Study in Healthy Volunteers, to Evaluate the Safety, Efficacy and Dose Responses of SB-751689 (Ronacaleret)

Inclusion Criteria:

• A male or female between 18 and 65 years of age (inclusive).
• Healthy as determined by a physician, based on a medical evaluation and with an estimated Glomerular Filtration Rate (GFR) of >=60 mL/min /1.73 m^2 using the four variable Modification of Diet in Renal Disease (MDRD) equation.
• Aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase and bilirubin <=1.5 x upper limit of normal (ULN) (isolated bilirubin >1.5 x ULN is acceptable if bilirubin is fractionated and direct bilirubin <35%).
• Female of non-child bearing potential, or female subjects and male subjects with female partners of child-bearing potential willing to use protocol-specified methods of contraception to prevent pregnancy during the study.
• Body weight of 55 kg or more and body mass index (BMI) of 20.0 to 35.0 kg/m^2 (inclusive).
• Capable of giving written informed consent.

Exclusion Criteria:

• A positive pre-study drug/alcohol screen.
• A positive test for HIV, B surface antigen or positive Hepatitis C antibody result within 3 months of screening.
• History of or therapy for osteoporosis
• Subject has had treatment for any condition relating to the thyroid/parathyroid gland which in the opinion of the investigator may influence the subjects production of PTH
• Subjects with any contraindications or know allergies to receiving plerixafor
• Current or chronic history of liver disease, or known hepatic or biliary abnormalities (with the exception of asymptomatic gallstones).
• Subjects taking calcium and/or vitamin D supplements, during or within 2 weeks of study initiation
• Subjects taking any concomitant medications
• Specific laboratory abnormalities at screening like Serum calcium (total or albumin-adjusted) outside the central laboratory reference range, PTH outside the normal range, Creatine phosphokinase (CPK) outside the normal range
• Subjects with abnormal Vitamin D (Vitamin D, 25-Hydroxy) levels may be enroled if repeat lab results, obtained within 14 days of initial screening assessments, are within the normal range
• History of regular alcohol consumption within 6 months of the study defined as an average weekly intake of >14 drinks for males or >7 drinks for females.
• Lactating or pregnant females as determined by positive serum human chorionic gonadotropin (hCG) test at screening or prior to dosing.
• The subject has participated in a clinical trial within 30 days or 5 half-lives of the IP prior to the first dosing day in the current study.
• Unable to refrain from consumption of red wine, Seville oranges, grapefruit or grapefruit juice from 7 days prior to the first dose.
• Where participation in the study would result in donation of blood or blood products in excess of 500 mL within a 56 day period.