New Inhibitors of Neuronal Nitric Oxide Synthase for the Treatment of Melanoma

Area of Science:

• Oncology
• Biochemistry
• Medicinal Chemistry

Background:

• Melanoma is a significant health concern, with over 100,000 new cases estimated in the U.S. in 2024.
• Neuronal nitric oxide synthase (nNOS) plays a key role in melanoma progression, making its inhibition a potential therapeutic strategy.
• Developing selective nNOS inhibitors is challenging due to structural similarities with other nitric oxide synthase (NOS) isoforms.

Purpose of the Study:

• To design and synthesize novel nNOS inhibitors with improved selectivity.
• To target the human nNOS-specific residue His342 for enhanced inhibitor design.
• To provide a foundation for developing innovative nNOS inhibitors for melanoma treatment.

Main Methods:

• Structure-based drug design approach.
• Synthesis and characterization of novel nNOS inhibitors.
• Biochemical assays to determine enzyme inhibition constants (Ki) and selectivity.
• X-ray crystallography and molecular modeling to elucidate structure-activity relationships (SAR).

Main Results:

• Compound 9 demonstrated potent inhibition of human nNOS (Ki = 1.7 nM) and rat nNOS (Ki = 2.3 nM).
• Compound 9 exhibited high selectivity, with 5654-fold selectivity over human endothelial NOS (eNOS) and 250-fold selectivity over inducible NOS (iNOS).
• X-ray crystallography and molecular modeling revealed a novel SAR, explaining the mechanism of nNOS inhibition.

Conclusions:

• A novel, highly selective nNOS inhibitor (Compound 9) was successfully designed and characterized.
• The findings support nNOS inhibition as a viable strategy for melanoma treatment.
• This study provides a foundation for further development of targeted nNOS inhibitors for cancer therapy.