Omalizumab safe for idiopathic anaphylaxis

Though clinical efficacy will still need further confirmation, omalizumab appears to be a safe intervention to administer among difficult-to-treat patients with idiopathic anaphylaxis (IA), a new study has found.

The double-blind, placebo-controlled trial included 16 prospectively enrolled patients who saw ≥6 episodes of IA per year. Eight patients each were assigned to omalizumab and placebo group, though despite randomization, all participants taking placebo were women. The primary study endpoint was the number of anaphylactic events occurring during the 6 months after randomization.

Of note, all participants underwent medical evaluation to rule out clonal mast cell disorder.

Thirteen of the 16 participants saw a first anaphylactic event occurring within 30 days after randomization. Between-group comparisons of the primary outcome did not reveal any significant difference between omalizumab and placebo. “Thus, there is insufficient evidence to support efficacy,” the researchers said.

The secondary efficacy analysis looked at the difference between the number of events 6 months prior to and after randomization. Numerically, omalizumab was superior to placebo in this regard, though statistical significance was not achieved (p=0.26).

Similarly, graphical comparison showed a possible advantage of omalizumab in terms of cumulative incidence rates beyond 60 days, suggesting delayed onset of action, but the difference failed to reach significance.

Despite no clear demonstration of efficacy, omalizumab appeared to be safe and did not cause anaphylaxis. One patient experienced lip oedema and flushing within 24 hours after administration, but other signs of anaphylaxis—such as hypotension, hypoxia, and syncope—were absent.