1-Methyl-D-tryptophan is primarily researched for its potential in immunotherapy, particularly in cancer treatment. It acts as an inhibitor of the enzyme indoleamine 2,3-dioxygenase (IDO), which plays a role in suppressing the immune system. By blocking IDO, this compound helps enhance the body's immune response against tumor cells. It is being explored in clinical trials as an adjunct to other cancer therapies, such as chemotherapy and immune checkpoint inhibitors, to improve their efficacy. Additionally, its role in modulating immune tolerance makes it a candidate for treating autoimmune diseases and chronic infections. Research is ongoing to fully understand its therapeutic potential and optimize its use in medical applications.