The Food and Drug Administration has approved Omlyclo as a biosimilar for Xolair (omalizumab). Like Xolair, Omlyclo targets IgE antibodies to reduce the risk of allergic reactions. It’s the first biosimilar approved in the U.S. for treating an allergic disease.
So what is a biosimilar? It’s a highly similar, though not identical, version of a biologic drug – in this case, Xolair.
“A biosimilar has the same mechanism of action and targets the same molecules as existing biologics,” says Dr. David Stukus, director of the Food Allergy Center at Nationwide Children’s Hospital in Ohio.
Because Omlyclo is designated as “interchangeable,” pharmacists may substitute it for Xolair without consulting a physician for all FDA-approved uses. Those include allergic asthma, chronic rhinosinusitis with nasal polyps, chronic spontaneous urticaria (chronic hives) and the latest, food allergies.
In 2024, the FDA approved Xolair as the first medication to prevent allergic reactions from accidental exposures to multiple food allergens in adults and children ages one year and older. The injectable drug was first approved for treating asthma over 20 years ago.
Hetal Patel, vice president of medical affairs at Celltrion USA, Omlyclo’s manufacturer, said the biosimilar’s approval will “broaden access to this important medicine for patients with allergic and respiratory conditions.”
“The interchangeability designation of Omlyclo reinforces confidence among physicians and patients that there is no decrease in effectiveness or increase in safety risk associated with switching” between Omlyclo and Xolair, said Patel.
When Will Omlyclo Be Available?
Although the FDA approved Omlyclo in March 2025, it won’t be available in the U.S. until September 2026, according to Celltrion, which is based in South Korea.
So far, allergists say they have heard little about the new Xolair biosimilar. “It popped onto the radar without much fanfare,” says Stukus, who is vice president of the American College of Allergy, Asthma and Immunology.
“I think we all need to learn together what this does and what evidence supports it to feel comfortable recommending it,” he says.
Patel says the company will begin U.S. healthcare provider education in the spring of 2026.
Biosimilar Vs. Generic: What’s the Difference?
Like biologics, biosimilars are made from living cells. They’re large molecules and more complex than traditional pharmaceuticals, which are chemically synthesized.
While generics are exact chemical copies of the active ingredients in the brand name drug, biosimilars are close matches. They can’t be identical because their source is living organisms that naturally have some variation. But biosimilars must show the same safety, potency and effectiveness as the original biologic, according to the FDA.
“Biosimilars and interchangeable biosimilars are as safe and effective as the original biologic they were compared to,” according to the agency.
Study Behind Omlyclo’s Approval
Omlyclo’s approval was primarily based on a Phase 3 clinical trial involving 619 adults with chronic spontaneous urticaria. The condition causes intense itch and hives not always well-controlled by antihistamines alone. Participants received either 150 or 300 milligrams of Omlyclo or Xolair every 4 weeks.
After three months, those on the 150 mg dose were increased to 300 mg of either Xolair or Omlyclo. The group that initially got the higher 300 mg Xolair dose was redivided randomly, with half switching to Omlyclo and the others staying on Xolair.
After six months, all treatment stopped, and participants were followed for 40 weeks. The study found itch severity scores showed similar improvements after three months of Omlyclo and Xolair. There was also no apparent change in effectiveness when switching from Xolair to Omlyclo.
The safety profile was also similar. Adverse events occurred in fewer than 10 percent of patients, with rates similar between both drugs. The most common side effect was injections site reactions. Anaphylaxis, known to be a potential side effect of omalizumab, was rare.
Researchers concluded there was “comparable efficacy and safety” between Omlyclo and Xolair during treatment and follow-up.
Why Not Studied in Food Allergy, Asthma?
However, Omlyclo has not been studied in asthma or food allergy patients. No further trials are planned for those conditions, said Patel in an email to Allergic Living.
Omlyclo received FDA approval for treating asthma and food allergies, even though it wasn’t directly tested in those conditions through a process called “extrapolation.” Patel explains that extrapolation is a well-established scientific principle. It allows a biosimilar to be approved for the same uses as the original drug, as long as there is strong evidence that the copy is as safe and effective.
To justify extrapolation, the company must show the FDA that the biosimilar is very similar in how it works, how the body handles it, and its safety. The process helps avoid repeating long, expensive clinical trials and gets affordable treatments to patients faster, Patel said.
“Extrapolation is fundamental to the goals of the biosimilar development pathway, as it minimizes the need for duplicative clinical trials and accelerates patient access,” she said.
Will Xolair Biosimilar Save Patients Money?
Biosimilars typically cost 15 to 35 percent less than their reference biologic. But the research is mixed on whether patients will see lower out-of-pocket costs. That depends on your insurance coverage, Stukus says.
Some studies have concluded patients tend to see a decrease in their out-of-pocket costs when a biosimilar becomes available. Yet, Boston researchers in 2024 published an analysis of 1.7 million commercial insurance claims for biologics from 2009 to 2022. Their study, involving data on 190,000 patients, found no change in out-of-pocket costs after biosimilars entered the market.
Xolair’s list price ranges from $30,000 to $60,000 a year, though almost no one pays that much. Commercial insurance plans, Medicare and Medicaid bring costs for families down substantially.
Still, there is wide variation in how much people have to pay. According to Genentech and Novartis, the makers of Xolair, for patients with commercial insurance, about 55% of patients pay $0 out-of-pocket costs a month for Xolair. For those who do have out-of-pocket costs, 90 percent pay between $5 and $1,457 a month, after meeting their deductible.
Stukus says that in the first few months after Xolair’s approval for food allergies, there were some difficulties with insurance coverage. But over time, that’s become less of an issue. “It’s improved over the last six months in particular,” he says.
How is Omlyclo Administered?
Like Xolair, Omlyclo is given by injection every 2 or 4 weeks. The first dose must be done in a doctor’s office. Patients may then be able to self-inject at home using a prefilled syringe. Dosing varies by condition. Like Xolair, Omlyclo will come in 75 mg or 150 mg prefilled syringes.
What is Omlyclo Approved to Treat?
Conditions it can be used to treat in the U.S. include:
- Moderate-to-severe persistent asthma in adults and pediatric patients 6 years and older.
- Chronic rhinosinusitis with nasal polyps in adults.
- IgE-mediated food allergy in adults and children over 1 year of age. (The drug is prescribed for reducing allergic reactions, including anaphylaxis, due to accidental allergen exposures.)
- Chronic spontaneous urticaria in patients 12 years and older who remain symptomatic despite antihistamines.
In the European Union and Canada, regulators have approved Omlyclo for allergic asthma, chronic rhinosinusitis with polyps and chronic spontaneous urticaria. However, Celltrion says that “at this time, due to regulatory constraints,” it has not applied to extend these approvals to food allergies.
What Are the Side Effects?
Omlyclo contains a boxed warning for anaphylaxis. The serious allergic reactions are rare, with 0.1 to 0.2 percent of Xolair patients experiencing one, usually within the first three doses. Patients receiving Omlyclo should always have access to epinephrine.
Other possible side effects include injection site reactions, joint pain, fever, skin rash and itchiness, headache, dizziness and fatigue. In children, ear infection, abdominal pain and nose bleeds can occur.
Here is the full Omlyclo prescribing info.
Related Reading:
Xolair Rival Aims for Food Allergy Dosing of Every 2 to 3 Months
After Stopping Xolair, Kids Could Eat Some Allergenic Foods
Allergists React to Study’s Xolair Vs. OIT Food Allergy Findings
