Drug Interactions between bortezomib and tazemetostat

GENERALLY AVOID: Consumption of grapefruit or grapefruit juice during tazemetostat therapy may significantly increase the plasma concentrations of tazemetostat. The proposed mechanism is inhibition of the CYP450 3A4-mediated metabolism of tazemetostat by certain compounds in grapefruit. Because grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4, the magnitude of interaction is greatest for those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability). According to the product labeling, coadministration of tazemetostat (400 mg twice daily) with the moderate CYP450 3A4 inhibitor fluconazole increased the tazemetostat steady state exposure (AUC 0 to 8 hours) by 3.1-fold and peak plasma concentration by 2.3-fold. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict. Clinically, this interaction may result in an increased risk of the frequency or severity of adverse reactions due to tazemetostat such as hemorrhage, pleural effusion, skin infection, dyspnea, pain, and respiratory distress.

MANAGEMENT: The manufacturer advises that patients treated with tazemetostat should avoid consumption of grapefruit or grapefruit juice.

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GENERALLY AVOID: Data from in vitro and animal (mice) studies suggest that green tea may antagonize the cytotoxic effects of bortezomib. Polyphenols in green tea such as (-)-epigallocatechin gallate (EGCG) have been shown to block the proteasome inhibitory action of bortezomib in multiple myeloma and glioblastoma cancer cell lines. The mechanism appears to involve a direct chemical reaction between the boronic acid moiety of bortezomib and the 1,2-benzenediol groups present in certain polyphenols leading to inactivation of bortezomib. However, one group of investigators reported that no antagonism of bortezomib was observed in preclinical in vivo experiments where EGCG plasma concentrations are commensurate with dietary or supplemental intake.

MANAGEMENT: Until more data are available, it may be advisable to avoid or limit consumption of green tea and green tea products during treatment with bortezomib. The interaction has not been demonstrated for other, non-boronic acid proteasome inhibitors.

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