Inhalable insulin specialist MannKind Corp. (NASDAQ:MNKD) announced that the FDA is extending its deadline to review United Therapeutics’ (NASDAQ:UTHR) new drug application (NDA) for Tyvaso DPI from February to May. MannKind is developing Tyvaso DPI (treprostinil) in collaboration with United Therapeutics. The drug candidate Tyvaso DPI would potentially treat pulmonary arterial hypertension and pulmonary hypertension…