Rational development of Stafib-2: a selective, nanomolar inhibitor of the transcription factor STAT5b

  • Sci Rep. 2017 Apr 11;7(1):819. doi: 10.1038/s41598-017-00920-3.
Nagarajan Elumalai  1 ,  Angela Berg  1 ,  Stefan Rubner  1 ,  Linda Blechschmidt  1 ,  Chen Song  2  3 ,  Kalaiselvi Natarajan  1 ,  Jörg Matysik  2 ,  Thorsten Berg  4
Affiliations
  • 1. Institute of Organic Chemistry, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany.
  • 2. Institute of Analytical Chemistry, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany.
  • 3. Leids Instituut voor Chemisch Onderzoek, Universiteit Leiden, 2300 RA, Leiden, The Netherlands.
  • 4. Institute of Organic Chemistry, Leipzig University, Johannisallee 29, 04103, Leipzig, Germany. [email protected].
PMID: 28400581 DOI: 10.1038/s41598-017-00920-3
Abstract

The transcription factor STAT5b is a target for tumour therapy. We recently reported catechol bisphosphate and derivatives such as Stafib-1 as the first selective inhibitors of the STAT5b SH2 domain. Here, we demonstrate STAT5b binding of catechol bisphosphate by solid-state nuclear magnetic resonance, and report on rational optimization of Stafib-1 (Ki = 44 nM) to Stafib-2 (Ki = 9 nM). The binding site of Stafib-2 was validated using combined isothermal titration calorimetry (ITC) and protein point mutant analysis, representing the first time that functional comparison of wild-type versus mutant protein by ITC has been used to characterize the binding site of a small-molecule ligand of a STAT protein with amino acid resolution. The prodrug Pomstafib-2 selectively inhibits tyrosine phosphorylation of STAT5b in human leukaemia cells and induces Apoptosis in a STAT5-dependent manner. We propose Pomstafib-2, which currently represents the most active, selective inhibitor of STAT5b activation available, as a chemical tool for addressing the fundamental question of which roles the different STAT5 proteins play in various cell processes.

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