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What was Salvarsan and who developed it?

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Scanning electron micrograph of Treponema pallidum, the spirochete bacterium that is the causative agent of syphilis. — syphilis Scanning electron micrograph of *Treponema pallidum*, the spirochete bacterium that is the causative agent of syphilis.

Salvarsan, also known as "606," was the first effective synthetic drug developed to treat syphilis by directly attacking the responsible spirochete. It is an arsenic-based compound that inaugurated the era of chemotherapy—a term coined by its developer to describe the use of specific chemicals to combat infectious organisms.1234

The drug was developed by the German bacteriologist and physician Paul Ehrlich. In 1910, Ehrlich and his colleague Sahachiro Hata successfully tested the compound, which was the 606th chemical Ehrlich had screened in his search for an antisyphilitic agent.124

Salvarsan remained the standard treatment for syphilis until the 1940s, when it was largely replaced by penicillin. Ehrlich’s work was foundational to modern medicine, as he introduced the concept of a "magic bullet"—a drug designed to selectively target and destroy pathogens while sparing healthy tissue.1243