Physiologically Based Pharmacokinetic Modeling of Palbociclib

Area of Science:

• Pharmacology
• Drug Metabolism and Pharmacokinetics
• Computational Modeling

Background:

• Palbociclib is an oral CDK4/6 inhibitor used in cancer therapy.
• Its metabolism involves CYP3A and SULT2A1, and it weakly inhibits CYP3A.
• Understanding drug-drug interactions (DDIs) is crucial for safe palbociclib use.

Purpose of the Study:

• Develop a physiologically based pharmacokinetic (PBPK) model for palbociclib.
• Validate the PBPK model using clinical DDI data with CYP3A modulators.
• Predict the DDI risk of palbociclib with various CYP3A inhibitors and inducers.

Main Methods:

• Constructed a PBPK model integrating in silico, in vitro, and in vivo data.
• Verified the model against clinical studies involving itraconazole, rifampin, and midazolam.
• Utilized the validated model to predict interactions with other CYP3A substrates/inhibitors/inducers.

Main Results:

• The PBPK model accurately described palbociclib pharmacokinetics after oral and IV administration.
• Model predictions for DDIs with itraconazole, rifampin, and midazolam generally aligned with observed data (within 20% discrepancy).
• Predicted negligible DDI risk with weak CYP3A inhibitors (fluoxetine, fluvoxamine).

Conclusions:

• The developed PBPK model is robust for predicting palbociclib pharmacokinetics and DDIs.
• Moderate CYP3A inhibitors (diltiazem, verapamil) may increase palbociclib AUC by ~40%.
• Moderate CYP3A inducers (efavirenz) may decrease palbociclib AUC by ~40%.