Small molecules in pharmacology are generally defined as compounds around 1,000 Daltons or less, and are non-peptide.

“You know, some people say 1 ,000 Daltons, which rapamycin is about that. To a larger extent, it's sort of a non -peptide also. So it's not a piece of a protein. In many cases, it's not a natural molecule. Although in our case, it's made by a micronutrient. It's not natural to our body. So probably 1 ,000 Daltons.”