Application of the Stable Isotope Label Approach in Clinical Development-Supporting Dissolution Specifications for a Commercial Tablet Product with Tafenoquine, a Long Half-life Compound

04 Jun 2018

Navin Goyal, Khadeeja Mohamed, Katie Rolfe, Satty Sahota, Terry Ernest, Stephan Duparc, Maxine Taylor, Linda Casillas, Gavin C. K. W. Koh

The American Association of Pharmaceutical Scientists Journal

DOI: 10.1208/s12248-018-0234-5 

Photo: Michael Nivelet/


Bioavailability/bioequivalence studies supporting clinical drug development or commercial supply of drug formulations are often time, cost, and resource intensive. The drug's pharmacokinetic (PK) variability, systemic half-life, and safety issues may pose additional challenges. The stable isotope label (SIL) approach provides a useful tool to significantly reduce the study size in clinical PK studies. Tafenoquine (TQ) is an 8-aminoquinoline under development for preventing Plasmodium vivax malaria relapse. This SIL study assessed the impact of differences in the in vitro dissolution profiles on in vivo exposure of TQ tablets.

Fourteen healthy volunteers received a single dose of 300 mg TQ Intermediate Aged or 300 mg TQ Control formulations in this single-center, two-arm, randomized, open-label, parallel-group study. Endpoints included the geometric means ratio of the area under the concentration-time curve (AUC(0-t) and AUC(0-∞); primary endpoint) and maximum plasma concentration (Cmax) for Intermediate Aged versus Control TQ; correlation of PK parameters for venous versus peripheral (via microsample) blood samples; and safety and tolerability endpoints. Geometric mean ratios for PK parameters (AUC and Cmax) and their 90% confidence intervals fell well within standard bioequivalence limits (0.80-1.25). Only one mild adverse event (skin abrasion) was reported.

In summary, this SIL methodology-based study demonstrates that the observed differences in the in vitro dissolution profiles between the Control and Intermediate Aged TQ tablets have no clinically relevant effect on systemic TQ exposure. The SIL approach was successfully implemented to enable the setting of a clinically relevant dissolution specification.This study (GSK study number 201780) is registered at with identifier NCT02751294.

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