The International Consortium for Innovation & Quality (IQ) in Pharmaceutical Development has established a Working Group focused on development and regulatory challenges unique to Deuterated Active Pharmaceutical Ingredients. The deuteration of an Active Pharmaceutical Ingredient (API) can slow and / or alter API metabolism by exploiting the primary kinetic isotope effect. Several deuterated APIs have entered the clinic, and to date one has been approved. In most cases, it is difficult to impossible to synthesize a 100% isotopically pure compound The isotopic distribution of the deuterated API raises synthetic, anal., and regulatory questions that warrant a science-based assessment and recommendations for synthetic methods, anal. methods, and specifications not addressed by current practices and regulatory guidance documents. A cross functional team of scientists with expertise in isotope chem., process chem., anal. chem., computational chem., regulatory science, and drug metabolism and pharmacokinetics have been meeting under the auspices of IQ to define and address these questions. This presentation will frame chem., manufacturing, and controls challenges and progress against these goals by the team.