Therapy of pulmonary arterial hypertension in systemic sclerosis: An update

Systemic sclerosis

This review updates the clinician on the pathogenesis, differential diagnosis and spectrum of disease in systemic sclerosis. The wide range of current therapeutic options and future targeted molecular therapies are also explored.

Prediction of pulmonary hypertension related to systemic sclerosis by an index based on simple clinical observations

OBJECTIVE

To develop a score to estimate the risk of developing pulmonary hypertension (PH) in patients with systemic sclerosis (SSc).

METHODS

We first examined the prevalence and characteristics of precapillary PH confirmed by right-heart catheterization in a cross-sectional (derivation) sample of 1,165 SSc patients, and we developed a risk prediction score (RPS) based on simple clinical observations associated with PH. We next prospectively tested the 3-year predictive power of the "Cochin RPS" in a separate (validation) sample of 443 patients presenting with PH-free SSc at baseline.

RESULTS

In the derivation sample, age, forced vital capacity, and diffusing capacity for carbon monoxide/alveolar volume were independently associated with the presence of PH and were used to create the Cochin RPS. PH developed during followup in 20 patients in the validation sample. The area under the receiver operating characteristic curve of the Cochin RPS was 0.87 (95% confidence interval 0.79-0.95). With a cutoff value of 2.73, patients at risk of PH during followup could be identified with 89.5% sensitivity and 74.1% specificity. PH occurred in 0.6% of patients in the lowest 2 quintiles of the Cochin RPS, in 1.7% of patients in the third and fourth quintiles, and in 17.1% of patients in the highest quintile (P<0.0001 by log rank test). Patients in the highest quintile incurred a >35-fold higher risk of developing PH compared with patients in the 2 lowest quintiles (P=0.001).

CONCLUSION

Using routine clinical observations, we developed a simple score that accurately predicted the risk of PH in SSc.

NO-independent, haem-dependent soluble guanylate cyclase stimulators

The nitric oxide (NO) signalling pathway is altered in cardiovascular diseases, including systemic and pulmonary hypertension, stroke, and atherosclerosis. The vasodilatory properties of NO have been exploited for over a century in cardiovascular disease, but NO donor drugs and inhaled NO are associated with significant shortcomings, including resistance to NO in some disease states, the development of tolerance during long-term treatment, and non-specific effects such as post-translational modification of proteins. The development of pharmacological agents capable of directly stimulating the NO receptor, soluble guanylate cyclase (sGC), is therefore highly desirable. The benzylindazole compound YC-1 was the first sGC stimulator to be identified; this compound formed a lead structure for the development of optimized sGC stimulators with improved potency and specificity for sGC, including CFM-1571, BAY 41-2272, BAY 41-8543, and BAY 63-2521. In contrast to the NO- and haem-independent sGC activators such as BAY 58-2667, these compounds stimulate sGC activity independent of NO and also act in synergy with NO to produce anti-aggregatory, anti-proliferative, and vasodilatory effects. Recently, aryl-acrylamide compounds were identified independent of YC-1 as sGC stimulators; although structurally dissimilar to YC-1, they have a similar mode of action and promote smooth muscle relaxation. Pharmacological stimulators of sGC may be beneficial in the treatment of a range of diseases, including systemic and pulmonary hypertension, heart failure, atherosclerosis, erectile dysfunction, and renal fibrosis. An sGC stimulator, BAY 63-2521, is currently in clinical development as an oral therapy for patients with pulmonary hypertension. It has demonstrated efficacy in a proof-of-concept study, reducing pulmonary vascular resistance and increasing cardiac output from baseline. A full, phase 2 trial of BAY 63-2521 in pulmonary hypertension is underway.

CPU0213, a non-selective ETA/ETB receptor antagonist, improves pulmonary arteriolar remodeling of monocrotaline-induced pulmonary hypertension in rats

1. The aim of the present study was to explore the effects of CPU0213, a dual endothelin ET(A)/ET(B) receptor antagonist, and nifedipine, a calcium antagonist, in relieving pulmonary hypertension (PH). Both endothelin receptor and calcium antagonists have been reported to be effective in alleviating the remodelling of pulmonary arteries induced by monocrotaline (MCT) in rats. 2. After an initial single dose of 60 mg/kg, s.c., MCT, CPU0213 was administered to rats at doses of 25, 50 or 100 mg/kg, p.o., for 28 days. In addition, nifedipine was administered to another group of rats at a dose of 10 mg/kg, p.o., for 28 days. The haemodynamics of the right ventricle, pulmonary vascular activity, remodelling of the pulmonary arterioles (< 150 microm) and biochemical changes were evaluated. 3. Right ventricular systolic pressure (RVSP), central venous pressure (CVP), the maximum rate of uprising pressure (dP/dT(max)) and the weight index of the right ventricle were significantly elevated in MCT-treated rats. In addition, increases in pulmonary endothelin-1, malonyldialdehyde (MDA) and hydroxyproline content and a reduction in superoxide dismutase activity was found after MCT treatment. The thickness and area of the pulmonary arterial wall were significantly increased in MCT-treated rats compared with control rats. At all three doses tested, CPU0213 ameliorated these changes in a dose-dependent manner and the effects were associated with a greater reduction in the remodelling of pulmonary arterioles. However, nifedipine was only partially effective in amelerioating biochemical and haemodynamic changes induced by MCT, significantly reducing RVSP, CVP, +dp/dt(max), tissue MDA, inducible nitric oxide synthase and hydroxyproline content, increasing -dp/dt(min) and having no effect on the other parameters investigated. In addition, nifedipine had no effect on remodelling of the arterial wall. 4. In conclusion, CPU0213 is more effective than nifedipine in suppressing the remodelling of pulmonary arterioles in PH induced by MCT treatment of rats. Furthermore, CPU0213 may have promise in treating PH secondary to connective tissue disease.