In the first years of treatment, Myozyme (alglucosidase alfa) — marketed in the U.S. as Lumizyme — can effectively increase physical endurance, and improve lung function and muscle strength in adults with late-onset Pompe disease (LOPD), a real-world study found.
Yet, despite this treatment, patients’ clinical outcomes, particularly lung function, tend to deteriorate over time, indicating that additional efforts must be made to improve Myozyme’s effectiveness.
These findings were reported in “STIG study: real-world data of long-term outcomes of adults with Pompe disease under enzyme replacement therapy with alglucosidase alfa,” a study published in the Journal of Neurology.
Pompe disease is characterized by the excessive accumulation, inside cells, of glycogen, a sugar molecule. This buildup is caused by the lack of an enzyme called acid alpha-glucosidase (GAA).
Enzyme replacement therapy (ERT), which provides patients a form of the enzyme they are missing, is currently the standard treatment for the rare genetic disease.
Myozyme is the sole ERT for Pompe, marketed by Sanofi Genzyme and approved in Europe in 2006 to treat patients of all ages and disease types. It was later approved for the same indication in the U.S., where it currently is marketed under the brand name Lumizyme.
Several studies have reported that Myozyme can significantly improve patients’ clinical outcomes in the first three to five years of treatment. However, a slow deterioration in muscle strength, walking ability, and lung function were found in subsequent assessments.
To explore in more detail the long-term effects of Myozyme on LOPD patients, an international group of researchers, led by scientists at the Ludwig-Maximilians-University Munich, in Germany, conducted a real-world study (NCT02824068). The team evaluated the muscle strength, lung function, and walking capacity of adults with the condition who had been receiving ERT for up to 14 years.
The final analysis included 68 LOPD patients (51.5% female) from Spain, Taiwan, Italy, and Germany, who had been receiving ERT for at least three years. The patients’ mean age at diagnosis was 41.78 years and nearly all (92.6%) were Caucasian. The mean follow-up duration was seven years.
Muscle strength, lung function, and walking abilities were evaluated at the study’s start (baseline) and then once each year during follow-up.
In general, the participants’ abilities across all three areas were found to improve in the first years of treatment. However, after that, muscle strength, lung function, and walking capability all gradually declined.
Of all the outcome measures evaluated, walking abilities and physical endurance — assessed by the six-minute walk test (6MWT) — were the ones that worsened the least over time, with most patients still experiencing positive effects from the treatment after seven years of follow-up.
In contrast, lung function deteriorated most over time. It was assessed by forced vital capacity (FVC), a parameter that measures the total amount of air a person is able to exhale after a deep breath. Despite remaining stable during the first year of treatment, FVC worsened by a mean of 3.88% after five years, and by 14.93% after a decade.
According to the researchers, the FVC decline observed in most patients (83.5%) could be explained by the degree of disease severity the individual had at the study’s start.
“Patients with lower disease severity at baseline showed a more moderate decline of [FVC] compared to patients with higher severity of disease at baseline,” the investigators wrote.
This decline in lung function was accompanied by an increase in the number of participants — 21 in total — who had to resort to non-invasive and invasive respiratory support techniques during follow-up. In contrast, a lower number of patients (nine in total) saw their mobility decline to the point of becoming wheelchair-bound during the study.
“The STIG real-world study confirms an initial efficacy of ERT in the first years with a secondary sustained decline in multiple outcome measures,” the researchers said.
“Further efforts are required to establish a more valid long-term monitoring and improved therapies,” they concluded.
As for safety, nine patients experienced infusion-associated reactions, with two having to stop treatment due to bronchial spasm (muscle contraction in the airway) with flushing and pulmonary artery blockage during infusion.
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