Does omalizumab (Xolair) cause bleeding or thrombocytopenia?

Case description:

A 34-year-old Caucasian female started treatment with omalizumab for uncontrolled asthma 3 weeks ago. Two weeks after the first injection she noticed a slightly heavier period than usual and a 7 x 10 cm bruise on the left calf. She read the medication brochure and wants to know if omalizumab is the cause of her perceived increased tendency to bleed.

Does omalizumab (Xolair) cause bleeding or thrombocytopenia?

No.

The medication information brochure lists thrombocytopenia among the potential adverse reactions from omalizumab with a frequency lower than 1%. Omalizumab binds to Cε3 region of IgE.

An extensive PubMed search does not show any articles that associate omalizumab with increased bleeding.

In pre-clinical studies, thrombocytopenia (reduced platelet count) was observed in juvenile cynomolgus monkeys receiving omalizumab at doses 3.7–20-fold greater than the highest dose recommended in humans. This observation was made after initiation of the phase III clinical trials and led to implementation of increased surveillance of platelet counts in all ongoing and subsequent clinical studies.

There was, however, no evidence of a clinically relevant impact on platelet count during omalizumab treatment in clinical studies. Shift analyses of platelet counts showed no differences between the omalizumab and control groups. In the all-controlled-studies population, a decrease in platelet count from baseline occurred frequently in both the omalizumab and control groups (70.7% and 65.7%, respectively).

The majority of patients had a decrease in platelet count of less than 50 × 10*9/L (55.2% with omalizumab and 52.4% with controls) or no change/increase in platelet counts (29.3% with omalizumab and 34.3% with controls). In the omalizumab group, 3.4% of patients had a decrease in platelet count of 100 × 10*9/L or greater, compared with 2.3% of patients in the control group.

References:
Safety and tolerability of omalizumab. Corren J, Casale TB, Lanier B, Buhl R, Holgate S, Jimenez P. Clin Exp Allergy. 2009 Mar 17. [Epub ahead of print].
Omalizumab: A Monoclonal Anti-IgE Antibody: Laboratory Values. Medscape.
Image source: Wikipedia, public domain.