FDA Approves First Treatment for MCT8 Deficiency, a Rare Genetic Disorder

The U.S. Food and Drug Administration has approved Emcitate (tiratricol), made by Egetis Therapeutics, as the first therapy for people with MCT8 deficiency, also known as Allan-Herndon-Dudley syndrome. The approval was announced on September 28.

The drug is approved to treat peripheral thyrotoxicosis, an excess of thyroid hormone in the blood, in patients with the condition.

"Until now, patients living with MCT8 deficiency and their families had no FDA-approved treatment option." — Dr. Marina Zemskova, FDA

About the condition

MCT8 deficiency is a rare genetic disorder that mainly affects males. A faulty gene disrupts a protein that moves thyroid hormone into the brain, so the brain receives too little while the blood accumulates too much. Patients can have difficulty walking or sitting unassisted, limited or no speech, intellectual disability, feeding problems, and ongoing strain on the heart and metabolism.

How the drug works

The FDA's Dr. Hylton Joffe explained that the active ingredient can enter cells without the faulty transporter, saying the drug "sidesteps that problem."

• Evidence: a randomized, placebo-controlled trial and a longer open-label study, covering patients from infancy to adulthood
• Results: lower excess thyroid hormone levels in the blood, plus improvements in systolic blood pressure and heart rate
• Dosing: a once-daily liquid, taken by mouth or through a feeding tube
• Common side effects: diarrhea, vomiting, rash and excessive sweating

What to know

The approval addresses the hormone imbalance in the body; the FDA's announcement does not claim it reverses the neurological features of the disorder. People taking another thyroid medication should consult their provider first, as the two should not be combined. The FDA noted that the drug had Orphan Drug, Rare Pediatric Disease, Fast Track, Breakthrough Therapy and Priority Review designations, reflecting how urgent the unmet need was.