title: Developing drugs to treat osteoporosis: lessons learned?
abstract: BACKGROUND
  Selective estrogen-receptor modulators (SERMs) are drugs that act as estrogen receptor agonists or antagonists depending on the target tissue. Theoretically this class of agents would be an ideal substitute for hormone replacement therapy (HRT), if their effects on the skeleton matched those of estrogen while their actions on other tissues were either neutral or beneficial.
  
  
  OBJECTIVE
  To evaluate a Phase III trial of a new SERM, arzoxefine, for prevention of osteoporosis in younger postmenopausal women.
  
  
  RESULTS
  Arzoxifene induced modest but significant increases in bone mineral density versus a control group during 2 years of therapy, with minor adverse events. However, fracture efficacy and other patient-specific outcomes were not evaluated.
  
  
  CONCLUSIONS
  Despite a positive study of surrogate end points (bone density and biochemical markers of bone turnover), arzoxifene was withdrawn from further FDA evaluation, principally because of long-term side effects and lack of non-vertebral fracture efficacy in the companion Phase III fracture study. Each SERM has a unique profile on bone and other tissues. Regulatory approval of this class of agents may remain problematic for the immediate future.
authors.affiliation: Maine Medical Center Research Institute, Center for Clinical and Translational Research, 81 Research Drive, Scarborough, ME 04074-7205, USA.
authors.forename: Francisco J A
authors.initials: FJ
authors.lastname: de Paula
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Rosen