PROTACs Targeting BRM (SMARCA2) Afford Selective In Vivo Degradation over BRG1 (SMARCA4) and Are Active in BRG1 Mutant Xenograft Tumor Models

J Med Chem. 2024 Jan 25;67(2):1262-1313. doi: 10.1021/acs.jmedchem.3c01781. Epub 2024 Jan 5.

Abstract

The identification of VHL-binding proteolysis targeting chimeras (PROTACs) that potently degrade the BRM protein (also known as SMARCA2) in SW1573 cell-based experiments is described. These molecules exhibit between 10- and 100-fold degradation selectivity for BRM over the closely related paralog protein BRG1 (SMARCA4). They also selectively impair the proliferation of the H1944 "BRG1-mutant" NSCLC cell line, which lacks functional BRG1 protein and is thus highly dependent on BRM for growth, relative to the wild-type Calu6 line. In vivo experiments performed with a subset of compounds identified PROTACs that potently and selectively degraded BRM in the Calu6 and/or the HCC2302 BRG1 mutant NSCLC xenograft models and also afforded antitumor efficacy in the latter system. Subsequent PK/PD analysis established a need to achieve strong BRM degradation (>95%) in order to trigger meaningful antitumor activity in vivo. Intratumor quantitation of mRNA associated with two genes whose transcription was controlled by BRM (PLAU and KRT80) also supported this conclusion.

MeSH terms

  • Carcinoma, Non-Small-Cell Lung* / pathology
  • Cell Line
  • DNA Helicases / genetics
  • Heterografts
  • Humans
  • Lung Neoplasms* / genetics
  • Nuclear Proteins / genetics
  • Proteolysis Targeting Chimera
  • Transcription Factors / genetics

Substances

  • Proteolysis Targeting Chimera
  • SMARCA2 protein, human
  • Transcription Factors
  • SMARCA4 protein, human
  • DNA Helicases
  • Nuclear Proteins