Analysis of the primary endpoint showed that treatment with AMG 416 at 10mg ( Cohort 2 ) and 5mg ( Cohort 3 ) for up to 4 weeks resulted in mean 49.4 % and 33.0 % reductions from baseline in PTH during the efficacy assessment phase , respectively ( p < 0.05 for both cohorts compared to placebo group within the cohort ) .