Bosentan for the treatment of adult pulmonary hypertension

Comparative Treatment Persistence and Adherence to Endothelin Receptor Antagonists Among Patients with Pulmonary Arterial Hypertension in Japan: A Real-World Administrative Claims Database Study

INTRODUCTION

Real-world data on the comparative effectiveness of endothelin receptor antagonists (ERAs; macitentan, bosentan, ambrisentan) for pulmonary arterial hypertension (PAH), particularly in Asian countries, are scarce. We evaluated the persistence of these ERAs before and after macitentan approval in Japan (2015).

METHODS

We used real-world data from the Japanese Medical Data Vision administrative claims database between April 2008 and November 2020. Patients with PAH were identified from the dataset. Persistence to ERA treatment before and after approval of macitentan in Japan was defined as the time between start of the index ERA and treatment discontinuation or death. Propensity score adjustment was applied to minimize confounding effects among treatment groups.

RESULTS

In the pre-macitentan approval cohort, 153 and 51 patients received bosentan and ambrisentan, respectively. In the post-macitentan approval cohort, 331, 284, and 91 patients received macitentan, bosentan, and ambrisentan, respectively. Unadjusted median persistence for ambrisentan- and bosentan-treated patients was 19 and 10 months, respectively (adjusted HR 0.87 [95% CI 0.61-1.24]; P = 0.434 [bosentan as reference]). In the post-macitentan approval cohort, unadjusted median persistence was 18 months for macitentan-treated patients versus 6 and 8 months for ambrisentan- and bosentan-treated patients, respectively. Adjusted HRs for ambrisentan and bosentan were 1.48 (95% CI 1.12-1.95; P = 0.006) and 1.63 (95% CI 1.30-2.04; P < 0.001 [macitentan as reference]), respectively.

CONCLUSIONS

Real-world data for Japanese patients with PAH showed that persistence was significantly higher for macitentan, versus ambrisentan and bosentan, since its approval.

Cardioprotective effects of bosentan in 5-fluorouracil-induced cardiotoxicity

5-fluorouracil (5-FU) is a widely used chemotherapeutic agent but cardiotoxicity challenges its clinical usefulness. Thus, searching for more cardioprotective drugs is highly required to prevent the accompanied cardiac hazards. Up to date, the different mechanisms involved in 5-FU cardiotoxicity are still unclear and there is no evaluation of bosentan's role in controlling these cardiac complications. This forced us to deeply study and evaluate the possible cardiopreserving properties of bosentan and different mechanisms involved in mediating it. 32 Wistar albino rats were included in our experiment and induction of cardiotoxicity was performed via administration of 5-FU (150 mg/kg) on 5th day of the experiment by intraperitoneal (i.p.) injection with or without co-administration of bosentan (50 mg/kg/day) orally for 7days. Our data revealed that 5-FU could induce cardiotoxicity which was detected as significant increases of troponin I, lactate dehydrogenase (LDH), creatine kinase- MB (CK-MB), endothelin receptors, malondialdehyde (MDA), toll like receptor4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor kappa B (NFκB), and caspase 3 levels. However, there is marked decrease in endothelial nitric oxide synthase (eNOS), reduced glutathione (GSH) and total antioxidant capacity (TAC). In addition, the histopathological examination showed severe toxic features of cardiac injury. Interestingly, co-administration of bosentan could ameliorate 5-FU-induced cardiotoxicity via improving the detected biochemical and histopathological changes besides modulation of TLR4/MyD88/NFκB signaling pathway, eNOS, and endothelin receptors. Bosentan had a significant cardioprotective effect against 5-FU induced cardiac damage. This effect may be attributed to its ability to inhibit endothelin receptors, stimulates eNOS, anti-oxidant, anti-inflammatory, anti-apoptotic properties with modulation of TLR4/MyD88/NFκB signaling pathway.

Repurposing of the PDE5 Inhibitor Sildenafil for the Treatment of Persistent Pulmonary Hypertension in Neonates

Nitric oxide (NO), an important endogenous signaling molecule released from vascular endothelial cells and nerves, activates the enzyme soluble guanylate cyclase to catalyze the production of cyclic guanosine monophosphate (cGMP) from guanosine triphosphate. cGMP, in turn, activates protein kinase G to phosphorylate a range of effector proteins in smooth muscle cells that reduce intracellular Ca²⁺ levels to inhibit both contractility and proliferation. The enzyme phosphodiesterase type 5 (PDE5) curtails the actions of cGMP by hydrolyzing it into inactive 5'-GMP. Small molecule PDE5 inhibitors (PDE5is), such as sildenafil, prolong the availability of cGMP and therefore, enhance NO-mediated signaling. PDE5is are the first-line treatment for erectile dysfunction but are also now approved for the treatment of pulmonary arterial hypertension (PAH) in adults. Persistent pulmonary hypertension in neonates (PPHN) is currently treated with inhaled NO, but this is an expensive option and around 1/3 of newborns are unresponsive, resulting in the need for alternative approaches. Here the development, chemistry and pharmacology of PDE5is, the use of sildenafil for erectile dysfunction and PAH, are summarized and then current evidence for the utility of further repurposing of sildenafil, as a treatment for PPHN, is critically reviewed.

Atrial Arrhythmias in Pulmonary Hypertension: Pathogenesis, Prognosis and Management

Atrial arrhythmias, including atrial fibrillation and atrial flutter, are common in patients with pulmonary hypertension and are closely associated with clinical decompensation and poor clinical outcomes. The mechanisms of arrhythmogenesis and subsequent clinical decompensation are reviewed. Practical implications and current evidence for the management of atrial arrhythmias in patients with pulmonary hypertension are summarised.

Pulmonary arterial hypertension: basis of sex differences in incidence and treatment response

Pulmonary arterial hypertension (PAH) is a complex disease characterized by elevated pulmonary arterial pressure, pulmonary vascular remodelling and occlusive pulmonary vascular lesions, leading to right heart failure. Evidence from recent epidemiological studies suggests the influence of gender on the development of PAH with an approximate female to male ratio of 4:1, depending on the underlying disease pathology. Overall, the therapeutic strategy for PAH remains suboptimal with poor survival rates observed in both genders. Endogenous sex hormones, in particular 17β oestradiol and its metabolites, have been implicated in the development of the disease; however, the influence of sex hormones on the underlying pathobiology remains controversial. Further understanding of the influence of sex hormones on the normal and diseased pulmonary circulation will be critical to our understanding the pathology of PAH and future therapeutic strategies. In this review, we will discuss the influence of sex hormones on the development of PAH and address recent controversies.

Ambrisentan and tadalafil synergistically relax endothelin-induced contraction of rat pulmonary arteries

Endothelin receptor antagonists and phosphodiesterase type 5 inhibitors are used to treat pulmonary arterial hypertension. We tested the hypothesis that a selective endothelin type A receptor antagonist (ambrisentan) and a phosphodiesterase type 5 inhibitor (tadalafil) may act synergistically to relax endothelin-constricted pulmonary arteries. Rat isolated intrapulmonary arterial rings contracted with 8 nmol/L endothelin-1 were relaxed by 10 nmol/L ambrisentan and 30 nmol/L tadalafil alone by 26±3% and 21±1%, respectively, whereas both drugs in combination acted synergistically to relax arterial rings by 83±6%. The nonselective endothelin type A and B receptor antagonists bosentan (100 nmol/L) and macitentan (30 nmol/L) alone relaxed endothelin-contracted rings by 30±5% and 24±3%, respectively. Combinations of 30 nmol/L tadalafil with 100 nmol/L bosentan or 30 nmol/L macitentan relaxed endothelin-contracted rings by 53±5% or 46±7%, respectively; these values are similar to the calculated sums of the individual effects of these compounds. Denudation of endothelium from pulmonary arterial rings abolished the vasodilator response to 30 nmol/L tadalafil and the synergistic vasorelaxant effect of tadalafil with ambrisentan. In the presence of 1 μmol/L BQ-788, a selective endothelin type B receptor antagonist, the vasorelaxant effects of 10 nmol/L ambrisentan and 30 nmol/L tadalafil were additive but not synergistic. These data can be interpreted to suggest that ambrisentan and tadalafil synergistically inhibit endothelin-1-induced constriction of rat intrapulmonary arteries and that endothelin type B receptors in endothelium are necessary to enable a synergistic vasorelaxant effect of the drug combination.