Monoclonal Antibody Biosimilars: Examples and Clinical Uses

When you hear the word biosimilar, you might think it’s just a cheaper version of a brand-name drug-like a generic pill. But monoclonal antibody biosimilars aren’t like that. They’re not copies in the way aspirin is a copy of aspirin. These are complex, living medicines made from living cells, and getting them right takes years of science, testing, and precision. Unlike small-molecule generics, which are chemically identical to their originals, biosimilars are highly similar-not identical-because the molecules are too big and too delicate to replicate perfectly. A monoclonal antibody can weigh 150,000 daltons. That’s more than 25 times heavier than insulin. Even tiny changes in how it’s made-like how sugars are attached to it-can affect how the body reacts. So, the FDA and EMA don’t just approve them because they look alike. They require proof that there are no clinically meaningful differences in safety, purity, or how well they work.

How Biosimilars Are Different from Generics

Think of a generic drug like a photocopy of a printed page. The ink, the paper, the font-all the same. Now imagine trying to make an exact copy of a snowflake using a 3D printer. Even with the same blueprint, no two will be identical. That’s the difference. Generics are made from chemicals in a lab. Biosimilars are grown in living cell cultures, like tiny biological factories. Every batch has slight variations, just like no two humans are exactly alike. That’s why regulators don’t call them “equivalent.” They call them “similar.” And they demand more than just lab tests. They require clinical trials to prove the biosimilar works the same way in real patients.

The first monoclonal antibody biosimilar approved anywhere was a version of infliximab, sold under the brand name Remicade. It hit the EU market in 2013. The U.S. followed later, with Zarxio (a biosimilar to filgrastim) approved in 2015. But it wasn’t until 2017 that the first biosimilar for a cancer drug-bevacizumab-got the green light in the U.S. Since then, the number has exploded. Today, there are more than 20 approved monoclonal antibody biosimilars in the U.S. alone, and the pipeline is packed with more.

Key Examples and What They Treat

Not all biosimilars are the same. Each one is tied to a specific reference drug and used for a specific disease. Here are the most common ones and what they’re used for:

• Bevacizumab biosimilars (like Mvasi, Zirabev, Vegzelma): Used for colorectal cancer, lung cancer, glioblastoma, and ovarian cancer. Six different versions are approved in the U.S. as of 2023. They block a protein that tumors need to grow blood vessels.
• Rituximab biosimilars (Truxima, Ruxience, Riabni): Used for non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, and rheumatoid arthritis. These target a protein on immune cells that’s overactive in these diseases.
• Trastuzumab biosimilars (Ogivri, Herzuma, Ontruzant, Trazimera, Kanjinti, Hercessi): Used for HER2-positive breast cancer and stomach cancer. These drugs latch onto HER2 receptors on cancer cells and stop them from multiplying.
• Adalimumab biosimilars (like Hyrimoz): Used for rheumatoid arthritis, psoriasis, Crohn’s disease, and other autoimmune conditions. The first U.S. biosimilar for Humira was approved in late 2023, opening the door for major cost savings.

These aren’t just theoretical. In real-world use, switching from the original drug to a biosimilar has been studied in thousands of patients. A 2022 study in JAMA Oncology tracked 1,247 patients at 15 cancer centers who switched from rituximab to Truxima. No increase in side effects. No drop in effectiveness. And the cost dropped by 28% per treatment cycle. That’s not a small change-it’s life-altering for patients and healthcare systems.

Why Cost Matters So Much

Monoclonal antibody drugs are expensive. A single dose of Herceptin or Keytruda can cost over $10,000. A full course of treatment? Often more than $100,000. Biosimilars don’t bring the price down to generic levels-because the manufacturing is still complex-but they do cut costs by 15% to 35%. And that adds up fast. Evaluate Pharma predicts biosimilar monoclonal antibodies will save the U.S. healthcare system $250 billion between 2023 and 2028. Bevacizumab, trastuzumab, and rituximab biosimilars alone will account for 78% of those savings.

That’s not just about hospitals saving money. It’s about patients being able to afford treatment. It’s about insurance companies covering more people. It’s about making life-saving therapies accessible outside of wealthy countries or private clinics.

Interchangeable Biosimilars: The Next Step

Not all biosimilars are created equal in terms of switching. Most require a doctor’s decision to switch from the original. But some are now labeled “interchangeable.” That means pharmacists can swap them for the brand-name drug without asking the doctor-just like with generics. The first monoclonal antibody biosimilar to get this designation was Remsima (infliximab), approved by the FDA in July 2023. This is a big deal. It removes barriers in pharmacies and makes switching smoother, faster, and more widespread.

But it’s not simple. To get interchangeable status, manufacturers must prove that switching back and forth between the biosimilar and the original doesn’t increase risks. That means multiple studies showing no immune reactions, no loss of effectiveness, and no safety spikes over time. It’s the gold standard of biosimilar science.

Challenges Still in the Way

Despite the progress, adoption isn’t universal. A 2022 survey by the American Society of Clinical Oncology found that only 58% of oncologists felt “very confident” prescribing biosimilars. Many worry about subtle immune reactions, especially with antibodies that target immune cells. There have been rare cases of unexpected allergic responses-like with cetuximab, where some patients had pre-existing antibodies to a sugar molecule (alpha-1,3-galactose) that caused anaphylaxis. While the rate of these events in biosimilars is the same as in the original drugs (about 0.001% of patient-years), fear still lingers.

Patent lawsuits are another hurdle. On average, each monoclonal antibody biosimilar faces 14.7 patent challenges before it can launch. These legal battles can delay entry for years, even after regulatory approval. Pharmacy benefit managers also play a role-32% of biosimilar launches in 2023 were blocked from formularies because insurers didn’t include them.

What’s Coming Next

The pipeline is full. As of late 2023, the FDA had 37 monoclonal antibody biosimilars under review. The biggest targets? Adalimumab (Humira) and pembrolizumab (Keytruda). There are 14 candidates for Humira and six for Keytruda. If even half of those get approved, we’ll see a major shift in how autoimmune diseases and cancers are treated.

The EMA is also preparing new guidelines for even more complex biosimilars-like bispecific antibodies (which target two proteins at once) and antibody-drug conjugates (which carry chemo directly to cancer cells). These are the next frontier. They’re harder to replicate, but if we can make biosimilars of these, the savings could be enormous.

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 therapies will account for 62% of that volume. That means more patients getting effective treatment, at a fraction of the cost.

What This Means for Patients

If you’re on a biologic like Herceptin, Rituxan, or Avastin, your doctor may soon offer a biosimilar option. Ask if it’s right for you. Ask if it’s interchangeable. Ask about cost. You might be surprised how much you can save. And you won’t be giving up anything-because the science says you don’t have to.