An Open Label, Single Center, Adaptive Phase I Study in Healthy Volunteers, to Evaluate the Safety, Efficacy and Dose Responses of SB-751689 (Ronacaleret; a Calcium Sensing Receptor Antagonist)

The present study aims to evaluate the impact of 5 days oral administration of ronacaleret 100 miligram (mg) and 400 mg on changes in circulating CD34+ cells, when ronacaleret is followed by the administration of a single dose of plerixafor in healthy human volunteers. This single centre adaptive design study will be carried out in 2 parts. The part A will evaluate the change in peripheral circulating CD34+ cells in response to two different 5 day regimens of ronacaleret (100 mg or 400 mg once daily), given in conjunction with a single dose of plerixafor (0.24 mg/kilogram [kg]) sub-cutaneously (SC) on the evening of the final days dosing approximately 12 hours before collection of CD34+ cells on day 6. Subjects (5 each) will be assigned to either one of the ronacaleret arms, in an open fashion. Comparisons will be made in the change from baseline to end of treatment peripheral CD34+ cell counts. Part A will be conducted in two cohorts with 5 subjects being enrolled into each of the 2 treatment arms making up the first cohort. Cohort 2 will involve up to 5 further subjects being enrolled into each treatment arm. The structure of part B will be finalized following a review of data generated in part A. The total study duration of Part A for each subject including the screening, treatment and follow-up periods will be approximately 7 weeks.