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Drug rediscovery in gastroenterology: from off-label to on-label use of thioguanine in inflammatory bowel disease
  1. Nanne K H de Boer1,2,
  2. Melek Simsek1,3,
  3. Berrie Meijer1,3,
  4. Markus F Neurath4,
  5. Ad van Bodegraven5,
  6. Chris J J Mulder1
  1. 1 Gastroenterology and Hepatology, Amsterdam University Medical Centres, Amsterdam, The Netherlands
  2. 2 Research Institute, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, Noord-Holland, The Netherlands
  3. 3 School of Medicine, VU University, Amsterdam, The Netherlands
  4. 4 First Department of Medicine, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
  5. 5 Department of Gastroenterology, Geriatrics, Internal and Intensive Care Medicine (Co-MIK), Zuyderland Medical Centre, Heerlen-Sittard-Geleen, The Netherlands
  1. Correspondence to Dr Nanne K H de Boer, Gastroenterology and Hepatology, Amsterdam University Medical Centres, Amsterdam, 1081HZ, The Netherlands; khn.deboer{at}


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.

  • drug development
  • drug metabolism
  • inflammatory bowel disease
  • crohn's disease
  • azathioprine

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  • Contributors NKHdB and MFN were the guarantors of the article. BM and NKHdB drafted the manuscript. AvB, MS and CJJM critically revised the manuscript and added important intellectual input. BM and NKHdB drafted the figures. All authors approved with the final version of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests NdB served as a speaker for AbbVie and MSD and as consultant and principal investigator for TEVA Pharma BV and Takeda; and received an unrestricted research grant from Dr Falk, TEVA Pharma BV, MLDS and Takeda. MS received unrestricted research grants from TEVA Pharma BV. BM has nothing to declare. MN served as an adviser to Boehringer, MSD, AbbVie, Celgene, Pentax, Takeda, Janssen, Giuliani and PPM. AAvB received speaker, consultancy or advisory board fees from AbbVie, BMS, Galapagos, Ferring, Janssen and TEVA Pharma BV. Galapagos, Ferring and Janssen supported educational programmes. TEVA Pharma BV and Pfizer supported research projects. CM served as an adviser to TEVA UK, Arega Belgium and Douglas Pharma NZ.

  • Provenance and peer review Not commissioned; externally peer reviewed.