ATB200/AT2221 is an investigative treatment being developed by Amicus Therapeutics for the treatment of Pompe disease, an inherited lysosomal storage disorder (LSD) caused by a deficiency in the enzyme acid alpha-glucosidase (GAA). This deficiency is caused by mutations in the GAA gene that provides instructions to build this enzyme.

The age of the patient at disease onset depends on the extent of how much the mutation affects the function of the GAA enzyme.

The complete or near-complete loss of enzyme function is associated with the early childhood form of the condition, where glycogen, the complex sugar molecule that the GAA enzyme is responsible for breaking down, accumulates inside cells, especially muscle cells. The excess glycogen disrupts the function of cells and causes their death. This leads to muscle weakness, respiratory problems, and other symptoms associated with Pompe disease.

How ATB200/AT2221 works

ATB200/AT2221 consists of a recombinant human GAA enzyme with an optimized structure (ATB200), administered with a small molecule pharmacological chaperone (AT2221).

ATB200 compensates for the lack of natural GAA enzyme while the chaperone AT2221 stabilizes the structure of ABT200 that could be partially disrupted during drug delivery. (Chaperones are designed to enhance the structural stability or correct folding of proteins).

The co-administration of ATB200 and AT2221 allows the delivery of active functional recombinant GAA to the target cells in the body. The chaperone molecule may also stabilize the misfolded and dysfunctional molecules of the patient’s own GAA enzyme and thus partially restore its functions.

ATB200/AT2221 in clinical trials

ATB200/AT2221 is currently being investigated in an open-label Phase 1/2 clinical trial (NCT02675465) in patients with Pompe disease. The study’s objectives is to evaluate the safety, tolerability, pharmacokinetics (the drug’s movement in the body), pharmacodynamics (the drug’s effects on the body), and efficacy of ATB200/AT2221 over an 18-week primary treatment period followed by a long-term extension study.

The trial enrolled 20 patients, 15 of whom have previously been treated with enzyme replacement therapy (ERT).

Preliminary results from the trial showed that patients treated with ATB200/AT2221 for up to 12 months showed improvements in motor function measured by the six-minute walk test and in respiratory function measured by forced vital capacity, as well as durable reductions in biomarkers of muscle damage.

Other information

The U.S. Food and Drug Administration granted orphan drug status to ATB200/AT2221 in 2017 for the treatment of Pompe disease.

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