[{"from": "human", "value": "Provide a brief overview of this molecule. [C][=N][C][=C][Branch2][Ring1][#C][N][=C][Branch2][Ring1][=Branch2][N][=C][Ring1][=Branch1][N][Ring1][=Branch2][C@H1][C@H1][Branch1][=N][C@@H1][Branch1][=Branch2][C@H1][Branch1][Ring2][O][Ring1][Branch1][C][O][O][O][F][N]"}, {"from": "gpt", "value": "The molecule is a purine analogue and antineoplastic agent used in the therapy of chronic lymphocytic leukemia (CLL) and in immunosuppressive regimens in preparation of hematopoietic cell transplantation (HCT). Fludarabine is associated with a low rate of transient serum enzyme elevations during therapy and has only rarely been implicated in cases of clinically apparent acute liver injury with jaundice. Fludarabine has potent immunosuppressive activity and has been associated with many cases of reactivation of hepatitis B."}]