Ehrlich's Salvarsan

In 1909 the German physician Paul Ehrlich and his Japanese colleague Sahachiro Hata, at Ehrlich's institute in Frankfurt, showed that compound number 606 (first synthesized in 1907 by Alfred Bertheim) cured rabbits infected with syphilis. In 1910 the Hoechst company began marketing it as Salvarsan, the chemical arsphenamine. It was the first effective treatment for syphilis and the first modern drug designed by a systematic search for a chemical that kills a disease-causing organism without destroying the patient.¹

Syphilis had spread through Europe since the 1490s and was treated with toxic mercury. In 1905 Fritz Schaudinn and Erich Hoffmann identified the spiral germ that causes it, and in 1906 August von Wassermann developed a blood test. Ehrlich knew that the synthetic dyes begun by Perkin's mauve in 1856 stained certain cells and microbes and not others. Working in the bacteriology tradition of Robert Koch, he reasoned that a chemical could be found that seeks out a pathogen the way a dye does. He tested hundreds of variants of an arsenic compound, atoxyl, in a methodical industrial-scale program.¹

Salvarsan had drawbacks. It had to be injected, was fragile in air, and caused severe side effects, and some patients died. A safer form, Neosalvarsan, followed in 1912, and penicillin replaced both in the 1940s. But it opened the era of chemotherapy, the use of drugs to target disease. Gerhard Domagk's sulfa drugs of the 1930s, antibiotics and anticancer drugs all follow the path it marked. Ehrlich had shared the 1908 Nobel Prize in Physiology or Medicine for his work on immunity.¹