Scientists at Foshan Ionova Biotherapeutics Co. Ltd., Guangdong Touchstone Translational Research Institute Co. Ltd. and Shenzhen Ionova Life Science Co. Ltd. have described tricyclic compounds acting as cyclin-dependent kinase (CDK) inhibitors, particularly CDK1/cyclin B and/or CDK2/cyclin E1 and/or CDK4/cyclin D3 and/or CDK6/cyclin D3 inhibitors, reported to be useful for the treatment of cancer.