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Technical Brief - Final – Jan. 2, 2013
Enzyme-Replacement Therapies for Lysosomal Storage Diseases
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Archived: This report is greater than 3 years old. Findings may be used for research purposes, but should not be considered current.
Lysosomal storage diseases (LSDs) comprise about 50 unique monogenic autosomal or X-linked diseases with an estimated combined incidence of 1 in 7,000 to 8,000 live births. They occur secondary to genetic mutations that result in deficiency or reduced activity of native intracellular enzymes that catabolize biological macromolecules. These enzyme defects result in accumulation of specific macromolecular compounds within lysosomes in various tissues and organs, causing progressive damage that can become life-threatening in some diseases. LSD management traditionally involved supportive care measures tailored to disease stage, the organs and systems involved, and the degree of impairment. However, enzyme-replacement therapy (ERT) is now commercially available for six LSDs, typically used lifelong with traditional management practices for each.
The objective of this Technical Brief is to provide an overview of U.S. Food and Drug Administration (FDA)-approved ERT for the treatment of six LSDs. The purpose of a Technical Brief is to report what outcomes (benefits and harms) have been studied for a technology, drug or procedure; it does not enumerate those outcomes. The Technical Brief also addresses research gaps identified during its preparation. It is not intended as a comparative effectiveness review or systematic review that draws conclusions as to the clinical benefits and harms of a drug, device, or procedure. It does not assess study quality or the strength of the body of evidence on specific outcomes.
Four Guiding Questions were used to frame this Technical Brief. An inspection of the literature from 1990 through mid-April 2012 included primary studies, as well as narrative and systematic review articles to create an overview of potential clinical outcomes. Other information sources included dosing and other treatment-related information from the FDA-approved product labels; scientific information packages from the product manufacturers that included unpublished data; and, interviews with physician Key Informants and patient advocates.
Published clinical studies report a variety of outcomes associated with nine FDA-approved ERT products. They include disease-specific intermediate outcomes, such as plasma or urinary levels of macromolecular compounds. Others were common hematological measures (e.g., anemia, thrombocytopenia), bone pain and skeletal abnormalities, renal function, cardiac function, pulmonary function, growth, and walking tests. Harms reported to the FDA and in clinical studies were primarily allergic, including infusion-associated reactions and anaphylaxis. Immunogenic responses, primarily an IgG-type antibody response and neutralizing antibodies, have been reported. This Technical Brief identified a number of research gaps, including the need for comparative effectiveness studies, dose optimization, optimal timing for initiation of ERT, and mechanisms involved in uptake and distribution of ERT products.