Asthma is one of the planet's more common diseases. It affects roughly 300 million people and despite the availability of treatment designed to help reduce asthma attacks, millions of people's asthma is poorly controlled.

As a result, a host of companies, including Teva Pharmaceuticals (NYSE:TEVA), hope to usher new asthma drugs to market that could help reduce the number of attacks annually, particularly for patients with moderate or severe asthma.

Last week, Teva updated the industry on reslizumab performance in late stage clinical trials, so let's take a closer look.

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Source: Teva Pharmaceuticals

First, a bit of background
Twelve percent of the world's adults and 10% of all children suffer from asthma. In the United States, 44,000 Americans suffer an asthma attack every day and the severity of those attacks means that asthma accounts for roughly a quarter of all emergency room admissions.

As a result, Express Scripts reports that the direct costs associated with caring for asthma patients totals $50 billion a year, the majority of which is spent on costly hospitalization for attacks in moderate and severe asthma patients. Overall, asthma is the fifth most expensive indication in terms of annual drug spending.

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Source: Teva Pharmaceuticals

Current treatment
Rescue inhalers that deliver albuterol and levalbuterol are commonly used by asthma patients. Those two medications are short-acting beta agonists, or SABAs, and they work by activating beta receptors on the smooth muscles of the lungs, which causes muscles to relax and stop constricting. Often, these drugs can be overused by patients, which mask the severity of the disease in patients and can result in patients developing a resistance to the medicine.

Controller inhalers that deliver corticosteroids are also typically prescribed to deliver longer-lasting medicine and are taken once or twice a day, even when patients are symptom-free. Corticosteroids can also be prescribed alongside long-acting beta agonists, or LABAs.

The most widely used maintenance therapy for asthma is the drug Singulair, which holds 30% market share thanks in part to increased use of the generic version of the drug.

GlaxoSmithKline's Advair Diskus is another commonly prescribed maintenance asthma therapy and only three other medications sold in the U.S. account for more drug spending annually than Advair. According to Express Scripts, spending on Advair accounted for 2.5% of all drug spending last year, which translated into $4 billion in U.S. sales. Globally, Advair sales totaled $8 billion last year.

Improving outcomes with new medications
The overuse of rescue inhalers and poor adherence to controller medication mean that too many asthma patients suffer too many annual asthma attacks.

Since education on adherence can only go so far as to reducing annual asthma attacks, drugmakers like Teva are developing new medicines that work differently.

Teva's reslizumab, for example, is a monoclonal antibody that targets interleukin-5. Interleukin-5 is believed to play a key role in the production of eosinophils, a type of white blood cell that is commonly over expressed in moderate and severe asthma patients.

During two phase 3 trials, patients receiving reslizumab by IV every four weeks endured significantly fewer asthma attacks than those receiving placebo. The two trials included more than 950 patients globally and reslizumab patients saw the number of attacks fall by more than 50%.

Dr. Michael Hayden, Teva's president of global R&D and chief scientific officer, said in a press release:

These pivotal Phase III study results are striking. Asthma that is inadequately controlled by current standard of care therapy continues to present a serious problem for patients, physicians and healthcare systems. The success of these studies gives us confidence that we may have a valuable potential new treatment option for asthma patients, with elevated levels of blood eosinophils, who are at risk of exacerbation.

Fool-worthy final thoughts
Teva estimates that the global market for medicine used to treat moderate and severe asthma could total $7.5 billion annually in Europe and America alone. That heady prediction may suggest that Teva thinks reslizumab could have billion-dollar blockbuster potential.

However, Teva is far from the only drugmaker investigating treatments aimed at reducing eosinophils. GlaxoSmithKline hopes to file an eosinophils reducing drug for FDA approval this fall and Regeneron and Sanofi are conducting mid-stage trials on their own eosinophilic asthma drug, dupilumab, too.

Regardless, Teva plans to file for FDA approval of reslizumab in the U.S. and Europe early next year, and that could mean that if the drug is approved patients with moderate and severe asthma could have another treatment option in 2016.

Todd Campbell has no position in any stocks mentioned. The Motley Fool recommends Teva Pharmaceutical Industries. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.