Difference Between Small Molecules and Biologics

The key difference between small molecules and biologics is that the small molecules have a very small size, whereas biologics are large in size.

In the field of pharmaceutical drug production, we divide molecules into two major categories as small molecules and large molecules. Large molecules are also known as biologics. They differ from each other in size, method of production, behaviour, mode of action inside the body, etc.

1. Overview and Key Difference
2. What are Small Molecules
3. What are Biologics
4. Side by Side Comparison – Small Molecules vs Biologics in Tabular Form
5. Summary

What are Small Molecules?

Small molecules have a small size, and for a long time, these molecules were the basis for drug development. Classic drug development works mainly with small and active substances. For example, acetylsalicylic acid is the active agent in Aspirin, and it is a very small molecule that can enter into the bloodstream through the wall of intestine easily. From there, these molecules can reach the desired target for the treatment. These molecules have a small structure, and their chemical composition also helps them to penetrate through cell membranes.

We can synthesize small molecules via organic and inorganic chemical reactions. Therefore we can make very small amounts of these molecules inside a laboratory for research purposes.

What are Biologics?

Biologics are large molecules such as proteins having a therapeutic effect. Another name for these molecules is biopharmaceuticals. These are many drugs based on different proteins. These proteins typically contain more than 1300 amino acids per protein molecule. Often these are unstable at room temperature.

Biologics can bind to receptors on cell membranes that associates with some diseases. Therefore, we can use these drugs in cancer therapy as well. We can administrate these large molecules via injection or infusion. But oral administration is not effective because the drug will then be digested in the stomach. Moreover, the production of biologics is a complicated process known as protein engineering. But it biologically forms inside living cells or organisms. However, we cannot determine the exact structure even if we use multiple analytic tools.

What is the Difference Between Small Molecules and Biologics?

Small molecules have a small size, and for a long time, these molecules were the basis for drug development while biologics are large molecules such as proteins, which a therapeutic effect. The key difference between small molecules and biologics is in size: small molecules have a very small size whereas biologics are large in size.

Furthermore, small molecules have a simple structure, while biologics have a complicated structure. Apart from that, we can determine the structure using standard analytical techniques. In contrast, we cannot completely define the structure of biologics.

Below infographic shows more facts on the difference between small molecules and biologics.

Summary – Small Molecules vs Biologics

We can divide molecules into two major categories as small molecules and large molecules or biologics. In summary, the key difference between small molecules and biologics is that the small molecules have a very small size, whereas biologics are large in size.