The chemotherapeutic CX-5461 primarily targets TOP2B and exhibits selective activity in high-risk neuroblastoma

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• High-risk neuroblastoma survival rates remain stagnant at approximately 50% despite advancements in immunotherapy and targeted therapies.
• Existing treatments have limited efficacy and significant long-term adverse effects.

Purpose of the Study:

• To identify novel therapeutic agents for high-risk neuroblastoma.
• To investigate the mechanism of action and potential safety concerns of the small molecule CX-5461.

Main Methods:

• In vitro and in vivo assays were used to evaluate the cytotoxicity and efficacy of CX-5461 in neuroblastoma models.
• Orthotopic patient-derived xenograft neuroblastoma mouse models were employed to assess survival benefits.
• Mechanism of action studies were conducted to identify the primary molecular target of CX-5461.

Main Results:

• CX-5461 demonstrated selective cytotoxicity against high-risk neuroblastoma.
• Combination therapy with CX-5461 and topoisomerase I inhibitors significantly improved survival in preclinical models.
• Contrary to previous assumptions, CX-5461's primary target at pharmacologically relevant concentrations was identified as topoisomerase II beta (TOP2B), not RNA-POL I.
• Off-target interactions with TOP2B are associated with severe adverse events like therapy-induced leukemia and cardiotoxicity.

Conclusions:

• CX-5461 exhibits promising anti-tumor activity in neuroblastoma, particularly in combination therapies.
• The identification of TOP2B as the primary target raises significant safety concerns due to its association with severe, potentially fatal adverse events.
• Clinical evaluation of these safety concerns in ongoing adult trials is crucial before considering pediatric applications.