A006: Microfluidic Blood-Milk Barrier & Physiologically-based Pharmacokinetic Model to Predict Lofexidine Secretion into Breast Milk

Statement of Purpose, Innovation or Hypothesis: Lofexidine (LUCEMYRA®) is the only FDA-approved, non-opioid, non-addictive treatment for relieving multiple symptoms of opioid withdrawal. Despite its established efficacy, there is currently a lack of lactation data for this medication. This study aims to estimate the secretion of Lofexidine into breast milk to ensure the safety of lactating mothers and their infants. We pioneered the innovative approach of using a novel microfluidic device with flow and shear stress, identified normal human mammary epithelial cells to from an integrated mammary barrier, and a physiologically based pharmacokinetic (PBPK) lactation model to predict breast milk secretion of Lofexidine.

Description of Methods & Materials: A novel microfluidic device was developed to build a mammary epithelium-on-a-chip model, and a transwell plate was used to develop a static mammary epithelium using a human noncarcinogenic mammary epithelial cell (MEC) population that can form an integrated barrier with tight junctions. Both models were used to evaluate the transfer of lofexidine through the in vitro mammary cell barrier. The fraction of unbound lofexidine in the breast milk was determined by a Rapid Equilibrium Dialysis (RED) assay. Eleven approaches, including a novel, previously published in vitro in vitro extrapolation (IVIVE) approach and various other approaches, were used to estimate milk-to-plasma (M/P) ratios of lofexidine. A whole-body lactation PBPK model was built using Simcyp® simulator v22 and used to predict the concentration-time profiles of lofexidine in both human plasma and breast milk.

Data & Results: A subpopulation of human normal mammary epithelial MCF10A cells (named MCF10A-TJ) was found to form an integrated barrier that reaches trans-epithelial electrical resistance (TEER) values of over 1000 Ω·cm² by culturing with in-house designed maintenance and boosting medium. The microfluidic device-based mammary epithelium-on-a-chip model generated slightly higher lofexidine permeability values than the static transwell mammary epithelial cell model. Out of the 11 approaches, ten predicted the M/P ratio of 0.40 to 5.48. The whole-body lactation PBPK model was validated with single and multiple doses of lofexidine clinical data in the plasma. The PBPK model predicted the concentration-time profile of lofexidine in the breast milk as well.

Interpretation, Conclusion or Significance: A novel microfluidic device was developed to estimate the permeability of lofexidine using a screened subpopulation of human normal mammary epithelial MCF10A cells that can form tight junctions. Eleven approaches were used to predict the M/P ratios of lofexidine with the majority predicted a range of 0.40 to 5.48. A whole-body lactation PBPK model was also established to simulate the concentration-time profiles of lofexidine in breast milk. The predicted results need to be validated when the clinical pharmacokinetic lactation data of lofexidine is available. This systemic and comprehensive approach provides a promising IVIVE linked PBPK modeling strategy.

Disclosures: We thank the funding support from the Food and Drug Administration (FDA) Office of Women’s Health (OWH) and valuable input from Dr. Susan Bersoff-Matcha and Dr. Joyce Obidi at OWH for this work. This work was also partially supported by the Binghamton University Interdisciplinary Collaboration Grants (ICG) Program. We also thank Simcyp Limited., a Certara Company, for providing academic licenses for the Simcyp Population-based Simulator. All authors declare no conflicts of interest relevant to the content of this article.