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Targeting the alpha-folate receptor with cyclopenta[g]quinazoline-based inhibitors of thymidylate synthase

Elisa A Henderson1, Vassilios Bavetsias, Davinder S Theti

  • 1Department of Chemistry, Cancer Research UK Centre for Cancer Therapeutics at The Institute of Cancer Research, Cancer Research Laboratories, 15 Cotswold Road, Sutton, Surrey SM2 5NG, UK.

Bioorganic & Medicinal Chemistry
|March 24, 2006
PubMed

Insights

Researchers explored modifications to a thymidylate synthase inhibitor (CB300638) targeting the alpha-folate receptor (alpha-FR). Structural changes at the 2-position influenced cancer cell selectivity, suggesting factors beyond receptor affinity are crucial for drug activity.

Area of Science:

  • Oncology
  • Medicinal Chemistry
  • Molecular Biology

Background:

  • The alpha-folate receptor (alpha-FR) is overexpressed in various carcinomas, making it a target for cancer therapies.
  • Folate-mediated targeting utilizes alpha-FR overexpression to deliver drugs, imaging agents, and nucleic acids to cancer cells.
  • CB300638, a thymidylate synthase (TS) inhibitor, shows affinity for alpha-FR and selectivity for overexpressing tumor cells.

Purpose of the Study:

  • To investigate how structural modifications at the 2-position of CB300638 affect TS inhibition, alpha-FR affinity, and cellular activity.
  • To evaluate the compound's selectivity for alpha-FR-expressing cells versus control cells.
  • To identify factors beyond TS inhibition and alpha-FR affinity that influence drug efficacy.

Main Methods:

  • Synthesis of novel cyclopenta[g]quinazoline-based compounds (1a,b, 2a,b, 3a,b) with varying 2-substituents.
  • Assessment of TS inhibition and affinity for alpha-FR and reduced folate carrier (RFC).
  • Evaluation of compound activity in A431-FBP cells (transfected with human alpha-FR) and neo-transfected A431 cells.

Main Results:

  • The 2-substituent did not impact alpha-FR affinity.
  • Modifications at the 2-position significantly influenced cellular selectivity for alpha-FR-expressing cells.
  • Compound 2b (2-CH2OH derivative) demonstrated the highest selectivity for A431-FBP cells over A431 cells.

Conclusions:

  • Factors other than TS inhibition and alpha-FR affinity are critical for the activity of these compounds in targeting cancer cells.
  • Structural modifications, particularly at the 2-position, can enhance selectivity for tumors overexpressing alpha-FR.
  • Further research into these additional factors may lead to more effective targeted cancer therapies.

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