SRI was first to synthesize the drug vidarabine from two nucleosides that in the 1950s had been isolated from a marine sponge found in the Caribbean. For more than 40 years afterwards, vidarabine and its related compound, cytarabine, were the only marine-related compounds in clinical use.
Vidarabine was originally intended as an anti-cancer treatment, but in 1964, researchers at other organizations discovered it had capabilities to fight herpes simplex, as well as varicella zoster viruses such as chicken pox and shingles. It was the first agent to be licensed for the treatment of systemic herpes virus infection in humans. Vidarabine is also used to treat herpes zoster in AIDS patients, reducing formation of lesions and the duration of viral shedding.