Therapeutic challenges for systemic sclerosis - Facts and future targets

Pulmonary arterial hypertension (PAH) is an important cause of death in systemic sclerosis (SSc), despite the improvement of therapies. An early diagnosis and the use of drugs interfering with the main pathogenic pathways of PAH is pivotal for the improvement of prognosis in primary PAH and PAH secondary to autoimmune rheumatic diseases, mainly SSc. Lately, new specific therapies have been developed targeting prostacyclin, endothelin, and nitric oxide pathways, the major pathogenic pathways leading to endothelial dysfunction in PAH. Epoprostenol improved life expectancy of patients with primary and secondary PAH, but its continuous intravenous administration requires experienced centers. More stable analogues of prostacyclin, administrated by intravenous (iloprost, treprostinil), subcutaneous, inhalatory (treprostinil, iloprost), and oral route (Beraprost) have shown efficacy in PAH. Bosentan, the first oral endothelin receptor antagonist (with affinity for endothelin A and B receptors) improves exercise function and survival in PAH, both primary and secondary to autoimmune rheumatic diseases. This is confirmed also for Sitaxsentan and Ambrisentan, selective A receptor antagonists. Because of its short half-life and systemic side effects, short-term NO inhalation is used only in short-term management of PAH in critically ill adults. Inhibitors of NO degradation, such as sildenafil, a phosphodiesterase (PDE) type 5 inhibitor, improved functional and hemodynamic parameters without significant side effects. Vardenafil and taladafil, longer-acting PDE inhibitors, also have vascular pulmonary selectivity. All these drugs may be used in combination, to maximize their clinical benefit not only in patients unresponsive to single drugs, but also potentially as initial therapy of PAH.