Antibody-Mediated Delivery of Chimeric BRD4 Degraders. Part 1: Exploration of Antibody Linker, Payload Loading, and Payload Molecular Properties

J Med Chem. 2021 Mar 11;64(5):2534-2575. doi: 10.1021/acs.jmedchem.0c01845. Epub 2021 Feb 17.

Abstract

The biological and medicinal impacts of proteolysis-targeting chimeras (PROTACs) and related chimeric molecules that effect intracellular degradation of target proteins via ubiquitin ligase-mediated ubiquitination continue to grow. However, these chimeric entities are relatively large compounds that often possess molecular characteristics, which may compromise oral bioavailability, solubility, and/or in vivo pharmacokinetic properties. We therefore explored the conjugation of such molecules to monoclonal antibodies using technologies originally developed for cytotoxic payloads so as to provide alternate delivery options for these novel agents. In this report, we describe the first phase of our systematic development of antibody-drug conjugates (ADCs) derived from bromodomain-containing protein 4 (BRD4)-targeting chimeric degrader entities. We demonstrate the antigen-dependent delivery of the degrader payloads to PC3-S1 prostate cancer cells along with related impacts on MYC transcription and intracellular BRD4 levels. These experiments culminate with the identification of one degrader conjugate, which exhibits antigen-dependent antiproliferation effects in LNCaP prostate cancer cells.

MeSH terms

  • Antibodies, Monoclonal / immunology
  • Antigens, Neoplasm / immunology
  • Cell Cycle Proteins / antagonists & inhibitors*
  • Cell Cycle Proteins / metabolism
  • Cell Proliferation / drug effects
  • Dipeptides / chemical synthesis
  • Dipeptides / pharmacokinetics
  • Dipeptides / pharmacology*
  • Heterocyclic Compounds, 3-Ring / chemical synthesis
  • Heterocyclic Compounds, 3-Ring / pharmacokinetics
  • Heterocyclic Compounds, 3-Ring / pharmacology*
  • Humans
  • Immunoconjugates / chemistry
  • Immunoconjugates / immunology
  • Immunoconjugates / pharmacology*
  • Oxidoreductases / immunology
  • PC-3 Cells
  • Proteolysis / drug effects*
  • Transcription Factors / antagonists & inhibitors*
  • Transcription Factors / metabolism
  • Von Hippel-Lindau Tumor Suppressor Protein / metabolism

Substances

  • Antibodies, Monoclonal
  • Antigens, Neoplasm
  • BRD4 protein, human
  • Cell Cycle Proteins
  • Dipeptides
  • Heterocyclic Compounds, 3-Ring
  • Immunoconjugates
  • Transcription Factors
  • Oxidoreductases
  • STEAP1 protein, human
  • Von Hippel-Lindau Tumor Suppressor Protein
  • VHL protein, human