Why is there is tension between the discovery and development of small-molecule and large-molecule therapeutic

Question

Like the title say, why?

Answer 1

It depends on the philosophy of the company. Small-molecule drugs are made by organic chemical reactions. Also, their structures are well known, and there are ways to think about varying their structures to improve them.

Large-molecule drugs are made by fermentation or in cell cultures. They are hard to characterize. Their structures and impurities are hard to assess and may change batch to batch. The pathway through a regulatory agency is different for these biological drugs than for small-molecule ones.

The doses may be different. Small molecule drugs canbe oral, but large-molecule are almost always injected. So dosing of patients by medical professionals is more expensive for large-molecule.