Omalizumab: potential risk of arterial thrombotic events

Prescribers should be vigilant for possible thrombotic adverse reactions.

Article date: February 2011

Omalizumab (Xolair▼) is a monoclonal antibody, which inhibits immunoglobulin E and is licensed for the treatment of severe persistent allergic asthma in patients (age 6 years or older) in whom standard treatment has failed. Omalizumab is usually administered subcutaneously every 2–4 weeks. It is available as a 150 mg powder and solvent for solution for injection.

Arterial thrombotic events with omalizumab

In controlled clinical trials and an unpublished ongoing observational study (EXCELS), a numerical imbalance of arterial thrombotic events (ATEs) was observed in association with use of omalizumab; however, this finding was not statistically significant at the 95% level. ATEs included stroke, transient ischaemic attack, myocardial infarction, unstable angina, and cardiovascular death (including death from unknown cause).

EXCELS is an ongoing observational study of approximately 5000 patients receiving omalizumab and a control group of approximately 2500 patients not receiving this drug. The study aims to evaluate the clinical effectiveness and long-term safety of omalizumab in patients with moderate to severe asthma followed up for 5 years.

The table below summarises interim data from EXCELS and data from controlled clinical trials.

Arterial thrombotic events per 1000 patient-years of treatment (patient years) Risk versus controls: hazard ratio, HR (95% CI)
Omalizumab Controls
EXCELS 5.59 (79/14140) 3.71 (31/8366) Adjusted* HR 1.11 (0.70–1.76) (Controlling for baseline cardiovascular risk factors)
Controlled clinical trials 6.29 (17/2703) 3.42 (6/1755) Unadjusted HR 1.86 (0.73–4.72)

*Controlling for baseline cardiovascular risk factors

Call for reporting

Prescribers should be vigilant for possible thrombotic adverse reactions. All suspected adverse reactions, including arterial thrombotic events, to omalizumab▼ should be reported via the Yellow Card Scheme at

Further information

BNF section 3.4.2 Allergen immunotherapy

Article citation: Drug Safety Update Feb 2011, vol 4 issue 7: A4.

Published 11 December 2014