Drug Interaction Report

MONITOR CLOSELY: Coadministration with potent inhibitors of CYP450 3A4 may increase exposure to unconjugated monomethyl auristatin E (MMAE), the anti-mitotic and cytotoxic component of polatuzumab vedotin. Polatuzumab vedotin is an antibody-drug conjugate (ADC) that releases MMAE via proteolytic cleavage, and MMAE has been shown in vitro to be primarily metabolized by CYP450 3A4. Concomitant use of polatuzumab vedotin with ketoconazole, a potent CYP450 3A4 inhibitor, is predicted to increase unconjugated MMAE exposure (AUC) by 45% according to the product labeling. The risk and/or severity of toxicities of polatuzumab vedotin may increase.

MANAGEMENT: Caution is advised when polatuzumab vedotin is used concomitantly with potent CYP450 3A4 inhibitors. Patients should be closely monitored for development or exacerbation of toxicities such as peripheral neuropathy, myelosuppression, opportunistic infections, tumor lysis syndrome and hepatotoxicity, and the dosing of polatuzumab vedotin adjusted or withheld as necessary in accordance with the product labeling.

Grapefruit juice may delay the gastrointestinal absorption of clarithromycin but does not appear to affect the overall extent of absorption or inhibit the metabolism of clarithromycin. The mechanism of interaction is unknown but may be related to competition for intestinal CYP450 3A4 and/or absorptive sites. In an open-label, randomized, crossover study consisting of 12 healthy subjects, coadministration with grapefruit juice increased the time to reach peak plasma concentration (Tmax) of both clarithromycin and 14-hydroxyclarithromycin (the active metabolite) by 80% and 104%, respectively, compared to water. Other pharmacokinetic parameters were not significantly altered. This interaction is unlikely to be of clinical significance.