The purpose of this webinar is to define the requirements for regulatory development of excipients used in respiratory formulations. As a part of the regulatory development pathway, pharmacology, toxicology, and clinical studies are conducted. These studies require specialized approaches to determination of maximum feasible dose, determination of drug absorption/pharmacokinetics, and design of the toxicology programs. This webinar will describe the approach for the technical and regulatory approval, utilizing two case studies that involve excipients of broad importance to respiratory therapy and represent pressurized meter dose inhalers [1,1-Difluoroethane (HFA-152a)] and dry powder excipients [phosphatidylcholine (PC), 1,2-distearoyl-sn-glycero-3-phosphocholin, DSPC)]. The regulatory discussion will consider both US and international requirements. The webinar will include an overall approach and technical details that include system characterization (in vitro, rodent, canine, human), analytical and bioanalytical assessment, pharmacokinetics, and toxicology including dose range finding, safety pharmacology, carcinogenicity, IND, and NDA studies.