ABCG2 and cholestasis: Of note, baricitinib does not possess physiochemical and pharmacokinetic features known to be implicated in liver injury; the drug is not highly lipophilic, only marginally metabolized by CYP3A4, and it did not inhibit OATP1B1, glycoprotein P (P-gp), and breast cancer resistance protein (BCRP), nor bile salt export pump (BSEP), a key transporter involved in cholestasis.