Efficacy and Safety of Risedronate (Actonel), a Third Generation Bisphosphonate in Patients With Ankylosing Spondylitis: a Phase 2 Pilot Study

Randomized, controlled, double-blind, multicenter phase II study comparing risedronate 35mg (ActonelR 35mg weekly tablet) versus placebo in patients with active ankylosing spondylitis (AS) treated with standard first and second-line therapies. Primary efficacy endpoint: Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). The time schedule for performing the BASDAI was at screening, upon inclusion (T0), then after 3, 6 and 12 months or at the time of premature withdrawal in case of drop-out. secondary endpoints: * Clinical endpoints: The secondary efficacy measures were the following: Bath Ankylosing Spondylitis Functional Index (BASFI) , Bath Ankylosing Spondylitis Metrology Index (BASMI), ASAS (Assessments in Ankylosing Spondylitis) Working Group core set of domains, Spinal pain VAS, ESR, CRP and the percentage of patients achieving 20% or greater decrease in each of these parameters. These parameters were determined at T0, T3, T6, T12 or at the time of premature withdrawal in case of drop-out. The spinal pain assessed by VAS was also done at screening. * DEXA: Dual Energy X-Ray-Absorptiometry (DEXA) measurements were performed in all patients upon inclusion (T0) and at the end of the study (T12). * Biochemical markers: selected biochemical markers of bone metabolism were measured at T0, T3, T6 and T12 or at the time of premature withdrawal in case of drop-out using commercially available kits. Bone formation was assessed by serum bone-specific alkaline phosphatase (BAP) and osteocalcin (OC) levels using commercially available kits. Bone resorption was assessed in serum by the C-terminal telopeptide of type I collagen degradation (Crosslaps R) and urinary N-terminal telopeptide of type I collagen degradation (Osteomark R). * Trial with medicinal product