Comparison of the permeability of RdRp inhibitors, remdesivir, molnupiravir and azvudine, in placental barrier cell models and exploration of their transport mechanisms.

OBJECTIVES

Pregnant women are at increased risk of severe coronavirus disease 2019 with potential adverse consequences for maternal and fetal health. Although remdesivir (RDV), molnupiravir and azvudine are RNA-dependent RNA polymerase (RdRp) inhibitors of SARS-CoV-2, their placental transport characteristics are unclear. This study aimed to compare the placental permeability and transport mechanisms of these antiviral drugs using placental cell models.

METHODS

A cost-effective LC-MS/MS method quantified these drugs and their metabolites. Drug accumulation in placental cell models was compared, and drug permeability was assessed using BeWo Transwell transport assay. Transporter inhibitors, siRNA knockdown and transporter-overexpression cell models were used to investigate the transmembrane transport mechanisms.

RESULTS

RDV, GS-441524 and EIDD-1931 accumulated more in BeWo cells at 37°C than at 4°C, indicating carrier-mediated uptake. RDV and GS-441524 exhibited lower permeability, whereas EIDD-1931 and azvudine exhibited higher permeability in BeWo cells. RDV was a potential substrate of equilibrative nucleoside transporter (ENT) 1/2 and concentrative nucleoside transporter (CNT) 3; GS-441524 of ENT1/2, CNT2/3 and organic anion transporter (OAT) 4; and EIDD-1931 of ENT1/2 and OAT4. Breast cancer resistance protein (BCRP) was implicated in efflux of all four compounds in BeWo cells, whereas P-glycoprotein (P-gp) was involved in efflux of RDV and GS-441524.

CONCLUSIONS

RDV and GS-441524 displayed low placental permeability in BeWo cells, whereas EIDD-1931 and azvudine displayed high permeability. Multiple ENTs, CNTs, OAT4, P-gp and BCRP might be involved in placental transport of RDV, GS-441524, EIDD-1931 and azvudine. These findings offer new insights into the placental transport of RdRp inhibitors during pregnancy.