Omalizumab serum levels predict treatment outcomes in patients with
chronic spontaneous urticaria: A three months prospective study
Abstract
Aim: To examine the association between serum levels and
effectiveness of omalizumab in patients with chronic spontaneous
urticaria (CSU), and explore patient-specific factors associated with
omalizumab pharmacokinetics. Methods: Patients with CSU, who
were refractory to high-dose antihistamines and who initiated treatment
with omalizumab (300 mg every four weeks) were eligible for the study.
Treatment was evaluated every 4 th week during 12
weeks of treatment with urticaria activity score in the past week (UAS7)
as primary outcome and urticaria control test (UCT), Chronic Urticaria
Quality of Life Questionnaire (CU 2QoL) and dermatology
life quality index (DLQI) as secondary outcomes. Serum drug level of
omalizumab was measured before (trough level) and at day seven (peak
level) after each injection. Results: A total of 23 patients
were included. After 12 weeks of treatment with omalizumab, an
improvement of 16.8 UAS7 points (95% CI 10.8-22.8), p<0.001
was seen. The omalizumab trough and peak levels were 7.0-33.1 µg/mL and
11.4-54.0 µg/mL and reached a plateau (steady state) after 8-12 weeks of
treatment. Among the patient-specific factors measured at baseline (age,
sex, body mass index (BMI), angioedema, basophil histamine release (HR)
test, blood basophils and eosinophils, and serum total IgE), BMI was the
only significant predictor of omalizumab peak concentrations during the
study (difference -2.75, p<0.05), whereas omalizumab trough
concentrations were significantly associated with UAS7 scores
(difference -0.82, p<0.001). The same was observed for UCT,
DLQI, and CU 2QoL. Conclusion: In patients with
CSU initiating treatment with omalizumab, a higher BMI predicts lower
peak concentrations of omalizumab during treatment, whereas lower trough
concentrations of omalizumab are associated with a poorer response on
UAS7 and other patient reported outcomes.