VIP and pulmonary arterial hypertension: Regarding inhaled vasoactive intestinal peptide (VIP) and tyrosine kinase inhibitors, even though they theoretically seem promising medical therapies for PAH (Ghofrani et al. 2005; Leuchte et al. 2008; Nayyar et al. 2014; Petkov et al. 2003), their role in PAH treatment is controversial due to the recent negative clinical studies(Frost et al. 2015; Hoeper et al. 2013a,).