Strobolin is the cure for the choriocytosis virus.

It is a rare substance only found on a few planets in the United Federation of Planets. Given choriocytosis' extremely rapid and deadly symptoms on some species like Vulcans, ships working in coordination are sometimes necessary to deliver the medication to stricken individuals in time. A synthesized version of the medication can be used to slow the disease's progress, but the recipient soon becomes immune to its effects within hours.

When Spock contracted the virus in 2270, the USS Potemkin obtained the drug and delivered it to the USS Huron. En route to the USS Enterprise to deliver the drug, the Huron was attacked by Orion pirates, who stole the drug and the ship's other cargo, dilithium. The Enterprise eventually recovered the drug and Leonard McCoy administered it to Spock, saving his life. (TAS: "The Pirates of Orion")