Evolutionary redesign of the lysosomal enzyme arylsulfatase A increases efficacy of enzyme replacement therapy for metachromatic leukodystrophy.

Protein engineering is a means to optimize protein therapeutics developed for the treatment of so far incurable diseases including cancers and genetic disorders. Here we report on an engineering approach in which we successfully increased the catalytic rate constant of an enzyme that is presently evaluated in enzyme replacement therapies (ERT) of a lysosomal storage disease (LSD). Although ERT is a treatment option for many LSDs, outcomes are lagging far behind expectations for most of them. This has been ascribed to insufficient enzyme activities accumulating in tissues difficult to target such as brain and peripheral nerves. We show for human arylsulfatase A (hARSA) that the activity of a therapeutic enzyme can be substantially increased by reversing activity-diminishing and by inserting activity-promoting amino acid substitutions that had occurred in the evolution of hominids and non-human mammals, respectively. The potential of this approach, here designated as evolutionary redesign, was highlighted by the observation that murinization of only 1 or 3 amino acid positions increased the hARSA activity 3- and 5-fold, with little impact on stability, respectively. The two kinetically optimized hARSA variants showed no immunogenic potential in ERT of a humanized ARSA knockout mouse model of metachromatic leukodystrophy (MLD) and reduced lysosomal storage of kidney, peripheral and central nervous system up to 3-fold more efficiently than wild-type hARSA. Due to their safety profile and higher therapeutic potential the engineered hARSA variants might represent major advances for future enzyme-based therapies of MLD and stimulate analogous approaches for other enzyme therapeutics.