Drug rediscovery in gastroenterology: from off-label to on-label use of thioguanine in inflammatory bowel disease

Gut. 2023 Oct;72(10):1985-1991. doi: 10.1136/gutjnl-2023-329679. Epub 2023 Jun 28.


Drug rediscovery refers to the principle of using 'old' drugs outside the indications mentioned in the summary of product characteristics. In the past decades, several drugs were rediscovered in a wide variety of medical fields. One of the most recent examples is the unconditional registration of thioguanine (TG), a thiopurine derivative, in patients with inflammatory bowel disease in the Netherlands. In this paper, we aim to visualise potential hurdles that hamper drug rediscovery in general, emphasise the global need for optimal use and development of potentially useful drugs, and provide an overview of the registration process for TG in the Netherlands. With this summary, we aim to guide drug rediscovery trajectories in the near future.

Keywords: azathioprine; crohn's disease; drug development; drug metabolism; inflammatory bowel disease.

Publication types

  • Review

MeSH terms

  • Azathioprine / therapeutic use
  • Gastroenterology*
  • Humans
  • Immunosuppressive Agents / therapeutic use
  • Inflammatory Bowel Diseases* / drug therapy
  • Mercaptopurine / therapeutic use
  • Netherlands
  • Off-Label Use
  • Thioguanine / therapeutic use


  • Thioguanine
  • Azathioprine
  • Mercaptopurine
  • Immunosuppressive Agents