Omalizumab Biosimilar Shows QoL Gains in CSU Phase 3 Post Hoc Data

A 44.4% complete response rate with no quality-of-life (QoL) impact at Week 24 anchors post hoc results for omalizumab-igec (CT-P39; Omlyclo, Celltrion USA), the first and only FDA-approved interchangeable biosimilar to Xolair (omalizumab). Investigators presented the analyses from a Phase 3 study at the American College of Allergy, Asthma and Immunology (ACAAI) 2026 Annual Scientific Meeting in Phoenix, AZ. The product launched in the United States in October 2026.

The data matter to dermatologists because chronic spontaneous urticaria (CSU), a condition of recurring wheals and angioedema without an identifiable external trigger, routinely escapes control with antihistamines alone. Biosimilar entry also carries reimbursement implications for practices managing biologic budgets.

What did the disease-activity analysis show?

One post hoc analysis examined the relationship between CSU disease activity and QoL during omalizumab treatment. Patients received omalizumab 300mg every four weeks for 24 weeks, followed by a 16-week off-treatment period. Investigators assessed disease activity with the Weekly Urticaria Activity Score (UAS7, a 0–42 composite of wheal and itch severity) and QoL with the Dermatology Life Quality Index (DLQI, a 0–30 dermatology-specific instrument). They grouped both measures into five previously established categories and tracked patient movement between categories over time.

At baseline, the largest patient group — 36.7% — had severe disease and reported a very large effect of CSU on their QoL.

The category shifts unfolded as follows:

• Week 12: 43.9% of patients reached the well-controlled or complete response categories, while 72.5% reported no or small effect of CSU on their QoL.
• Week 24 (end of treatment): 44.4% achieved a complete response with no effect of CSU on QoL.
• Week 40 (16 weeks off treatment): 41.7% remained in the well-controlled or complete response categories with no or small effect on QoL.

QoL improvements occurred earlier than improvements in disease activity. Week 40 results suggest persistent treatment effects up to 16 weeks after omalizumab was stopped, according to the study team. That durability claim rests on a single post hoc look at 16 weeks; no follow-up beyond that window exists in these data.

Does baseline itch severity change the outcome?

A second post hoc analysis stratified 409 patients who received CT-P39 or reference omalizumab 300mg every four weeks by baseline Weekly Itch Severity Score (ISS7): ISS7 ≥13 (n=331) or ISS7 <13 (n=78). Reductions in UAS7 and in the Chronic Urticaria Quality of Life Questionnaire (CU-Q2oL, a CSU-specific QoL measure) appeared at all time points regardless of baseline itch severity.

At Week 24, mean UAS7 reductions were comparable between CT-P39 and the reference product within each itch-severity stratum:

• ISS7 ≥13: –24.8 with CT-P39 versus –26.3 with reference omalizumab.
• ISS7 <13: –15.7 with CT-P39 versus –16.0 with reference omalizumab.

The authors conclude that improvements in disease activity and QoL occurred regardless of baseline itch severity, with comparable efficacy between CT-P39 and reference omalizumab.

What was not presented?

A third, separate post hoc subgroup analysis evaluated the pharmacokinetics (drug exposure over time) and target engagement of CT-P39 versus reference omalizumab in CSU patients with physician-reported asthma at baseline; the presented summaries did not detail its quantitative findings.

Two caveats deserve weight. All three analyses are post hoc — exploratory by design, hypothesis-generating rather than confirmatory — and no confidence intervals or statistical tests for the between-group comparisons appear in the reported results. The interchangeability designation, however, rests on the FDA's own totality-of-evidence review, not on these subgroup data.

What comes next?

As the first interchangeable omalizumab biosimilar on the US market, Omlyclo will face early scrutiny over real-world switching, pharmacy substitution patterns, and whether the Week 40 durability signal holds in clinical practice beyond 16 weeks off therapy.