Omalizumab adherence in an observational study of patients with moderate to severe allergic asthma

Adherence to omalizumab is not well characterized and its association with asthma control has not been well established.

To evaluate adherence in patients initiating omalizumab in the Epidemiologic Study of Xolair (omalizumab): Evaluating Clinical Effectiveness and Long-term Safety in Patients with Moderate to Severe Asthma (EXCELS) observational study.

Adherence was assessed over 5 years using the proportion of patients who missed any dose, rates of doses missed, and proportions of patients with good (<10% doses missed) or poor (≥30% doses missed) adherence. Multivariable analyses identified independent predictors of good adherence. Associations between adherence and asthma control were assessed using the minimum important difference for the Asthma Control Test at various time points.

A total of 289 patients newly initiated on omalizumab completed 5 years of EXCELS. Of these, 83.0% on the 2-week dosing regimen (n = 152) and 65.0% on the 4-week dosing regimen (n = 137) missed at least 1 dose. More frequent dosing was associated with a larger number of missed doses. Older age (odds ratio per year 1.02, 95% confidence interval 1.01-1.03) and lower prebronchodilator percentage of predicted forced expiratory volume in 1 second (<76; odds ratio 1.88, 95% confidence interval 1.09-3.24) were independent predictors of good adherence.

Adherence to omalizumab is characterized by distinct factors. Patients receiving the 4-week dosing regimen achieved better adherence than those treated every 2 weeks. Improved adherence could be associated with better asthma control. Age and lung function could interact with dosing frequency to affect patient adherence, thus warranting prospective planning at the time of prescribing to support long-term adherence.