Preclinical study of the long-range safety and anti-inflammatory effects of high-dose oral meglumine

Meglumine is a methylamino derivative of sorbitol that is an approved drug excipient. Recent preclinical studies suggest that administration of high-dose oral meglumine can exert beneficial medicinal effects to treat diabetes, obesity, and fatty liver disease (NAFLD/nonalcoholic steatohepatitis [NASH]). Here we address gaps in knowledge about the pharmacology and toxicology of this substance administered at high concentrations to explore its medicinal potential. We observed that high-dose meglumine limited secretion of proinflammatory cytokines and cell adhesion molecules from activated human THP-1 or murine RAW264.7 monocytes. Preclinical pharmacokinetic analysis in Swiss mice confirmed that meglumine was orally available. Informed by this data, oral doses of 18 to 75 mM meglumine were administered ad libitum in the drinking water of Sprague-Dawley rats and two cohorts of C57BL/6 mice housed in different vivariums. In a 32-week study, urinary isoprostane levels trended lower in subjects consistent with the possibility of anti-inflammatory effects. In full lifespan studies, there was no detrimental effect on longevity. Heart function evaluated in C57BL/6 mice using an established noninvasive cardiac imaging system showed no detrimental effects on ejection fraction, fractional shortening, left ventricle function or volume, and cardiac output in mice up to 15-month old, with a potential positive trend in heart function noted in elderly mice consistent with earlier reported benefits on muscle stamina. Finally, in a transgenic model of inflammation-associated skin carcinogenesis, the incidence, number, and growth of skin tumors trended lower in subjects receiving meglumine. Overall, the evidence obtained illustrating the long-range safety of high-dose oral meglumine support the rationale for its evaluation as a low-cost modality to limit diabetes, hypertriglyceridemia, and NAFLD/NASH.

Thrombin inhibition and cisplatin block tumor progression in ovarian cancer by alleviating the immunosuppressive microenvironment

Cancer is often associated with an increased risk of thrombotic complications which can be aggravated by treatment with chemotherapeutics such as cisplatin. Multiple lines of evidence suggest that thrombin activity promotes tumor growth and metastasis. We examined the effect of co-treatment with dabigatran etexilate, a direct thrombin inhibitor, and cisplatin using the murine ID8 ovarian cancer model. Mice receiving co-treatment with both dabigatran etexilate and low dose cisplatin had significantly smaller tumors, developed less ascites and had lower levels of circulating activated platelets and tissue factor (TF) positive microparticles than those treated with dabigatran etexilate or cisplatin alone. Co-treatment with dabigatran etexilate and cisplatin significantly decreased the number of Gr1+/CD11b+ myeloid derived suppresser cells and CD11b+/CD11c+ dendritic cells in the ascites of ID8 tumor-bearing mice. Co-treatment also significantly reduced levels of pro-tumorigenic cytokines including TGF-β, VEGF, IL-6, IL-10, and MCP-1 in the ascites while increasing IFN-γ production by CD8+ effector T cells in the tumor ascites. These results demonstrate that co-treatment with dabigatran etexilate significantly augments the anti-tumor activity of cisplatin in ovarian tumor progression by alleviating the immunosuppressive microenvironment, suggesting that thrombin may be a potential therapeutic target for treatment of ovarian cancer.

Thrombin inhibition and cyclophosphamide synergistically block tumor progression and metastasis

Cancer is often associated with an increased risk of thrombotic events which are exacerbated by treatment with chemotherapeutics such as cyclosphosphamide (CP). Evidence suggests that thrombin can stimulate tumor progression via formation of fibrin and activation of protease-activated receptors (PARs) and platelets. We examined the effect of co-treatment with CP and dabigatran etexilate, a direct inhibitor of thrombin, using the murine orthotopic 4T1 tumor model. Mice receiving co-treatment with both low dose CP and dabigatran etexilate had significantly smaller mammary tumors and fewer lung metastases than mice treated with CP or dabigratran etexilate alone. Co-treatment with dabigatran etexilate and low dose CP also significantly decreased the number of arginase(+)Gr-1(+)CD11b(+) myeloid derived suppressor cells as well as levels of TGF-β in spleens from tumor bearing mice. 4T1 tumors express procoagulant tissue factor (TF) and spontaneously release TF(+) microparticles which are potent procoagulant factors that promote thrombin generation. Treatment with dabigatran etexilate alone prevented tumor-induced increases in circulating TF(+) microparticles and also decreased the numbers of tumor-induced activated platelets by 40%. These results show that co-treatment with dabigatran etexilate and CP synergistically inhibits growth and metastasis of mammary tumors, suggesting that oral administration of the thrombin inhibitor dabigatran etexilate may be beneficial in not only preventing thrombotic events in cancer patients but also in treating malignant tumors themselves.

Abstract 392: Synergistic anti-tumor effects of dabigatran etexilate and cyclophosphamide co-treatment are associated with decreased circulating tissue factor positive microparticles

Introduction: Coagulation proteases and the generation of thrombin are increased in tumors. The incidence of cancer-associated thromboses is also increased by treatment with chemotherapeutic agents commonly used to treat malignant cancers. Thrombin can drive cancer progression directly through the activation of protease-activated receptors and platelets or indirectly by generating fibrin matrices.

Aim: To investigate the extent to which treatment with the oral thrombin inhibitor, dabigatran etexilate (Pradaxa®) may increase the anti-tumor efficacy of a chemotherapeutic agent that promotes a pro-thrombotic state.

Materials and Methods: The effect of combined treatment with the standard chemotherapeutic agent, cyclophosphamide (CP), and dabigatran etexilate was evaluated following orthotopic injection of 4T1 mammary adenocarcinoma cells in the mammary fat pad of Balb/c mice. Treatment was initiated when 4T1 primary tumors were 25-50 mm3 in size, at 2 weeks following 4T1 tumor cell injection. Mice were treated once a week with cyclophosphamide (15-25 mg/kg, i.p.) with or without dabigatran etexilate (oral gavage, 80 mg/kg, bid or ad lib chow supplemented with dabigatran, 10 mg/g chow).

Results: Mice receiving co-treatment with both low dose CP and dabigatran etexilate had significantly smaller mammary tumors and fewer lung metastases than mice treated with CP or dabigratran etexilate alone. 4T1 tumors express procoagulant tissue factor (TF) and spontaneously release TF+ microparticles which are potent procoagulant factors that promote thrombin generation. Treatment with chemotherapeutic agents increased the number of shed TF+ microparticles from tumor cells in vitro as well as circulating TF+ microparticles in vivo. Treatment with dabigatran etexilate with or without CP attenuated the increased platelet activation seen in 4T1 tumor bearing mice by 40% and prevented tumor-induced increases in circulating TF+ microparticles. Co-treatment with dabigatran etexilate and CP also inhibited the accumulation of splenic arginase/Gr-1/CD11b positive myeloid derived suppressor cells more than either treatment alone.

Conclusion: Co-treatment with dabigatran etexilate and low dose CP synergistically inhibits the growth and metastasis of mammary tumors, and is accompanied by inhibition of platelet activation and decreased generation of circulating TF+ microparticles. These results suggest that the oral administration of the thrombin inhibitor dabigatran etexilate may be beneficial in not only preventing thrombotic events in cancer patients but also as adjunct therapy to treat malignant tumors.

(Supported by funds from Boehringer Ingelheim Pharma)

Citation Format: Eric T. Alexander, Allyson R. Minton, Candace S. Hayes, Ashley Goss, Joanne Van Ryn, Susan K. Gilmour. Synergistic anti-tumor effects of dabigatran etexilate and cyclophosphamide co-treatment are associated with decreased circulating tissue factor positive microparticles. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 392. doi:10.1158/1538-7445.AM2015-392