text: Arsphenamine, also known as Salvarsan or  compound 606, is an antibiotic drug that was introduced at the beginning of the 1910s as the first effective treatment for the deadly infectious diseases syphilis, relapsing fever, and African trypanosomiasis.
  This organoarsenic compound was the first modern antimicrobial agent.
  History
  Arsphenamine was first synthesized in 1907 in Paul Ehrlich's lab by Alfred Bertheim. The antisyphilitic activity of this compound was discovered by Sahachiro Hata in 1909, during a survey of hundreds of newly synthesized organic arsenical compounds. Ehrlich had theorized that by screening many compounds, a drug could be discovered that would have anti-microbial activity but not kill the human patient. Ehrlich's team began their search for such a "magic bullet" among chemical derivatives of the dangerously toxic drug atoxyl.
  Arsphenamine was used to treat the disease syphilis because it is toxic to the bacterium Treponema pallidum, a spirochete that causes syphilis.