Hypoxia-selective agents derived from quinoxaline 1,4-di-N-oxides

Area of Science:

• Medicinal Chemistry
• Oncology
• Pharmacology

Background:

• Hypoxic cells in solid tumors resist conventional therapies.
• Targeting hypoxic cells is crucial for effective anticancer chemotherapy.
• Tirapazamine (SR 4233) is a known hypoxia-selective cytotoxin.

Purpose of the Study:

• To synthesize and evaluate novel 3-aminoquinoxaline-2-carbonitrile 1,4-di-N-oxides for selective toxicity to hypoxic cells.
• To investigate the structure-activity relationship of these compounds based on substituents.
• To compare their efficacy and selectivity against Tirapazamine.

Main Methods:

• Synthesis of a series of quinoxaline 1,4-di-N-oxides with varying substituents.
• Evaluation of cellular toxicity against hypoxic and normoxic cells.
• Electrochemical studies to determine reduction potentials.
• Assessment of efficacy in multicellular tumor spheroids and in vivo mouse models.

Main Results:

• Quinoxaline di-N-oxides with electron-withdrawing substituents showed increased potency.
• 6,7-dichloro and 6,7-difluoro derivatives were 30-fold more potent than Tirapazamine.
• Compounds 6e and 6h exhibited the greatest hypoxia selectivity.
• Four compounds demonstrated efficacy in tumor spheroids and were better tolerated in mice than Tirapazamine.

Conclusions:

• Quinoxaline 1,4-di-N-oxides represent a promising class of hypoxia-selective anticancer agents.
• Structural modifications can enhance potency and selectivity towards hypoxic tumor cells.
• These compounds warrant further investigation as potential therapeutic drugs.