The U.S. Food and Drug Administration today approved Emcitate (tiratricol) tablets for oral suspension for the treatment of peripheral thyrotoxicosis in patients with MCT8 deficiency, also known as Allan-Herndon-Dudley syndrome. Peripheral thyrotoxicosis refers to excess thyroid hormone levels in the blood that causes symptoms, such as rapid heart rate, increased blood pressure and adverse effects on metabolism. Emcitate is the first therapy approved by the FDA to address symptoms associated with this very rare and devastating genetic disease. The approval also reflects the FDA’s dedication to patients with rare genetic diseases, including those who continue to face serious unmet medical needs.
“Until now, patients living with MCT8 deficiency and their families had no FDA-approved treatment option,” said Marina Zemskova, M.D., Deputy Director of the Division of General Endocrinology in the FDA’s Center for Drug Evaluation and Research.
MCT8 deficiency is a rare genetic disorder that primarily affects males. It results from a faulty gene that provides instructions for making the MCT8 transporter, a critical protein responsible for carrying thyroid hormone into the brain. Without the MCT8 transporter, thyroid hormone cannot cross the blood-brain barrier. As a result, the brain receives too little of the hormone, while excessive levels accumulate in the bloodstream. Patients with MCT8 deficiency can experience debilitating effects, including the inability to walk or sit independently, absent or severely limited speech, intellectual disability, feeding difficulties and chronic stress on the heart and metabolism.
Tiratricol Addresses Elevated Thyroid Hormone Levels
The treatment challenge associated with MCT8 deficiency is linked to the malfunctioning transporter required to deliver thyroid hormone into cells. “The challenge in treating MCT8 deficiency has always been that the protein needed to deliver thyroid hormone into cells is the one that isn’t working,” said Hylton V. Joffe, M.D., MMSc, Director of the Office of Cardiology, Hematology, Endocrinology, and Nephrology in the FDA’s Center for Drug Evaluation and Research.
“This drug sidesteps that problem, as its active ingredient, tiratricol, can enter cells on its own without relying on the broken transporter, leading to a decrease in the elevated blood thyroid hormone levels,” he added.
The effectiveness of Emcitate was assessed through two clinical studies involving patients ranging from infants to adults. These included an international, multi-center, randomized, placebo-controlled trial (NCT05579327) and a longer-term open-label study. Across the two studies, patients receiving Emcitate experienced reductions in excess thyroid hormone levels in the bloodstream, along with improvements in cardiovascular and metabolic symptoms affected by thyroid levels, including systolic blood pressure and heart rate.
Once-Daily Emcitate Treatment
Emcitate is administered once daily as a liquid suspension and can be taken by mouth or through a feeding tube for patients who have difficulty swallowing. This provides an administration option for patients with a wide range of abilities. The most common side effects reported were diarrhea, vomiting, rash and excessive sweating. Patients who are taking another thyroid medication should consult their healthcare provider before beginning Emcitate because the two medications should not be used together. Emcitate received Orphan Drug, Rare Pediatric Disease, Fast Track and Breakthrough Therapy designations, along with Priority Review. The approval of Emcitate was granted to Egetis Therapeutics US Inc.
