 This randomized, placebo-controlled study in patients with primary HPT was designed to evaluate the efficacy, safety, pharmacokinetics, and health-related quality of life HRQOL of AMG 073 when administered 2 times a day BID. The study consisted of 3 phases: a 12-week dose-titration phase, a 12-week maintenance phase, and a 28-week follow-up phase. 