Drug Interactions between ruxolitinib topical and selpercatinib

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of selpercatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but has been reported for other CYP450 3A4 inhibitors. When a single dose of selpercatinib (160 mg) was coadministered with multiple doses of itraconazole (200 mg once daily), a potent CYP450 3A4 inhibitor, selpercatinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 30% and 133%, respectively. Based on pharmacokinetic modeling, administration of multiple doses of selpercatinib (160 mg twice daily) with multiple doses of the moderate CYP450 3A4 inhibitors diltiazem (60 mg three times daily), fluconazole (200 mg once daily), or verapamil (80 mg three times daily) is predicted to increase selpercatinib Cmax by 46% to 76% and AUC by 60% to 99%. 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. Increased exposure to selpercatinib may increase the risk of serious adverse effects such as QT interval prolongation, liver transaminase and bilirubin elevations, hypertension, hemorrhage, edema, and hypersensitivity reactions (e.g., fever, rash, arthralgias/myalgias with concurrent decreased platelets or transaminitis).

MANAGEMENT: Until further information is available, it may be advisable for patients to limit or avoid consumption of grapefruit and grapefruit juice during treatment with selpercatinib.

MONITOR CLOSELY: Smoking during treatment with topical ruxolitinib may increase the risk of major adverse cardiovascular events (MACE) and the risk of developing malignancies, including lymphomas. During clinical trials, patients who were current or past smokers and received oral Janus Kinase (JAK) inhibitors to treat inflammatory conditions had an additional increased risk of overall malignancies. Additionally, oral JAK inhibitors reportedly increase patients' risk of MACE, including cardiovascular death, myocardial infarction, and stroke, particularly in patients who are current or past smokers or patients with other cardiovascular risk factors.

MANAGEMENT: The potential risks and benefits of topical ruxolitinib should be carefully weighed prior to initiating therapy, particularly in patients with cardiovascular risk factors, as well as those with a history of malignancy, those who develop a malignancy while on treatment, and/or patients who are current or past smokers. Patients should be informed about the symptoms of serious cardiovascular events and the steps to take if they occur. The manufacturer recommends discontinuing topical ruxolitinib in patients who have experienced a myocardial infarction or stroke.