A ray of hope for MCT8 deficiency

MCT8 deficiency is caused by mutations in the SLC16A2 gene, which encodes the MCT8 protein. This protein is crucial for transporting thyroid hormones through the blood-brain barrier. If the MCT8 protein is missing or not functioning correctly, it significantly affects brain development and function, since the supply with thyroid hormones is cut. 

Currently, there is no cure for MCT8 deficiency. Treatment primarily involves managing symptoms and providing supportive care, including physical therapy for mobility and speech therapy for communication difficulties. However, these interventions do not address the underlying cause of the disease – progression is not slowed down. 

Potential candidates for the treatment of MCT8 deficiency, such as Emcitate®, a T3 analog, offer hope. Emcitate® has been granted an orphan designation and is the first causal therapy currently under submission review by the European Medicines Agency (EMA). Emcitate® can cross the blood-brain barrier independently of MCT8 and may restore T3 supply due to its chemical structure as a chemical T3 analog in the brain. In the pipelines of pharmaceutical manufacturers, other drugs e.g. SRW101 are currently in development. 

Manufacturers of orphan drugs face specific challenges due to the ultra-rarity of the disease. These include a small population size and studies with lower evidence levels than the recommended Randomized Controlled Studies (RCT). This leads to considerable uncertainty about the added value of the drug, which can result in intense and sometimes strenuous negotiations with high rebates. Therefore, a sound strategy and convincing value story are crucial for successful market access.

As Market Access Special Forces focused on orphan drugs, SKC supports the successful market access of pharmaceutical companies in the AMNOG and is committed to ensuring that new drugs for rare diseases gain access to the German market in order to improve the care of affected patients. In this Rare Disease Day blog series, we are therefore reporting on selected rare diseases in order to raise awareness and perception of them.

Sources:

• Groeneweg S et al. Disease characteristics of MCT8 deficiency: an international, retrospective, multicentre cohort study. Lancet Diabetes Endocrinol. 2020  
• Vancamp P, Demeneix BA, Remaud S. Monocarboxylate Transporter 8 Deficiency: Delayed or Permanent Hypomyelination? Front Endocrinol. 2020  
• Biomedtracker.com 
• Clinicaltrials.gov