BMPR2 and pulmonary arterial hypertension: Previously, the use of low-dose tacrolimus (FK506) over a period of 12 months in three patients with end-stage PAH demonstrated improvements in heart failure symptoms, the 6-MWD, N-terminal pro-brain natriuretic peptide (NT-proBNP) levels, and increased BMPR2 expression in peripheral blood mononuclear cells (PBMCs) [38].