Mito research around the world

Cysteamine Bitartrate (RP103)

What is Cysteamine Bitartrate?

Cysteamine Bitartrate, also known as RP103 or Procysbi, is a drug developed by a US based pharmaceutical company called Horizon Pharma (formerly Raptor Pharmaceuticals).

Procysbi is currently prescribed for a condition known as nephropathic cystinosis but has been ‘repurposed’ with the aim of treating patients affected by mitochondrial disease.

What is it supposed to do?

Cysteamine Bitartrate is thought to increase production of a naturally occurring protein called glutathione, which works as a super antioxidant and protects against reactive oxygen species that can cause mitochondrial damage. 

Is it a cure?

Unfortunately not. Cysteamine Bitartrate cannot correct the underlying genetic defect that causes Mitochondrial Disease.

Have there been any trials of Cysteamine Bitartrate?

In 2014, a phase 2 clinical trial (MITO-001) was started which aimed to evaluate the safety, tolerability and efficacy of Cysteamine Bitartrate in 36 children aged 6 to 17 years with inherited mitochondrial disease, including Leigh Syndrome. The study took place over 24 weeks, with a progressive increase in the dose of the drug over 6 weeks. This was an open-label trial, meaning that both the researchers and the participants (or their families) knew what treatment they were taking.

What happened next?

It was reported that 25 patients completed the full 24 weeks of study. Reasons for early withdrawal included noncompliance, adverse events or withdrawal of consent.

The trial was extended in 2015 to assess the long-term safety, tolerability and efficacy of Cysteamine Bitartrate (MITO-002). This study involved 22 participants enrolled on the initial trial, who were offered the opportunity to continue taking the drug for up to 2 years until the results of the earlier trial were known.

What is the latest on this trial?

Horizon Pharma took the decision to terminate the development of Cysteamine Bitartrate for mitochondrial disease. This was due to a lack of efficacy demonstrated in the initial trial and meant that no participants completed the extended trial.

Is there any more information?

An update on this clinical trial was published in a medical journal in October 2017. To read more:



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