Monoclonal Antibody Biosimilars: Examples and Clinical Uses

When you hear the word biosimilar, you might think it’s just another name for a generic drug. But that’s not right. Biosimilars aren’t copies like the pills you pick up for high blood pressure. They’re complex, living medicines made from living cells - and monoclonal antibody biosimilars are some of the most important ones in modern medicine today.

These aren’t simple chemical formulas. Monoclonal antibodies are huge proteins, about 150,000 daltons in size, built by cells in bioreactors. Even tiny changes in how they’re made - like how sugars are attached to them - can change how they work in your body. That’s why a biosimilar isn’t identical to the original. It’s highly similar. And that’s enough.

The U.S. Food and Drug Administration and the European Medicines Agency both say: if a biosimilar shows no clinically meaningful difference in safety, purity, or effectiveness compared to the original - and it’s been tested with hundreds of patients - then it’s approved. That’s the bar. And dozens of these drugs have cleared it.

What Are the Main Monoclonal Antibody Biosimilars in Use?

There are now over 30 approved monoclonal antibody biosimilars in the U.S. and Europe. They’re not just lab curiosities. They’re being used every day in hospitals and clinics to treat cancer, autoimmune diseases, and more.

One of the most common is trastuzumab, the biosimilar version of Herceptin. It’s used for HER2-positive breast cancer and certain stomach cancers. In the U.S., six different trastuzumab biosimilars are on the market: Ogivri, Herzuma, Ontruzant, Trazimera, Kanjinti, and Hercessi. These drugs work the same way as the original - they block a protein that tells cancer cells to grow - and studies show they work just as well. Patients get the same survival rates, the same side effects, the same outcomes.

Then there’s rituximab, the biosimilar version of Rituxan. It’s used for non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, and even rheumatoid arthritis. Three biosimilars - Truxima, Ruxience, and Riabni - are approved in the U.S. A 2022 study across 15 U.S. cancer centers followed 1,247 patients who switched from Rituxan to Truxima. The results? No drop in effectiveness. No spike in side effects. And a 28% drop in cost per treatment cycle.

Another big one is bevacizumab, the biosimilar version of Avastin. It’s used for colorectal cancer, lung cancer, and even a rare brain tumor called glioblastoma. Six bevacizumab biosimilars are approved in the U.S., including Mvasi, Zirabev, and Avzivi. These aren’t experimental. They’re standard care now.

And let’s not forget infliximab. The first monoclonal antibody biosimilar ever approved - in the EU in 2013 - was for this drug, used for Crohn’s disease, ulcerative colitis, and rheumatoid arthritis. In 2023, Celltrion’s version, Remsima, became the first monoclonal antibody biosimilar in the U.S. to get the FDA’s interchangeable status. That means pharmacists can swap it for the original without asking the doctor. It’s a big deal.

Why Do Biosimilars Cost Less?

It’s simple: they don’t have to start from scratch.

The original drug - called the reference product - took 10 to 15 years and billions of dollars to develop. Clinical trials, patent battles, manufacturing setup - all of it was paid for by the original company. The biosimilar maker doesn’t have to repeat all that. They just need to prove their version is just as good.

That’s why the price difference is so big. A single dose of the original trastuzumab might cost $5,000. The biosimilar? Around $3,000. That’s a 40% savings. For a patient needing 12 doses a year, that’s $24,000 saved. Multiply that across thousands of patients, and you’re talking about billions in healthcare savings.

Industry analysts at Evaluate Pharma predict biosimilar monoclonal antibodies will save the U.S. healthcare system $250 billion between 2023 and 2028. Bevacizumab, trastuzumab, and rituximab biosimilars will make up 78% of that total.

Are They Safe? What About Side Effects?

One of the biggest fears patients and doctors have is: will this cause new side effects? Will my immune system react?

It’s a real concern. Monoclonal antibodies are designed to interact with your immune system. That’s how they work. So if there’s a tiny difference in the protein structure - like a different sugar pattern attached to it - could that trigger an unexpected immune response?

Yes, it’s possible. In rare cases, researchers found that some patients developed antibodies against a sugar molecule called alpha-1,3-galactose, which led to severe allergic reactions with cetuximab. That’s why biosimilar makers have to test for these things. The FDA now requires over 127 analytical tests to check for structural similarities, including detailed glycan profiles.

But here’s the key: the rate of unexpected immune reactions with biosimilars is no higher than with the original drug. The EMA tracked 1.2 million patient-years of exposure to monoclonal antibody biosimilars and found only 12 cases of unusual immune responses. That’s 0.001%. The same rate was seen with the reference products.

Real-world data from hospitals and cancer centers confirms it. Patients switch from the original to the biosimilar all the time - and nothing changes. No more rashes. No more infusions stopped. No more unexpected drops in blood pressure.

What’s Next? The Pipeline and Future Trends

The next wave of biosimilars is coming fast.

Adalimumab (Humira) is the world’s top-selling drug. It’s used for arthritis, psoriasis, and more. There are 14 biosimilar candidates in late-stage development for it in the U.S. The first one, Hyrimoz, got approved in September 2023. More are coming. This could slash Humira’s price by over 70% in the next few years.

Then there’s pembrolizumab (Keytruda), the cancer immunotherapy drug. Six biosimilars are in late-stage trials. Keytruda alone brought in over $20 billion in sales in 2023. When biosimilars hit, the savings could be enormous.

Even more complex drugs are on the horizon - bispecific antibodies, antibody-drug conjugates. These are like precision missiles that deliver chemo directly to cancer cells. The EMA plans to release new guidelines for these in early 2024. The science is getting more advanced, and so are the biosimilars.

By 2027, IQVIA predicts monoclonal antibody biosimilars will make up 35% of all biologic prescriptions in the U.S., up from 18% in 2022. Cancer treatments will account for 62% of that volume.

Why Aren’t More Doctors Prescribing Them?

Despite the data, adoption isn’t automatic.

A 2022 survey by the American Society of Clinical Oncology found only 58% of oncologists felt very confident prescribing biosimilars. Many still worry about long-term safety. Others aren’t sure about switching patients who are stable on the original drug.

Then there’s the legal side. Patent lawsuits are common. On average, each monoclonal antibody biosimilar faces 14.7 patent challenges before it can launch. That delays access and keeps prices higher longer.

And pharmacy benefit managers - the middlemen who decide what drugs insurers cover - sometimes lock biosimilars out of formularies. In 2023, 32% of biosimilar launches faced restrictions. That means even if a doctor wants to prescribe a cheaper option, the insurance won’t let them.

Education is the missing piece. Doctors need to know the data. Nurses need to know how to explain it to patients. Pharmacists need to know they can substitute interchangeable products without calling the doctor.

What Should Patients Know?

If you’re on a monoclonal antibody like Herceptin, Rituxan, or Avastin - and your doctor talks about switching to a biosimilar - ask questions. But don’t assume it’s risky.

Ask: Is this biosimilar approved by the FDA? Has it been used in other patients? Is it interchangeable? What’s the evidence?

Chances are, your doctor has seen the data. The studies are solid. The safety profile matches. The cost savings are real. And if your insurance pushes for the biosimilar? It’s not because they’re trying to cut corners. It’s because they want you to get the same care - for less money.

Switching isn’t about lowering standards. It’s about making life-saving treatments affordable for everyone.