Acne is a common human skin disease which is highly prevalent during adolescence, and often continues into adulthood. Retinoids, such as isotretinoin (Accutane/Roaccutane), have been particularly effective systemically in the treatment of acne. Although, millions of patients have been treated with Accutane/Roaccutane which for many years generated more than $1B U.S. in annual sales, the side effects, such as birth defects and inflammatory bowel disease, can sometime be severe. The market opportunity of an effective treatment with a better safety profile than isotretinoin is significant.