The U.S. Food and Drug Administration announced on September 28, 2026 that it has approved Emcitate (tiratricol) tablets for oral suspension, the first therapy ever cleared to treat symptoms of MCT8 deficiency, according to the official release. The drug is approved to treat peripheral thyrotoxicosis, a buildup of excess thyroid hormone in the blood, in patients with the rare genetic disease.
Key takeaways
- The FDA approved Emcitate (tiratricol) on September 28, 2026, as the first-ever treatment for MCT8 deficiency, also known as Allan-Herndon-Dudley syndrome.
- The drug treats peripheral thyrotoxicosis, excess thyroid hormone in the blood, by letting tiratricol enter cells without relying on the broken MCT8 transporter protein.
- Effectiveness was shown in two studies, including a randomized placebo-controlled trial, with patients seeing reductions in excess thyroid hormone and improvements in blood pressure and heart rate.
- Emcitate received Orphan Drug, Rare Pediatric Disease, Fast Track, Breakthrough Therapy and Priority Review designations and was approved for manufacturer Egetis Therapeutics US Inc.
What the FDA Approved
The FDA's approval covers Emcitate for peripheral thyrotoxicosis, described in the agency's release as excess thyroid hormone levels in the blood that cause symptoms such as rapid heart rate, increased blood pressure and adverse effects on metabolism, in patients with MCT8 deficiency. The agency called Emcitate the first therapy it has approved to treat symptoms of this disease, which it described as very rare and devastating.
"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, in the release. "Emcitate's approval reflects the FDA's deep commitment to patients with rare conditions who are in need of meaningful treatment options."
The approval was granted to Egetis Therapeutics US Inc., according to the FDA.
Understanding MCT8 Deficiency
MCT8 deficiency, also known as Allan-Herndon-Dudley syndrome, is a rare genetic disorder that primarily affects males, according to the FDA. It is caused by a faulty gene that provides instructions for making the MCT8 transporter, a protein responsible for carrying thyroid hormone into the brain. Because thyroid hormone cannot cross the blood-brain barrier without this transporter, the brain receives too little hormone while excessive levels build up in the bloodstream instead.
The FDA states that many patients with the condition experience a range of 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. The agency's approval of Emcitate marks its latest action addressing a disease with what it calls serious unmet medical needs, following a pattern of recent rare-disease clearances such as the first gene therapy for Sanfilippo Syndrome Type A.
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, explained the mechanism in the release: "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. 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."
Clinical Evidence Behind the Approval
The FDA said Emcitate's effectiveness was evaluated in two clinical studies enrolling patients ranging in age from infants to adults. These included an international, multi-center, randomized, placebo-controlled trial, identified as NCT05579327, and a longer-term open-label study. Across both studies, patients treated with Emcitate had reductions in excess thyroid hormone levels in the bloodstream and improvements in cardiovascular and metabolic symptoms affected by thyroid levels, such as systolic blood pressure and heart rate, according to the agency.
The release does not provide specific percentage figures or patient counts from the trials. The table below summarizes the headline figures stated in the FDA's announcement.
| Measure | Before Approval | After Approval | Change |
|---|---|---|---|
| FDA-approved treatments for MCT8 deficiency | 0 | 1 (Emcitate) | First approval |
| Clinical studies supporting approval | Not stated | 2 | Not stated |
| Special regulatory designations granted | Not stated | 5 (Orphan Drug, Rare Pediatric Disease, Fast Track, Breakthrough Therapy, Priority Review) | Not stated |
Dosing, Side Effects and Regulatory Pathway
Emcitate is taken once daily as a liquid suspension, either by mouth or through a feeding tube for patients who have difficulty swallowing, which the FDA said makes it accessible for patients with a wide range of abilities. The most common side effects reported were diarrhea, vomiting, rash and excessive sweating. The FDA also noted that patients taking another thyroid medication should talk to their healthcare provider before starting Emcitate, as the two should not be used together.
To reach approval, Emcitate received Orphan Drug, Rare Pediatric Disease, Fast Track and Breakthrough Therapy designations, along with Priority Review, according to the release. These designations are tools the FDA uses to speed development and review of drugs for rare or serious conditions, a pathway that has also applied to other recent agency actions such as the first-of-its-kind treatment for chronic hepatitis B.
The FDA is an agency within the U.S. Department of Health and Human Services. Per its standard mission statement included in the release, the FDA protects public health by assuring the safety, effectiveness and security of human and veterinary drugs, vaccines and other biological products, as well as medical devices, while also overseeing the safety of the nation's food supply, cosmetics, dietary supplements, radiation-emitting electronic products and tobacco products.
Frequently asked questions
What is Emcitate approved to treat?
Emcitate (tiratricol) is approved to treat peripheral thyrotoxicosis, excess thyroid hormone in the blood that causes symptoms like rapid heart rate and high blood pressure, specifically in patients with MCT8 deficiency, according to the FDA.
How does Emcitate work differently from normal thyroid hormone regulation?
In MCT8 deficiency, a faulty transporter protein prevents thyroid hormone from entering the brain, causing it to build up in the blood instead. The FDA says tiratricol, Emcitate's active ingredient, can enter cells on its own without needing that broken transporter, which lowers the elevated blood hormone levels.
Who manufactures Emcitate and what designations did it receive?
The approval was granted to Egetis Therapeutics US Inc. The drug received Orphan Drug, Rare Pediatric Disease, Fast Track and Breakthrough Therapy designations, along with Priority Review, according to the FDA's release.