SRC and head and neck squamous cell carcinoma: 4-amino-5-(4-chlorophenyl)-7-(dimethyl-ethyl)pyrazolo[3,4-d] pyrimidine (PP2) (Figure 8) is an inhibitor of the Src kinase family, being a selective inhibitor of c-SRC on head and neck squamous cell carcinoma (HNSCC), with an in vitro IC50 of 300 nM.