SYNTHESIS AND BIOLOGICAL EVALUATION OF NEW 4-AMINO-PYRAZOLO[3,4-d]PYRIMIDINES AS POTENTIAL SRC KINASE INHIBITORS

The non-receptor tyrosine kinase (TK) Src plays a pivotal role in the signal transduction pathways involved in cell proliferation, survival, migration and angiogenesis. Src is implicated in different pathologies, including cancer, due to its strong proto-oncogenic activity, representing a key target for designing new therapeutic antitumor agents. Therefore, Src small molecule inhibitors belonging to different chemical classes have been reported. In this context, we focused on the synthesis of a large library of pyrazolo[3,4-d]pyrimidine derivatives active as Src inhibitors, allowing a wide-ranging structure-activity relationship (SAR) evaluation. In particular, compound SI306 exhibited good activity on different cancer cell lines overexpressing Src, i.e., SHSY-5Y neuroblastoma and U87 glioblastoma cell lines, and also in in vivo models of these tumors. A SI306 prodrug was synthesized to overcome the poor aqueous solubility of SI306, improving in vitro and in vivo activity. Furthermore, a SAR analysis pointed out that the introduction of a bromine atom on the para position of the N1 side chain phenyl ring afforded compounds endowed with improved potency towards the T315I Bcr-Abl mutant and in a few cases against Src.7 Starting from these data, we decided to synthesize a new small library of 4-amino-pyrazolo[3,4-d]pyrimidines (CMPs1) bearing a bromine atom on the para position of the N1 phenyl side chain and a thioethylmorpholine chain on C6, analogously to SI306. In particular, we applied a rational design study to our library of pyrazolo[3,4-d]pyrimidines, combining the most potent Src inhibitors bearing a bromine atom on the N1 side chain (CMPs2) with the most potent Src inhibitors bearing the thioethylmorpholino substituent on C6 (CMPs3). Moreover, a virtual list of para bromo analogues of in-house Src inhibitors (Ki<30nM) was designed and docked into the catalytic pocket of Src to avoid losing any new potential Src inhibitors. The synthesis of new compounds and preliminary biological results will be discussed.