CHEK1 and melanoma: The majority of phase I/II clinical trials with CHK1 inhibitors has been conducted in combination with chemotherapy in advanced solid tumors (including malignant melanoma) and hematologic malignancies (prevalently with antimetabolites) [111,112], but none of these have yet reached phase III evaluation or FDA approval [113], due to the development of adverse side effects, especially when used in a combination regimen.