An FDA complete response letter (CRL) for the chronic obstructive pulmonary disease (COPD) therapy SUN-101 (glycopyrrolate) and the Eflow nebulizer used to deliver it is sending Sunovion Pharmaceuticals Inc. back into talks with the agency and pushing out the potential realization of up to $210 million in commercial milestones for former backers of Elevation Pharmaceuticals Inc., from which Sunovion acquired the program in 2012.