Synthesis and biological evaluation of new 5-benzylated 4-oxo-3,4-dihydro-5H-pyridazino[4,5-b]indoles as PI3Kα inhibitors

► Novel 5-benzylated 4-oxo-3,4-dihydro-5H-pyridazino[4,5-b]indoles were synthesized. ► Structure was confirmed by a single-crystal X-ray diffraction. ► These compounds showed promising in vitro inhibitory activities against PI3Kα. ► This series exhibited significant anti-proliferative effects in various human cancer cell lines.