell line NIH3T3 in which MRGD is stably expressed. The expression pattern of MRGD in clinical samples was also analyzed. We found that overexpression of MRGD in NIH3T3 induced focus formation and multi-cellular spheroid formation, and promoted tumors in nude mice. In other words, overexpression of MRGD in NIH3T3 induced the loss of contact inhibition, anchorage-independent growth and in vivo tumorigenesis. Furthermore, it was found that the ligand of MRGD, beta-alanine, enhanced spheroid formation in MRGD-expressing NIH3T3 cells. From investigation of clinical cancer tissues, we found high expression of MRGD in several lung cancers by immunohistochemistry as well as real time PCR. Based on these results, MRGD could be involved in tumorigenesis and could also be a novel anticancer drug target.

Meningoencephalitis associated with Sarcocystis spp. in a free-living Japanese raccoon dog (Nyctereutes procyonoides viverrinus)

A free-living, young adult, male Japanese raccoon dog (Nyctereutes procyonoides viverrinus) was rescued in Gifu, Japan in March 2009. The animal was weak and emaciated with neurological signs that included head tilt, tremor and tic. The brain showed no gross abnormality at necropsy, but microscopically there was severe meningoencephalitis associated with protozoa, which were morphologically consistent with the asexual developmental stage of Sarcocystis spp. The protozoa were immunohistochemically negative for Toxoplasma gondii and Neospora caninum, but reacted weakly with antiserum specific for Sarcocystis cruzi. Analysis of the partial 18S rRNA gene sequence revealed that the protozoa were most closely related to an unidentified Sarcocystis species that was isolated from the white-fronted goose (Anser albifrons).

Molecular phylogeny of Trypanosoma cruzi from Central America (Guatemala) and a comparison with South American strains

Molecular phylogenetic analysis was carried out for 21 strains of Trypanosoma cruzi, nine of which were obtained from Guatemala and 12 from South America. Phylogenetic trees were constructed using the nucleotide sequences of two nuclear gene regions, dihydrofolate reductase-thymidylate synthase (DHFR-TS) and trypanothione reductase (TR), and contiguous portions of two mitochondrial genes, cytochrome oxidase subunit II (COII) and reduced nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1). Possible genetic exchange between the rather divergent lineages of T. cruzi II from South America was suggested in the trees of the two nuclear genes. T. cruzi I strains obtained from Guatemala and Colombia were identical in all the genes examined, but other T. cruzi I isolates from South America were rather polymorphic in the DHFR-TS and mitochondrial genes. No genetic exchange was identified between T. cruzi I populations from Central and South America in the present study.

The origin of the triploid in Paragonimus westermani on the basis of variable regions in the mitochondrial DNA

Triploid, parthenogenetic forms of the lungfluke, Paragonimus westermani, occur in Japan, Korea and China. The origin(s) of triploidy has been debated over the years. Sequences of two regions in the mitochondrial DNA, i.e. partial lrRNA (16S), and a portion of the non-coding region, were obtained from natural populations of P. westermani. All triploid individuals (Japan, Korea, China) and a single tetraploid individual (China) had identical sequences in the 16S region studied. Some sequence variation was observed among diploids, with those from Taiwan being distinct from the remainder. Both neighbour joining and parsimony trees using the 16S region placed diploid individuals from southwestern Japan close to the triploids and the tetraploid. The fragment amplified from the mitochondrial non-coding region showed dimorphism. One form (type A) consisted of 239 bp comprising two identical tracts of 70 bp separated by a tract of 93 bp. The second form (Type B) consisted of only a single 70 bp tract. All diploid individuals from Taiwan, China and Korea possessed type A, while those from Japan were polymorphic; individuals from Oita and Hyogo had type B, those from Chiba had type A, but both types were found in Mie. On the other hand, all of the triploid individuals and two tetraploid individuals possessed type B. Both the form present in the non-coding region and the 16S sequence suggest an affinity between a south-eastern group of diploid populations in Japan and the triploid form. A possible mechanism responsible for the origin of the triploid is discussed.

New filarial nematode from Japanese serows (Naemorhedus crispus: Bovidae) close to parasites from elephants

A new onchocercid species, Loxodontofilaria caprini n. sp. (Filarioidea: Nematoda), found in subcutaneous tissues of 37 (33%) of 112 serows (Noemorhedus crispus) examined in Japan, is described. The female worm had the characteristics of Loxodontofilaria, e.g., the large body size, well-developed esophagus with a shallow buccal cavity, and the long tail with three caudal lappets. The male worm of the new species, which was first described in the genus, had unequal length of spicules, 10 pairs of pre- and post-caudal papillae, and three terminal caudal lappets. Deirids were present in both sexes. Among four species of the genus loxodontofiloria: one from the hippopotamus and three from the Elepantidae, L. caprini n. sp. appears close to L. asiatica Bain, Baker & Chabaud, 1982, a subcutaneous parasite of Elephas indicus in Myanmar (Burma). However, L. caprini n. sp. is distinct from L. asiatica in that the Japanese female worm has an esophagus half as long and the microfilariae also half as long with a coiled posterior. The microfilariae were found in the skin of serows. The new parasite appears to clearly illustrate a major event in the evolution of onchocercids: the host-switching. This might have occurred on the Eurasian continent, where elephantids and the lineage of rupicaprines diversified during the Pliocene-Pleistocene, or in Japan, into which some of these hosts migrated.

Synthesis and evaluation of 3-methyl-4-oxo-6-phenyl-4,5,6,7-tetrahydrobenzofuran-2-carboxylic acid ethyl ester derivatives as potent antitumor agents

For the construction of new combinatorial libraries, a lead compound was created by replacing the core structure of a hit compound discovered by screening for cytotoxic agents against a tumorigenic cell line. The newly designed compound maintained biological activity and allowed alternative library construction for antitumor drugs.

Synthesis and biological evaluation of benzothiazole derivatives as potent antitumor agents

Based on 2-methyl-4-nitro-2H-pyrazole-3-carboxylic acid[2-(cyclohexanecarbonylamino)benzothiazol-6-yl]amide (1), which shows selective cytotoxicity against tumorigenic cell lines, 2,6-dichloro-N-[2-(cyclopropanecarbonylamino)benzothiazol-6-yl]benzamide (13b) was designed and synthesized as a biologically stable derivative containing no nitro group. The highly potent derivative 13b exhibited excellent in vivo inhibitory effect on tumor growth.

A library synthesis of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester derivatives as anti-tumor agents

As a result of a hit-to-lead program using a technique of solution-phase parallel synthesis, a highly potent (2,4-dimethoxyphenyl)-[6-(3-fluorophenyl)-4-hydroxy-3-methylbenzofuran-2-yl]methanone (15b) was synthesized as an optimized derivative of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester (1), which was discovered as a screening hit from small-molecule libraries and exhibited selective cytotoxicity against a tumorigenic cell line.

Thienopyridine and benzofuran derivatives as potent anti-tumor agents possessing different structure–activity relationships

(3-Amino-6-thiophen-2-yl-thieno[2,3-b]pyridin-2-yl)phenylmethanone (3) was discovered as a new type of cytotoxic agent selective against a tumorigenic cell line. The molecular structure of a previously reported compound, (4-hydroxy-3-methyl-6-phenylbenzofuran-2-yl)phenylmethanone (2), had remarkably similar bioisosteric substructures to that of compound 3. Although the relationship between the molecular structure and biological activity of each derivative synthesized from these two hit compounds (2 and 3) were studied, unexpectedly no correlation was observed. However, after further synthetic study from 3, one of the most potent derivative (10k) having a different SAR profile from 2, was discovered.

4-Hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester derivatives as potent anti-tumor agents

Based on the structure of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester (1), which exhibits selective cytotoxicity against a tumorigenic cell line, (2,4-dimethoxyphenyl)-(4-hydroxy-3-methyl-6-phenylbenzofuran-2-yl)-methanone (18m) was designed and synthesized as a biologically stable derivative containing no ester group. Although the potency of 18m was almost the same as our initial hit compound 1, 18m is expected to last longer in the human body as an anticancer agent.

Identities of two Paragonimus species from Sri Lanka inferred from molecular sequences

Metacercariae of Paragonimus spp. were obtained from field-collected freshwater crabs in Sri Lanka. Genomic DNA was extracted from single metacercariae. Two gene regions (partial mitochondrial cytochrome c oxidase subunit 1 (CO1) and the second internal transcribed spacer of the nuclear ribosomal gene repeat (ITS2)) were amplified using the polymerase chain reaction. Two differing sequences were obtained for each of these gene regions. Phylogenetic analyses placed the type 1 sequences as sister to a clade containing P. westermani and P. siamensis whereas the type 2 sequences were close to published sequences of P. siamensis from Thailand. The possible taxonomic status of these two types are discussed. This is the first report of molecular data about Paragonimus from Sri Lanka.

[Acute massive pulmonary embolism occurring during orthopedic surgery]

We present an emergent surgical case of massive pulmonary embolism (MPE) that happened during orthopedic surgery. A 38-year-old man, who had bone fractures with his lumbar vertebra and ankle, underwent the internal fixation of the tibial bone with tourniquet under general anesthesia in our hospital. During this surgery, the pulse oxymeter showed a drop of arterial oxygen saturation suddenly. Immediately we installed a transesophageal echo (TEE) probe in the patient, and detected enlargement of the right ventricle and right atrial thrombus. Half an hour later, the thrombus disappeared from the right atrium and the patient showed hemodynamic shock. We performed emergent embolectomy immediately under moderate hypothermic complete cardiopulmonary bypass. The postoperative course was uneventful, and one month later, his orthopedic surgery underwent completely. We conclude that TEE was a useful devise for the diagnosis of intraoperative MPE.

The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858

Schistosomes are digenean flukes, parasitic of birds, mammals and crocodiles. The family Schistosomatidae contains species of considerable medical and veterinary importance, which cause the disease schistosomiasis. Previous studies, both morphological and molecular, which have provided a good deal of information on the phylogenetics of this group, have been limited in the number of species investigated or the type or extent of molecular data used. This paper presents the most comprehensive phylogeny to date, based on the sequences of 3 genes, complete ribosomal small subunit rRNA and large ribosomal subunit rRNA, and mitochondrial cytochrome oxidase 1, sequenced from 30 taxa including at least 1 representative from 10 of the 13 known genera of the Schistosomatidae and 17 of the 20 recognized Schistosoma species. The phylogeny is examined using morphological characters, intermediate and definitive host associations and biogeography. Theories as to the origins and spread of Schistosoma are also explored. The principal findings are that Ornithobilharzia and Austrobilharzia form a sister group to the Schistosoma; mammalian schistosomes appear paraphyletic and 2 Trichobilharzia species, T. ocellata and T. szidati, seem to be synonymous. The position of Orientobilharzia within the Schistosoma is confirmed, as is an Asian origin for the Schistosoma, followed by subsequent dispersal through India and Africa.

A molecular phylogeographic study based on DNA sequences from individual metacercariae of Paragonimus mexicanus from Guatemala and Ecuador

A molecular phylogeographic study of Paragonimus mexicanus collected from Guatemala and Ecuador was performed. Genomic DNA was extracted from individual metacercariae, and two gene regions (partial mitochondrial cytochrome c oxidase subunit 1 (CO1) and the second internal transcribed spacer of the nuclear ribosomal gene repeat (ITS2)) were amplified by the polymerase chain reaction (PCR). Sequences segregated in a phylogenetic tree according to their geographic origins. ITS2 sequences from Ecuador and Guatemala differed at only one site. Pairwise distances among CO1 sequences within a country were always lower than between countries. Nevertheless, genetic distances between countries were less than between geographical forms of P. westermani that have been suggested to be distinct species. This result suggests that populations from Guatemala and Ecuador are genetically differentiated perhaps at the level of subspecies.