Drug Interaction Report

MONITOR: Coadministration with other hepatotoxic agents may increase the risk of liver injury and decrease the therapeutic efficacy of fidanacogene elaparvovec and etranacogene dezaparvovec, liver-directed adeno-associated virus (AAV) vectors designed to help replace missing coagulation factor IX. Increased transaminase levels, particularly those observed in the first 3 to 4 months after administration of these agents, have been attributed to immune-mediated injury of transduced hepatocytes, which may decrease its therapeutic efficacy. In a prospective, open-label, single-arm, multinational clinical study of adult male patients with moderately severe to severe hemophilia B (n=45) receiving a single dose of fidanacogene elaparvovec (5 x 10[11] vector genomes [vg]/kg), 29 patients experienced increased transaminase levels greater than or equal to 1.5 times baseline. Of these patients, 28 received treatment with corticosteroids due to increased transaminases and/or a decline in factor IX activity, with a mean initiation time to corticosteroid therapy reported at 45 days. However, no serious adverse reactions were reported. Likewise, clinical studies with etranacogene dezaparvovec have also reported asymptomatic and mostly mild elevations in transaminases. The majority of elevated ALT levels returned to baseline; however, there were cases where they remained between 48 IU/L to 193 IU/L at two years post-administration of etranacogene dezaparvovec.

MANAGEMENT: As part of monitoring post-administration of fidanacogene elaparvovec, the manufacturer generally recommends monitoring of ALT and factor IX activity levels (e.g., one to two times a week for at least 4 months). The manufacturer of etranacogene dezaparvovec advises weekly transaminase level monitoring at weekly intervals for 3 months after its administration and, in patients with elevated levels, until those enzymes return to baseline. Initiation of corticosteroid therapy and monitoring of Factor IX activity should be considered in cases where ALT levels rise above the upper limit of normal or double baseline levels. The risk of additive hepatotoxicity and decreased therapeutic efficacy of fidanacogene elaparvovec should be considered after coadministration with other hepatotoxic agents. Alternative treatment may be required if an interaction is suspected. The manufacturer of etranacogene dezaparvovec does not provide specific recommendations concerning coadministration with other hepatotoxic agents. Local protocols and/or the product labeling of the concomitant drug(s) should be consulted for additional guidance.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of carbamazepine. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

In a small, randomized, crossover study, the administration of carbamazepine with grapefruit juice (compared to water) increased plasma drug concentrations by approximately 40%. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

MANAGEMENT: Patients receiving carbamazepine should be advised to avoid or limit consumption of alcohol. Given the drug's narrow therapeutic index, patients receiving carbamazepine therapy should preferably avoid the regular consumption of grapefruits and grapefruit juice to prevent any undue fluctuations in plasma drug levels. Patients should be advised to report signs of carbamazepine toxicity (nausea, visual disturbances, dizziness, or ataxia) to their physicians.

GENERALLY AVOID: Coadministration with other hepatotoxic agents such as alcohol may increase the risk of liver injury and decrease the therapeutic efficacy of liver-directed adeno-associated virus (AAV) vector fidanacogene elaparvovec, designed to help replace missing and coagulation factor IX. Increased transaminase levels from AAV therapy have been attributed to immune-mediated injury of transduced hepatocytes, which may decrease their therapeutic efficacy. In addition, alcohol may impact liver enzyme elevation as well as reduce the activity of coagulation factor IX. In a prospective, open-label, single-arm, multinational clinical study of adult male patients with moderately severe to severe hemophilia B (n=45) receiving a single dose of fidanacogene elaparvovec (5 x 10[11] vector genomes [vg]/kg), increased transaminase levels greater than or equal to 1.5 times baseline were reported in 29 patients. Of these patients, 28 received treatment with corticosteroids due to increased transaminases and/or a decline in factor IX activity, with a mean initiation time to corticosteroid therapy reported at 45 days.

MANAGEMENT: According to the manufacturer, for the first year after administration of fidanacogene elaparvovec, alcohol consumption should be limited.