Synthesis, SAR study, and biological evaluation of novel quinoline derivatives as phosphodiesterase 10A inhibitors with reduced CYP3A4 inhibition.

A novel class of phosphodiesterase 10A inhibitors with potent PDE10A inhibitory activity and reduced CYP3A4 inhibition was designed and synthesized starting from 2-[4-({[1-methyl-4-(pyridin-4-yl)-1H-pyrazol-3-yl]oxy}methyl)phenyl]quinoline (1). Replacement of pyridine ring of 1 with N-methyl pyridone ring drastically improved CYP3A4 inhibition, and further optimization of these quinoline analogues identified 1-methyl-5-(1-methyl-3-{[4-(quinolin-2-yl)phenoxy]methyl}-1H-pyrazol-4-yl)pyridin-2(1H)-one (42b), which showed potent PDE10A inhibitory activity and a good CYP3A4 inhibition profile. A PET study with (11)C-labeled 42b indicated that 42b exhibited good brain penetration and specifically accumulated in the rodent striatum. Further, oral administration of 42b dose-dependently attenuated phencyclidine-induced hyperlocomotion in mice with an ED50 value of 2.0mg/kg and improved visual-recognition memory impairment at 0.1 and 0.3mg/kg in mice novel object recognition test.

Synthesis and Preliminary Evaluation of an 18F-labeled Oleate Analog to Image Fatty Acid Beta-Oxidation in the Absence of Metabolic Defluorination.

PURPOSE: Fatty acid oxidation (FAO) is a key parameter for evaluating cardiovascular, oncologic, neurologic, and other metabolic diseases. Several single-photon emission computed tomography and positron emission tomography (PET) tracers have been developed to measure FAO. Among these, 18-[18F]fluoro-4-thia-oleate ([18F]FTO), first developed by DeGrado et al., is well characterized. Here, we synthesized several analogs of [18F]FTO to improve the metabolic stability of the C-18F bond, and preliminarily evaluated their performance in monkey PET studies. PROCEDURES: Several secondary 18F-fluorinated analogs, 17-[18F]fluoro-4-thia-oleate (17-[18F]FTO), 15-[18F]fluoro-4-thia-oleate (15-[18F]FTO), 12-[18F]fluoro-4-thia-oleate (12-[18F]FTO), 7-[18F]fluoro-4-thia-oleate, (7-[18F]FTO, [18F]AS3504073-00), and 6-[18F]fluoro-4-thia-oleate (6-[18F]FTO), were synthesized from tosylate or bromide precursors using similar procedures. Nucleophilic 18F fluorination on each precursor was performed using [18F]tetrabutylammonium fluoride/tetrabutylammonium hydrocarbonate, followed by hydrolysis of methylester. All synthesized 18F-labeled compounds were administered to cynomolgus monkeys, and PET measurements were performed. From the monkey PET studies, 7-[18F]FTO was selected as the best tracer and used to perform preliminary evaluations in mice. RESULTS: All five compounds had sufficient quality and stability for animal experiments. In monkey PET studies, 12-, 7-, and 6-[18F]FTO showed greater accumulation in the heart than [18F]FTO, but not 17- and 15-[18F]FTO. Only 7-[18F]FTO did not show significant accumulation in the bone. The standardized uptake values (SUVs) for 12-[18F]FTO, 7-[18F]FTO, and 6-[18F]FTO were 9.77, 9.26, and 7.25 in the heart, and 3.17, n.d., and 1.96 in the bone 1 h after administration, respectively. In mouse distribution studies, SUVs 1 h after administration of 7-[18F]FTO and [18F]FTO were 10.4 and 10.0 in the heart, and 0.37 and 3.48 in the femur, respectively. Administration of etomoxir, a carnitine palmitoyltransferase inhibitor, reduced SUVs of 7-[18F]FTO and [18F]FTO in the heart by 91% and 87%, respectively. CONCLUSIONS: We developed a novel PET tracer 7-[18F]FTO/[18F]AS3504073-00 for FAO imaging. 7-[18F]FTO had an excellent PET tracer profile, suggesting it may be a useful tracer for FAO imaging. Further evaluations of the tracer are ongoing.

Preclinical Development and Validation of ASP5354: A Near-Infrared Fluorescent Agent for Intraoperative Ureter Visualization.

PURPOSE: Iatrogenic ureteral injury (IUI) can complicate minimally invasive and open abdominopelvic surgery. The incidence of IUI is low and dependent on the type of surgery (< 10 %), but it is associated with high morbidity. Therefore, intraoperative visualization of the ureter is critical to reduce the incidence of IUI, and some methodologies for ureter visualization have been developed. Amongst these, near-infrared fluorescence (NIRF) visualization is thought to bring an advantage with real-time retroperitoneal visualization through the retroperitoneum. We investigated an indocyanine green (ICG) derivative, ASP5354, which emits NIRF at 820 nm when exposed to near-infrared light at a wavelength of 780 nm, in a rodent and porcine model. PROCEDURES: Wistar rats and Göttingen minipigs under anesthesia were laparotomized and then administered ASP5354 chloride intravenously at dose of 0.03 and 0.3 mg/kg for rats and 0.001 and 0.01 mg/kg for minipigs, respectively. Videos of the abdominal cavity in minipigs were taken using a near-infrared fluorescent camera (pde-neo) and assessed visually by three independent clinicians. Toxicological evaluation was demonstrated with cynomolgus monkeys. RESULTS: The proportion of animals whose ureters were visible up to 3 h after administration of ASP5354 chloride were 33 % at 0.001 mg/kg and 100 % at 0.01 mg/kg, respectively. In a toxicological study in cynomolgus monkeys, ASP5354 chloride demonstrated no significant toxicity, suggesting that 0.01 mg/kg provides an optimal dose when used clinically and could allow for ureter visualization during routine surgical procedures. CONCLUSIONS: The dose of 0.01 mg/kg provided an optimal dose for ureter visualization up to 3 h after administration. ASP5354 shows promise for ureter visualization during abdominopelvic surgery, which may potentially lower the risk of IUI.

A novel anti-NGF PEGylated Fab' provides analgesia with lower risk of adverse effects.

Nerve growth factor (NGF) has emerged as a key driver of pain perception in several chronic pain conditions, including osteoarthritis (OA), and plays an important role in the generation and survival of neurons. Although anti-NGF antibodies improve pain control and physical function in patients with clinical chronic pain conditions, anti-NGF IgGs are associated with safety concerns such as effects on fetal and postnatal development and the risk of rapidly progressive osteoarthritis. To overcome these drawbacks, we generated a novel anti-NGF PEGylated Fab' antibody. The anti-NGF PEGylated Fab' showed specific binding to and biological inhibitory activity against NGF, and analgesic effects in adjuvant-induced arthritis model mice in a similar manner to an anti-NGF IgG. In collagen-induced arthritis model mice, the anti-NGF PEGylated Fab' showed higher accumulation in inflamed foot pads than the anti-NGF IgG. In pregnant rats and non-human primates, the anti-NGF PEGylated Fab' was undetectable in fetuses, while the anti-NGF IgG was detected and caused abnormal postnatal development. The PEGylated Fab' and IgG also differed in their ability to form immune complexes in vitro. Additionally, while both PEGylated Fab' and IgG showed analgesic effects in sodium monoiodoacetate-induced arthritic model rats, their effects on edema were surprisingly quite different. While the anti-NGF IgG promoted edema over time, the anti-NGF PEGylated Fab' did not. The anti-NGF PEGylated Fab' (ASP6294) may thus be a potential therapeutic candidate with lower risk of adverse effects for various diseases in which NGF is involved such as OA and chronic back pain.

Selective M3 muscarinic receptor antagonist inhibits small-cell lung carcinoma growth in a mouse orthotopic xenograft model.

In small cell lung carcinoma (SCLC), acetylcholine (ACh) is synthesized and secreted, and it acts as an autocrine growth factor through activation of its receptors, muscarinic receptor (mAChR) and nicotinic receptor (nAChR). Alteration of tumor growth by blockade of M(3) mAChR in a human SCLC cell line, NCI-H82, was investigated in the present study. We used a highly selective M(3) muscarinic antagonist, N-(2-[3-([3R]-1-(cyclohexylmethyl)-3-piperidinyl]methylamino)-3-oxopropyl]amino-2-oxoethyl)-3,3,3-triphenyl-propioamide (J-115311). Our results show that J-115311 inhibited the increased intracellular calcium elicited by carbachol, a muscarinic agonist, in SCLC cells. J-115311 also inhibited SCLC cell growth in vitro. In a mouse orthotopic xenograft model, J-115311 dose-dependently reduced tumor growth when NCI-H82 cells were inoculated into the upper left lobe of the lung. These findings indicate that blockade of M(3) mAChR can suppress tumor growth in SCLC, suggesting the potential therapeutic utility of M(3) muscarinic antagonists as anti-cancer agents.

In vivo imaging of obesity-induced inflammation in adipose tissue.

Obesity is associated with low-grade inflammation in adipose tissue, which contributes to the development of obesity-related diseases such as insulin resistance, hypertension and arteriosclerosis. Here we developed an animal model that non-invasively monitors inflammation in adipose tissue using in vivo bioluminescent imaging (BLI) technique. In vitro, stimulation with TNFalpha or co-culture with RAW264 macrophages increased bioluminescence in 3T3-L1 adipocytes expressing NF-kappaB-mediated luciferase gene (3T3-L1/NF-kappaB-re-luc2P). In vivo, lipopolysaccharide increased bioluminescence in mice transplanted with 3T3-L1/NF-kappaB-re-luc2P cells. Moreover, light emission derived from implanted cells was significantly higher in diet-induced obese mice transplanted with 3T3-L1/NF-kappaB-re-luc2P than in lean mice. Our results showed that BLI technique and 3T3-L1/NF-kappaB-re-luc2P cells provide a useful approach to non-invasively monitor obesity-induced inflammation in adipose tissue in in vivo.

Quantification of mouse pulmonary cancer models by microcomputed tomography imaging.

The advances in preclinical cancer models, including orthotopic implantation models or genetically engineered mouse models of cancer, enable pursuing the molecular mechanism of cancer disease that might mimic genetic and biological processes in humans. Lung cancer is the major cause of cancer deaths; therefore, the treatment and prevention of lung cancer are expected to be improved by a better understanding of the complex mechanism of disease. In this study, we have examined the quantification of two distinct mouse lung cancer models by utilizing imaging modalities for monitoring tumor progression and drug efficacy evaluation. The utility of microcomputed tomography (micro-CT) for real-time/non-invasive monitoring of lung cancer progression has been confirmed by combining bioluminescent imaging and histopathological analyses. Further, we have developed a more clinically relevant lung cancer model by utilizing K-ras(LSL-G12D)/p53(LSL-R270H) mutant mice. Using micro-CT imaging, we monitored the development and progression of solitary lung tumor in K-ras(LSL-G12D)/p53(LSL-R270H) mutant mouse, and further demonstrated tumor growth inhibition by anticancer drug treatment. These results clearly indicate that imaging-guided evaluation of more clinically relevant tumor models would improve the process of new drug discovery and increase the probability of success in subsequent clinical studies.

Preclinical Evaluation of an Anti-Nectin-4 ImmunoPET Reagent in Tumor-Bearing Mice and Biodistribution Studies in Cynomolgus Monkeys.

PURPOSE: Nectin-4 is selectively overexpressed in a variety of cancers and is currently under clinical investigation as a therapeutic target. A monoclonal antibody against nectin-4 (AGS-22M6) was evaluated as an Immuno-positron emission tomography (ImmunoPET) reagent. Its ability to assay nectin-4 expression as well as detect nectin-4 positive tumors in the liver and bone was evaluated using mouse models. PROCEDURES: The biodistribution of [(89)Zr]AGS-22M6 was evaluated in mice bearing tumors with varying levels of nectin-4 expression. An isogenic breast cancer tumor line was used to model metastatic liver and bone disease in mice. The biodistribution of [(18)F]AGS-22M6 in cynomolgus monkeys was evaluated. RESULTS: A positive correlation was demonstrated between tumor nectin-4 expression and [(89)Zr]AGS-22M6 uptake. Tumors in the liver and bone were detected and differentiated based on nectin-4 expression. [(18)F]AGS-22M6 showed limited uptake in cynomolgus monkey tissues. CONCLUSIONS: [(89)Zr]AGS-22M6 is a promising ImmunoPET reagent that can assay nectin-4 expression in both primary and metastatic lesions.

[A trial of biweekly paclitaxel administration in consideration of QOL for advanced or recurrent gynecologic cancer].

At present there is no oral medicine available which is effective for advanced or recurrent case of elderly patients with gynecologic cancer. We report that a low-dose biweekly paclitaxel administration preserves quality of life (QOL) and seems to be "tumor dormancy like" therapy of good compliance with few side effects. A total of 11 cases were in ovarian cancer (5), uterine cancer (3), cervical cancer (2), and uterine sarcoma (1). The median age was 68 years old and the age range was 50 to 79 years old. We performed a standard treatment as a first time treatment. Afterwards, we obtained complete informed consent from the patients for progressive or recurrent cancer and administered biweekly paclitaxel 70 mg/m2 (80-100 mg/body) on an outpatient basis. We reviewed the effect, side effect and compliance of the medication. We judged the side effect based on the Japanese cancer treatment society common toxicity criteria. The result was only one patient death from PD and the other 10 patients were PR or a state of NC without side effect. An ovary cancer case patient lived for 67 months at best, an endometrial cancer case patient lived for 62 months at best, a cervical cancer case patient lived for 74 months at best, and a recurrent uterine sarcoma case patient lived for 76 months after recurrence and the QOL was good. In addition, there was no onset of side effect more than grade 2 in all of the cases and a compliance of medical administration was good. In these cases, we thought that a low-dose of biweekly paclitaxel administration was regarded as a therapy to preserve QOL without a serious side effect and a good compliance of medication. Furthermore, we intend to increase more cases and would like to report them in the future.

PET imaging for tyrosine kinase inhibitor (TKI) biodistribution in mice.

Receptor tyrosine kinases play a critical role in cell growth, survival, and proliferation, and are considered potential molecular targets for the treatment of cancer. Although several tyrosine kinase inhibitors (TKIs), such as erlotinib and gefitinib, have demonstrated clinical efficacy via the inhibition of the epidermal growth factor receptor (EGFR), most TKIs are only effective in a small proportion of patients. Positron emission tomography (PET) imaging is a methodology of molecular imaging based on nuclear imaging. PET imaging in combination with radiolabeled TKIs improves accuracy of quantitative imaging strategies and the probability of successful drug development, and may facilitate the stratification of patients. Here, we describe a protocol for PET imaging using radiolabeled TKI in preclinical trials.

Investigation of Mechanisms for MK-801-Induced Neurotoxicity Utilizing Metabolomic Approach.

Single treatment of rats with the noncompetitive N-methyl-D-aspartate receptor antagonist MK-801 induces neuronal cell degeneration and death in the retrosplenial/posterior cingulate cortex (RS/PC) region, along with local cerebral glucose utilization. However, the relationship between this neuronal cell degeneration and death and glucose utilization remains unclear. To investigate the mechanism of MK-801-induced neurotoxicity and its relation to glucose utilization, changes in endogenous metabolites in the RS/PC region of MK-801 treated rats were assessed using metabolomics. Inverse correlation between citrulline and arginine levels suggested increased nitric oxide (NO) production. In addition, decreased levels of purine metabolites suggested enhanced xanthine oxidase activity accompanied with reactive oxygen species (ROS) production. Histopathological analysis confirmed that the production of ROS in the RS/PC region was increased by MK-801 and that the nonspecific NO synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME) prevented MK-801-induced neuronal cell death. These results suggest that NO increases oxidative stress-related cell death. Increased levels of metabolites of glucose metabolism suggested enhanced energy production via glycolysis. To confirm the relationship between NO and glucose utilization, positron emission tomography (PET) imaging with [(18)F] fluoro-2-deoxy-d-glucose ([(18)F] FDG) was conducted. [(18)F] FDG-PET imaging accompanied by co-treatment of L-NAME with MK-801 demonstrated that L-NAME ameliorated MK-801-induced glucose utilization.In conclusion, MK-801 induces NO and ROS production in the RS/PC region, which might subsequently induce oxidative stress and in turn neuronal cell death. In addition, MK-801-induced NO production increased glucose utilization and affected glucose metabolism, the imbalance of which might generate additional oxidative stress related to neuronal cell death.

A free radical initiator, 2,2'-azobis (2-aminopropane) dihydrochloride enhances hyperthermia-induced apoptosis in human uterine cervical cancer cell lines.

Hyperthermia-induced apoptosis and its enhancement in the presence of a temperature-dependent free radical initiator, 2,2'-azobis (2-aminopropane) dihydrochloride (AAPH) were examined in human uterine cervical cancer cell lines, CaSki and HeLa. When both cell lines were treated with hyperthermia at 44 degrees C for 60 min, minimal apoptosis was observed. When combined with nontoxic AAPH (50mM), significant enhancement of apoptosis was observed, where the initial rate of free radical formation was about twice as high than that at 37 degrees C. Augmentation of the growth delay, lipid peroxidation (LPO), activation of caspase-3 and increase in [Ca2+]i were also observed after the combined treatment. A water-soluble vitamin E, Trolox, blocked the increase in [Ca2+]i and an intracellular Ca2+ chelator, BAPTA-AM, prevented the DNA fragmentation induced by the combination. Cytochrome c release was also revealed by fluorescence microscopy. However, no significant change in mitochondrial membrane potential and expression of Bax and Bcl-2 was observed. A slight increase in Fas expression was observed only in CaSki cells after the combined treatment. These results indicate that hyperthermia and AAPH induce enhanced apoptosis and subsequent cell killing via two pathways; a pathway dependenton increase in LPO and [Ca2+]i, and a pathway associated with cytochrome c release and subsequent caspase activation without changes of mitochondrial membrane potential and Bax/Bcl-2 expression in these cell lines. Since it is known that cancer cells are generally resistant to physical and chemical stress-induced apoptosis, free radical generators like AAPH appear to be a useful thermosensitizer for hyperthermic cancer therapy.

[A case of uterine endometrial cancer with lung metastases improved by various treatments including taxane].

Surgery is the treatment of choice for uterine endometrial cancer. However, partial response anticancer chemotherapies for advanced cases with metastasis may also be effective. Current therapy is CAP (CDDP + ADM + CPM), which is centered on CDDP, but sufficient effect is not provided, and a new regimen is needed. We herein report a case of endometrial cancer with metastasis to the lung in which multidisciplinary treatment including taxanes was effective.

[Apoptosis as a measure of chemosensitivity to anti-cancer drugs in gynecological cancer].

OBJECTIVE: To examine apoptosis as a measure of chemosensitivity to anti-cancer drugs in gynecological cancer xenografted into nude mice. METHODS: The TUNEL method was used to investigate the induction of apoptosis after exposure to anti-cancer drugs in thirteen gynecological cancers xenografted into nude mice. Moreover, in vivo sensitivities of gynecologic cancer to anti-cancer drugs were determined according to the protocol developed by Battle Laboratories, Columbus, Ohio USA. Both methods were examined for correlation. RESULTS: The apoptosis index by the TUNEL method showed a correlation with the findings using the protocol developed by Battle Laboratories, Columbus, Ohio USA. CONCLUSIONS: Our findings indicate the ability to determine the measure of chemosensitivity by the apoptosis index.

The selective anaplastic lymphoma receptor tyrosine kinase inhibitor ASP3026 induces tumor regression and prolongs survival in non-small cell lung cancer model mice.

Activation of anaplastic lymphoma receptor tyrosine kinase (ALK) is involved in the pathogenesis of several carcinomas, including non-small cell lung cancer (NSCLC). Echinoderm microtubule-associated protein like 4 (EML4)-ALK, which is derived from the rearrangement of ALK and EML4 genes, has been validated as a therapeutic target in a subset of patients with NSCLC. Here, we investigated the effects of ASP3026, a novel small-molecule ALK inhibitor, against ALK-driven NSCLC. ASP3026 inhibited ALK activity in an ATP-competitive manner and had an inhibitory spectrum that differed from that of crizotinib, a dual ALK/MET inhibitor. In mice xenografted with NCI-H2228 cells expressing EML4-ALK, orally administered ASP3026 was well absorbed in tumor tissues, reaching concentrations >10-fold higher than those in plasma, and induced tumor regression with a wide therapeutic margin between efficacious and toxic doses. In the same mouse model, ASP3026 enhanced the antitumor activities of paclitaxel and pemetrexed without affecting body weight. ASP3026 also showed potent antitumor activities, including tumor shrinkage to a nondetectable level, in hEML4-ALK transgenic mice and prolonged survival in mice with intrapleural NCI-H2228 xenografts. In an intrahepatic xenograft model using NCI-H2228 cells, ASP3026 induced continuous tumor regression, whereas mice treated with crizotinib showed tumor relapse after an initial response. Finally, ASP3026 exhibited potent antitumor activity against cells expressing EML4-ALK with a mutation in the gatekeeper position (L1196M) that confers crizotinib resistance. Taken together, these findings indicate that ASP3026 has potential efficacy for NSCLC and is expected to improve the therapeutic outcomes of patients with cancer with ALK abnormality.

Pre-clinical validation of orthotopically-implanted pulmonary tumor by imaging with 18F-fluorothymidine-positron emission tomography/computed tomography.

The development of positron-emission tomography (PET) and X-ray computed tomography (CT) imaging has improved the detection of tumor burden and, in turn, pre-clinical drug development and clinical treatment. In pre-clinical drug development, clinically-relevant murine cancer models, such as orthotopic models of lung cancer, have provided an accurate representation of tumor burden in humans. However, evidence demonstrating the capability of imaging-guided evaluation of these clinically-relevant models is limited. Here, we combined (18)F-fluorothymidine (FLT)-PET/CT imaging and a murine model of human non-small cell lung cancer (NSCLC) to improve the accuracy of anticancer drug evaluation in pre-clinical studies. We found that FLT-PET/CT imaging enabled the progression of pulmonary tumors to be longitudinally monitored rather than FDG-PET/CT. Furthermore, in an efficacy study of a standard treatment of docetaxel in a murine lung cancer model, FLT-PET imaging detected the anticancer response earlier than volumetric analysis by CT imaging. We, thus, observed a relationship between the alteration of FLT signals and Ki-67 index in the pulmonary tumor during the period of chemotherapy. These results indicate that the combination of FLT-PET/CT imaging and an orthotopic NSCLC model is an effective strategy for evaluating clinical efficacy and potential of an anticancer agent during pre-clinical development.

Brain penetration of telmisartan, a unique centrally acting angiotensin II type 1 receptor blocker, studied by PET in conscious rhesus macaques.

INTRODUCTION: Telmisartan is a widely used, long-acting antihypertensive agent. Known to be a selective angiotensin II type 1 (AT(1)) receptor (AT(1)R) blocker (ARB), telmisartan acts as a partial agonist of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and inhibits centrally mediated effects of angiotensin II in rats following peripheral administration, although the brain penetration of telmisartan remains unclear. We investigated the brain concentration and localization of telmisartan using (11)C-labeled telmisartan and positron emission tomography (PET) in conscious rhesus macaques. METHODS: Three male rhesus macaques were bolus intravenously administered [(11)C]telmisartan either alone or as a mixture with unlabeled telmisartan (1mg/kg). Dynamic PET images were acquired for 95min following administration. Blood samples were collected for the analysis of plasma concentration and metabolites, and brain and plasma concentrations were calculated from detected radioactivity using the specific activity of the administered drug preparation, in which whole blood radioactivity was used for the correction of intravascular blood radioactivity in brain. RESULTS: Telmisartan penetrated into the brain little but enough to block AT(1)R and showed a consistently increasing brain/plasma ratio within the PET scanning period, suggesting slow clearance of the compound from the brain compared to the plasma clearance. Brain/plasma ratios at 30, 60, and 90min were 0.06, 0.13, and 0.18, respectively. No marked localization according to the AT(1)R distribution was noted over the entire brain, even on tracer alone dosing. CONCLUSIONS: Telmisartan penetrated into the brain enough to block AT(1)R and showed a slow clearance from the brain in conscious rhesus macaques, supporting the long-acting and central responses of telmisartan as a unique property among ARBs.

YM155, a selective survivin suppressant, inhibits tumor spread and prolongs survival in a spontaneous metastatic model of human triple negative breast cancer.

Metastatic triple negative breast cancer [TNBC, with negative expression of estrogen and progesterone receptors and no overexpression of HER2/neu (ErbB-2)] remains a major therapeutic challenge because of its poor overall prognosis and lack of optimal targeted therapies. Survivin has been implicated as an important mediator of breast cancer cell growth and dysfunctions in apoptosis, and its expression correlates with a higher incidence of metastases and patient mortality; thus, survivin is an attractive target for novel anti-cancer agents. In previous studies, we identified YM155 as a small molecule that selectively suppresses survivin expression. YM155 inhibits the growth of a wide range of human cancer cell lines. Tumor regression induced by YM155 is associated with decreased intratumoral survivin expression, increased apoptosis and a decreased mitotic index. In the present study, we evaluated the antitumor efficacy of YM155 both in vitro and in vivo using preclinical TNBC models. We found that YM155 suppressed survivin expression, including that of its splice variants (survivin 2B, δEx3 and 3B), resulting in decreased cellular proliferation and spontaneous apoptosis of human TNBC cells. In a mouse xenograft model, continuous infusion of YM155 led to the complete regression of subcutaneously established tumors. Furthermore, YM155 reduced spontaneous metastases and significantly prolonged the survival of animals bearing established metastatic tumors in the MDA-MB-231-Luc-D3H2-LN orthotopic model. These results suggest that the survivin-suppressing activity of YM155 may offer a novel therapeutic option for patients with metastatic TNBC.