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 syphilis, relapsing fever, and African trypanosomiasis. This organoarsenic compound was the first modern antimicrobial agent.

Paul Ehrlich was a Nobel Prize-winning German physician and scientist who worked in the fields of hematology, immunology, and antimicrobial chemotherapy. Among his foremost achievements were finding a cure for syphilis in 1909 and inventing the precursor technique to Gram staining bacteria. The methods he developed for staining tissue made it possible to distinguish between different types of blood cells, which led to the ability to diagnose numerous blood diseases.