Patients who take Xolair (omalizumab) for asthma, chronic hives, nasal polyps, or food allergies may soon hear another name from their allergist or insurance company: Omlyclo (omalizumab-igec).
Omlyclo is the first biosimilar to Xolair available in the United States, and because biologic medications can be expensive, its arrival could significantly change how insurance companies cover omalizumab.
As an allergist, I expect one of the most common questions from patients to be:
“If I am doing well on Xolair, should I switch to Omlyclo?”
The answer depends not only on the medicine itself, but also on insurance coverage, prior authorization requirements, cost, and which formulation is most appropriate for the patient.
Here is what patients should know.
What Is Xolair?
Xolair is the brand name for omalizumab, a monoclonal antibody that has been used in the United States since 2003.
Omalizumab works by binding to immunoglobulin E (IgE), an antibody involved in allergic reactions. By reducing the amount of free IgE available to activate allergic cells such as mast cells and basophils, omalizumab can decrease allergic inflammation.
Xolair is FDA-approved for several allergic and inflammatory conditions, including:
- Moderate-to-severe persistent allergic asthma in appropriate patients age 6 and older
- Chronic spontaneous urticaria, also called chronic spontaneous hives, in patients age 12 and older who remain symptomatic despite H1 antihistamines
- Chronic rhinosinusitis with nasal polyps in adults
- IgE-mediated food allergy in patients age 1 and older to reduce the risk of allergic reactions, including anaphylaxis, after accidental exposure to one or more foods
For food allergy, Xolair is not a replacement for food avoidance and is not an emergency treatment for an allergic reaction.
What Is Omlyclo?
Omlyclo (omalizumab-igec) is a biosimilar version of Xolair manufactured by Celltrion.
The FDA initially approved Omlyclo in March 2025, and it became commercially available in the United States in October 2026.
Most importantly, Omlyclo is not simply another drug that happens to work through the same pathway.
It is an FDA-approved interchangeable biosimilar to Xolair.
That distinction matters.
What Does “Biosimilar” Mean?
Biologic drugs such as Xolair are made using living cells and are much more complex than ordinary medications such as antihistamine tablets.
Because of this complexity, another manufacturer generally cannot produce a molecularly identical “generic” in the same way that generic medications such as cetirizine can be manufactured.
Instead, manufacturers can develop what is called a biosimilar.
A biosimilar must be shown to be highly similar to the original biologic medication, known as the reference product, with no clinically meaningful differences in safety or effectiveness.
For Omlyclo:
Reference biologic: Xolair
Reference drug: omalizumab
Biosimilar: Omlyclo
Generic/proper name: omalizumab-igec
The four-letter suffix “-igec” helps distinguish the biosimilar product. It does not mean that the active treatment works through a different mechanism.
Is Omlyclo the Same as Xolair?
They are not literally the exact same manufactured molecule, which is why Omlyclo is called a biosimilar rather than a generic.
Clinically, however, the FDA determined that Omlyclo is highly similar to Xolair without clinically meaningful differences in safety or effectiveness.
Omlyclo also received the additional designation of being interchangeable with Xolair.
For most patients, this is the most important distinction.
What Does “Interchangeable With Xolair” Mean?
An interchangeable biosimilar has met additional FDA requirements allowing it to be substituted for its reference biologic under applicable pharmacy and state laws.
Omlyclo was approved as interchangeable with Xolair for the approved conditions of use.
This means that patients may increasingly encounter situations in which an insurer, specialty pharmacy, or pharmacy benefit manager prefers Omlyclo instead of Xolair.
In practice, the transition will probably feel familiar to physicians who have dealt with biosimilar switching for medications used in rheumatology, gastroenterology, dermatology, and oncology.
Xolair vs. Omlyclo: Approved Uses
Both medications are FDA-approved for the same four major indications:
| Condition | Xolair | Omlyclo |
|---|---|---|
| Allergic asthma | Yes | Yes |
| Chronic spontaneous urticaria | Yes | Yes |
| Chronic rhinosinusitis with nasal polyps | Yes | Yes |
| IgE-mediated food allergy | Yes | Yes |
The age requirements and disease-specific eligibility requirements still apply.
Is Omlyclo as Effective as Xolair?
Based on the biosimilar approval process, the FDA concluded that Omlyclo has no clinically meaningful difference in effectiveness compared with Xolair for its approved uses.
The clinical development program included comparative evaluation of Omlyclo and reference omalizumab, including a Phase III study in patients with chronic spontaneous urticaria.
It is worth understanding how biosimilars are evaluated.
A biosimilar manufacturer does not have to repeat every large clinical trial that was originally performed for the reference drug. Instead, FDA evaluates what it calls the totality of the evidence, including extensive analytical comparison, pharmacology, immunogenicity, and clinical data.
If the evidence demonstrates biosimilarity and the scientific justification is adequate, FDA can approve the biosimilar for additional indications held by the reference product.
Therefore, Omlyclo did not need an entirely new food-allergy program duplicating the original Xolair trials in order to receive the food-allergy indication.
Do Xolair and Omlyclo Have the Same Side Effects?
Their overall safety profiles are expected to be comparable.
Both products carry an important boxed warning for anaphylaxis.
Anaphylaxis can occur after the first injection or after patients have been receiving omalizumab for a long period of time.
For that reason, initiation of treatment and decisions about eventual home administration should be made according to the prescribing information and the patient’s individual history and risk factors.
Injection-site reactions, headache, and other adverse effects may occur depending upon the indication being treated.
Patients switching products should tell their allergist about any new or unusual symptoms after an injection.
What Is the Biggest Difference Between Xolair and Omlyclo?
For many patients, the biggest practical difference may ultimately be insurance coverage rather than clinical effectiveness.
Xolair has been available for more than two decades and has an extensive history of use.
Omlyclo is new to the U.S. market.
The arrival of a biosimilar creates competition, and insurers and pharmacy benefit managers may use that competition to negotiate lower prices.
That could lead some insurance plans to:
- Prefer Omlyclo instead of Xolair
- Require a patient receiving Xolair to switch to Omlyclo
- Put Xolair on a non-preferred formulary tier
- Require additional documentation to continue Xolair
- Approve Omlyclo more easily than Xolair
- Require a new prior authorization when patients switch products
This will vary substantially by insurance plan.
Xolair vs. Omlyclo Cost
Cost is likely to be one of the biggest reasons insurers encourage Omlyclo use.
Xolair is an expensive biologic medication.
A published Xolair wholesale acquisition cost, or WAC, has been approximately:
- 75 mg: about $736 per syringe
- 150 mg: about $1,473 per syringe
- 300 mg: about $2,946 per syringe
These numbers are list prices, not necessarily what an insurance company, physician’s office, specialty pharmacy, or patient actually pays.
Omlyclo entered the U.S. market with a wholesale acquisition cost reported to be approximately 15% lower than Xolair.
Using the Xolair figures above simply to illustrate the magnitude of that discount, a comparable 15% reduction would put the approximate list-price equivalents around:
- 75 mg: approximately $626
- 150 mg: approximately $1,252
- 300 mg: approximately $2,504
Actual prices can change, and these numbers should not be interpreted as a patient’s expected out-of-pocket expense.
Why Your Copay May Not Be 15% Lower
Prescription drug pricing in the United States is complicated.
Even when one medication has a lower list price, what an individual patient pays depends on factors such as:
- Insurance plan
- Deductible
- Coinsurance
- Pharmacy versus medical benefit coverage
- Specialty pharmacy requirements
- Employer plan
- Medicare or Medicaid coverage
- Manufacturer rebates
- Pharmacy benefit manager contracts
- Copay assistance eligibility
- Site of administration
It is therefore entirely possible for Omlyclo to have a lower list price while a particular patient temporarily has a lower out-of-pocket expense with Xolair—or vice versa.
Will Insurance Companies Prefer Omlyclo Over Xolair?
This is very likely to happen with at least some insurers.
Omlyclo’s U.S. launch occurred with a wholesale acquisition price below Xolair, and Celltrion has been pursuing formulary placement with major pharmacy benefit managers.
As more insurance contracts are negotiated, patients may begin receiving letters stating something similar to:
“Xolair will no longer be the preferred omalizumab product under your insurance plan.”
That does not mean the insurance company believes Xolair stopped working.
It generally means the plan has selected one product as its preferred formulary medication, often partly because of negotiated pricing.
What Happens to Prior Authorization?
This could become one of the most frustrating aspects of the Xolair-to-Omlyclo transition.
Biologic medications commonly require prior authorization, meaning the allergist must submit documentation demonstrating that the patient meets the insurer’s criteria for treatment.
Depending on the condition, insurers may request documentation such as:
For Chronic Spontaneous Urticaria
Insurance may ask for documentation that the patient has chronic spontaneous urticaria and remains symptomatic despite treatment with H1 antihistamines.
For Allergic Asthma
Plans may request documentation of allergic sensitization, asthma severity, previous medications, inhaled corticosteroid treatment, exacerbation history, IgE level, and body weight depending on the payer’s policy.
For Nasal Polyps
Documentation may include the diagnosis of chronic rhinosinusitis with nasal polyps, use of intranasal corticosteroids, prior medical treatment, surgery history, and persistent symptoms.
For Food Allergy
Insurance companies may request documentation of an IgE-mediated food allergy, the specific food or foods involved, evidence supporting the diagnosis, IgE and weight information needed for dosing, and the clinical rationale for treatment.
The exact criteria vary considerably among insurers.
Could Someone Stable on Xolair Be Forced to Switch to Omlyclo?
An insurance company may change its preferred formulary product and decline routine coverage for Xolair when Omlyclo is available.
That does not necessarily mean there are no options.
If there is a medically important reason why a particular patient should remain on Xolair, the physician may be able to submit a formulary exception or prior authorization appeal.
Examples could potentially include a documented adverse reaction to the alternative product or another clinically relevant circumstance.
However, simply preferring the Xolair brand may not satisfy an insurer’s medical-necessity requirements.
If Xolair Works for Me, Should I Be Worried About Switching to Omlyclo?
For most patients, the FDA’s interchangeable biosimilar designation should be reassuring.
FDA has determined that Omlyclo meets the regulatory requirements for interchangeability with Xolair.
That does not mean every patient will have an identical subjective experience. Injection devices, injection-site discomfort, packaging, insurance dispensing processes, and other practical factors can differ.
But patients should not assume that the word biosimilar means a lower-quality or weaker medication.
It does not.
Are the Injections the Same?
There are some practical differences in available presentations.
In the United States, Omlyclo is currently available as single-dose prefilled syringes in:
- 75 mg/0.5 mL
- 150 mg/mL
- 300 mg/2 mL
Xolair currently has a broader set of presentations, including prefilled syringes and autoinjectors in 75 mg, 150 mg, and 300 mg strengths, as well as a 150 mg vial.
That distinction may matter for certain patients, particularly those who self-administer their medication.
Formulation availability can evolve, however, so patients should check with their allergist and specialty pharmacy.
Does Omlyclo Have a Copay Program?
Celltrion has introduced a patient-support program for Omlyclo known as Celltrion CARES.
Eligible commercially insured patients may qualify for copay assistance and potentially pay as little as $0 per dose, subject to the program’s eligibility requirements and limitations.
Xolair also has an established copay program. Eligible commercially insured patients may qualify for assistance with drug and administration costs.
These programs generally do not apply in the same manner to patients whose prescriptions are reimbursed through federal healthcare programs such as Medicare or Medicaid.
Eligibility should always be confirmed directly with the applicable program.
What If My Insurance Suddenly Denies Xolair?
Do not assume that the medication itself is no longer covered.
The denial may be asking the prescribing physician to:
- Submit a new prior authorization.
- Document the indication again.
- demonstrate previous treatment failure.
- Use the insurer’s preferred specialty pharmacy.
- Change from Xolair to Omlyclo.
- Submit a formulary exception explaining why Xolair remains medically necessary.
A denial is therefore often the beginning of the insurance process rather than the final answer.
Our office frequently works with insurance companies on prior authorization requirements for biologic medications because understanding why a medication was denied is essential before deciding how to respond.
Xolair vs. Omlyclo: Which Is Better?
From an efficacy standpoint, there is currently no basis to say that Xolair is “better” simply because it is the original product, or that Omlyclo is “better” because it is newer or less expensive.
FDA has determined Omlyclo to be an interchangeable biosimilar to Xolair with no clinically meaningful differences in safety or effectiveness.
For an individual patient, the more practical questions may be:
- Which product does the insurance company cover?
- Will prior authorization be approved?
- What will the patient’s actual out-of-pocket cost be?
- Which delivery device is available?
- Has the patient previously tolerated omalizumab?
- Is there a clinical reason to remain on one particular product?
Those factors may ultimately determine the most appropriate choice.
An Allergist’s Perspective on Omlyclo
The introduction of Omlyclo represents a major change for allergy practices because omalizumab is now used across several of the most important conditions we treat: asthma, chronic spontaneous urticaria, nasal polyps, and increasingly food allergy.
Competition in the omalizumab market could potentially make anti-IgE treatment available to more patients.
At the same time, the transition may temporarily create additional insurance complexity.
Patients who have been stable on Xolair for years may understandably be concerned when they receive a letter telling them that their medication is changing.
The important point is that Omlyclo is not an untested generic substitute. It has undergone the FDA’s biosimilar review process and has received the additional designation of interchangeability with Xolair.
For many patients, the decision between Xolair vs. Omlyclo may ultimately come down less to a difference in expected medical effectiveness and more to insurance coverage, prior authorization, cost, and formulation availability.
As formularies evolve following the October 2026 U.S. launch of Omlyclo, patients receiving Xolair should discuss any proposed switch with their allergist rather than stopping or delaying treatment on their own.
Frequently Asked Questions About Xolair vs. Omlyclo
Is Omlyclo generic Xolair?
Not exactly. Omlyclo is a biosimilar to Xolair rather than a conventional generic medication.
Is Omlyclo interchangeable with Xolair?
Yes. The FDA has designated Omlyclo an interchangeable biosimilar to Xolair.
Is Omlyclo cheaper than Xolair?
Its U.S. wholesale acquisition cost was launched at approximately 15% below Xolair’s. The amount an individual patient pays may be very different because of insurance coverage, rebates, deductibles, and copay programs.
Does Omlyclo work as well as Xolair?
FDA approval as a biosimilar means Omlyclo has been demonstrated to be highly similar to Xolair with no clinically meaningful differences in safety or effectiveness.
Can my insurance make me switch from Xolair to Omlyclo?
An insurer can make Omlyclo its preferred formulary product and may require patients to use it before covering Xolair. Whether Xolair can still be covered through an exception or appeal depends on the plan and the patient’s circumstances.
Is Omlyclo approved for food allergies?
Yes. Omlyclo is FDA-approved for IgE-mediated food allergy in patients age 1 year and older to reduce allergic reactions, including anaphylaxis, from accidental exposure. It must be used together with food-allergen avoidance and is not an emergency treatment for an allergic reaction.
Is Omlyclo approved for chronic hives?
Yes. It is approved for chronic spontaneous urticaria in adults and adolescents age 12 and older who remain symptomatic despite H1 antihistamine treatment.
Should I switch from Xolair to Omlyclo?
That decision should be made with your allergist after considering the indication, insurance coverage, formulation, previous response to treatment, and individual medical history.