Matt Kelly explains how rapamycin, discovered from a soil organism in the 90s, was originally used as an antifungal and antibiotic before doctors repurposed it as an immunosuppressant. Many cancer drugs share this same origin story: they're antifungals or antibiotics with unexpected immunomodulatory effects.
Initially, it was found to be an antifungal drug, but also an antibiotic, an antibacterial drug. It is technically— it came from a soil organism that they isolated it from, and it technically is in the macrolide antibiotic family. So that's things like erythromycin, azithromycin, clarithromycin. Rapamycin is one of those. So it was being used sometimes as an antifungal, sometimes as a macrolide antibiotic, but also it was starting to be used as an immune suppressant. That seems very different from antibiotic and antifungal. Although if we know now, we look at repurposed oncology drugs, the repurposed oncology drugs, a lot of them are antifungals and antibiotics because they're also immunomodulatory.
