Although major attention was given towards therapeutic modulation of HDACs in the context of PH by employing pan-HDAC inhibitors3, to circumvent the adverse off-target effects reported on pan-HDAC inhibition, precise identification of dysregulated isoforms in the PAH setting is indispensable to design isoform-selective targeting strategies. This evidence concerns the gene HDAC9 and pulmonary arterial hypertension.