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In Silico Modeling to Identify Alternatives to Charcoal Block Pharmacokinetics Bioequivalence Studies

Walenga RL, Tsakalozou E, Chopski S, Hopefl R, Gong Y, Babiskin A, Fang L.

Respiratory Drug Delivery 2026. Volume 1, 2026: 11-0.

Abstract:

Many of the product-specific guidances (PSGs) published by the US Food and Drug Administration (FDA) for orally inhaled drug products (OIDPs) include a recommendation to conduct a charcoal block pharmacokinetics (PK) bioequivalence (BE) study comparing the test product and the reference listed drug (RLD). This article summarizes two case studies that describe the use of physiologically based pharmacokinetics (PBPK) modeling to assist regulatory decision making in this area. For the first case study, PBPK modeling was used to support the decision to not include a charcoal block PK BE study for beclomethasone dipropionate (BDP) inhalation metered aerosol. For the second case study, PBPK modeling was used to identify a potential alternative BE approach without a charcoal block PK BE study for tiotropium bromide inhalation powder. FDA will continue to evaluate PSG recommendations for OIDPs when a charcoal block PK BE study is included, using PBPK modeling when appropriate.