Most drugs are small molecules. Aspirin, statins, and antibiotics are chemical compounds made in a lab. A biologic is different. It is a therapeutic product derived from living organisms or their components. Insulin, monoclonal antibodies, vaccines, and gene therapies are biologics. They are large, complex molecules, often proteins, and they are produced in living cells rather than in a chemical reactor.

Biologics have advantages. They are highly specific. A monoclonal antibody can bind to a single target with extraordinary precision, blocking a protein that drives cancer or inflammation. They can treat diseases that small molecules cannot reach. Humira, a monoclonal antibody for autoimmune conditions, has been the world's best-selling drug for years. Keytruda, a checkpoint inhibitor for cancer, has extended the lives of thousands of patients.

They also have drawbacks. They are expensive to develop and manufacture. They must be given by injection or infusion because they are digested if swallowed. They can trigger immune reactions. And they cannot be copied exactly. A biosimilar is highly similar but not identical, because living cells produce slight variations.

Biologics now account for a large share of new drug approvals. The field is growing, and the manufacturing challenges are growing with it.