The CLK inhibitor SM08502 induces anti-tumor activity and reduces Wnt pathway gene expression in gastrointestinal cancer models

Cancer Lett. 2020 Mar 31;473:186-197. doi: 10.1016/j.canlet.2019.09.009. Epub 2019 Sep 24.


The Wnt/β-catenin signaling pathway is aberrantly activated in colorectal (CRC) and many other cancers, and novel strategies for effectively targeting it may be needed due to its complexity. In this report, SM08502, a novel small molecule in clinical development for the treatment of solid tumors, was shown to reduce Wnt pathway signaling and gene expression through potent inhibition of CDC-like kinase (CLK) activity. SM08502 inhibited serine and arginine rich splicing factor (SRSF) phosphorylation and disrupted spliceosome activity, which was associated with inhibition of Wnt pathway-related gene and protein expression. Additionally, SM08502 induced the generation of splicing variants of Wnt pathway genes, suggesting that its mechanism for inhibition of gene expression includes effects on alternative splicing. Orally administered SM08502 significantly inhibited growth of gastrointestinal tumors and decreased SRSF phosphorylation and Wnt pathway gene expression in xenograft mouse models. These data implicate CLKs in the regulation of Wnt signaling and represent a novel strategy for inhibiting Wnt pathway gene expression in cancers. SM08502 is a first-in-class CLK inhibitor being investigated in a Phase 1 clinical trial for subjects with advanced solid tumors (NCT03355066).

Keywords: Alternative splicing; Beta-catenin; CDC-Like kinase; Colorectal cancer; SRSF.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing / drug effects
  • Animals
  • Apoptosis / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / pathology
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Knockout Techniques
  • Humans
  • Inhibitory Concentration 50
  • Mice
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology*
  • Protein Kinase Inhibitors / therapeutic use
  • Protein Serine-Threonine Kinases / antagonists & inhibitors*
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism
  • Rats
  • Serine-Arginine Splicing Factors / metabolism*
  • Stomach Neoplasms / drug therapy*
  • Stomach Neoplasms / pathology
  • Wnt Signaling Pathway / drug effects*
  • Wnt Signaling Pathway / genetics
  • Xenograft Model Antitumor Assays


  • Protein Kinase Inhibitors
  • Serine-Arginine Splicing Factors
  • Clk dual-specificity kinases
  • Protein-Tyrosine Kinases
  • Protein Serine-Threonine Kinases

Associated data