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Licensed Unlicensed Requires Authentication Published by De Gruyter May 30, 2019

Drug-drug interaction (DDI) assessments of ruxolitinib, a dual substrate of CYP3A4 and CYP2C9, using a verified physiologically based pharmacokinetic (PBPK) model to support regulatory submissions

  • Kenichi Umehara EMAIL logo , Felix Huth , Yi Jin , Hilmar Schiller , Vassilios Aslanis , Tycho Heimbach and Handan He


Ruxolitinib is mainly metabolized by cytochrome P450 (CYP) enzymes CYP3A4 and CYP2C9 followed by minor contributions of other hepatic CYP enzymes in vitro. A physiologically based pharmacokinetic (PBPK) model was established to evaluate the changes in the ruxolitinib systemic exposures with co-administration of CYP3A4 and CYP2C9 perpetrators. The fractions metabolized in the liver via oxidation by CYP enzymes (fm,CYP3A4 = 0.75, fm,CYP2C9 = 0.19, and fm,CYPothers = 0.06) for an initial ruxolitinib model based on in vitro data were optimized (0.43, 0.56, and 0.01, respectively) using the observed exposure changes of ruxolitinib (10 mg) with co-administered ketoconazole (200 mg). The reduced amount of fm,CYP3A4 was distributed to fm,CYP2C9. For the initial ruxolitinib model with co-administration of ketoconazole, the area under the curve (AUC) increase of 2.60-fold was over-estimated compared with the respective observation (1.91-fold). With the optimized fm values, the predicted AUC ratio was 1.82. The estimated AUC ratios of ruxolitinib by co-administration of the moderate CYP3A4 inhibitor erythromycin (500 mg) and the strong CYP3A4 inducer rifampicin (600 mg) were within a 20% error compared with the clinically observed values. The PBPK modeling results may provide information on the labeling, i.e. supporting a dose reduction by half for co-administration of strong CYP3A4 inhibitors. Furthermore, an AUC increase of ruxolitinib in the absence or presence of the dual CYP3A4 and CYP2C9 inhibitor fluconazole (100–400 mg) was prospectively estimated to be 1.94- to 4.31-fold. Fluconazole simulation results were used as a basis for ruxolitinib dose adjustment when co-administering perpetrator drugs. A ruxolitinib PBPK model with optimized fm,CYP3A4 and fm,CYP2C9 was established to evaluate victim DDI risks. The previous minimal PBPK model was supported by the FDA for the dose reduction strategy, halving the dose with the concomitant use of strong CYP3A4 inhibitors and dual inhibitors on CYP2C9 and CYP3A4, such as fluconazole at ≤200 mg. Fluconazole simulation results were used as supportive evidence in discussions with the FDA and EMA about ruxolitinib dose adjustment when co-administering perpetrator drugs. Thus, this study demonstrated that PBPK modeling can support characterizing DDI liabilities to inform the drug label and might help reduce the number of clinical DDI studies by simulations of untested scenarios, when a robust PBPK model is established.


The authors wish to acknowledge Kim Crewe and Karen Rowland Yeo at Simcyp Limited (A Certara Company, Blades Enterprise Centre, John Street, S2 4SU Sheffield, UK) for their great support for verifying the fluconazole PBPK model as a CYP2C9 inhibitor.

  1. Author contributions: Participated in research designs: Umehara, Huth, Jin, and Schiller. Conducted experiments: Umehara, Huth, Jin, and Schiller. Performed data analysis: Umehara, Huth, Jin, and Schiller. Wrote or contributed to the writing of the manuscript: Umehara, Huth, Jin, Schiller, Aslanis, Heimbach, and He. All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Ethical approval: This PBPK study does not require ethics approval; for the cited clinical studies ethical approval has been granted.

  3. Research funding: None declared.

  4. Employment or leadership: None declared.

  5. Honorarium: None declared.

  6. Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.


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Supplementary Material

The online version of this article offers supplementary material (DOI:

Received: 2018-12-14
Accepted: 2019-03-26
Published Online: 2019-05-30

© 2019 Walter de Gruyter GmbH, Berlin/Boston

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