A silk-based platform to stabilize phenylalanine ammonia-lyase (PAL) for orally administered enzyme replacement therapy

ABSTRACT Phenylalanine ammonia-lyase (PAL) has gained attention in recent years for the treatment of phenylketonuria (PKU), a genetic disorder that affects ∼1 in 15,000 individuals globally. However, the enzyme is easily degraded by proteases, unstable at room temperature, and is currently administered in PKU patients as daily subcutaneous injections. We report here the stabilization of the PAL from Anabaena variabilis , which is currently used to formulate pegvaliase, through incorporation in a silk fibroin matrix. The combination with silk stabilizes PAL at 37 °C. In addition, in vitro studies showed that inclusion in a silk matrix preserves the biological activity of the enzyme in simulated intestinal fluid, enabling the oral administration of pegvaliase for the treatment of PKU.