The Food and Drug Administration approved Emcitate, known generically as tiratricol, on Sept. 28 as the first treatment for MCT8 deficiency, a rare genetic disorder also called Allan-HerndonDudley syndrome. The once-daily liquid is approved for patients of all ages. Egetis Therapeutics US Inc. makes the drug, according to the FDA’s announcement.
The agency approved it for peripheral thyrotoxicosis, an excess of thyroid hormone in the body outside the
brain, in adults and children with the disorder. Marina Zemskova, deputy director of the FDA’s Division of General Endocrinology, said patients and families previously had “no FDA-approved treatment option.”
What MCT8 Deficiency Does to the Body
MCT8 deficiency is an X-linked disorder caused by changes in the SLC16A2 gene, and it mainly affects males. The gene makes a transporter protein that carries thyroid hormone into brain cells. When it fails, the brain has too little of the active hormone, T3, and the rest of the body has too much, according to Egetis.
Egetis says the brain shortage causes profound neurodevelopmental delays and severe intellectual and motor disability. It says the excess in the body causes arrhythmias, low body weight and a risk of premature death. The company puts median life expectancy at about 35 years, according to its release. Children’s Hospital of Philadelphia says a carrier mother has a
50% chance of passing the condition to each son and that doctors often diagnose it months to
years after birth.
Emcitate treats the excess in the body. Hylton Joffe, director of the FDA’s Office of Cardiology, Hematology, Endocrinology and Nephrology, said the drug works around the broken transporter because its active ingredient can enter cells on its own. The FDA’s announcement describes the treatment as directed at the excess hormone in the body.
Evidence Behind the Approval
The FDA based the approval on two studies. One was an international, randomized, placebocontrolled trial registered as NCT05579327. The other was a longer open-label study. Both enrolled patients from infants to adults. The FDA said the drug lowered the excess thyroid hormone in patients’ blood and lowered their systolic blood pressure and heart rate. Egetis reported results from the randomized study, called ReTRIACt, in a November 2025 release.
The primary measure, the rate of change in blood T3, met statistical significance at p=0.034. T3 rose in all eight placebo patients, by 0.49 to 2.08 nanomoles per liter. It changed little in the seven patients who stayed on tiratricol, from a drop of 0.24 to a rise of 0.40. Four placebo patients met the study’s rescue criterion, and none on tiratricol did. Those counts add
up to 15 patients.
An earlier study, Triac Trial II, enrolled 22 boys younger than 30 months. Its secondary measures showed a significant and lasting drop in T3, but it did not meet its primary goal, according to Egetis. An Erasmus Medical Center cohort followed 67 patients at 33 centers for up to six years.
The most common side effects, occurring in at least 5% of patients, are diarrhea, vomiting, rash
and excessive sweating, the FDA said. The label carries a boxed warning that the drug is not for obesity or weight loss. Patients take it once a day by mouth or through a feeding tube.
How Families Will Get Emcitate
Egetis expects the drug to reach patients in eight to 10 weeks through specialty distribution. Eight weeks from Sept. 28 is Nov. 23, and 10 weeks is Dec. 7. The company launched a support program called Egetis RareLink with the specialty pharmacy PANTHERx Rare.
Nicklas Westerholm, Egetis’s chief executive, called the approval “a turning point” for patients and caregivers. The MCT8-AHDS Foundation, a patient advocacy group, said in the company’s release that the approval shows what a community can accomplish together. The drug is already approved in Europe. The European Commission approved it in February 2025, and Egetis launched it in Germany in May 2025. Egetis’s releases give the approval date as Feb. 12 in one place and Feb. 13 in another. The European indication starts at birth.
The Voucher That Comes With the Approval
The FDA granted Egetis a rare pediatric disease priority review voucher with the approval. A voucher lets its holder get a faster FDA review of a different drug, and companies can sell it. Egetis said it expects to sell the voucher in the fourth quarter of 2026, subject to market conditions.
That window overlaps with the launch timeline, which ends Dec. 7. Recent sales give a range. Fortress Biotech sold a voucher for $205 million in February, and Jazz Pharmaceuticals sold one for $200 million in January, Fierce Pharma reported. Sales in 2025 ranged from $150 million to $175 million, the outlet said. Egetis did not disclose the drug’s price
in its announcement.
