Considerations for development of surrogate endpoints for antifracture efficacy of new treatments in osteoporosis: a perspective

Abstract

Because of the broad availability of efficacious osteoporosis therapies, conduct of placebo-controlled trials in subjects at high risk for fracture is becoming increasing difficult. Alternative trial designs include placebo-controlled trials in patients at low risk for fracture or active comparator studies, both of which would require enormous sample sizes and associated financial resources. Another more attractive alternative is to develop and validate surrogate endpoints for fracture. In this perspective, we review the concept of surrogate endpoints as it has been developed in other fields of medicine and discuss how it could be applied in clinical trials of osteoporosis. We outline a stepwise approach and possible study designs to qualify a biomarker as a surrogate endpoint in osteoporosis and review the existing data for several potential surrogate endpoints to assess their success in meeting the proposed criteria. Finally, we suggest a research agenda needed to advance the development of biomarkers as surrogate endpoints for fracture in osteoporosis trials. To ensure optimal development and best use of biomarkers to accelerate drug development, continuous dialog among the health professionals, industry, and regulators is of paramount importance.

FIG. 1

Models characterizing the relationship between treatment, biomarker (or surrogate endpoint), and clinical outcome. (A) A “perfect surrogate,” where the biomarker mediates all of the effect of the treatment on the clinical outcome. (B) The more likely situation where the biomarker mediates some, but not all, of the effect of the treatment on the clinical endpoint.