Finding next-generation treatments for pulmonary arterial hypertension (PAH) is proving to be difficult. Last week two companies made the point. Gilead Sciences Inc. terminated a Phase II trial of cicletanine for PAH due to a failure of the trial to meet its primary endpoint of improvement in exercise capacity; and Novartis AG pulled its new drug application (NDA) for QTI571 (imatinib mesylate) for PAH treatment.