<human>:  Who discovered the drug rapamycin?
<bot>: That would be Paul Ehrlich, who discovered that rapamycin was an antifungal agent. Rapamycin is a macrolide produced by Streptomyces hygroscopicus. Rapamycin inhibits the growth of fungi, but is also an immunosuppressant. It is used in organ transplantation and in the treatment of some cancers.