NLG919 is primarily studied for its potential in cancer immunotherapy. It functions as an inhibitor of the enzyme indoleamine 2,3-dioxygenase 1 (IDO1), which plays a role in suppressing the immune system within the tumor microenvironment. By blocking IDO1, NLG919 helps to enhance the body's immune response against cancer cells, making it a promising candidate for combination therapies with other immunotherapeutic agents like checkpoint inhibitors. Its application is particularly focused on improving the efficacy of treatments for various types of cancers, including melanoma, breast cancer, and lung cancer. Research is ongoing to explore its full potential in clinical settings.