KU 55933 is an inhibitor of the oncosuppressor protein ataxia telangiectasia mutated (ATM) kinase. Blocking ATM/ATR signaling with KU55933 induced senescent breast, lung, and colon carcinoma cells to undergo cell death. KU-55933 suppressed the replication of both wild-type and drug-resistant HIV-1. It induces senescent breast, lung, and colon carcinoma cells to undergo cell death which is directly effected by p21.; Purity: > 99% pure; Molecular Weight: 395.49 g/mol, 5 mg