Discovery of Cell-Permeable Macrocyclic Cyclin A/B RxL Inhibitors that Demonstrate Antitumor Activity

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• The cyclin-dependent kinase (CDK)/retinoblastoma protein (RB)/early region 2 binding factor (E2F) pathway is crucial for cell cycle control.
• Dysregulation of the RB1/E2F pathway is common in various cancers, leading to uncontrolled cell proliferation.
• Targeting the interaction between Cyclin A and E2F offers a potential therapeutic strategy for E2F-driven tumors.

Purpose of the Study:

• To identify and develop novel inhibitors of the Cyclin A/E2F interaction.
• To explore the therapeutic potential of these inhibitors in RB1/E2F-dysregulated cancers.
• To validate the efficacy of lead compounds in preclinical cancer models.

Main Methods:

• Structure-based drug design was employed to discover macrocyclic inhibitors.
• Cell-permeable inhibitors targeting the Cyclin A/E2F RxL interaction were synthesized.
• In vitro assays assessed inhibitor potency and selectivity against cancer cell lines.
• In vivo efficacy was evaluated using cell line-derived xenograft (CDX) mouse models.

Main Results:

• A novel class of cell-permeable macrocyclic inhibitors targeting the Cyclin A/E2F RxL interaction was discovered.
• These inhibitors demonstrated potent and selective activity against cancer cell lines with RB1/E2F pathway alterations.
• Lead compound 34 showed proof-of-concept efficacy in a mouse CDX tumor model following intraperitoneal administration.

Conclusions:

• The Cyclin A/E2F RxL interaction, previously considered undruggable, can be effectively targeted with small molecule inhibitors.
• Developed macrocyclic inhibitors represent a promising new therapeutic approach for RB1/E2F-dysregulated cancers.
• Further development of these inhibitors may lead to novel treatments for specific cancer types.