The FDA has approved tiratricol (Emcitate) as the first treatment for monocarboxylate transporter 8 (MCT8) deficiency, also known as Allan-Herndon-Dudley syndrome. The rare, life-limiting disorder is caused by mutations in the SLC16A2 gene and primarily affects males. Because the MCT8 transporter is defective, thyroid hormone signaling becomes imbalanced: the central nervous system is deprived of thyroid hormone while peripheral tissues are overexposed to active T3, leading to severe neurodevelopmental impairment and chronic stress on the heart and metabolism.
Tiratricol works by entering cells on its own, bypassing the broken transporter. In two clinical studies—a randomized, placebo-controlled trial with 20 participants and an open-label trial with 46 participants—the drug lowered excess blood thyroid hormone levels and improved cardiovascular and metabolic symptoms such as systolic blood pressure and heart rate.
The therapy is given once daily as a liquid suspension, either orally or through a feeding tube. The most common adverse effects include diarrhea, vomiting, rash, and hyperhidrosis. The label carries a boxed warning that the drug is not intended for weight loss, and it cautions against use in patients with primary hyperthyroidism or alongside other thyroid medications. Egetis Therapeutics said tiratricol will be available in the U.S. within 8 to 10 weeks.