Vemurafenib

Avoid concomitant administration of ZELBORAF with strong CYP3A4 inhibitors or inducers. ( 7.1 ) CYP1A2 Substrates: ZELBORAF can increase concentrations of CYP1A2 substrates. Avoid concomitant use of ZELBORAF with CYP1A2 substrates with a narrow therapeutic window. If coadministration cannot be avoided, monitor closely for toxicities and consider dose reduction of CYP1A2 substrates. ( 7.2 ).

7.1 Effect of Strong CYP3A4 Inhibitors or Inducers on Vemurafenib Strong CYP3A4 Inhibitors Coadministration of a strong CYP3A4 inhibitor increased vemurafenib plasma concentrations and may lead to increased toxicity. Avoid coadministration of ZELBORAF with strong CYP3A4 inhibitors. If coadministration of a strong CYP3A4 inhibitor is unavoidable, consider dose reduction of ZELBORAF, if clinically indicated. [see Dosage and Administration (2.3) , Clinical Pharmacology (12.3) ] . Strong CYP3A4 Inducers Coadministration of ZELBORAF with rifampin, a strong CYP3A4 inducer, decreased vemurafenib plasma concentrations and may result in decreased efficacy.

Avoid coadministration of ZELBORAF with strong CYP3A4 inducers (e.g., phenytoin, carbamazepine, rifampin), and replace these drugs with alternative drugs when possible. If coadministration of a strong CYP3A4 inducer is unavoidable, increase the dose of ZELBORAF by 240 mg (one tablet) as tolerated [see Dosage and Administration (2.4) , Clinical Pharmacology (12.3) ] .

7.2 Effect of Vemurafenib on CYP1A2 Substrates Coadministration of ZELBORAF with tizanidine, a sensitive CYP1A2 substrate, increased tizanidine systemic exposure by 4.7-fold. Avoid concomitant use of ZELBORAF with drugs having a narrow therapeutic window that are predominantly metabolized by CYP1A2 [see Clinical Pharmacology (12.3) ] . If coadministration cannot be avoided, monitor closely for toxicities and consider a dose reduction of concomitant CYP1A2 substrates.

7.3 Concurrent Ipilimumab Increases in transaminases and bilirubin occurred in a majority of patients who received concurrent ipilimumab and ZELBORAF [see Warnings and Precautions Section 5.6 ].

7.4 Effect of Vemurafenib on P-gp Substrates Coadministration of ZELBORAF with digoxin, a sensitive P-glycoprotein (P-gp) substrate, increased digoxin systemic exposure by 1.8-fold. Avoid concurrent use of P-gp substrates known to have narrow therapeutic indices. If use of these medications is unavoidable, consider dose reduction of P-gp substrates with narrow therapeutic indices.

8.1 Pregnancy Risk Summary Based on its mechanism of action, ZELBORAF can cause fetal harm when administered to a pregnant woman [see Clinical Pharmacology (12.1) ] . There are no available data on the use of ZELBORAF in pregnant women to determine the drug-associated risk; however, placental transfer of vemurafenib to a fetus has been reported. Exposure to vemurafenib could not be achieved in animals at levels sufficient to fully address its potential toxicity in pregnant women. Advise pregnant women of the potential harm to a fetus. The estimated background risks of major birth defects and miscarriage for the indicated population(s) are unknown. In the U.S.

general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively. Data Animal Data Vemurafenib showed no evidence of developmental toxicity in rat fetuses at doses up to 250 mg/kg/day (approximately 1.3 times the clinical exposure at 960 mg twice daily based on AUC) or rabbit fetuses at doses up to 450 mg/kg/day (approximately 0.6 times the clinical exposure at 960 mg twice daily based on AUC). Fetal drug levels were 3–5% of maternal levels, indicating that vemurafenib has the potential to be transmitted from the mother to the developing fetus.