Slowly Progressive, Low-Prevalence Rare Diseases With Substrate Deposition That Results From Single Enzyme Defects: Providing Evidence of Effectiveness for Replacement or Corrective Therapies; Draft Guidance for Industry; Availability

The Food and Drug Administration (FDA or Agency) is announcing the availability of a draft guidance for industry entitled ``Slowly Progressive, Low-Prevalence Rare Diseases with Substrate Deposition That Results from Single Enzyme Defects: Providing Evidence of Effectiveness for Replacement or Corrective Therapies.'' This document is intended to provide guidance to sponsors on the evidence necessary to demonstrate the effectiveness of new drugs, including biological drugs, or new drug uses intended for slowly progressive, low-prevalence rare diseases that are associated with substrate deposition and are caused by single enzyme defects. This guidance applies only to those low-prevalence rare diseases with a well-characterized pathophysiology and in which changes in substrate deposition can be readily measured in relevant tissue(s).