Drug Interaction Report

ADDITIONAL CONTRACEPTION RECOMMENDED: Concomitant use with lorlatinib may decrease the plasma concentrations and efficacy of contraceptive hormones. In vitro studies show that lorlatinib is an inducer of CYP450 3A, the isoenzyme primarily responsible for the metabolic clearance of sex hormones. The use of hormonal contraceptives during treatment with lorlatinib can result in contraception failure. Lorlatinib can also cause embryo-fetal harm when administered to a pregnant woman.

MANAGEMENT: Hormonal contraceptives, including oral, injectable, transdermal, and implantable forms, may not be reliable during concomitant therapy with lorlatinib. Since the use of lorlatinib is likely associated with embryo-fetal harm, it is particularly important that patients not become pregnant during treatment. Therefore, hormonal contraceptives should not be used as the sole method of birth control in women of childbearing potential treated with lorlatinib. Women of childbearing potential should use a highly effective, non-hormonal method of contraception during treatment with lorlatinib and for 6 months after the last dose. Male patients with female partners of reproductive potential should use effective contraception during treatment with lorlatinib and for 3 months after the last dose.

MONITOR: Coadministration with lorlatinib may decrease the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme. The proposed mechanism is increased clearance due to lorlatinib-mediated induction of CYP450 3A4 metabolism. The interaction has been studied with midazolam, a sensitive substrate of CYP450 3A4. When a single 2 mg oral dose of midazolam was administered with lorlatinib (150 mg orally once daily for 15 days), midazolam peak plasma concentration (Cmax) decreased by 50% and systemic exposure (AUC) decreased by 64%.

MANAGEMENT: Caution is advised when lorlatinib is used concomitantly with drugs that are substrates of CYP450 3A4. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever lorlatinib is added to or withdrawn from therapy. Avoid concomitant use with lorlatinib where minimal decreases in concentration of the CYP450 3A4 substrate may lead to serious therapeutic failure. If coadministration is required, the CYP450 3A4 substrate dosage should be increased in accordance with approved product labeling.

GENERALLY AVOID: Grapefruit and grapefruit juice may significantly increase the plasma concentrations of lorlatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruit. Because grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4, the magnitude of interaction is greatest for those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability). In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Patients treated with lorlatinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. If coadministration is unavoidable, some authorities recommend reducing the initial dosage of lorlatinib from 100 mg orally once daily to 75 mg orally once daily. In patients who have had a dosage reduction to 75 mg orally once daily due to adverse reactions, the lorlatinib dosage should be further reduced to 50 mg orally once daily upon initiation of a potent CYP450 3A4 inhibitor. After 3 plasma half-lives following discontinuation of the potent CYP450 3A4 inhibitor, the lorlatinib dosage may be increased to that used prior to initiation of the inhibitor.

Coadministration with grapefruit juice may increase the bioavailability of oral estrogens. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In a small, randomized, crossover study, the administration of ethinyl estradiol with grapefruit juice (compared to herbal tea) increased peak plasma drug concentration (Cmax) by 37% and area under the concentration-time curve (AUC) by 28%. Based on these findings, grapefruit juice is unlikely to affect the overall safety profile of ethinyl estradiol. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability. Also, the effect on other estrogens has not been studied.