In early January 2021, pharmaceutical company Astellas Pharma Inc. (“Astellas”) shared that its New Drug Application (NDA) and supplemental NDA for Myrbetriq (mirabegron) received Priority Review status from the FDA. The drug is designed to treat neurogenic detrusor overactivity (NDO), a type of overactive bladder dysfunction frequently found in patients with conditions like spina bifida or multiple sclerosis (MS), in patients ages 3+. If all goes well, Astellas should receive a decision on their NDA and sNDA by the end of March.

Mirabegron

In 2012, Myrbetriq (mirabegron) was approved in the US for the treatment of adult patients with overactive bladders. Associated symptoms included frequent urination, urinary incontinence, and related urgency. Now, Astellas is looking at Myrbetriq as a potential treatment option for pediatric patients with NDO whose symptoms include involuntary bladder contractions, frequent urination, and urinary incontinence.

Both the NDA and sNDA are under Priority Review status. The FDA defines an NDA as:

the vehicle through which drug sponsors formally propose that the FDA approve a new pharmaceutical for sale and marketing in the U.S. The goals of the NDA are to provide enough information to permit FDA reviewer to [determine] whether the drug is safe and effective in its proposed use(s), and whether the benefits of the drug outweigh the risks; whether the drug’s proposed labeling (package insert) is appropriate, and what it should contain; [and] whether the methods used in manufacturing the drug and the controls used to maintain the drug’s quality are adequate to preserve the drug’s identity, strength, quality, and purity.

The Priority Review status was based on data from a Phase 3 clinical trial which analyzed Myrbetriq for patients with NDO older than 3 years old. 91 patients enrolled. Ultimately, the goal of the study was to determine the drug’s safety, efficacy, tolerability, and pharmacokinetics. The FDA defines Priority Review status as:

[directing] overall attention and resources to the evaluation of applications for drugs that, if approved, would be significant improvements in the safety or effectiveness of the treatment, diagnosis, or prevention of serious conditions when compared to standard applications.

While Myrbetriq was relatively safe and well-tolerated, associated side effects include:

• High blood pressure
• Flu-like symptoms
• Dry mouth
• Urinary tract infections
• Dizziness
• Back and joint pain
• Headache
• Constipation
• Bladder inflammation

Neurogenic Detrusor Overactivity (NDO)

According to Physio.co.uk, neurogenic detrusor overactivity (NDO):

previously known as hyperreflexia, is increased or involuntary muscle contractions of the detrusor muscle in the bladder. It is a neurological condition causing urinary incontinence and is due to damage or disruption of the nerves supplying the detrusor muscle.

An article in the American Journal of Managed Care also explains that NDO can result from a variety of disorders or conditions, from spina bifida and multiple sclerosis to Parkinson’s disease, spinal cord injuries, or strokes. Symptoms of NDO, which can heavily impede patients’ quality of life (QOL), include (but are not limited to):

• Stress or urge incontinence
• Frequent urination
• Impeded sleep (waking up in the night to use the bathroom)
• Depression and social isolation
• Involuntary bladder contractions
• Urinary tract infections
• Sexual dysfunction

Spina Bifida

Doctors believe that a blend of hereditary and environmental factors contribute to spina bifida, which occurs when the neural tube (which later develops into the brain and spinal cord) fails to close during embryonic development. As a result, some of the nerves of the spinal cord are exposed, causing nerve damage. Although spina bifida is usually found at birth, it can, in rarer cases, occur during adolescence.

There are multiple forms of spina bifida, including spina bifida occulta, closed neural tube defects, meningocele, and myelomeningocele, all of which vary in symptoms and severity. Symptoms may include:

• Seizures
• Poor bladder control or bowel dysfunction
• Back pain
• Partial or complete paralysis
• A fluid-filled sac protruding from the spinal canal
• Difficulty walking
• Intellectual or developmental delays
• Hydrocephalus

Learn more about spina bifida here.

Multiple Sclerosis (MS)

There is no known cause for multiple sclerosis (MS), a neurological disease which alters the communication between the brain and the body. However, many doctors consider MS to be an autoimmune disease in which the immune system mistakenly attacks parts of the body. In this case, the immune system mistakenly attacks the myelin sheath, or the protective nerve cell covers. MS can be relapsing and remitting or progressive; symptoms and disease progression vary based on type. Generally, MS affects females 2x more often than males.

Symptoms include:

• Eye or back pain
• Muscle weakness or numbness
• Loss of coordination and balance
• Muscle spasms
• Excessive urination
• Depression or anxiety
• Difficulty swallowing