There is a method of treating or preventing pulmonary arterial hypertension (PAH) or associated pulmonary arterial hypertension (APAH) in a patient. The method has the step of systemically administering to the patient a therapeutically effective amount of one or more compounds: (S)-ethyl 8-(2-amino-6-((R)-1-(5-chloro-[1,1′；-biphenyl]-2-yl)-2,2,2-trifluoroethoxy)pyrimidin-4-yl)-2,8-diazaspiro[4.5]decane-3-carboxylate or a pharmaceutically acceptable salt thereof, or (S)-8-(2-amino-6-((R)-1-(5-chloro-[1,1′；-biphenyl]-2-yl)-2,2,2-trifluoroeth-oxy)pyrimidin-4-yl)-2,8-diazaspiro[4.5]decane-3-carboxylic acid or a pharmaceutically acceptable salt thereof, or a combination of the foregoing. There is also a method of treating or preventing PAH or APAH in a patient by systemically administering a therapeutically effective amount of a THP1 inhibitor from about 1 mg/kg/day to about 50 mg/kg/day. There is a method for treating PAH or APAH in a patient with a single daily dose.
