Vitamin A in excess of 10,000 IU per day, heparin, lithium, or anticonvulsant medications (except benzodiazepines) Current therapy with digoxin Subjects taking daily, long-term (i.e., > 1 year) non-steroidal anti-inflammatory drugs (NSAIDs) for diseases such as inflammatory arthritis are excluded. The use of low dose aspirin for prevention of heart disease is permitted. Short term use of NSAIDs is permitted for acute pain management but the use of alternative, non-NSAIDs is encouraged Total serum calcium levels outside the local laboratory reference range at the Screening visit Liver chemistries (aspartate aminotransferase [AST], alanine aminotransferase [ALT], or total bilirubin) exceeding 2‑fold the upper limit of the local laboratory reference range at the Screening visit Glomerular filtration rate (GFR) <35 mL/min as calculated by the Modification of Diet in Renal Disease (MDRD) equation as follows: GFR (mL/min/1.73 m2) = 186 x (Serum creatinine mg/dL)-1.154 x (Age)-0.203 x (0.742 if female) x (1.210 if African American) (conventional units) Women who are pregnant or breast-feeding are not allowed in the study. Females of child-bearing potential must have a negative urine bhCG pregnancy test at the Screening and Randomization visit and agree to practice acceptable highly effective methods of birth control through the duration of the study and for 4 weeks following the last dose of study medication. Highly effective birth control methods include those preventative measures taken to avoid pregnancy that have a failure rate of less than 1% per year.