(T1230-03-21) Application of Lecithin (PL90) and Poloxamer 188 in SLC Transporter-Mediated Drug Interaction Studies

Purpose: Solute Carrier (SLC) transporter-mediated drug interaction studies are essential in drug development. However, poor solubility and/or non-specific binding issues of highly lipophilic compounds pose significant challenges in in vitro research. Pharmaceutical excipients such as lecithin (PL90) and poloxamer 188 can improve solubility and/or reduce non-specific binding of highly lipophilic compounds. This study aimed to evaluate the effects of PL90 and poloxamer 188 on SLC transporter activities and to establish a good method for assessing transporter-mediated drug interaction studies of highly lipophilic compounds.

Methods: Human embryonic kidney 293 (HEK293) cells stably expressing OATP1B1, OATP1B3, OAT1, OAT3, OCT2, MATE1, MATE2-K, and mock cells were purchased from GenoMembrane (Kanagawa, Japan) and used in this study. Estradiol 17-(β-D-glucuronide) (for OATP1B1 and OATP1B3), p-aminohippuric acid (for OAT1), estrone 3-sulfate (for OAT3) and metformin (for OCT2, MATE1 and MATE2-K) were used as the probe substrates, and rifampicin (for OATP1B1 and OATP1B3), probenecid (for OAT1 and OAT3), cimetidine (for OCT2), pyrimethamine (for MATE1 and MATE2-K) were used as the reference inhibitors. HEK293 mock cells were incubated in the absence and presence of 0.5 and 1 mM PL90 and 1.0% and 2.0% (w/v) poloxamer 188 in the cytotoxicity assay. These 7 transfected HEK293 and mock cells were incubated in the absence and presence of 0.5 and 1 mM PL90 and 1.0% and 2.0% poloxamer 188 in the transporter activity assay, and the transfected HEK293 cells were incubated in the absence and presence of 0.5 mM PL90 and 1.0% poloxamer 188 in the inhibition assay. The transporter activities that mediate uptake of each probe substrate and the IC₅₀ values of each reference inhibitor, were compared with and without the excipients.

Results: The %Released LDH (percentage of the released LDH in the transport buffer) values of HEK293 mock cells treated with 0.5 and 1 mM PL90 and 1.0% and 2.0% (v/v) poloxamer 188 were 2.7, 3.4, 2.2, and 2.4, respectively, suggesting no or limited cytotoxicity. In the absence and presence of 0.5 mM PL90 or 1% poloxamer 188, the relative transport activities (ratio of the transporter activity in the absence the excipient to that in the presence of the excipient) of all 7 transporters were greater than 70%, and the IC₅₀ values of the reference inhibitors for all 7 transporters did not change significantly (p > 0.05), indicating that 0.5 mM PL90 and 1% poloxamer 188 had no or limited impact on the activities of all these 7 SLC transporters.

Conclusion: PL90 at 0.5 mM and poloxamer 188 at 1% (w/v) can be applied in all these 7 SLC transporter-mediated drug interaction studies to improve solubility and reduce non-specific binding for highly lipophilic compounds.