Effects of Denosumab on the Pharmacokinetics of Etanercept

Inclusion Criteria: * Postmenopausal women (postmenopausal is defined as no vaginal bleeding or spotting for at least 12 months) * Low bone mineral density (BMD) as determined by screening BMD T-scores of the lumbar spine (L1 to L4), or total evaluable vertebrae (if fewer than L1 to L4), or total hip ≤ -1.0 * Receiving a 50 mg dose of etanercept once weekly ≥ 6 months prior to screening and expected to continue etanercept treatment at this dose and frequency through end of study (EOS) * If currently taking methotrexate (MTX), receiving a stable dose (7.5 to 20 mg/week) of MTX ≥ 8 weeks prior to screening * Willing and able to take ≥ 1,000 mg elemental calcium and ≥ 400 IU vitamin D daily upon enrollment Exclusion Criteria: * Type 1 diabetes; OR poorly controlled Type 2 diabetes (hemoglobin A1c (HbA1c) \> 8.0% at screening; HbA1c ≤ 8.0% within 6 months of screening is acceptable if supporting laboratory documentation is available) * History of heart failure, coronary artery bypass graft, or cardiac arrhythmia; OR history of acute coronary syndrome * Comorbid autoimmune disease, demyelinating disease, or hematologic abnormalities * History of joint replacement in hand and/or wrist; OR history of fused joint in hand and/or wrist * Prior history or current evidence of osteonecrosis/osteomyelitis of the jaw; OR active dental or jaw condition that requires oral surgery, or non-healed dental/oral surgery; OR planned invasive dental procedure(s) during the course of the study * Previous exposure to denosumab