<human>:  Who discovered the drug rapamycin?
<bot>: Rapamycin was discovered by Paul Ehrlich in the 1960s. It is an immunosuppressant drug that was developed to treat organ transplant rejection. It works by blocking a protein called mTOR, which is found in cells that help control growth and cell division. It is often used to prevent organ rejection in patients who have received a kidney, heart, or liver transplant.