OBJECTIVES: Fabry disease (FD) is a rare, progressive X-linked lysosomal storage disorder that can lead to peripheral neuropathy, cardiovascular disease, stroke, end-stage renal disease, gastrointestinal disorders and premature death. Pegunigalsidase alfa (PRX-102, Elfabrio^®) is an enzyme-replacement therapy (ERT) with a longer half-life and improved biodistribution compared with current ERTs, agalsidase alfa and agalsidase beta. In the Phase III BALANCE trial (n=75), the efficacy and safety of PRX-102 was compared with agalsidase beta in patients with deteriorating renal function previously treated with agalsidase beta. This utility analysis aimed to estimate the health-related quality of life (HRQoL) of patients in BALANCE.

METHODS: Utility score estimates were derived from EQ-5D-5L questionnaires completed in BALANCE at baseline and every 6 months up to Month 24. EQ-5D-5L data were mapped to EQ-5D-3L using the EEPRU algorithm as per NICE guidance. A linear mixed-effects model was fitted to the data, and 10 covariates that could be considered clinically relevant were used within a forwards selection algorithm.

RESULTS: The stepwise algorithm determined that baseline utility values and Fabry clinical events (FCEs covariate; a binary variable indicating whether a patient experienced any type of FCE [renal, cardiac or cerebrovascular] during the trial) should be included in the regression model. Both covariates were statistically significant and displayed improved model fit (based on Akaike and Bayesian information criteria) versus models with additional covariates.

The mean baseline utility was 0.764 for patients in BALANCE. Applying the regression model to this estimated a utility of 0.779 for patients prior to experiencing an FCE, which reduced to 0.686 after patients experienced an FCE (n=11).

CONCLUSIONS: The results demonstrate that patients with FD who experience an FCE are expected to report a reduced HRQoL. Given the renally impaired population of BALANCE, estimates of their HRQoL may be lower than the general Fabry population.