Sousuke Miyoshi

SGLT2 selective inhibitor ipragliflozin reduces body fat mass by increasing fatty acid oxidation in high-fat diet-induced obese rats

Ipragliflozin is a novel and selective sodium-glucose cotransporter 2 (SGLT2) inhibitor that induces sustained increases in urinary glucose excretion by inhibiting renal glucose reabsorption and thereby exerting a subsequent antihyperglycemic effect. Here, we examined the effect of ipragliflozin on body weight in high-fat diet-induced (HFD) obese rats. Treatment of ipragliflozin (10mg/kg once daily) reduced body weight despite a slight increase in food intake. Dual-energy X-ray absorptiometry and computed tomography demonstrated that the reduction in body weight was accompanied by reduced visceral and subcutaneous fat masses but not lean mass or bone mineral content. Analysis of plasma and urinary parameters suggested the possibility that ipragliflozin enhanced lipolysis and fatty acid oxidation, and indirect calorimetry showed that ipragliflozin decreased the heat production rate from glucose but increased the rate from fat and lowered the respiratory exchange ratio. In conclusion, these data demonstrate that ipragliflozin-induced urinary glucose excretion specifically reduces fat mass with steady calorie loss by promoting the use of fatty acids instead of glucose as an energy source in HFD rats. By improving hyperglycemia and promoting weight reduction, ipragliflozin may prove useful in treating type 2 diabetes in obese individuals.

[18F]FDG-PET as an Imaging Biomarker to NMDA Receptor Antagonist-Induced Neurotoxicity

Positron emission tomography (PET) is an effective tool for noninvasive examination of the body and provides a range of functional information. PET imaging with [(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) has been used to image alterations in glucose metabolism in brain or cancer tissue in the field of clinical diagnosis but not in the field of toxicology. A single dose of N-methyl-d-aspartate (NMDA) receptor antagonist induces neuronal cell degeneration/death in the rat retrosplenial/posterior cingulate (RS/PC) cortex region. These antagonists also increase local cerebral glucose utilization. Here, we examined the potential of [(18)F]FDG-PET as an imaging biomarker of neurotoxicity induced by an NMDA receptor antagonist, MK-801. Using [(18)F]FDG-PET, we determined that increased glucose utilization involved the neurotoxicity induced by MK-801. The accumulation of [(18)F]FDG was increased in the rat RS/PC cortex region showing neuronal cell degeneration/death and detected before the onset of neuronal cell death. This effect increased at a dose level at which neuronal cell degeneration recovered 24h after MK-801 administration. Scopolamine prevented the neurotoxicity and [(18)F]FDG accumulation induced by MK-801. Furthermore, in cynomolgus monkeys that showed no neuronal cell degeneration/death when treated with MK-801, we noted no differences in [(18)F]FDG accumulation between test and control subjects in any region of the brain. These findings suggest that [(18)F]FDG-PET, which is available for clinical trials, may be useful in generating a predictive imaging biomarker for detecting neurotoxicity against NMDA receptor antagonists with the same pharmacological activity as MK-801.

Abstract 2678: First demonstration of in vivo PET imaging for ALK inhibitor using [11C]ASP3026, a novel brain-permeable type of ALK inhibitor.

The recent breakthrough identifying the onco-driver fusion mutant of ALK kinase and its inhibitor crizotinib commercially termed as Xalkori has brought significant benefit to a portion of non-small cell lung cancer (NSCLC) patients. However, a number of clinical issues in ALK-positive lung cancer remain, involving resistance to crizotinib caused by secondary mutation, amplification of the ALK gene, activation of alternative pathways, and metastatic resistance, etc. Among these mechanisms, brain metastasis is a critical issue because of its poor prognosis. We have recently identified ASP3026 as a novel type of ALK inhibitor under development, and have reported that ASP3026 shows antitumor activities in several crizotinib-refractory models including gate keeper mutants. Here, we report the first PET imaging of an ALK inhibitor using [11C]ASP3026. The study has revealed that ASP3026 shows a brain tumor permeability in an intracranial xenograft model of H2228-luc ALK fusion positive cells. In this model, significant growth inhibition of H2228 intracranial tumor was observed by treatment with ASP3026 (10 mg/kg, q.d.), but not with crizotinib (10 mg/kg, q.d.) as determined by a bioluminescent imaging technique. Pharmacokinetic measurements of ASP3026 and crizotinib indicated that ASP3026 showed a four-fold better brain penetration than crizotinib on AUC0-24 base analysis, with a brain/plasma ratio=0.72 and 0.18 for ASP3026 and crizotinib, respectively. Further, we synthesized positron-labeled [11C]ASP3026 and performed PET imaging to clarify penetration of ASP3026 into cranial tumors. Quantitative analysis of [11C]ASP3026-PET data indicated that ASP3026 showed higher uptake into cranial tumors (SUV=3.0) than brain parenchyma (SUV=0.8). Moreover, comparison of pharmacokinetic profiles in several tumor models showed that tumor uptake of ASP3026 was higher than that of surrounding tissue, suggesting that tumor accumulation of ASP3026 was dependent on the microenvironment of tumor. Taken together, these results suggest that ASP3026 has favorable properties that may be useful for the treatment of brain metastases in ALK-positive NSCLC patients. Thus, PET imaging using 11C-labeled ASP3026 may allow the tumor penetration of ASP3026 to be clarified in any primary or metastatic tumor site. Citation Format: Hiroshi Fushiki, Rika Saito, Makoto Jitsuoka, Itsuro Shimada, Yutaka Kondoh, Hideki Sakagami, Yukiko Funatsu, Akihiro Noda, Yoshihiro Murakami, Sousuke Miyoshi, Yoko Ueno, Satoshi Konagai, Takatoshi Soga, Shintaro Nishimura, Masamichi Mori, Sadao Kuromitsu. First demonstration of in vivo PET imaging for ALK inhibitor using [11C]ASP3026, a novel brain-permeable type of ALK inhibitor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2678. doi:10.1158/1538-7445.AM2013-2678

Abstract 918: ASP3026, a selective ALK inhibitor, shows anti-tumor activity in a mouse model xenografted with NCI-H2228 intracranially.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC EML4-ALK translocation has been validated as a therapeutic target in a subset of non-small cell lung cancer (NSCLC) patients. Crizotinib, an FDA-approved ALK inhibitor, is effective against several types of human cancers with ALK abnormalities including EML4-ALK, RANBP2-ALK and ALK mutations. However, long-term treatment is often limited by the development of resistant tumors and distant metastases. Multiple brain metastases are a critical issue because of their poor prognosis despite the standard radiotherapy. The reason for metastases and development of tumor in the brain could be attributable to the poor penetration of crizotinib into central nervous system, as previously reported. ASP3026 is a selective ALK inhibitor which shows antitumor activities in several crizotinib-refractory models including gate keeper mutants. Here, we established an intracranial xenograft model by implanting NCI-H2228 cells directly in the brain of immunocompromised mice. Xenografted cells develop intracranial tumors which grow in murine brain and eventually become lethal, resembling the clinical tumors that metastasized in the brain. To determine the anti-tumor activity against tumors in the brain, mice were treated with ASP3026 or crizotinib for 2 weeks and held to observe survival duration. Ten, 30 and 100 mg/kg daily oral administration of ASP3026 dose dependently inhibited tumor growth in brain, and tumor regression was achieved in 30 and 100 mg/kg groups confirmed by MR imaging. These results were supported by the observation that Ktrans and IAUC (90s) were significantly decreased in 30 and 100 mg/kg groups using dynamic contrast enhanced MR imaging (DCE-MRI). Furthermore, ASP3026 significantly prolonged the survival of tumor bearing mice compared to vehicle treatment group. On the other hand, 30mg/kg daily oral administration of crizotinib inhibited the tumor growth during the treatment period but did not produce significant survival benefit. Taken together, these results indicate that ASP3026 shows better efficacy than crizotinib and improves overall survival in an intracranial mouse xenograft model, suggesting that ASP3026 may have potential to benefit EML4-ALK positive NSCLC patients with brain metastases. Citation Format: Satoshi Konagai, Hiroshi Fushiki, Hideki Sakagami, Yoko Ueno, Masamichi Mori, Itsuro Shimada, Yutaka Kondoh, Sousuke Miyoshi, Shintaro Nishimura, Sadao Kuromitsu. ASP3026, a selective ALK inhibitor, shows anti-tumor activity in a mouse model xenografted with NCI-H2228 intracranially. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 918. doi:10.1158/1538-7445.AM2013-918