Asthma, a condition characterized by the narrowing and inflammation of airways and excess mucus, affects 1 in 12 individuals in the United States—approximately 25 million people, or 8% of the US population.1 Overall, 53% of patients with asthma experience an asthma attack (ie, exacerbation) annually.1
Although asthma therapy, when used according to the current management guidelines, controls the disease in the majority of patients, an estimated 10% of patients have severe asthma, characterized by reduced responsiveness to standard therapy, as well as increased morbidity and reduced quality of life.2,3 Severe asthma exacerbations often lead to hospitalization and can be life-threatening.4 Overall, asthma exacerbations can result in substantial morbidity, mortality, and healthcare utilization and associated costs.5 According to the Centers for Disease Control and Prevention, asthma accounts for an estimated 3630 deaths annually in the United States, and 1.8 million emergency department visits with asthma as the primary diagnosis.6 In addition, there are 439,000 asthma-related hospitalizations annually, with an average length of stay of 3.6 days.6
In the United States, asthma costs accounted for $56 billion annually in 2007, representing a 6% increase from $53 billion in 2002.1 Between 2002 and 2007, the annual per-person cost for patients with asthma was $3300 in medical expenses, missed school or work days, and early mortality.1
The diagnostic tests for asthma may include spirometry or a peak flow meter to measure lung function.7 Other diagnostic tools may include imaging; allergy tests; a nitric oxide test; methacholine response; provocative tests (postphysical activity); or a sputum eosinophils test, which measures the presence of eosinophils in the saliva and sputum.7
Eosinophils play a role in asthma-related airway inflammation.8 Some patients with eosinophilic airway inflammation experience recurrent asthma exacerbations, despite receiving inhaled glucocorticoid treatment (with or without oral glucocorticoids); long-term use of oral glucocorticoids is associated with potentially serious adverse reactions.2,9,10
The management of asthma includes the recognition and avoidance of disease triggers, ongoing control of symptoms, and, in the event of a flare-up, the use of a quick-relief (rescue) inhaler, such as albuterol.11 Long-term control medications include inhaled corticosteroids, leukotriene modifiers, long-acting beta agonists, combination inhalers, and theophylline.11 Rescue medications include the short-acting beta agonists, the anticholinergic bronchodilator ipratropium, and oral and intravenous (IV) corticosteroids.
For asthma that is worsened by allergies, pharmacotherapy options include immunotherapy (ie, allergy shots) or omalizumab.11 There is a need for additional treatment options for patients with severe asthma and the eosinophilic phenotype.4,11
Mepolizumab Approved for Maintenance Treatment in Severe Asthma
On November 4, 2015, mepolizumab (Nucala; GlaxoSmithKline), a humanized, interleukin-5 (IL-5) antagonist monoclonal antibody, was approved by the US Food and Drug Administration (FDA) as an add-on subcutaneous maintenance treatment for patients aged ≥12 years with an eosinophilic phenotype who have severe asthma.4,8 Mepolizumab is not indicated for the treatment of other eosinophilic conditions, or for the relief of acute bronchospasm or status asthmaticus.8 Mepolizumab is the first FDA-approved biologic agent that targets IL-5, which regulates the function of eosinophils.12
Badrul Chowdhury, MD, PhD, Director of the FDA's Division of Pulmonary, Allergy, and Rheumatology Products, commented, "This approval offers patients with severe asthma an additional therapy when current treatments cannot maintain adequate control of their asthma."4
According to Professor Ian Pavord, University of Oxford, an investigator for a phase 3 clinical trial with mepolizumab, "Severe asthma is a debilitating condition in which patients are at high risk of frequent and serious asthma attacks. Half of all severe asthma patients have at least one urgent care visit per year. As a clinician, the prospect of a treatment that can specifically target the underlying cause of the disease for patients whose condition is driven by eosinophilic inflammation is exciting."11
Mechanism of Action
Mepolizumab is a humanized, IL-5 antagonist monoclonal antibody (immunoglobulin G1 kappa).8 The IL-5 cytokine regulates the growth, recruitment, activation, and life cycle of eosinophils—one of several cell types involved in asthma-related airway inflammation.8
Mepolizumab controls severe asthma exacerbations by reducing the levels of blood eosinophils that contribute to the pathogenesis of asthma.4 Mepolizumab binds to IL-5 and inhibits IL-5 signaling, thereby reducing the production and survival of eosinophils; however, the exact mechanism of action of mepolizumab in asthma has not been firmly established.8
Dosing and Administration
Mepolizumab injection is available as 100 mg of lyophilized powder in a single-dose glass vial for reconstitution. Mepolizumab 100 mg is administered via subcutaneous injection once every 4 weeks by a healthcare professional into the upper arm, thigh, or abdomen.8
Before administration, mepolizumab is reconstituted in a vial with sterile water, as instructed in the prescribing information. Patients should be monitored after the administration of mepolizumab, as is the standard clinical practice after the administration of a biologic agent.8
Clinical Trials
The clinical development program that evaluated mepolizumab in patients with asthma included 3 double-blind, randomized, placebo-controlled studies, including Study 1 (DREAM), a dose-ranging and exacerbation clinical trial, and Study 2 (MENSA) and Study 3 (SIRIUS)—2 confirmatory trials.2,5,8,9
In all 3 studies, mepolizumab was administered every 4 weeks as an add-on treatment to background treatment, with patients continuing their background asthma therapy throughout the duration of the study.8 To be included in the 2 confirmatory clinical trials, patients had to have blood eosinophils levels ≥150 cells/mcL at screening (within 6 weeks of dosing) or blood eosinophils levels ≥300 cells/mcL within 12 months of enrollment (Table 1).
Study 1 (DREAM): Dose-Ranging and Exacerbation Trial
The findings from Study 1 (DREAM)—a 52-week, dose-ranging and exacerbation-reduction clinical trial—and the findings from a pharmacodynamic study supported the evaluation of mepolizumab 100 mg administered subcutaneously and mepolizumab 75 mg administered intravenously in subsequent clinical trials; however, mepolizumab was ultimately approved by the FDA for subcutaneous administration only.5,8
Study 2 (MENSA): Confirmatory Trial
The MENSA study, a 32-week clinical trial, included patients with asthma who had a history of ≥2 exacerbations in the previous year, despite regular treatment with high-dose inhaled corticosteroids plus an additional controller, with or without oral corticosteroids.8,9
Results from Study 1 and 2
The primary end point for Study 1 and 2 was the frequency of exacerbation, defined as the worsening of asthma necessitating the use of an oral or systemic corticosteroid and/or hospitalization and/or emergency department visits.8
Study 2 results showed that the time to the first exacerbation was longer in patients who received subcutaneous mepolizumab 100 mg and IV mepolizumab 75 mg compared with placebo.8,9 In both studies, patients who received subcutaneous mepolizumab 100 mg and IV mepolizumab 75 mg had significantly fewer exacerbations compared with patients who received placebo (Table 2). Furthermore, patients in the mepolizumab group had fewer exacerbations that required hospitalization and/or emergency department visits and exacerbations requiring only in-patient hospitalization compared with the placebo group.8
Study 3 (SIRIUS): Confirmatory Trial
SIRIUS, a 24-week clinical trial, evaluated the effect of mepolizumab on reducing the use of maintenance oral corticosteroids; the primary efficacy outcome was the percent reduction of the oral corticosteroid dose in weeks 20 to 24 compared with the baseline dose, while maintaining asthma control.8
Treatment with mepolizumab demonstrated a significant glucocorticoid-sparing effect compared with placebo (Table 3).8 Mepolizumab was 2.39 times more likely to reduce glucocorticoid doses versus placebo (95% confidence interval, 1.25-4.56; P =.008).2
Lung Function: Study 1, 2, and 3
In Study 1, 2, and 3, treatment with mepolizumab did not show consistent improvements in the mean change from baseline in the forced expiratory volume in 1 second (Table 4).8
Adverse Reactions
The most common adverse reactions (≥5% incidence) associated with mepolizumab were headache (19%), injection-site reaction (8%), back pain (5%), and fatigue (5%).8
Based on the data from the 3 randomized, placebo-controlled studies lasting 24 to 52 weeks, 2% of patients receiving mepolizumab withdrew from the studies because of adverse events compared with 3% of patients receiving placebo.8 One serious adverse event (herpes zoster) occurred in 2 patients who received mepolizumab versus none in patients receiving placebo. Additional cases of herpes zoster have been reported in ongoing open-label, extension clinical trials in the 998 patients receiving mepolizumab.8
Overall, 6% (15/260) of patients who received mepolizumab developed antimepolizumab antibodies, which increased by approximately 20% the clearance of mepolizumab.8 The clinical relevance of these antimepolizumab antibodies is unknown; there was no evidence that these antibody titers effected changes in the blood eosinophil levels.8
Contraindications
Mepolizumab is contraindicated in patients with a history of hypersensitivity to mepolizumab or its excipients in the formulation.8
Warnings and Precautions
Hypersensitivity reactions. Hypersensitivity reactions (eg, angioedema, bronchospasm, hypotension, rash, urticaria) have been reported after mepolizumab administration; mepolizumab should be discontinued in a patient with hypersensitivity reaction.8
Acute asthma symptoms or deteriorating disease. Mepolizumab should not be used for the treatment of patients with acute asthma symptoms, acute exacerbations, acute bronchospasm, or status asthmaticus. Patients whose asthma worsens or remains uncontrolled after initial treatment with mepolizumab should seek medical advice.8
Herpes zoster. In clinical studies, 2 serious herpes zoster adverse reactions occurred in patients who received mepolizumab. Varicella vaccination should be considered before starting treatment with mepolizumab.8
Reduction of corticosteroid dosage. Systemic or inhaled corticosteroids should not be discontinued abruptly when initiating treatment with mepolizumab. Any reductions of the corticosteroid dose should be gradual and performed under a physician's direct supervision.8
Helminth infection. Patients with preexisting helminth infections should receive treatment before starting mepolizumab therapy. If a patient is helminth-infected while receiving mepolizumab and does not respond to antihelminth treatment, mepolizumab should be discontinued until the infection resolves.8
Use in Specific Populations
Pregnancy. Clinical trial data on mepolizumab exposure during pregnancy are insufficient to determine drug-associated risks. It is recommended that healthcare providers enroll patients in a pregnancy exposure registry to monitor pregnancy outcomes in women exposed to mepolizumab during pregnancy.8
Lactation. No data are available on the presence of mepolizumab in human milk, its effects on breast-fed infants, or its effects on the production of milk.8
Pediatric use. The safety and efficacy of mepolizumab in patients aged ≤12 years have not been determined.8
Geriatric use. There were insufficient numbers of patients aged ≥65 years in the mepolizumab clinical trials to determine whether their treatment response was different from that of younger patients. The dose selection for elderly patients should start at the low end of the dosing range. Available data suggest that no dosage adjustment is required in geriatric patients, but the potential for increased sensitivity should be considered.8
Conclusion
The FDA approval of mepolizumab marks the availability of the first biologic agent to target IL-5, a cytokine that regulates the growth, activity, and survival of eosinophils—the inflammatory cells that play a key role in the pathogenesis of asthma. Mepolizumab, an IL-5 antagonist monoclonal antibody administered subcutaneously once monthly, is indicated as an add-on maintenance treatment for patients aged ≥12 years with severe asthma, and with an eosinophilic phenotype.
In clinical trials, patients who received mepolizumab had significantly fewer exacerbations than patients receiving placebo. Patients who received mepolizumab also had fewer exacerbations requiring hospitalization and/or emergency department visits, and fewer exacerbations requiring in-patient hospitalization compared with placebo. Treatment with mepolizumab was more than twice as likely to reduce glucocorticoid doses as placebo.
References
1. Asthma & Allergy Center. Asthma statistics. www.asthmaandallergycenter.net/education/asthma/asthma-statistics. Accessed February 22, 2016.
2. Bel EH, Wenzel SE, Thompson PJ, et al; for the SIRIUS Investigators. Oral glucocorticoid-sparing effect of mepolizumab in eosinophilic asthma. N Engl J Med. 2014;371:1189-1197.
3. ENFUMOSA Study Group. The ENFUMOSA cross-sectional European multicentre study of the clinical phenotype of chronic severe asthma. Eur Respir J. 2003;22:470-477.
4. US Food and Drug Administration. FDA approves Nucala to treat severe asthma. Press release. November 4, 2015. www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm471031.htm. Accessed December 3, 2015.
5. Pavord ID, Kom S, Howarth P, et al. Mepolizumab for severe eosinophilic asthma (DREAM): a multicentre, double-blind, placebo-controlled trial. Lancet. 2012;380:651-659.
6. Centers for Disease Control and Prevention. FastStats: asthma. Updated May 14, 2015. www.cdc.gov/nchs/fastats/asthma.htm. Accessed December 9, 2015.
7. Mayo Clinic staff. Tests and diagnosis. October 17, 2015. www.mayoclinic.org/diseases-conditions/asthma/basics/tests-diagnosis/con-20026992. Accessed February 22, 2016.
8. Nucala (mepolizumab) for injection [prescribing information]. Research Triangle Park, NC: GlaxoSmithKline; November 2015.
9. Ortega HG, Liu MC, Pavord ID, et al; for the MENSA Investigators. Mepolizumab treatment in patients with severe eosinophilic asthma. N Engl J Med. 2014;371:1198-1207. Erratum in: N Engl J Med. 2015;372:1777.
10. Mayo Clinic staff. Prednisone and other corticosteroids. November 26, 2015. www.mayoclinic.org/steroids/art-20045692?pg=2. Accessed December 9, 2015.
11. Mayo Clinic staff. Disease and conditions: asthma: treatments and drugs. October 17, 2015. www.mayoclinic.org/diseases-conditions/asthma/basics/treatment/con-20026992. Accessed February 22, 2016.
12. GlaxoSmithKline. GSK's Nucala (mepolizumab) receives approval from US FDA. Press release. November 4, 2015. www.gsk.com/en-gb/media/pressreleases/2015/gsk-s-nucala-mepolizumab-receives-approval-from-us-fda/. Accessed December 4, 2015.