Scientific and regulatory activities initiated by the U.S. Food and drug administration to foster approvals of generic dry powder inhalers: Bioequivalence perspective.

Regulatory science for generic dry powder inhalers (DPIs) in the United States (U.S.) has evolved over the last decade. In 2013, the U.S. Food and Drug Administration (FDA) published the draft product-specific guidance (PSG) for fluticasone propionate and salmeterol xinafoate inhalation powder. This was the first PSG for a DPI available in the U.S., which provided details on a weight-of-evidence approach for establishing bioequivalence (BE). A variety of research activities including in vivo and in vitro studies were used to support these recommendations, which have led to the first approval of a generic DPI in the U.S. for fluticasone propionate and salmeterol xinafoate inhalation powder in January of 2019. This review describes the scientific and regulatory activities that have been initiated by FDA to support the current BE recommendations for DPIs that led to the first generic DPI approvals, as well as research with novel in vitro and in silico methods that may potentially facilitate generic DPI development and approval.