Drug Interactions between dexamethasone / moxifloxacin and enfortumab vedotin

MONITOR CLOSELY: Concomitant administration of corticosteroids may potentiate the risk of tendinitis and tendon rupture associated with fluoroquinolone treatment. The mechanism is unknown. Tendinitis and tendon rupture have most frequently involved the Achilles tendon, although cases involving the rotator cuff (the shoulder), the hand, the biceps, and the thumb have also been reported. Some have required surgical repair or resulted in prolonged disability. Tendon rupture can occur during or up to several months after completion of fluoroquinolone therapy.

MANAGEMENT: Caution is recommended if fluoroquinolones are prescribed in combination with corticosteroids, particularly in patients with other concomitant risk factors (e.g., age over 60 years; recipient of kidney, heart, and/or lung transplant). Patients should be advised to stop taking the fluoroquinolone, avoid exercise and use of the affected area, and promptly contact their physician if they experience pain, swelling, or inflammation of a tendon. In general, fluoroquinolones should only be used to treat conditions that are proven or strongly suspected to be caused by bacteria and only if the benefits outweigh the risks.

Coadministration with inducers of CYP450 3A4 or dual P-glycoprotein (P-gp) and CYP450 3A4 inducers may decrease the plasma concentrations and effects of unconjugated monomethyl auristatin E (MMAE), the cytotoxic component of enfortumab vedotin. Enfortumab vedotin is an antibody-drug conjugate (ADC) that releases MMAE, via proteolytic cleavage. MMAE has been shown in vitro to be primarily metabolized by CYP450 3A4 as well as being a substrate of P-gp. According to physiologically-based pharmacokinetic (PBPK) modeling, concomitant use of enfortumab vedotin with rifampin, a dual P-gp and strong CYP450 3A4 inducer, is predicted to decrease unconjugated MMAE peak plasma concentration (Cmax) by 28% and systemic exposure (AUC) by 53%, with no change in ADC exposure. Some authorities suggest that the PBPK model may underestimate the full impact of rifampin on the Cmax of MMAE. The clinical significance of the interaction is unclear, since the intact ADC is required to bind to Nectin-4, an adhesion protein found on the surface of cells, which allows for internalization and cleavage by lysosomal proteases to enable intracellular delivery of MMAE. It is not known if, and to what extent, enfortumab vedotin may interact with less potent CYP450 3A4 inducers.