Endpoints in PAH clinical trials in the era of combination therapy: how do we decide whether something is working without going bankrupt?

There has been substantial progress in the treatment of pulmonary arterial hypertension using specific disease-targeted therapies. As the number of agents available grows, and as new treatment strategies emerge, it is essential that the endpoints we use to assess efficacy are sufficiently meaningful and sensitive enough to detect changes that are often subtle. Although the six-minute walk has been the traditional primary endpoint in clinical trials, there is now a move towards more patient-centred composite endpoints such as time to clinical worsening. These endpoints need to be more clearly defined and universally applied so as to make direct comparison between new drugs and new combinations possible.