Results from a new survey shows that enzyme replacement therapy [ERT; Myozyme (alglucosidase alfa), also known as Lumizyme in the U.S.] for patients with late-onset Pompe disease significantly reduces the risk of them becoming wheelchair dependent. The study supports earlier work showing ERT improves muscle strength in Pompe disease and reaffirms the value that Myozyme has on this rare disease population. Interestingly, the use of ERT did not reduce the risk of a patient eventually requiring respiratory assistance.

The results were published this week in the Orphanet Journal of Rare Diseases.

Pompe disease is a rare lysosomal storage disease in which patients have insufficient levels of the enzyme lysosomal acid alpha-glucosidase that leads to the accumulation of glycogen in lysosomes that in turn leads to muscle deterioration.  In late-onset Pompe disease, the disease may go undiagnosed for years but once signs of muscle deterioration are noticeable, patients are advised to begin ERT as soon as possible to reduce the progression of muscle strength.  It is well documented that ERT can delay muscle deterioration but until now, it has not been documented whether ERT delays two outcomes of paramount concern to Pompe patients– unassisted walking and breathing. At some point, most adults with Pompe disease will require a wheelchair to get around as well as respiratory assistance. These are two outcomes that can significantly impact their daily life activities and quality of life.

The new study by researchers at the Erasmus MC University in the Netherlands used survey data they collected with the International Pompe Association (IPA) from 2002 to 2016 to assess the impact ERT has had on the need for a wheelchair and respiratory assistance. By going back to 2002, the researchers were able to assess the risk of a patient requiring a wheelchair before and after ERT was approved (2006).

A total of 458 patients participated in the IPA/Erasmus MC Pompe survey between 2002 and July 2016. Of those, the effect of ERT on wheelchair dependency was examined in 189 patients and respiratory support in 131 patients. Patients using a wheelchair or requiring respiratory support when starting the survey were excluded from the analysis.

What the researchers found was that patients using ERT had a 64% lower risk for becoming wheelchair dependent compared to untreated patients. However, no significant difference was observed in using respiratory support in patients taking ERT versus those who had not.

In their discussion, the authors note that since ambulation requires sufficient muscle strength and function, they were not surprised that ERT reduced the risk of become wheelchair dependent. However, the observation that ERT did not impact respiratory assistance in this study was hypothesized by the researchers as possibly due to the smaller effect that ERT has on respiratory muscles compared to skeletal muscles.

While the results and conclusions of the study may not be new to the Pompe community, the study should be applauded for using patient data collected largely from a patient advocacy group. These type of studies can help future policy makers and regulators understand the important role that patient groups have in data collection and analysis.

Reference

Van der Meijden JC, Kruijshaar ME, Rizopoulos D, et al. Enzyme replacement therapy reduces the risk for wheelchair dependency in adult Pompe patients. Orphanet J Rare Dis. 2018;13:82 https://doi.org/10.1186/s13023-018-0824-4