Are we near to an effective drug treatment for bronchiolitis obliterans?

Lung transplantation remains the only effective therapeutic option for well-selected patients with end-stage (cardio) pulmonary diseases such as emphysema, cystic fibrosis, lung fibrosis and pulmonary arterial hypertension. Although the results have improved lately, the long-term survival is still far behind other organ transplantations. This is mainly due to the development of chronic lung allograft dysfunction (CLAD), with bronchiolitis obliterans (BO) being the most frequent manifestation and restrictive CLAD or restrictive allograft syndrome (RAS) being a rather novel distinct entity, with a worse survival. Although the pathology of BO has been well described, this is not an obvious diagnosis after lung transplantation, because of the low sensitivity of transbronchial biopsies to detect BO. As a consequence, BO syndrome (BOS), the clinical correlate of BO, characterized by a progressive and obstructive decline in FEV1, has been introduced and is used worldwide to describe patients affected by this condition. BOS is the major long-term problem after lung transplantation, occurring in some 50% of patients within 5 years after the transplant procedure and causing up to 30% of late mortality between 3 and 5 years after transplantation. Its treatment remains very difficult, although recent advances have certainly improved the survival after diagnosis of BOS. We will here review the current therapeutic options to try to prevent BOS on the one hand and to treat BOS on the other hand.