Q:

4/1/2013
As I was reading some information about Xolair, I ran across a statement by Novartis reporting a dose-related thrombocytopenia at serum concentrations in excess of maximum human exposure in primates. Do you recommend routinely checking a cbc prior to starting Xolair and periodically during treatment? If yes, how often should we be checking it during treatment? Thank you.

A:

Thank you for your inquiry.

No, we do not recommend checking a complete blood count prior to starting Xolair, nor checking periodically during treatment for thrombocytopenia. The reasons for this are summarized in the abstract from a review article copied for you below. If you wish further, more detailed discussion of the reasons behind this conclusion, I have copied below for you two links to websites speaking to this issue. One is a statement from the FDA.

Thank you again for your inquiry and we hope this response is helpful to you.

Briefing Document on Safety
BLA STN 103976/0
Genentech, Inc.
Omalizumab (Xolair) (recombinant humanized monoclonal antibody to IgE) for treatment of allergic asthma

Omalizumab Does Not Cause Thrombocytopenia

Safety and tolerability of omalizumab
Clinical & Experimental Allergy
Volume 39, Issue 6, pages 788–797, June 2009
Summary
Background: Omalizumab (Xolair®) is a recombinant humanized monoclonal anti-IgE antibody with proven efficacy in patients with moderate-to-severe and severe persistent allergic (IgE-mediated) asthma.
Objective: To review clinical study data to assess the safety profile of omalizumab.
Methods: We analysed the safety of omalizumab using data from completed clinical studies (up to 1 year) involving more than 7500 patients with asthma, rhinitis or related conditions and up to 4 years in one study of patients with severe allergic asthma, as well as post-marketing safety data. Analysis focuses on the risk of immune-system effects, hypersensitivity reactions, malignant neoplasia, parasitic infections and thrombocytopenia.
Results: Omalizumab exhibited a good safety and tolerability profile that was maintained up to 4 years in one study. The incidence of anaphylaxis was 0.14% in omalizumab-treated patients and 0.07% in control patients. No omalizumab-treated patient developed measurable anti-omalizumab antibodies. Post-marketing, based on estimated exposure of 57 300 patients (June 2003–December 2006), the frequency of anaphylaxis attributed to omalizumab use was estimated to be at least 0.2% of patients. Current clinical trial data do not support an increased risk of malignant neoplasia or thrombocytopenia with omalizumab.
Conclusion: Data indicate that the proven efficacy of add-on omalizumab in patients with moderate-to-severe or severe allergic asthma is accompanied by a favourable safety and tolerability profile.

Sincerely,
Phil Lieberman, M.D.

AAAAI - American Academy of Allergy Asthma & Immunology