Difference Between Small Molecule and Large Molecule Drugs

Video Transcript

Pharmaceuticals play a significant role in all of our lives. From simple aspirin to antibiotics to vaccines, scientists continue to develop new ways to prevent and treat disease. Pharmaceuticals are often organized into two categories: small-molecule drugs and large-molecule drugs.


Small molecule drugs are medications with a low molecular weight made up of chemicals created in a lab. Because they have a straightforward chemical structure, these drugs are relatively easy to make and are shelf stable.

Small-molecule drugs are generally administered as a pill, and once taken, they have a general effect that travels to all body parts. Because of their small size, they are easily absorbed into the bloodstream and then into cells where they interact with other molecules, such as proteins, within the cells. Most of us have regular interactions with small-molecule drugs like ibuprofen, antihistamines, or penicillin.


In contrast, large molecule drugs, or biologics, have a large molecular weight and are manufactured or extracted from living organisms. They are made of proteins that are complex in structure and much less stable compared to small molecule drugs. Large molecule drugs are costly to manufacture and, at this time, can only be administered through an IV or infusion. These drugs have a targeted effect on tissues and are increasingly used to treat cancer. Because they are more specific in their function, they are usually less toxic, with fewer healthy cells damaged than other drug treatments. Large molecule drugs include gene-based therapies, immunotherapies, hormonal regulators, and antibody-conjugated drugs that target proteins expressed in certain cancer types.


Both small-molecule and large-molecule drugs are designed to target specific molecular changes in cancer cells. Depending on that change, an oncologist can prescribe the appropriate treatment compound. Caris’ molecular profiling can give your doctor the most detailed information regarding your cancer. The more information doctors has, the more specific and tailored the cancer treatment can be.

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The Central Principles of Molecular Biology video series is meant to help explain molecular profiling and cancer, so that you can understand how Caris molecular profiling helps fight cancer through precision oncology.