Drug Interaction Report

MONITOR CLOSELY: The use of tumor necrosis factor (TNF) blockers with other immunosuppressive or myelosuppressive agents may increase the risk of infections. Serious infections and sepsis, including fatalities, have been reported with the use of TNF blockers, particularly in patients on concomitant immunosuppressive therapy. Agents that may be significantly myelo- or immunosuppressive include antineoplastic agents, radiation, zidovudine, linezolid, some antirheumatic agents, high dosages of corticosteroids or adrenocorticotropic agents (greater than 10 mg/day to 1 mg/kg/day, whichever is less, of prednisone or equivalent for more than 2 weeks), and long-term topical or inhaled corticosteroids. Concomitant use of TNF blockers with other immunosuppressants such as azathioprine or mercaptopurine may also increase the risk of a rare and often fatal cancer of white blood cells known as hepatosplenic T-Cell lymphoma (HSTCL), which has primarily been reported in adolescent and young adult males receiving treatment for Crohn's disease or ulcerative colitis. Cases of HSTCL have also occurred during use of these agents alone. Because individuals with rheumatoid arthritis, Crohn's disease, ankylosing spondylitis, psoriatic arthritis, or plaque psoriasis may be more likely to develop lymphoma than the general population, it is difficult to assess the added risk of TNF blockers, azathioprine, and/or mercaptopurine.

MANAGEMENT: Patients receiving a TNF blocker alone or with other immunosuppressive or myelosuppressive agents should be monitored closely for the development of infections. TNF blocker therapy should be discontinued if a serious infection or sepsis occurs. Close monitoring for signs and symptoms of HSTCL (e.g., splenomegaly, hepatomegaly, abdominal pain, persistent fever, night sweats, weight loss) is also recommended during use of TNF blockers, particularly in combination with other immunosuppressants such as azathioprine and mercaptopurine.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of pirtobrutinib, which is primarily metabolized by CYP450 3A4. 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 pirtobrutinib (200 mg single dose) was administered with itraconazole, a potent CYP450 3A4 inhibitor, pirtobrutinib systemic exposure (AUC) increased by 49%. Concomitant use of diltiazem or verapamil, moderate CYP450 3A4 inhibitors, is predicted to increase pirtobrutinib AUC by 20% and 30%, respectively. 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 pirtobrutinib may increase the risk of infection, bruising, bleeding, fatigue, musculoskeletal pain, diarrhea, edema, and dyspnea.

MANAGEMENT: It may be advisable for patients to avoid consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with pirtobrutinib.