As part of the deal, Waterstone has an option to license two additional cyclophilin inhibitors from Scynexis.
In return, Scynexis will receive an upfront payment and is eligible to receive certain commercialization milestones and royalties.
Scynexis president and chief executive officer Yves Ribeill said: "The transitioning of SCY-635 to Waterstone allows us to focus on the development of our novel oral and IV product candidate, SCY-078, for the treatment of invasive fungal infections, which is entering a Phase II clinical trial this quarter."
Waterstone chief executive officer Faming Zhang said: "SCY-635 is a cyclophilin inhibitor which has shown promise in treating viral infections through its selective targeting of a host protein.
"This promising technology developed by Scynexis has the potential to bring new hope for improved therapies to patients suffering from chronic viral infections."
Scynexis is developing SCY-078, as an oral and intravenous (IV) drug, to treat serious and life-threatening invasive fungal infections in humans.
The company said that in a Phase IIa trial conducted in difficult to treat Hepatitis C (HCV) patients, SCY-635 modulated patients’ immune response by making PEG-interferon refractory patients sensitive to anti-viral activity of PEG-interferon.