FDA approves mirdametinib for adult and pediatric patients with neurofibromatosis type 1

The US Food and Drug Administration (FDA) has approved mirdametinib (Gomekli) for adults and children aged 2 years and older with neurofibromatosis type 1 (NF1) who have symptomatic plexiform neurofibromas (PN) that cannot be completely removed with surgery.

This approval offers a new treatment option for families facing one of the more challenging complications of NF1.

Understanding NF1 and Plexiform Neurofibromas

Neurofibromatosis type 1 is a genetic condition that causes tumors to grow along nerves. Some of these tumors are called plexiform neurofibromas.

Plexiform neurofibromas can:

• Grow deep inside the body
• Wrap around vital organs, blood vessels, or nerves
• Cause pain, weakness, disfigurement, or other serious health problems

In many cases, surgery is not possible because removing the tumor completely could cause significant harm. These are referred to as inoperable tumors.

How Does Mirdametinib Work?

Mirdametinib is a type of targeted therapy known as a kinase inhibitor. It works by blocking signals that tell tumor cells to grow. By interrupting these signals, the medication can help shrink tumors or slow their growth.

How Well Did the Treatment Work?

The FDA approval was based on results from a clinical trial called ReNeu, which included 114 patients (58 adults and 56 children) with NF1-related plexiform neurofibromas that could not be removed surgically.

Researchers measured how many patients experienced meaningful tumor shrinkage.

What Were the Results?

• 41% of adults had significant tumor shrinkage
• 52% of children had significant tumor shrinkage

A meaningful response meant:

• The tumor disappeared completely, or
• The tumor shrank by at least 20% in volume

Tumor changes were measured using specialized MRI scans and independently reviewed by experts.

For many families, tumor shrinkage may help reduce pain, improve function, and ease other symptoms caused by tumor growth.

Possible Side Effects

Like all medications, mirdametinib can cause side effects. Some were more common than others.

Most Common Side Effects in Adults

• Rash
• Diarrhea
• Nausea
• Vomiting
• Muscle and joint pain
• Fatigue

Most Common Side Effects in Children

• Rash
• Diarrhea
• Muscle and joint pain
• Abdominal pain
• Vomiting
• Headache
• Nail infections (paronychia)
• Nausea
• Changes in heart function

Mirdametinib may also cause:

• Heart problems, including reduced heart pumping function (left ventricular dysfunction)
• Eye problems, such as blurred vision, retinal vein blockage, or changes in the retina
• Changes in certain blood tests

Because of these risks, patients taking mirdametinib will need regular monitoring. If side effects become severe, doctors may pause treatment, lower the dose, or stop the medication altogether.

What Patients and Caregivers Should Know

• The medication is approved for both adults and children as young as 2 years old.
• Dosing is based on body surface area, meaning the amount prescribed depends on the patient’s size.
• Ongoing follow-up visits and monitoring tests are important during treatment.

If you or your child has NF1 and symptomatic plexiform neurofibromas, talk with your healthcare provider about whether this newly approved treatment may be appropriate.