Enzyme replacement therapy (ERT) refers to the treatment of inherited enzyme deficiency syndromes such as Gaucher disease using purified human, animal, or recombinant enzyme substitutes. The replacement enzyme is usually prepared in such a way that it has a longer period of activity and more potency compared to the deficient enzyme.
The first ERT for Gaucher disease, Ceredase (alglucerase), was approved by the U.S. Food and Drug Administration (FDA) in 1991. The latest such therapy to get FDA approval was Elelyso (taliglucerase alpha) in 2012.
How ERT works for Gaucher disease
Enzymes are proteins that act as biological catalysts, i.e., they help in speeding up many biological reactions and are important for almost all chemical reactions in cells. Enzymes, like other proteins, are produced in the cells and are released into their site of action like digestive enzymes being released into the intestines, for example.
One such enzyme is beta-glucocerebrosidase; it helps break down a fatty chemical called glucocerebroside. In Gaucher disease, mutations in the GBA gene that encodes for beta-glucocerebrosidase result in an improper form of the enzyme or its deficiency, leading to the accumulation of glucocerebroside in the spleen and liver.
In people with Gaucher disease, ERT can help substitute the defective or deficient beta-glucocerebrosidase. ERT is usually a lifelong treatment that is administered into the bloodstream. The process lasts between one and two hours and usually has to be repeated every two weeks. ERT can be given at specialized infusion centers, clinics, or at home.
It must be noted that ERT is effective only for non-neuronopathic forms of the disease, such as type 1 Gaucher disease, as enzymes cannot cross the blood-brain barrier. However, ERT is still part of the standard care for type 3 Gaucher disease patients in whom the nervous system is affected much more slowly compared to type 2 Gaucher disease.
Available ERTs for Gaucher disease
There are several ERTs currently available for Gaucher disease.
Cerezyme (imiglucerase)
Cerezyme is a recombinant enzyme developed by Sanofi Genzyme that works as a substitute for beta-glucocerebrosidase that was approved by the FDA in 1994 as a successor of Ceredase.
VPRIV (Velaglucerase alpha)
VPRIV is another long-term ERT developed by Shire using a proprietary gene activation method. It was approved for the treatment of type 1 Gaucher disease by the FDA in 2010.
Elelyso (taliglucerase alpha)
Elelyso is a plant cell-based recombinant ERT developed by Pfizer that can substitute defective human beta-glucocerebrosidase. It was approved by the FDA in 2012.
Other information
ERT has several advantages over substrate replacement therapy (SRT), another treatment for Gaucher disease, including fewer side effects and wider availability. ERT also has been available for a longer time with proven action.
Some patients may find ERT inconvenient as it requires taking regular infusions compared to SRT, which just requires taking a pill. Also, individuals with Gaucher disease can have varying dose responses that might necessitate individualized treatments with lower or higher doses in order to see the benefits.
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