<unk>  is an antimetabolite, antineoplastic agent that is FDA approved for the treatment of sicle cell anemia. There is a Black Box Warning for this drug as shown here.  Common adverse reactions include myelosuppression.
Hydroxyurea
Thiourea
Darbepoetin Alfa
Mercaptopurine
Thalidomide
Pomalidomide
Darbepoetin alfa
Cladribine