STS-E412 and STS-E424

STS-E412 and STS-E424 are two small molecules that scientists are investigating as potential therapies for patients with Friedreich’s ataxia.

The genetic defect responsible for FA leads to abnormally low levels of a protein called frataxin, so a lot of research is being done on whether increasing frataxin levels can be a way to treat the disease.

Preclinical-trial studies have shown that STS-E412 and STS-E424 increase frataxin levels in human cells cultivated in a laboratory and in mice.

How STS-E4 and STS-E424 work

Erythropoietin, or EPO, is a naturally occurring protein that regulates the production of red blood cells. Studies have shown that it may also fight inflammation and protect cells — including nerve cells — from DNA damage.

A laboratory study found that synthetic erythroepoetin, or rhEPO, increased frataxin protein levels in human heart and immune cells, and in mouse neurons, or nerve cells.

RhEPO exerts its effects by binding to specialized receptors on the surface of cells. Some rhEPO receptors stimulate blood cell production, while others trigger cell-protecting effects.

STS-E412 and STS-E424 bind to the EPO receptors responsible for protecting cells but not to the receptors that regulate blood cells. This means they have the potential to increase frataxin levels in the same way that rhEPO does, without affecting blood cell levels.

STS-E4 and STS-E424 in preclinical-trial studies

A study published in Neuropharmacology in 2017 supports the notion that STS-E412 and STS-E424 could be used to treat FA.

Investigators tested rhEPO, STS-E412, and STS-424 on mouse cells and human brain cells grown in a laboratory, and on frataxin-deficient mice. They found that all three compounds increased frataxin production in a laboratory, but STS-E4/STS-424 had greater effects in mice. They also noted that mice treated with rhEPO developed enlarged spleens, while mice treated with the small molecules did not.

Additional information

STS-E412 and STS-E424 have not been tested in clinical trials. But several trials have evaluated the safety and effectiveness of EPO or EPO-like molecules in Friedreich ataxia patients.

In these studies, EPO increased frataxin levels and patients tolerated it well. But it did not significantly improve patients’ functioning, such as their neurologic symptoms and ability to exercise. Nor did it improve their quality of life.

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