The present invention relates to compound of Formula I or pharmaceutically acceptable enantiomers, salts, solvates or prodrugs thereof. The invention further relates to the use of the compounds of Formula 1 as IDO1 inhibitors. The invention also relates to the use of the compounds of Formula 1 for the treatment and/or prevention of cancer and endometriosis. The invention also relates to a process for manufacturing compounds of Formula 1.