MannKind Corp. announced the first of several development milestones under a licensing and collaboration agreement with United Therapeutics as of April 1. The Westlake Village company received $12.5 million from United Therapeutics, located in Silver Spring, Md., for the development and commercialization of a dry powder formula currently under evaluation to treat pulmonary arterial hypertension. The formula is called Treprostinil Technosphere, or TreT. MannKind is eligible to earn additional payments up to $37.5 million at other defined milestones, according to a statement from the company, as well as low double-digit royalties on net sales of the product. A new shelf registration was filed by MannKind on March 29 to replace a an existing registration that expires April 27. Shares of MannKind (MNKD) closed Monday down 17 cents, or 8.6 percent, to $1.80 on the Nasdaq.