SBT-20 is an investigational compound being developed by Stealth Biotherapeutics to possibly slow neurodegeneration in people with Huntington’s disease.

How SBT-20 works

Huntington’s patients have a mutation in their HTT gene. Research suggests that, besides causing other problems, this mutation impairs the function of mitochondria in nerve cells. Mitochondria are the “powerpacks” that break down oxygen and glucose to supply energy to cells. Poorly or abnormally working mitochondria result in lower-than-normal cellular energy levels, and allow toxic byproducts of oxygen metabolism to accumulate inside cells.

Because nerve cells have a high energy demand, they are particularly vulnerable to mitochondrial dysfunction. The events associated with malfunctioning mitochondria are, for this reason, thought to contribute to the neurodegeneration seen in Huntington’s disease.

SBT-20 aims to improve how mitochondria function in nerve cells to slow neurodegeneration in Huntington’s patients and the disease’s progression. Preclinical studies show that the compound is able to act on the nerve cells of the brain and spinal cord more effectively than elamipretide because of its extended stability in the fluid that surrounds the both the brain and spinal cord, which make up the central nervous system. (Elamipretide is investigational compound that aims to restore mitochondrial function, also being developed by Stealth Biotherapeutics.)

SBT-20 in clinical trials

Stealth Biotherapeutics has begun testing SBT-20 in a Phase 1/2 double-blinded, randomized and placebo-controlled trial (2016-003730-25). The trial, called CHALLENGE-HD, aims to assess the safety, pharmacodynamics (how a drug is processed by the body), and pharmacokinetics (how it moves inside the body) of SBT-20 in people with early-stage Huntington’s disease. Researchers will also assess the effect of SBT-20 on mitochondrial function, and on cognitive and motor abilities in these patients.

The trial consists of two parts. In the first, patients are given one of three different concentrations of SBT-20 (5, 15 or 25 mg) as an injection under the skin for seven days to determine an optimal concentration that will be used in the trial’s second part. In that part, patients in the active treatment arm will be given that optimal dose for another four weeks while others will continue on placebo.

The trial is ongoing at the Center for Human Drug Research in The Netherlands. A total of 24 adults with Huntington’s disease were enrolled.

Other information

In addition to being investigated as a potential therapy for Huntington’s disease, SBT-20 was investigated in preclinical studies on mice models of myocardial ischemia, a condition where heart muscle cells die due to the blood supply to the heart being reduced. The results of these studies showed that mice that had blood flow to their hearts temporarily stopped had larger amounts of healthy heart muscles remaining after receiving SBT-20 compared to mice that did not receive this treatment. 

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