Influence of Rituximab on markers of bone remodeling in patients with rheumatoid arthritis: a prospective open-label pilot study.

Immune system and bone are interacting in a complex way. Rheumatoid arthritis is characterized not only by joint destruction, but also by development of systemic osteopenia and osteoporosis. The CD20-depleting antibody Rituximab (Rtx) is a novel therapeutic option able significantly to slow the destructive joint process of rheumatoid arthritis. However, there are little data whether Rtx influences systemic bone remodeling. In the present prospective study, we evaluated the influence of Rtx on markers of bone metabolism with a follow-up of 3-15 months after Rtx therapy (2 dose of each 1,000 mg) in 13 patients with rheumatoid arthritis. There was no significant change of the bone formation markers bone alkaline phosphatase and c-terminal propeptide of collagen I. However, a non-significant tendency of decrease of RANKL (with no chance of osteoprotegerin) and a significant decrease of the bone degradation marker desoxypyridinolin crosslinked collagen I was observed 15 months after Rtx application. These initial results provide no evidence of a negative systemic influence of Rtx on bone remodeling. In contrast, it appears that Rtx lowered osteoclast activity often found increased in active rheumatoid arthritis contributing to osteoporosis in this disease.