Strong increase of leukocyte apha-galactosidase A activity in two male patients with Fabry disease following oral chaperone therapy

[Chaperone molecules: The example of Fabry disease]

Fabry disease is due to mutations in the GLA gene that cause a deficiency of the activity of the lysosomal enzyme alpha-galactosidase A (α-gal A) resulting in intra-tissue accumulation of globotriaosylceramide. Recently, a novel therapeutic approach based on the pharmacological chaperone migalastat has been developed. It binds, in a specific and reversible manner, to the catalytic site of α-gal A mutants, to prevent their degradation by the quality control system of the endoplasmic reticulum and allow them to catabolize globotriaosylceramide in the lysosomes. This treatment concerns approximately 35% of the GLA gene mutations recognized as sensitive to migalastat according to an in vitro pharmacogenetic test. Two pivotal Phase III studies, FACETS: migalastat vs. placebo and ATTRACT: migalastat vs. enzyme replacement therapy analyzed the in vivo effects of migalastat. Despite some methodological limitations, promising results were found. Migalastat seems to be more effective than enzyme replacement therapy in reducing left ventricular mass index in case of cardiac hypertrophy and has comparable renal effects. This oral treatment is the first personalized treatment, based on the genetic profile of Fabry patients and opens a new era in the management of conformational diseases.

Strong increase of leukocyte apha-galactosidase A activity in two male patients with Fabry disease following oral chaperone therapy

Background

Fabry disease (OMIM 301500) is an X‐linked disorder caused by alpha‐galactosidase A (α‐Gal A) deficiency. The administration of a pharmacologic chaperone (migalastat) in Fabry patients with amenable mutations has been reported to improve or stabilize organ damages and reduce lyso‐Gb3 plasma level. An increase of α‐Gal A activity has been observed in vitro in cells expressing amenable GLA mutations when incubated with migalastat. The impact of the drug on α‐Gal A in vivo activity has been poorly studied.

Methods

We conducted a retrospective analysis of two unrelated male Fabry patients with p.Asn215Ser (p.N215S) variant.

Results

We report the important increase of α‐Gal A activity in blood leukocytes reaching normal ranges of activity after about 1 year of treatment with migalastat. Cardiac parameters improved or stabilized with the treatment.

Conclusion

We confirm in vivo the effects of migalastat that have been observed in N215S carriers in vitro. The increase of α‐Gal A activity may be the strongest marker for biochemical efficacy. The normalization of enzyme activity could become the new therapeutic target to achieve.