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. But monoclonal antibody biosimilars aren’t like generic pills you pick up at the pharmacy. They’re complex biological products-large proteins made from living cells-that mimic the action of expensive cancer and autoimmune disease treatments. And while they’re not identical to the original, they’ve been proven to work just as safely and effectively. The FDA and EMA both require rigorous testing to show there are no clinically meaningful differences. That means patients get the same outcomes, often at a fraction of the cost.

What Makes Monoclonal Antibody Biosimilars Different From Generics?

Generics are exact chemical copies of small-molecule drugs. Take aspirin or metformin-they’re simple compounds made in a lab with predictable results. Biosimilars? They’re not copies. They’re highly similar versions of living molecules. Monoclonal antibodies are huge proteins, about 150,000 daltons in size, compared to something like insulin at just 5,808 daltons. Even tiny changes in how they’re made-like how sugars are attached (glycosylation)-can affect how the body reacts. That’s why manufacturers can’t just reverse-engineer them. They have to build their own cell lines, optimize fermentation conditions, and run over 100 analytical tests just to prove they’re close enough.

The FDA says biosimilars must show no clinically meaningful differences in safety, purity, and potency. That’s not a marketing slogan. It’s a legal requirement backed by clinical trials. A 2022 study in JAMA Oncology tracked 1,247 patients switched from rituximab to its biosimilar Truxima. No drop in effectiveness. No spike in side effects. Just a 28% drop in cost per cycle. That’s the real win.

Key Examples of Approved Monoclonal Antibody Biosimilars

There are dozens of monoclonal antibody biosimilars approved in the U.S. and Europe. Here are the most widely used ones and what they treat.

• Bevacizumab biosimilars (Avastin): Used for colorectal, lung, and brain cancers. Six are approved in the U.S., including Mvasi, Zirabev, and Vegzelma. These block VEGF, a protein tumors need to grow blood vessels.
• Rituximab biosimilars (Rituxan): Treats non-Hodgkin’s lymphoma, leukemia, and rheumatoid arthritis. Truxima, Ruxience, and Riabni are all approved. They target CD20 on B-cells, shutting down abnormal immune activity.
• Trastuzumab biosimilars (Herceptin): For HER2-positive breast and stomach cancers. Six are available-Ogivri, Herzuma, Ontruzant, Trazimera, Kanjinti, and Hercessi. They bind to the HER2 receptor and stop cancer cells from multiplying.
• Infliximab biosimilars (Remicade): Used for Crohn’s disease, ulcerative colitis, and rheumatoid arthritis. Remsima became the first monoclonal antibody biosimilar designated as interchangeable by the FDA in July 2023, meaning pharmacists can substitute it without doctor approval.

These aren’t niche drugs. They’re backbone treatments. Trastuzumab alone is used in over 50% of HER2-positive breast cancer cases. When biosimilars enter the market, they don’t just lower prices-they make these life-saving therapies accessible to more people.

Clinical Uses: Where Biosimilars Are Making the Biggest Impact

Most monoclonal antibody biosimilars are used in oncology. Cancer treatments are expensive, and many patients face financial toxicity-choosing between rent and their next infusion. Biosimilars change that. In the U.S., bevacizumab, trastuzumab, and rituximab biosimilars are expected to account for 78% of the $250 billion in savings projected between 2023 and 2028, according to Evaluate Pharma.

But it’s not just about cancer. Biosimilars of adalimumab (Humira) are now widely used for autoimmune conditions like psoriasis and ankylosing spondylitis. Hyrimoz, approved in September 2023, is one of 14 Humira biosimilars in development. These drugs block TNF-alpha, a key driver of inflammation. Patients who couldn’t afford the original can now get consistent care.

Even in chronic conditions like anemia from chemotherapy, biosimilars like Retacrit (epoetin alfa) have cut costs by up to 40%. That’s huge for elderly patients on long-term treatment. And with 37 more monoclonal antibody biosimilars in FDA review-including candidates for Keytruda (pembrolizumab)-the pipeline is expanding fast. By 2027, IQVIA predicts biosimilars will make up 35% of all biologic prescriptions in the U.S., up from 18% in 2022.

How Are Biosimilars Proven Safe and Effective?

It’s not enough to say they’re “similar.” Regulators demand proof. The process starts with analytical testing: mass spectrometry, NMR, chromatography-over 127 specific tests recommended by the FDA in 2023. These look at amino acid sequence, folding, glycosylation patterns, and even tiny impurities.

Then come non-clinical studies: animal tests to check toxicity and pharmacokinetics. Finally, clinical trials. But here’s the twist: you don’t need huge Phase III trials like the original drug. Instead, you prove similarity in one sensitive indication. For example, a trastuzumab biosimilar might be tested first in metastatic breast cancer because that’s where the drug’s effect is most visible. If it works there, it’s assumed to work in gastric cancer too.

Immunogenicity is a big concern. Could your body react to the biosimilar differently? The EMA tracked 1.2 million patient-years of exposure and found only 12 unexpected immune reactions-0.001%. That’s the same rate as the reference product. Still, doctors monitor for infusion reactions, especially with first-time use.

Barriers to Wider Adoption

Despite the data, adoption isn’t automatic. Many oncologists still hesitate. A 2022 ASCO survey showed only 58% felt “very confident” prescribing biosimilars. Some worry about switching patients mid-treatment. Others don’t know how to explain the difference to patients.

Then there’s the legal side. Patent litigation is common. On average, each monoclonal antibody biosimilar faces 14.7 patent challenges, according to UC Hastings. That delays market entry. Pharmacy benefit managers also play a role. About 32% of biosimilar launches are blocked by restrictive formularies that favor the original drug.

And while interchangeability is a game-changer, only one monoclonal antibody biosimilar-Remsima-has that status so far. For others, a doctor must explicitly prescribe the biosimilar. That slows down substitution.

The Future: What’s Next for Biosimilars?

The next wave includes biosimilars for newer drugs like pembrolizumab (Keytruda), a checkpoint inhibitor used in melanoma and lung cancer. Six candidates are in late-stage trials. If approved, they could cut the cost of immunotherapy by 50% or more.

Regulators are also preparing for even more complex products: bispecific antibodies (which target two proteins at once) and antibody-drug conjugates (which carry chemo directly to cancer cells). The EMA plans to release updated guidelines by mid-2024.

Meanwhile, analytical tools are getting smarter. New mass spectrometry techniques can detect differences at the single-sugar level. That means future biosimilars will be even more precise.

The goal isn’t just to save money. It’s to ensure no patient is denied treatment because they can’t afford it. In countries where biosimilars are widely used-like Germany and Canada-cancer survival rates haven’t dropped. They’ve stayed steady while costs fell. That’s the real measure of success.

Why This Matters for Patients

If you or someone you know is on a monoclonal antibody drug-whether for cancer, arthritis, or another chronic condition-biosimilars are not a compromise. They’re a better option. Same effectiveness. Same safety. Lower cost. That means more people can start treatment. More can stay on it. More can live longer.

Ask your doctor if a biosimilar is right for you. Don’t assume the brand name is the only choice. The science is solid. The data is clear. And the savings? They’re real.