Structure-Aided Development of Small-Molecule Inhibitors of ENPP1, the Extracellular Phosphodiesterase of the Immunotransmitter cGAMP

  • Cell Chem Biol. 2020 Nov 19;27(11):1347-1358.e5. doi: 10.1016/j.chembiol.2020.07.007.
Jacqueline A Carozza  1 ,  Jenifer A Brown  2 ,  Volker Böhnert  3 ,  Daniel Fernandez  4 ,  Yasmeen AlSaif  5 ,  Rachel E Mardjuki  1 ,  Mark Smith  6 ,  Lingyin Li  7
Affiliations
  • 1. Department of Chemistry, Stanford University, Stanford, CA 93405, USA; Stanford ChEM-H, Stanford University, Stanford, CA 93405, USA.
  • 2. Stanford ChEM-H, Stanford University, Stanford, CA 93405, USA; Biophysics Program, Stanford University, Stanford, CA 93405, USA.
  • 3. Stanford ChEM-H, Stanford University, Stanford, CA 93405, USA; Department of Biochemistry, Stanford University, Stanford, CA 93405, USA.
  • 4. Stanford ChEM-H Macromolecular Structure Knowledge Center, Stanford University, Stanford, CA 93405, USA.
  • 5. Stanford ChEM-H, Stanford University, Stanford, CA 93405, USA; Department of Biology, Stanford University, Stanford, CA 93405, USA.
  • 6. Stanford ChEM-H Medicinal Chemistry Knowledge Center, Stanford, CA 93405, USA.
  • 7. Stanford ChEM-H, Stanford University, Stanford, CA 93405, USA; Department of Biochemistry, Stanford University, Stanford, CA 93405, USA. Electronic address: [email protected].
PMID: 32726585 DOI: 10.1016/j.chembiol.2020.07.007
Abstract

Cancer cells initiate an innate immune response by synthesizing and exporting the small-molecule immunotransmitter cGAMP, which activates the anti-cancer Stimulator of Interferon Genes (STING) pathway in the host. An extracellular enzyme, ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1), hydrolyzes cGAMP and negatively regulates this anti-cancer immune response. Small-molecule ENPP1 inhibitors are much needed as tools to study the basic biology of extracellular cGAMP and as investigational Cancer Immunotherapy drugs. Here, we surveyed structure-activity relationships around a series of cell-impermeable and thus extracellular-targeting phosphonate inhibitors of ENPP1. In addition, we solved the crystal structure of an exemplary phosphonate inhibitor to elucidate the interactions that drive potency. This study yielded several best-in-class inhibitors with Ki < 2 nM and excellent physicochemical and pharmacokinetic properties. Finally, we demonstrate that an ENPP1 inhibitor delays tumor growth in a breast Cancer mouse model. Together, we have developed ENPP1 inhibitors that are excellent tool compounds and potential therapeutics.

Keywords
2′3′-cGAMP; ENPP1; STING; cancer immunotherapy; crystal structure; extracellular signaling; immunotransmitter; small-molecule inhibitors; structure-aided design.
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