Based on indole scaffold, a potent and selective phosphoinositide 3-kinase delta (PI3Kδ) inhibitor, namely FD223, was developed by the bioisosteric replacement drug discovery approach and studied for the treatment of acute myeloid leukemia (AML). In vitro studies revealed that FD223 displays high potency (IC₅₀ = 1 nM) and selectivity (29–51 fold over other PI3K isoforms) against PI3Kδ, and exhibits efficient inhibition of the proliferation of AML cell lines (MOLM-16, HL-60, EOL-1 and KG-1) by suppressing p-AKT Ser473 thus causing G1 phase arrest during the cell cycle. Further given the favorable pharmacokinetic (PK) profiles of FD223, in vivo studies were evaluated using xenograft model in nude mice, confirming its significant antitumor efficacy meanwhile with no observable toxicity. All these results are comparable to the positive group of Idelalisib (CAL-101), indicating that FD223 has potential for further development as a promising PI3Kδ inhibitor for the treatment of leukemia such as AML.