Pulmonary hypertension related to systemic sclerosis: points to consider for clinical trials.

There are proven successful approaches to clinical trial design in pulmonary arterial hypertension (PAH), which in turn have led to the licensing of a number of effective therapies. SSc has been included in trials of World Health Organization Group 1 PAH but has been under-represented. Responses in outcomes as diverse as exercise capacity, quality of life, durability of drug effect and survival have been reduced in comparison with those seen in idiopathic PAH. The PAH community has achieved international and interdisciplinary consensus guidelines for future studies. We consider the diverse outcome measures used in trials in the context of the complexities of scleroderma. An argument is advanced in favour of future trials focused exclusively on SSc but with adaptations of the core outcome measures and trial design templates applicable to more general studies of PAH.