Paget’s Disease of Bone: Reduction of Disease Activity With Oral Risedronate

Abstract

Risedronate monosodium [1-hydroxy-2-(3-pyridinyl)ethylidene bisphosphonic acid monosodium salt] is a pyridinyl bisphosphonate drug under development as a treatment for Paget’s disease of bone and other metabolic bone disorders. An open-label, single-center study was conducted to determine the efficacy and safety of oral risedronate in patients with severe Paget’s disease [mean baseline serum alkaline phosphatase (ALP) about six times the upper limit of normal]. 20 patients (12 men, 8 women; mean age 74 years) were treated with 30 mg/day of oral risedronate for 84 days, followed by 112 days without treatment. This 196 day period was repeated once in 19 patients in whom ALP did not reach the midpoint of the normal range or increased by ≥25% from the nadir value by the end of the first 196 day period. At the end of the first 196 day period, the mean percentage decrease from baseline in excess ALP and excess urinary hydroxyproline/creatinine (OHP/Cr) was 79.5% and 85.5%, respectively (excess defined as difference between the patient’s ALP or OHP/Cr and midpoint of the normal range). At the end of the second period, the decreases were 86.3% and 101.3%, respectively. The decreases in excess ALP and OHP/Cr were significant ( p < 0.0001). In 13 patients (65%), ALP normalized: 8 during the first treatment period and 5 during the second. There was a progressive decline and elimination of pagetic bone pain: 70% (14 of 20) of patients reported pagetic bone pain at baseline, 25% (5 of 20) reported pain after the first 196 day period; and 0% at retreatment day 56 ( p = 0.003). Thereafter, all patients remained pain-free until the end of the study. No patients withdrew from the study due to adverse events, and no adverse events were judged related to the study drug. In summary, 30 mg/day of oral risedronate given in 3 month courses significantly reduced the biochemical indices of disease activity, showing normalization of ALP in the majority of patients with severe Paget’s disease, and was associated with a significant reduction in pagetic bone pain. Risedronate was well-tolerated and demonstrated a good safety profile.