Darexaban: anticoagulant effects in mice and human plasma in vitro, antithrombotic effects in thrombosis and bleeding models in mice and effects of anti-inhibitor coagulant complex and recombinant factor VIIa.

Here, we investigated the anticoagulant effects of darexaban in mice and human plasma in vitro, effects of darexaban in thrombosis and bleeding models in mice, and reversal effects of anti-inhibitor coagulant complex (ACC) and recombinant factor VIIa (rFVIIa) on anticoagulant effects of darexaban. In mice, darexaban inhibited FXa activity in plasma with an ED50 value of 24.8 mg/kg. Both darexaban and warfarin prolonged prothrombin time (PT) at 3 mg/kg and 0.3 mg/kg/day, respectively. PT and activated partial thromboplastin time (aPTT) prolonged by darexaban were dose-dependently reversed by intravenously-administered rFVIIa, significantly so at 1 mg/kg. In a pulmonary thromboembolism (PE) mouse model, both darexaban and warfarin dose-dependently reduced the mortality rate, significantly so at 10 mg/kg and 3 mg/kg/day, respectively. In a FeCl3-induced venous thrombosis (VT) mouse model, darexaban (0.3-10 mg/kg) dose-dependently decreased the thrombus protein content, significantly so at doses of 3 mg/kg or higher. In a tail-transection mouse model, darexaban had no significant effect on the amount of blood loss at doses up to 10 mg/kg, while warfarin showed a dose-dependent increase in blood loss, significantly so from 1 mg/kg/day. Darexaban and its metabolite darexaban glucuronide significantly prolonged PT and aPTT in human plasma in vitro, and while rFVIIa concentration-dependently reversed the prolonged PT in this plasma, ACC dose-dependently reversed both PT and aPTT changes prolonged by darexaban. Taken together, these results suggest that darexaban has a potential to be an oral anticoagulant with a better safety profile than warfarin, and that rFVIIa and ACC may be useful as antidotes to darexaban in cases of overdose.

Antithrombotic and anticoagulant effects of direct factor Xa inhibitor darexaban in rat and rabbit models of venous thrombosis.

The oral direct factor Xa inhibitor darexaban administered intraduodenally prevented venous thrombus formation in both rats and rabbits with no effect on bleeding. The indirect parenteral Factor Xa inhibitor fondaparinux exerted similar properties, only prolonging bleeding time at extremely high doses. In contrast, the thrombin inhibitor ximelagatran and low-molecular-weight heparin enoxaparin prolonged bleeding time at antithrombotic doses. Studies using human platelets showed darexaban glucuronide, a darexaban metabolite that predominantly determines darexaban antithrombotic effects in vivo, had no effect on platelet activation and aggregation, while heparin and enoxaparin activated platelets. Melagatran, heparin, and enoxaparin all inhibited thrombin-induced platelet aggregation at clinically relevant concentrations. Taken together, these results suggest that thrombin-inhibiting drugs may increase the risk of bleeding, while darexaban may have potential as an orally available antithrombotic agent with a wide therapeutic window.

Synergism between interleukin-11 and bone morphogenetic protein-2 in the healing of segmental bone defects in a rabbit model.

Recombinant human interleukin-11 (rHuIL-11) and recombinant human bone morphogenetic protein-2 (rHuBMP-2) have been shown to act synergistically in the induction of osteoblast differentiation. To determine whether these two proteins can be used clinically in fracture healing and reconstructive surgery, we investigated whether rHuIL-11 and rHuBMP-2 act synergistically to heal segmental bone defects in a rabbit model. A 1.5-cm segmental defect was created in the right ulnar diaphysis of 20 Japanese white rabbits. Polylactic-co-glycolic acid (PLGA)-coated gelatin sponges (PGS) permeated with rHuBMP-2 (n = 8), rHuIL-11 plus rHuBMP-2 (n = 8), or rHuIL-11 (n = 4) were implanted into the bone defects. Radiographs were scored by two independent observers for bone formation and union rates after 2, 3, 4, and 8 weeks. Bone formation was higher in rabbits implanted with rHuBMP-2 plus rHuIL-11 than in those implanted with rHuBMP-2 alone, reaching statistical significance after 4 weeks. At early time points, the union rate in rabbits implanted with rHuBMP-2 plus rHuIL-11 was higher than in rabbits implanted with rHuBMP-2. At 2, 4, and 8 weeks, new bone volume was significantly higher in rabbits administered rHuIL-11 plus rHuBMP-2 than in those given rHuBMP-2 alone. In contrast, mechanical testing after 8 weeks showed that bone strength in the two groups of rabbits was equivalent. These findings show that rHuIL-11 and rHuBMP-2 act synergistically to accelerate bone formation without affecting bone strength. Treatment with a combination of rHuIL-11 and rHuBMP-2 may thus be of great benefit in fracture healing and for patients undergoing reconstructive surgery.

Interleukin-11 acts synergistically with bone morphogenetic protein-2 to accelerate bone formation in a rat ectopic model.

We previously demonstrated that recombinant human interleukin-11 (rHuIL-11) induced osteoblast differentiation of C3H10T1/2 progenitor cells and also acted synergistically with recombinant human bone morphogenetic protein-2 (rHuBMP-2) in performing the same function. In this study, we investigated the effect of rHuIL-11 and rHuBMP-2 on bone formation in a rat ectopic model. When placed in rats, implants consisting of polymer-coated gelatin sponges containing various concentrations of rHuBMP-2 showed a dose-dependent increase in calcium content. This was confirmed by radiographic analysis of the implants. Although implants containing rHuIL-11 alone did not accumulate calcium, implants containing a combination of rHuBMP-2 and rHuIL-11 had significantly higher calcium levels than those containing rHuBMP-2 alone. This increase was rHuIL-11 dose dependent. The synergistic effect of 20 micrograms rHuIL-11 and 6 micrograms rHuBMP-2 on bone formation was estimated to be 1 week in advance of that of 6 micrograms rHuBMP-2 alone. Histologic examination revealed that the combination of rHuIL-11 and rHuBMP-2 caused spindle cells to accumulate around implants and induced cell infiltration into implants. Bone formation occurred faster in implants with the combination of rHuIL-11 and rHuBMP-2 compared with rHuBMP-2 alone. These results suggest that rHuIL-11 acts synergistically with rHuBMP-2 to more rapidly stimulate bone formation compared with rHuBMP-2 alone. This novel combined therapy may be of great clinical benefit in bone healing.

Effects of interleukin-11 on the hematopoietic action of granulocyte colony-stimulating factor.

Interleukin-11 (IL-11, CAS 145941-26-0) is a cytokine that ameliorates thrombocytopenia induced by chemotherapy. Granulocyte colony-stimulating factor (G-CSF) is frequently used clinically as an adjuvant therapy to ameliorate neutropenia. In this study, it has been investigated whether IL-11 influences the hematopoietic action of G-CSF in vitro. IL-11 alone did not stimulate CFU-Meg colony formation in the absence of interleukin-3 (IL-3), but did in the presence of IL-3. However, IL-11 alone stimulated the formation of CFU-E, BFU-E and CFU-GM colonies, which were further enhanced by IL-3. G-CSF alone stimulated in a concentration dependent manner colony formation of CFU-GM and CFU-E, but not BFU-E or CFU-Meg. The addition of IL-11 enhanced the stimulatory effect of G-CSF on CFU-GM colony formation, and enabled G-CSF to stimulate colony formation of BFU-E, but not CFU-E. The addition of IL-3 further enhanced the stimulatory effect of G-CSF on CFU-E, BFU-E, and CFU-GM colony formation. However, G-CSF was unable to stimulate CFU-Meg colony formation for any of the cytokine combinations tested. These studies demonstrate that IL-11 has significant stimulatory effects on G-CSF-induced CFU-GM colony formation, suggesting that the therapeutic combination of the two growth factors could be beneficial for the treatment of myelosuppression induced by chemotherapy.

Recombinant human interleukin-11 improved carboplatin-induced thrombocytopenia without affecting antitumor activities in mice bearing Lewis lung carcinoma cells.

PURPOSE: Interleukin-11 (IL-11) is a stromal cell derived multifunctional cytokine, which plays important roles in the hematopoietic and nonhematopoietic systems. Recombinant human IL-11 (rhIL-11) is used in the treatment of chemotherapy-induced thrombocytopenia. We have investigated the effects of rhIL-11 on the antitumor activity of chemotherapeutic agents and on thrombocytopenia in myelosuppressed mice bearing tumor cells. METHODS: We tested the effect of rhIL-11 on Lewis lung carcinoma (LLC) cell proliferation when used alone or in combination with three antitumor agents in vitro. Also, a newly developed chemotherapy-induced myelosuppressed mice model bearing LLC cells was used to study the effects of rhIL-11 on the antitumor activity and on thrombocytopenia. RESULTS: On its own, rhIL-11 (1-100 ng/ml) did not stimulate cell proliferation, and did not alter the antitumor activities of carboplatin, mitomycin C, or etoposide in vitro. In mice implanted with LLC cells (1 x 10(4)), carboplatin (50 mg/kg/day for 2 consecutive days, i.p.) inhibited tumor growth and caused thrombocytopenia. Treatment with rhIL-11 (500 microg/kg/day, from the day following the last dosing with carboplatin for 14 days, s.c.) successfully prevented thrombocytopenia without affecting the antitumor activity of carboplatin. With rhIL-11 there was no obvious effect on the red blood cell count, white blood cell count, or body weight. CONCLUSION: These results support the assertion that rhIL-11 may be a significant therapeutic agent for thrombocytopenia following cancer chemotherapy, and that it need be associated with little fear of tumor proliferation.