The FDA has approved Omlyclo (omalizumab-igec), manufactured by Celltrion, as the first biosimilar interchangeable with Xolair (omalizumab) for treating allergic diseases in the United States. This milestone approval marks a significant development in expanding access to anti-IgE monoclonal antibody therapy for patients with multiple allergic conditions.
Regulatory Breakthrough for Allergy Treatment
Omlyclo represents the first biosimilar approved in the U.S. for treating allergic diseases, targeting the same IgE antibodies as Xolair to reduce the risk of allergic reactions. The biosimilar has received FDA approval for the same indications as Xolair, including moderate-to-severe persistent asthma in adults and pediatric patients 6 years and older, chronic rhinosinusitis with nasal polyps in adults, chronic spontaneous urticaria in patients 12 years and older, and IgE-mediated food allergies in adults and children over 1 year of age.
The interchangeable designation is particularly significant, as it allows pharmacists to substitute Omlyclo for Xolair without consulting a physician. According to Hetal Patel, vice president of medical affairs at Celltrion USA, "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 the two medications.
Clinical Evidence Supporting Approval
Omlyclo's approval was primarily based on a Phase 3 clinical trial involving 619 adults with chronic spontaneous urticaria, a condition characterized by 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.
The study design included a dose escalation phase where participants on the 150 mg dose were increased to 300 mg after three months. The group initially receiving 300 mg Xolair was randomly redivided, with half switching to Omlyclo and the others continuing on Xolair. After six months of treatment, all participants were followed for an additional 40 weeks.
Results demonstrated that itch severity scores showed similar improvements after three months of treatment with both Omlyclo and Xolair. Importantly, there was no apparent change in effectiveness when patients switched from Xolair to Omlyclo during the study period.
Safety Profile Comparable to Reference Drug
The safety profile of Omlyclo closely matched that of Xolair in clinical studies. Adverse events occurred in fewer than 10 percent of patients, with similar rates between both drugs. The most common side effect was injection site reactions, consistent with the known profile of omalizumab therapy.
Anaphylaxis, a known potential side effect of omalizumab, was rare in the clinical trial. Like Xolair, Omlyclo carries a boxed warning for anaphylaxis, with serious allergic reactions occurring in 0.1 to 0.2 percent of patients, usually within the first three doses. Patients receiving Omlyclo must always have access to epinephrine.
Other possible side effects include joint pain, fever, skin rash and itchiness, headache, dizziness and fatigue. In pediatric patients, ear infection, abdominal pain and nose bleeds can occur.
Regulatory Extrapolation for Multiple Indications
While Omlyclo was directly studied only in chronic spontaneous urticaria, the FDA approved it for asthma and food allergies through a process called extrapolation. This well-established scientific principle allows a biosimilar to be approved for the same uses as the original drug when there is strong evidence that the biosimilar is equally safe and effective.
According to Patel, "Extrapolation is fundamental to the goals of the biosimilar development pathway, as it minimizes the need for duplicative clinical trials and accelerates patient access." The company demonstrated to the FDA that Omlyclo is very similar to Xolair in mechanism of action, pharmacokinetics, and safety profile.
Market Access and Cost Considerations
Despite FDA approval in March 2024, Omlyclo will not be available in the U.S. until September 2026, as Xolair's patent exclusivity expires in November 2025. The wholesale acquisition cost for a one-year supply of Xolair ranges from approximately $9,000 to $144,000 for treatment of food allergic reactions, with list prices ranging from $30,000 to $60,000 annually.
While biosimilars typically cost 15 to 35 percent less than their reference biologics, the actual impact on patient out-of-pocket costs varies significantly based on insurance coverage. According to Genentech and Novartis, the makers of Xolair, 90 percent of those with commercial insurance pay between $5 and $1,457 monthly after meeting their deductible.
Administration and Dosing
Like Xolair, Omlyclo is administered by injection every 2 or 4 weeks, with the first dose required in a doctor's office. Patients may subsequently be able to self-inject at home using a prefilled pen. The biosimilar will be available in 75 mg or 150 mg prefilled syringes, with dosing varying by condition.
Dr. David Stukus, director of the Food Allergy Center at Nationwide Children's Hospital and vice president of the American College of Allergy, Asthma and Immunology, noted that the biosimilar "popped onto the radar without much fanfare" and emphasized the need for healthcare providers to learn about the evidence supporting its use.
Celltrion plans to begin U.S. healthcare provider education in spring 2026, ahead of the product's commercial launch. Patel stated that the biosimilar's approval will "broaden access to this important medicine for patients with allergic and respiratory conditions."
