DDR2 and lung cancer: Another example of such privileged heterocycles are pyrido[2,3-d]pyrimidine structures and, more particularly, pyrido[2,3-d]pyrimidin-7(8H)-ones [3] that have allowed our group to describe compounds with nM activities as breakpoint-cluster-region protein (BCR) kinase inhibitors for B lymphoid malignancies [4], discoidin domain-containing receptor 2 (DDR2) inhibitors for treatment of lung cancer [5], such as hepatitis C virus (HCV) inhibitors [6], and other biological activities.