Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) are severe complications of dengue virus (DV) infection. However, the pathogenesis of hemorrhage induced by dengue virus infection is poorly understood. Since endothelial cells play a pivotal role in the regulation of hemostasis, we studied the effect of DV infection on the production of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) in vitro using both primary isolated endothelial cells, human umbilical cord veins cells, and a human microvascular endothelial cell line. DV infection significantly induced the secretion of tPA but not PAI-1 of human endothelial cells. In addition, tPA mRNA of endothelial cells was induced by DV as demonstrated by RT-PCR. Antibody against IL-6 but not control antibody inhibited DV-induced tPA production of endothelial cells. Furthermore, a good correlation between sera levels of IL-6 and tPA was found in DHF but not DF patients. These results suggest that IL-6 can regulate DV-induced tPA production of endothelial cells, which may play important roles in the pathogenic development of DHF/DSS.

Interaction between chemokine stromal cell-derived factor 1 and the CXC chemokine receptor 4 (CXCR4) governs the sequestration and mobilization of bone marrow stem cells. We investigated the therapeutic potential of TG-0054, a novel CXCR4 antagonist, in attenuating cardiac dysfunction after myocardial infarction (MI). In miniature pigs (minipigs), TG-0054 mobilized CD34(+)CXCR4(+), CD133(+)CXCR4(+), and CD271(+)CXCR4(+) cells into peripheral circulation. After isolation and expansion, TG-0054-mobilized CD271(+) cells were proved to be mesenchymal stem cells (designated CD271-MSCs) since they had trilineage differentiation potential, surface markers of MSCs, and immunosuppressive effects on allogeneic lymphocyte proliferation. MI was induced in 22 minipigs using balloon occlusion of the left anterior descending coronary artery, followed by intravenous injections of 2.85 mg/kg of TG-0054 or saline at 3 days and 7 days post-MI. Serial MRI analyses revealed that TG-0054 treatment prevented left ventricular (LV) dysfunction at 12 weeks after MI (change of LV ejection fraction from baseline, -1.0 ± 6.2% in the TG-0054 group versus -7.9 ± 5.8% in the controls). The preserved cardiac function was accompanied by a significant decrease in the myocardial expression of TNF-α, IL-1β, and IL-6 at 7 days post-MI. Moreover, the plasma levels of TNF-α, IL-1β, and IL-6 were persistently suppressed by the TG-0054 treatment. Infusion of TG-0054-mobilized CD271-MSCs reduced both myocardial and plasma cytokine levels in a pattern, which is temporally correlated with TG-0054 treatment. This study demonstrated that TG-0054 improves the impaired LV contractility following MI, at least in part, by mobilizing MSCs to attenuate the postinfarction inflammation. This insight may facilitate exploring novel stem cell-based therapy for treating post-MI heart failure.

CXCR4 antagonists (e.g., Plerixafor ) have been successfully validated as stem cell mobilizers for peripheral blood stem cell transplantation. Applications of the CXCR4 antagonists have heralded the era of cell-based therapy and opened a potential therapeutic horizon for many unmet medical needs such as kidney injury, ischemic stroke, cancer, and myocardial infarction. In this review, we first introduce the central role of CXCR4 in diverse cellular signaling pathways and discuss its involvement in several disease progressions. We then highlight the molecular design and optimization strategies for targeting CXCR4 from a large number of case studies, concluding that polyamines are the preferred CXCR4-binding ligands compared to other structural options, presumably by mimicking the highly positively charged natural ligand CXCL12. These results could be further justified with computer-aided docking into the CXCR4 crystal structure wherein both major and minor subpockets of the binding cavity are considered functionally important. Finally, from the clinical point of view, CXCR4 antagonists could mobilize hematopoietic stem/progenitor cells with long-term repopulating capacity to the peripheral blood, promising to replace surgically obtained bone marrow cells as a preferred source for stem cell transplantation.

3542 Poster Board III-479 Background The interaction between SDF-1 and its receptor, CXCR4, is responsible for retaining of stem cells in the bone marrow. CXCR4 antagonist disrupts the SDF-1/CXCR4 interaction and mobilizes CD34+ hematopoietic stem cells (CD34+ HSCs) and CD133+ endothelial progenitor cells (CD133+ EPCs) from bone marrow into circulation, which can be used as a source for stem cell transplantation and other potential clinical indications. TG-0054 is a novel CXCR4 antagonist. In vitro CXCR4 antagonistic activity and in vivo stem cell mobilization activity of TG-0054 were determined in this study. Materials and Methods In vitro pharmacological assays, including GTP-binding assay, calcium mobilization assay, and chemotaxis assays, were performed to assess the potency of TG-0054 as a CXCR4 antagonist. In addition, receptor-binding assays against a panel of human chemokine receptors as well as other 68 cellular receptors were screened to evaluate the specificity of TG-0054. Kinetics and dose-dependent response of stem cell mobilization by TG-0054 were demonstrated in BALB/c mice. Activity of stem cell mobilization of TG-0054 when used alone or combined with G-CSF was also studied. Results TG-0054 blocked SDF-1-binding to CXCR4 receptor with an IC50 of 10 nM and inhibited SDF-1–induced GTP-binding (IC50 = 6 nM), chemotaxis (IC50 = 43 nM), and calcium mobilization (IC50 = 59 nM). TG-0054 showed greater than 3000-fold selectivity for CXCR4 receptor over other chemokine receptors. It is noteworthy that the IC50 for the inhibitory effect of TG-0054 on hERG potassium currents was greater than 1000 μM when human embryonic kidney (HEK) cells were used to examine the in vitro effects on the hERG potassium channel currents. In animal studies, TG-0054 rapidly and effectively mobilized CD34+ HSCs and CD133+ EPCs into circulation. Single intravenous (IV) administration of TG-0054 resulted in a rapid increase of total white blood cell (WBC) counts, as well as CXCR4+, CD34+, and CD133+ cells in peripheral blood between 1–3 hour post-injection and the cell counts returned to baseline within 6 hours. At their maximum tolerated doses (MTD), TG-0054 increased CXCR4+ cells by 28.7-fold in mice. Furthermore, TG-0054 efficiently mobilized CD34+ (14.5-fold) and CD133+ (7.9-fold) cells. The combined effects of TG-0054 and G-CSF on HSCs and EPCs mobilization from the bone marrow in mice were also investigated. G-CSF (100 μg/kg/day) was administered subcutaneously (SC) from Day 1 to Day 4 followed by a single IV injection of TG-0054 or AMD3100 on Day 5. Synergistic effects were observed in all cell types in mice receiving combination of G-CSF and 50 mg/kg of TG-0054 (total WBC 23.0-fold, CXCR4+ 29.0-fold, CD34+ 37.1-fold, CD133+ 110.8-fold of increase in combination group). Conclusion It was concluded that TG-0054 was a potent and selective CXCR4 antagonist intended for the use of stem cell transplant and other clinical indications. It showed strong stem cell mobilization activity comparable to G-CSF when used alone, and demonstrated synergistic effects when combined with G-CSF in a nonclinical model. Disclosures: Huang: TaiGen Biotechnology Inc.: Employment. Liu:TaiGen Biotechnology Inc.: Employment. Yen:TaiGen Biotechnology Inc.: Employment. Chen:TaiGen Biotechnology Inc.: Consultancy. Chen:TaiGen Biotechnology Inc.: Consultancy. King:TaiGen Biotechnology Inc.: Employment. Hsu:TaiGen Biotechnology, Inc.: Membership on an entity's Board of Directors or advisory committees.

866 Background: Stem cells are retained in the bone marrow via the trophic effects of the binding of chemokine stromal cell-derived factor-1α (SDF-1α) to its receptor, CXC chemokine receptor 4 (CXCR4). TG-0054 inhibits SDF-1α/CXCR4 binding and therefore mobilizes stem cells into peripheral blood. Animal studies in mice showed rapid and effective mobilization of CD34+ hematopoietic stem cells (HSCs) and CD133+ endothelial progenitor cells (EPCs) into peripheral blood after TG-0054 administration. A Phase I study was conducted in healthy volunteers to assess safety, tolerability, pharmacokinetics (PK) and stem cell mobilization of TG-0054. Materials and Methods: This is a phase I, randomized, double-blind, placebo-controlled, single ascending dose study. In each cohort, 2 volunteers received placebo and 6 received 0.10, 0.14, 0.28, 0.56, 1.12, 2.24, 3.14, or 4.40 mg/kg of TG-0054 (dose was calculated based on TG-0054 free base) via 15 minutes single IV infusion. All subjects underwent PK sampling at pre-dose, 5 and 15 minutes during infusion, and at 1, 2.5, 5, 10, 30 minutes and 1, 2, 4, 6, 9, 12, 24, 36 hours after infusion. The pharmacodynamics (PD) sampling time points were at pre-dose, 1, 2, 4, 6, 9, 24, and 36 hours after infusion. General tolerability, adverse events (AEs), electrocardiogram (ECG), vital signs and laboratory tests were recorded. Results: In this study, the maximum tolerated dose (MTD) was not reached in TG-0054 doses up to 4.40 mg/kg in healthy volunteers. Dose escalation was stopped due to plateau of mobilized CD34+ and CD133+ cell numbers. TG-0054 was well tolerated up to 4.40 mg/kg. The majority of AEs were mild in severity (53 out of 55 events), and all AEs resolved by the end of the study without medical treatment. The number of subjects reporting the most common AEs included: abdominal pain (7/64, 11%), diarrhea/loose stools (5/64, 8%), dizziness (3/64, 5%), nausea (3/64, 5%), and diaphoresis (3/64, 5%). No significant abnormalities were noted in vital signs, ECG, holter monitoring, telemetry, pulse oximetry, physical examination, or laboratory tests. The area under the plasma concentration vs. time curve (AUC0-t) and maximum plasma concentration (Cmax) showed dose proportionality over the dose range studied. The mean of terminal elimination half-life (t1/2) was approximately 2.5 to 5 hrs. Single-dose administration of 1.12 - 4.40 mg/kg of TG-0054 significantly increased CD34+ cell counts in peripheral blood. At peak time, TG-0054 caused a 3 - 14 fold increase in circulating CD34+ cells from baseline. The mean CD34+ cell counts at peak time were 27.1 ± 9.3 cells/μL (1.12 mg/kg TG-0054), 35.9 ± 27.3 cells/μL (2.24 mg/kg), 32.5 ± 27.7 cells/μL (3.14 mg/kg), and 29.2 ± 12.9 cells/μL (4.40 mg/kg). The increase in circulating CD34+ cell counts was evident within 2 hours of TG-0054 administration, peaked at 4 - 6 hours after TG-0054 administration, followed by a gradual decline to baseline at 24 hours post-dosing. Similarly, increases in WBC and CD133+ cell counts were observed in all subjects. No AEs were deemed to be associated with WBC increases. Conclusion: TG-0054 exhibited a favorable safety and PK profile in healthy subjects in this Phase I study. PD analysis also displayed potent mobilization of CD34+ HSCs and CD133+ EPCs from TG-0054 dose levels of 1.12 - 4.40 mg/kg. These results support subsequent clinical investigations. Disclosures: Chung: TaiGen Biotechnology, Inc.: Employment. Chang:TaiGen Biotechnology, Inc.: Employment. Huang:TaiGen Biotechnology, Inc.: Employment. Tsai:TaiGen Biotechnology, Inc.: Employment. Hsu:TaiGen Biotechnology, Inc.: Employment. King:TaiGen Biotechnology, Inc.: Employment. Yuan:TaiGen Biotechnology, Inc.: Employment. Yen:TaiGen Biotechnology, Inc.: Employment. Chen:TaiGen Biotechnology, Inc.: Employment. Lu:TaiGen Biotechnology, Inc.: Employment. Hsu:TaiGen Biotechnology, Inc.: Membership on an entity's Board of Directors or advisory committees.