Vardenafil (Levitra) is an oral therapy for the treatment of erectile dysfunction. It is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Penile erection is a hemodynamic process initiated by the relaxation of smooth muscle in the corpus cavernosum and its associated arterioles. During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates the enzyme guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The cGMP in turn triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. The tissue concentration of cGMP is regulated by both the rates of synthesis and degradation via phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMPspecific phosphodiesterase type 5 (PDE5); therefore, the inhibition of PDE5 enhances erectile function by increasing the amount of cGMP.

Dexniguldipine (B8509-035, (-)-(R)-niguldipine) is a new dihydropyridine derivative, that exerts selective antiproliferative activity in a variety of tumor models and, in addition, has a high potency in overcoming multidrug resistance. Dexniguldipine is ( - )-(R)-enantiomer of niguldipine, of which the ( )-(S)-enantiomer shows pronounced cardiovascular hypotensive activity due to its high affinity for the voltage-dependent Ca2 channel. As compared with the (S)-enantiomer, the (R)-enantiomer has a 40-fold lower affinity for the Ca 2 channel and, accordingly, only minimal hypotensive activity in animal pharmacology models. Dexniguldipine have shown antiproliferative activity in several tumor cell lines, but the concentrations necessary to inhibit growth have varied by several orders of magnitude between cell lines. Initial results of preclinical investigations for the evaluation of the mechanism of its antiproliferative activity demonstrate that dexniguldipine interferes with intracellular signal transduction by affecting phosphoinositol pathways, protein kinase C expression, and intracellular Ca 2 metabolism. In a series of human tumor xenografts in vitro, dexniguldipine demonstrated selective antiproliferative activity against several tumor types, e.g., melanoma and renal-cell carcinoma. Striking results were obtained in a hamster model, in which neuroendocrine lung tumors could be completely eradicated by 20 weeks of oral treatment with 32.5mg/kg dexniguldipine, whereas Clara-cell-type lung tumors were not affected. In in vitro studies, dexniguldipine has been found to bind to P-glycoprotein (P-gp) and to enhance the cytotoxicity of chemotherapeutic agents such as doxorubicin and etoposide in several cell lines The synergistic effect may well be associated with the reversal of multidrug resistance (MDR) related to the activity of P-gp. In the clinical therapy of cancer, resistance to many cytostatic drugs is a major cause of treatment failure. However, the high potency of dexniguldipine (about 10-fold as compared with that of verapamil in vitro) and its low cardiovascular activity provide the opportunity to achieve blood or tumor concentrations that might be high enough to overcome Mdr 1 resistance in patients without producing dose-limiting cardiovascular effects.

Vardenafil (Levitra) is an oral therapy for the treatment of erectile dysfunction. It is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Penile erection is a hemodynamic process initiated by the relaxation of smooth muscle in the corpus cavernosum and its associated arterioles. During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates the enzyme guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The cGMP in turn triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. The tissue concentration of cGMP is regulated by both the rates of synthesis and degradation via phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMPspecific phosphodiesterase type 5 (PDE5); therefore, the inhibition of PDE5 enhances erectile function by increasing the amount of cGMP.

Vardenafil (Levitra) is an oral therapy for the treatment of erectile dysfunction. It is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Penile erection is a hemodynamic process initiated by the relaxation of smooth muscle in the corpus cavernosum and its associated arterioles. During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates the enzyme guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The cGMP in turn triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. The tissue concentration of cGMP is regulated by both the rates of synthesis and degradation via phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMPspecific phosphodiesterase type 5 (PDE5); therefore, the inhibition of PDE5 enhances erectile function by increasing the amount of cGMP.

Vardenafil (Levitra) is an oral therapy for the treatment of erectile dysfunction. It is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Penile erection is a hemodynamic process initiated by the relaxation of smooth muscle in the corpus cavernosum and its associated arterioles. During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates the enzyme guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The cGMP in turn triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. The tissue concentration of cGMP is regulated by both the rates of synthesis and degradation via phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMPspecific phosphodiesterase type 5 (PDE5); therefore, the inhibition of PDE5 enhances erectile function by increasing the amount of cGMP.

Dexniguldipine (B8509-035, (-)-(R)-niguldipine) is a new dihydropyridine derivative, that exerts selective antiproliferative activity in a variety of tumor models and, in addition, has a high potency in overcoming multidrug resistance. Dexniguldipine is ( - )-(R)-enantiomer of niguldipine, of which the ( )-(S)-enantiomer shows pronounced cardiovascular hypotensive activity due to its high affinity for the voltage-dependent Ca2 channel. As compared with the (S)-enantiomer, the (R)-enantiomer has a 40-fold lower affinity for the Ca 2 channel and, accordingly, only minimal hypotensive activity in animal pharmacology models. Dexniguldipine have shown antiproliferative activity in several tumor cell lines, but the concentrations necessary to inhibit growth have varied by several orders of magnitude between cell lines. Initial results of preclinical investigations for the evaluation of the mechanism of its antiproliferative activity demonstrate that dexniguldipine interferes with intracellular signal transduction by affecting phosphoinositol pathways, protein kinase C expression, and intracellular Ca 2 metabolism. In a series of human tumor xenografts in vitro, dexniguldipine demonstrated selective antiproliferative activity against several tumor types, e.g., melanoma and renal-cell carcinoma. Striking results were obtained in a hamster model, in which neuroendocrine lung tumors could be completely eradicated by 20 weeks of oral treatment with 32.5mg/kg dexniguldipine, whereas Clara-cell-type lung tumors were not affected. In in vitro studies, dexniguldipine has been found to bind to P-glycoprotein (P-gp) and to enhance the cytotoxicity of chemotherapeutic agents such as doxorubicin and etoposide in several cell lines The synergistic effect may well be associated with the reversal of multidrug resistance (MDR) related to the activity of P-gp. In the clinical therapy of cancer, resistance to many cytostatic drugs is a major cause of treatment failure. However, the high potency of dexniguldipine (about 10-fold as compared with that of verapamil in vitro) and its low cardiovascular activity provide the opportunity to achieve blood or tumor concentrations that might be high enough to overcome Mdr 1 resistance in patients without producing dose-limiting cardiovascular effects.