Mobocertinib and Letermovir Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mobocertinib
Letermovir Injection
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased mobocertinib exposure and increased risk of adverse reactions, including QT-interval prolongation
Interaction Deep Dive
Concomitant use of mobocertinib (CYP3A substrate) with a moderate CYP3A inhibitor may result in increased exposure of mobocertinib and should be avoided. Coadministration is predicted to increase the steady-state combined molar AUC of mobocertinib and its active metabolites by approximately 100% to 200%. If concomitant use of a moderate CYP3A inhibitor cannot be avoided, reduce the mobocertinib dose by approximately 50% (ie, from 160 to 80 mg, 120 to 40 mg, or 80 to 40 mg) and monitor the corrected QT interval more frequently. After the moderate CYP3A inhibitor has been discontinued for 3 to 5 elimination half-lives, resume mobocertinib at the dose taken prior to initiating the moderate CYP3A inhibitor1
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of mobocertinib.
Literature reports
1 report — tap to read
a) Coadministration of mobocertinib with multiple doses of a moderate CYP3A inhibitor is predicted to increase the steady-state combined molar AUC of mobocertinib and its active metabolites by approximately 100% to 200% 1.
Common questions
Can I take Mobocertinib and Letermovir Injection together?
Increased mobocertinib exposure and increased risk of adverse reactions, including QT-interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mobocertinib and Letermovir Injection interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Mobocertinib or Letermovir Injection need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: EXKIVITY(TM) oral capsules, mobocertinib oral capsules. Takeda Pharmaceuticals America Inc (per FDA), Lexington, MA, 2021.
Keep reading about Mobocertinib
Keep reading about Letermovir Injection
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