Drug Interactions between etrasimod and mumps skin test antigen

GENERALLY AVOID: Coadministration with moderate inhibitors of CYP450 3A4 such as grapefruit juice may increase the plasma concentrations of etrasimod in patients that are poor CYP450 2C9 metabolizers (e.g., *2/*3, *3/*3). Etrasimod is primarily metabolized by the CYP450 3A4, CYP450 2C8, and CYP450 2C9 isoenzymes. Pharmacokinetic studies reported that no single enzyme appears to dominate etrasimod elimination and that the involvement of multiple CYP450 isoforms reduces the likelihood of drug-drug interactions when only a single CYP450 isoform is strongly or moderately inhibited by a coadministered drug. In clinical drug interaction studies, when etrasimod was administered with the dual moderate CYP450 2C9 and 3A4 inhibitor fluconazole at steady-state levels, etrasimod systemic exposure (AUC) increased by 84%. However, concomitant use with the potent CYP450 3A4 inhibitor itraconazole increased the AUC of etrasimod by 32%, which was not considered by the manufacturer to be clinically significant. The effect on etrasimod systemic exposure in CYP450 2C9 intermediate metabolizers (e.g., *1/*2, *1/*3, *2/*2) treated with less potent CYP450 3A4 inhibitors is not known. Increased plasma concentrations of etrasimod may increase the risk of infection, bradyarrhythmia, AV conduction delays, elevated transaminase levels, and macular edema.

MANAGEMENT: Until further information is available, the consumption of grapefruit and grapefruit juice in combination with moderate to potent CYP450 2C8 inhibitors such as gemfibrozil should be avoided or limited during treatment with etrasimod in patients who are poor CYP450 2C9 metabolizers. Caution is recommended with grapefruit products consumption in patients who are intermediate CYP450 2C9 metabolizers. Patients should be advised to notify their physician if they experience potential adverse effects of etrasimod.

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