Background. Treatment with omalizumab, a humanized recombinant monoclonal
anti-IgE antibody, results in clinical efficacy in patients with Chronic
Spontaneous Urticaria (CSU). The mechanism of action of omalizumab in CSU has
not been elucidated in detail. Objectives. To determine the effects of
omalizumab on levels of high affinity IgE receptor-positive (FcεRI+) and IgE-
positive (IgE+) dermal cells and blood basophils. Treatment efficacy and
safety were also assessed. Study design. In a double-blind study, CSU patients
aged 18‑75 years were randomized to receive 300 mg omalizumab (n=20) or
placebo (n=10) subcutaneously every 4 weeks for 12 weeks. Changes in disease
activity were assessed by use of the weekly Urticaria Activity Score (UAS7).
Circulating IgE levels, basophil numbers and levels of expression of FcεRI+
and IgE+ cells in the skin and in blood basophils were determined. Results.
Patients receiving omalizumab showed a significantly greater decrease in UAS7
compared with patients receiving placebo. At Week 12 the mean difference in
UAS7 between treatment groups was -14.82 (p=0.0027), consistent with previous
studies. Total IgE levels in serum were increased after omalizumab treatment
and remained elevated up to Week 12. Free IgE levels decreased after
omalizumab treatment. Mean levels of FcεRI+ skin cells in patients treated
with omalizumab 300 mg were decreased at Week 12 compared with baseline in the
dermis of both non-lesional and lesional skin, reaching levels comparable with
those seen in healthy volunteers (HVs). There were no statistically
significant changes in mean FcɛRI+ cell levels in the placebo group. Similar
results were seen for changes in IgE+ cells, although the changes were not
statistically significant. The level of peripheral blood basophils increased
immediately after treatment start and returned to Baseline values after the
follow-up period. The levels of FcεRI and IgE expression on peripheral blood
basophils were rapidly reduced by omalizumab treatment up to Week 12.
Conclusions. Treatment with omalizumab resulted in rapid clinical benefits in
patients with CSU. Treatment with omalizumab was associated with reduction in
FcɛRI+ and IgE+ basophils and intradermal cells