A respiratory expert undermines GSK's case for new asthma drug mepolizumab

Parameswaran Nair

Investigators for GlaxoSmithKline ($GSK) detailed their promising Phase III data for the IL-5 biologic mepolizumab in asthma today, noting that the injectable halved the rate of exacerbations among a group of patients with uncontrolled cases of the respiratory disease. But while the pharma giant was making its case for a lower dosage of the drug for a particular profile of asthma patient, an expert in the field raised the prospect that GSK's biggest competitor in the real world may simply be cheaper therapies applied with proper compliance to the medical guidelines already in place.

Writing in the New England Journal of Medicine, asthma expert Parameswaran Nair carefully noted the positive data for the drug, which performed significantly better than a placebo in preventing asthma attacks. But he was also struck by the fact that the placebo arm of the study also performed strikingly well. Investigators in this study selected patients with a high baseline of exacerbations, averaging 3.6 per year. But in the placebo arm, the rate dropped to an average of 1.75 while the 75-mg dose of mepolizumab dropped the rate to 0.93 and the 100-mg arm saw the rate drop to 0.81.

These drugs work by knocking back levels of eosinophils, which are linked to uncontrolled asthma, a condition that afflicts up to half of the patient population.

"It is well recognized that even in the most well-characterized patients with severe asthma, the lack of adherence to the prescribed therapy is the most common cause of poor asthma control," Nair, a professor at McMaster University, writes. "Furthermore, the judicious use of currently available therapies guided by sputum cell counts has been shown to lead to substantial reductions in exacerbations, decreases that are clinically equivalent to those reported for biologic therapies and are likely to be more cost-effective. This finding would suggest that most patients in this clinical trial might have had improvement in symptoms without mepolizumab simply by the institution of good clinical practice, as recommended by current international guidelines."

That's not what you want to hear when you're advancing positive data on a new standard of care for uncontrolled diabetes. Analysts have estimated that these IL-5 drugs--including programs at Teva ($TEVA) and AstraZeneca ($AZN)--represent the cutting edge for a new class of injectables worth potentially billions of dollars a year. But with pharmacy benefit managers closely watching the arrival of cheaper generics, Nair's remarks raise the possibility that patients may find themselves steered back to less expensive remedies.

That's a particularly troublesome prospect for GSK, which has had trouble establishing the kind of trajectory for its respiratory franchise that would satisfy analysts.

Leerink's Seamus Fernandez has been hopeful that the IL-5 field could lead to a market worth $7.5 billion a year, looking for a price under $10,000 per year for payers. Others, though, have estimated that prices could go as high as $15,000 a year, according to a report from Reuters.

- here's the NEJM piece

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