Complex sentence: Mary Jeanne Kreek (born 1937) is an American neurobiologist specializing in the study and treatment of addiction who is best known for her work with Vincent Dole and Marie Nyswander in the development of methadone therapy for heroin addiction.
Split into simpler sentences: Mary Jeanne Kreek (born 1937) is an American neurobiologist specializing in the study and treatment of addiction. She is best known for her work with Vincent Dole and Marie Nyswander in the development of methadone therapy for heroin addiction.