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.

B7-H3 Negatively Modulates CTL-Mediated Cancer Immunity.

Purpose: Anti-programmed-death-1 (PD-1) immunotherapy improves survival in non-small cell lung cancer (NSCLC), but some cases are refractory to treatment, thereby requiring alternative strategies. B7-H3, an immune-checkpoint molecule, is expressed in various malignancies. To our knowledge, this study is the first to evaluate B7-H3 expression in NSCLCs treated with anti-PD-1 therapy and the therapeutic potential of a combination of anti-PD-1 therapy and B7-H3 targeting.Experimental Design: B7-H3 expression was evaluated immunohistochemically in patients with NSCLC (n = 82), and its relationship with responsiveness to anti-PD-1 therapy and CD8+ tumor-infiltrating lymphocytes (TILs) was analyzed. The antitumor efficacy of dual anti-B7-H3 and anti-programmed death ligand-1 (PD-L1) antibody therapy was evaluated using a syngeneic murine cancer model. T-cell numbers and functions were analyzed by flow cytometry.Results: B7-H3 expression was evident in 74% of NSCLCs and was correlated critically with nonresponsiveness to anti-PD-1 immunotherapy. A small number of CD8+ TILs was observed as a subpopulation with PD-L1 tumor proportion score less than 50%, whereas CD8+ TILs were still abundant in tumors not expressing B7-H3. Anti-B7-H3 blockade showed antitumor efficacy accompanied with an increased number of CD8+ TILs and recovery of effector function. CD8+ T-cell depletion negated antitumor efficacy induced by B7-H3 blockade, indicating that improved antitumor immunity is mediated by CD8+ T cells. Compared with a single blocking antibody, dual blockade of B7-H3 and PD-L1 enhanced the antitumor reaction.Conclusions: B7-H3 expressed on tumor cells potentially circumvents CD8+-T-cell-mediated immune surveillance. Anti-B7-H3 immunotherapy combined with anti-PD-1/PD-L1 antibody therapy is a promising approach for B7-H3-expressing NSCLCs. Clin Cancer Res; 24(11); 2653-64. ©2018 AACR.

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.

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.

Novel and potent inhibitors of stearoyl-CoA desaturase-1. Part I: Discovery of 3-(2-hydroxyethoxy)-4-methoxy-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide.

A series of structurally novel stearoyl-CoA desaturase-1 (SCD-1) inhibitors has been identified by optimizing a hit from our corporate library. Preliminary structure-activity relationship (SAR) studies led to the discovery of the highly potent and orally bioavailable thiazole-based SCD-1 inhibitor, 3-(2-hydroxyethoxy)-4-methoxy-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide (23a).

Potent and selective cathepsin K inhibitors.

A novel series of cathepsin K inhibitors derived from Novartis compound I is described. Optimization of the P1, P3, and P1' units led to the identification of 4-aminophenoxyacetic acid 24b with an IC(50) value of 4.8 nM, which possessed an excellent selectivity over other human cathepsins and good pharmacokinetic (PK) properties. Oral administration of compound 24b to ovariectomized (OVX) rats showed a trend toward an improvement of bone mineral density (BMD) in the femur bone.

Arylamine based cathepsin K inhibitors: investigating P3 heterocyclic substituents.

A modification of novel cathepsin K inhibitors I was carried out. The structural design was aimed at reducing the lipophilic character of compounds I for obtaining better pharmacokinetic profiles. This modification afforded several less lipophilic compounds with good inhibitory activities and pharmacokinetic profiles, although the enzyme selectivity over cathepsin S was left at issue.