title: Models and screening assays for drug discovery in osteoporosis.
abstract: BACKGROUND
  Osteoporosis affects nearly 100 million people in Europe, Japan and the US, and the number is increasing due to aging of the population. Preclinical efficacy studies performed according to regulatory guidelines are large, long and expensive, and there is a need for guidance and recommendations on how to perform preliminary studies prior to the regulatory studies.
  
  
  METHODS
  We review research models that can be used for preclinical efficacy testing of new drug candidates for osteoporosis. Our focus is on testing compounds targeted to directly decrease osteoclastic bone resorption or increase osteoblastic bone formation.
  
  
  RESULTS
  We provide an overview of in vitro bone cell culture systems and osteoporosis animal models useful for preclinical efficacy studies and a step-by-step approach on how the most interesting compound can be selected from thousands of drug candidates. Different approaches for testing anti-catabolic and anabolic compounds are provided.
  
  
  CONCLUSIONS
  Efficacy of new osteoporosis drug candidates can be first proven conveniently using in vitro bone cell cultures and then confirmed in short-term animal studies, followed by more extensive animal studies, and finally a regulatory study performed according to the guidelines of regulatory authorities.
authors: Pharmatest Services Ltd, Itäinen Pitkäkatu 4 C, 20520 Turku, Finland  +358 2 2784703 ;  +358 2 2784710 ;  jussi.halleen@pharmatest.fi.
authors: Jukka P
authors: JP
authors: Rissanen
authors: Jussi M
authors: JM
authors: Halleen