Erdafitinib

Moderate CYP2C9 or strong CYP3A4 inhibitors: Consider alternative agents or monitor closely for adverse reactions. ( 7.1 ) Strong CYP3A4 inducers: Avoid concomitant use with BALVERSA. ( 7.1 ) Moderate CYP3A4 inducers: Administer BALVERSA at a dose of 9 mg. ( 7.1 ) Serum phosphate level-altering agents: Avoid concomitant use with agents that can alter serum phosphate levels before the initial dose modification period. ( 2.3 , 7.1 ) P-gp substrates: Separate BALVERSA administration by at least 6 hours before or after administration of P-gp substrates with narrow therapeutic indices. ( 7.2 )

7.1 Effect of Other Drugs on BALVERSA Table 7 summarizes drug interactions that affect the exposure of BALVERSA or serum phosphate level and their clinical management. Table 7: Drug Interactions that Affect BALVERSA Moderate CYP2C9 or Strong CYP3A4 Inhibitors Clinical Impact Co-administration of BALVERSA with moderate CYP2C9 or strong CYP3A4 inhibitors increased erdafitinib plasma concentrations [see Clinical Pharmacology (12.3) ]. Increased erdafitinib plasma concentrations may lead to increased drug-related toxicity [see Warnings and Precautions (5) ].

Clinical Management Consider alternative therapies that are not moderate CYP2C9 or strong CYP3A4 inhibitors during treatment with BALVERSA. If co-administration of a moderate CYP2C9 or strong CYP3A4 inhibitor is unavoidable, monitor closely for adverse reactions and consider dose modifications accordingly [see Dosage and Administration (2.3) ]. If the moderate CYP2C9 or strong CYP3A4 inhibitor is discontinued, resume the BALVERSA dose before dose modifications in the absence of drug-related toxicity. Strong CYP3A4 Inducers Clinical Impact Co-administration of BALVERSA with strong CYP3A4 inducers decreased erdafitinib plasma concentrations [see Clinical Pharmacology (12.3) ].

Decreased erdafitinib plasma concentrations may lead to decreased activity. Clinical Management Avoid co-administration of strong CYP3A4 inducers with BALVERSA. Moderate CYP3A4 Inducers Clinical Impact Co-administration of BALVERSA with moderate CYP3A4 inducers may decrease erdafitinib plasma concentrations [see Clinical Pharmacology (12.3) ]. Decreased erdafitinib plasma concentrations may lead to decreased activity. Clinical Management If a moderate CYP3A4 inducer must be co-administered at the start of BALVERSA treatment, administer BALVERSA at a dose of 9 mg daily.

When a moderate CYP3A4 inducer is discontinued, continue BALVERSA at the same dose, in the absence of drug-related toxicity. Serum Phosphate Level-Altering Agents Clinical Impact Co-administration of BALVERSA with other serum phosphate level-altering agents may increase or decrease serum phosphate levels [see Pharmacodynamics (12.2) ]. Changes in serum phosphate levels due to serum phosphate level-altering agents (other than erdafitinib) may interfere with serum phosphate levels needed for the determination of initial dose increased based on serum phosphate levels [see Dosage and Administration (2.3) ].

Clinical Management Avoid co-administration of serum phosphate level-altering agents with BALVERSA before initial dose increase period based on serum phosphate levels (Days 14 to 21) [see Dosage and Administration (2.3) ].

7.2 Effect of BALVERSA on Other Drugs Table 8 summarizes the effect of BALVERSA on other drugs and their clinical management. Table 8: BALVERSA Drug Interactions that Affect Other Drugs P-glycoprotein (P-gp) Substrates Clinical Impact Co-administration of BALVERSA with P-gp substrates may increase the plasma concentrations of P-gp substrates [see Clinical Pharmacology (12.3) ]. Increased plasma concentrations of P-gp substrates may lead to increased toxicity of the P-gp substrates.

Clinical Management If co-administration of BALVERSA with P-gp substrates is unavoidable, separate BALVERSA administration by at least 6 hours before or after administration of P-gp substrates with narrow therapeutic index.

8.1 Pregnancy Risk Summary Based on the mechanism of action and findings in animal reproduction studies, BALVERSA can cause fetal harm when administered to a pregnant woman [see Clinical Pharmacology (12.1) ] . There are no available data on BALVERSA use in pregnant women to inform a drug-associated risk. Oral administration of erdafitinib to pregnant rats during organogenesis caused malformations and embryo-fetal death at maternal exposures that were less than the human exposures at the maximum recommended human dose based on AUC (see Data ) . Advise pregnant women and females of reproductive potential of the potential risk to the fetus.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. 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 In an embryo-fetal toxicity study, erdafitinib was orally administered to pregnant rats during the period of organogenesis.

Doses ≥4 mg/kg/day (at total maternal exposures <0.1% of total human exposures at the maximum recommended human dose based on AUC) produced embryo-fetal death, major blood vessel malformations and other vascular anomalies, limb malformations (ectrodactyly, absent or misshapen long bones), an increased incidence of skeletal anomalies in multiple bones (vertebrae, sternebrae, ribs), and decreased fetal weight.