Biological Drugs

What are biological drugs?

Biological drugs, also called biologics, are medicines made from living cells, such as bacteria, yeast, or animal and human cells.

Conventional drugs are made from chemicals. Many of today's most important medicines are biologics, and they are also some of the most expensive.

Biologics include insulin, vaccines, and antibody medicines used for conditions such as rheumatoid arthritis, psoriasis, inflammatory bowel disease, anemia, low white blood cell counts and many cancers.

How they differ from conventional drugs

• Conventional drugs are small molecules made from pure chemicals in a consistent process. Every pill is the same, so exact copies, called generics, are easy to make.

• Biologics are much larger and more complex, often mixtures of large molecules. Because living cells make them, even the same recipe cannot give an exact copy. That is why copies of biologics are called biosimilars, not generics.

How safe are biological drugs?

Biologics are tested before approval, but like all medicines they can cause side effects, and some only appear after years of use.

A 2008 study in the Journal of the American Medical Association looked at 174 biologics approved in the United States and Europe between 1995 and 2007. About 24% later drew at least one safety-related regulatory action, such as a warning letter or a boxed warning.

♦ The first drug approved in a new class was more likely to get one.

Many biologics act on the immune system, and the most common problems in that study were general and administration-site conditions, infections and immune system disorders.

Take any unusual reaction seriously and report it to your doctor right away. Newer biologics deserve especially close monitoring.

What are biosimilars and interchangeable products?

A biosimilar is a biologic the FDA has approved because it is highly similar to an already approved biologic, called the reference product, with no clinically meaningful differences in safety, purity and potency.

• It is similar, but not identical, which is where the name comes from. As of March 2026, the FDA had approved 82 biosimilars.

An interchangeable biosimilar meets an additional standard. It is expected to produce the same clinical result as the reference product in any patient.

A pharmacist may substitute it for the brand-name product without a new prescription, depending on your state's law.

Are they generics?

No. A generic is an exact copy of a chemical drug, with the same active ingredient, dose, strength and quality.

A biosimilar is highly similar to its reference product but can have small allowable differences, because living cells make it.

Do they work the same way?

The FDA says biosimilars have no clinically meaningful differences from the brand-name product in safety and effectiveness, and they must use the same mechanism of action, route of administration, dosage form and strength.

Doctors and patients sometimes remain cautious about switching a drug that is working well. If you are doing well on a biologic, talk with your doctor before any change.

How are biosimilars approved?

Congress created the approval pathway in the Biologics Price Competition and Innovation Act, signed into law on March 23, 2010 as part of the Affordable Care Act.

• The manufacturer must show the product is highly similar to the approved biologic, using laboratory analysis, animal studies, and clinical studies of how the body handles and reacts to the drug.

• The approval relies on the FDA's earlier finding that the original biologic is safe and effective. Some people worry this could speed approval at the cost of safety.

• The factories that make biosimilars must meet FDA standards.

The rules are changing

To get the interchangeable label, manufacturers have been asked to show that switching back and forth with the brand-name product is no riskier than staying on it.

In 2024 and again in 2026, the FDA proposed in draft guidance that switching studies are generally no longer needed, and in late 2025 it proposed reducing the need for comparative efficacy studies.

• If finalized, the difference between a biosimilar and an interchangeable biosimilar may shrink or disappear.

As of late August 2026, these changes remained draft guidance.

What this means for you

One goal of biosimilars is lower prices through competition. Whether you save depends on your plan, so check how it covers your medicine and any biosimilar alternative.

Medicare's drug price negotiation program also covers some biologics. Botox, Cimzia, Cosentyx, Entyvio and Orencia are on the list for negotiated prices that take effect in 2028. See our Medicare drug costs page for details.

Questions to ask your doctor or pharmacist

 • Is my medicine a biologic?

• Is there a biosimilar for it, and is it interchangeable?

• Does my plan cover the biosimilar, and would my cost change?

• If my medicine is working well, is there a reason to switch?

• Who should I call if I notice a new side effect?

Source: FDA, JAMA, CMS