Reports of a fifth patient experiencing immune-related adverse events is prompting Mirna Therapeutics Inc. to close out its phase I trial testing microRNA mimic MRX34 and to "reassess where we stand with our pipeline now," according to President and CEO Paul Lammers, a disclosure that sent shares of Mirna (NASDAQ:MIRN) down 47 cents, or 19 percent, to close Wednesday at $2.