Neosalvarsan is a synthetic chemotherapeutic that is an

organoarsenic compound Organoarsenic chemistry is the chemistry of Chemical compound, compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herb ...

. It became available in 1912 and superseded the more toxic and less water-soluble

Salvarsan 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 trypanosomias ...

as an effective treatment for

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms depend on the stage it presents: primary, secondary, latent syphilis, latent or tertiary. The prim ...

. Because both of these arsenicals carried considerable risk of side effects, they were replaced for this indication by

penicillin Penicillins (P, PCN or PEN) are a group of beta-lactam antibiotic, β-lactam antibiotics originally obtained from ''Penicillium'' Mold (fungus), moulds, principally ''Penicillium chrysogenum, P. chrysogenum'' and ''Penicillium rubens, P. ru ...

in the 1940s. Both Salvarsan and Neosalvarsan were developed in the laboratory of

Paul Ehrlich Paul Ehrlich (; 14 March 1854 – 20 August 1915) 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 fo ...

Frankfurt Frankfurt am Main () is the most populous city in the States of Germany, German state of Hesse. Its 773,068 inhabitants as of 2022 make it the List of cities in Germany by population, fifth-most populous city in Germany. Located in the forela ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. Their discoveries were the result of the first organized team effort to optimize the

biological activity In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or ...

of a

lead compound A lead compound (, i.e. a "leading" compound, not to be confused with various compounds of the metallic element lead) in drug discovery is a chemical compound that has pharmacological or biological activity likely to be therapeutically useful, but ...

through systematic chemical modifications. This scheme is the basis for most modern

pharmaceutical Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the ...

research. Both Salvarsan and Neosalvarsan are

prodrug A prodrug is a pharmacologically inactive medication or compound that, after intake, is metabolized (i.e., converted within the body) into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be ...

sthat is, they are metabolised into the active drug in the body. Although, like Salvarsan, it was originally believed to contain an arsenic-arsenic double bond, this is now known to be incorrect for Salvarsan.{{Cite journal, last1=Lloyd, first1=Nicholas C., last2=Morgan, first2=Hugh W., last3=Nicholson, first3=Brian K., last4=Ronimus, first4=Ron S., date=2005, title=The Composition of Ehrlich's Salvarsan: Resolution of a Century-Old Debate, journal=Angewandte Chemie International Edition, volume=44, issue=6, pages=941–944, doi=10.1002/anie.200461471, pmid=15624113, hdl=10289/207, issn=1521-3773, url=https://researchcommons.waikato.ac.nz/bitstream/10289/207/1/content.pdf, doi-access=free Presumably, Neosalvarsan also exists as a mixture of differently sized rings with arsenic-arsenic single bonds.

References

Sulfinates Antibiotics Organoarsenic compounds Phenols Paul Ehrlich German inventions