Allergy

Omalizumab: Uh, I'm a little slow

New asthma drug works but may take months
before effects are seen

By Henry Peters

Michelle Allen is 26 years old and has asthma. She's tried steroids to control her symptoms but the meds aren't working. At her wits end, she asks her doctor if there's anything else she could take. It turns out that there's a new drug in the pipeline that may well help her � although it may not seem to at first. Omalizumab, the new monoclonal antibody designed to treat asthma refractory to inhaled steroids, may only become effective after months of apparently useless treatment, according to a study headed by Dr Jean Bousquet of Arnaud de Villeneuve Hospital in Montpellier, France and published in the April issue of Chest.

The study examined the outcomes of two phase III trials of omalizumab. Aside from a delayed response, the results also suggested that, in stark contrast to most asthma drugs, this one is just as effective in severe as in mild cases. Unfortunately, although two-thirds of the treatment group showed an improvement in symptoms, so did half the placebo arm. However, the criteria for a response weren't particularly strict. The trials comprised 1,070 patients who were symptomatic despite taking relatively high doses of inhaled beclomethasone dipropionate (BDP). Omalizumab was doled out at a four-weekly subcutaneous dose of at least 0.016 mg/kg/IgE for 16 weeks in addition to stable BDP therapy.

The purpose of this trial was to predict the eventual response of patients to omalizumab, so patients were categorized according to their history to see which groups reacted best. A history of emergency asthma treatment in the past year was most predictive for omalizumab response. Response rate for those with such a history was 67% for omalizumab and 42% for placebo. Other predictive factors of successful treatment were high BDP dose and poor lung function. The good news is that these criteria describe precisely the sort of patient who's least likely to be helped by other drugs. The 76% of patients who fit at least one of these criteria were 2.25 times more likely to show improvement if they received omalizumab instead of placebo.

Interestingly, of those who eventually reacted to omalizumab, only 61% responded after four weeks, while 87% responded after 12 weeks. So giving up on omalizumab treatment after only four weeks means that one-third of patients who could potentially benefit from this drug are missing out. So, not surprisingly, the authors concluded that "patients should be treated with omalizumab for a minimum duration of 12 weeks."