 The FDA has issued a complete response to United Therapeutics Corporation NASDAQ: UTHR regarding the marketing application for Tyvaso DPI for pulmonary arterial hypertension PAH and pulmonary hypertension associated with interstitial lung disease PH-ILD. The FDAs letter noted only a single deficiency related to an open inspection issue at a third-party facility that performs analytical testing of the treprostinil drug substance. 