Tazemetostat and Abemaciclib: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 10, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Tazemetostat
Abemaciclib
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.
You've been prescribed tazemetostat (Tazverik) and abemaciclib (Verzenio) together. Here's the plain-language version: tazemetostat can speed up how your body breaks down abemaciclib. Abemaciclib is a cancer medicine that relies on an enzyme called CYP3A to be cleared, and when tazemetostat revs that enzyme up, less abemaciclib may stay in your body.
The concern here isn't extra side effects, it's that abemaciclib may not work as well as it should. The good news is your cancer care team can plan for this. They may adjust your dose or watch you more closely. Keep taking both exactly as prescribed and bring this up at your next visit.
Effect: Tazemetostat is a CYP3A inducer; abemaciclib is a CYP3A substrate. Coadministration is expected to increase abemaciclib clearance, lowering its exposure (AUC/Cmax) and potentially reducing antitumor efficacy.
Evidence: Probable. In a dedicated study, tazemetostat 800 mg BID reduced oral midazolam (sensitive CYP3A substrate) AUC by 40% and Cmax by 21%.
Onset: Unspecified. Severity: Major.
- Avoid the combination where a therapeutic alternative exists.
- If used together, the abemaciclib dose may need to be individualized and the patient monitored more closely for reduced clinical response.
What happens
Reduced CYP3A substrate exposure and reduced efficacy of CYP3A substrate
Interaction Deep Dive
When tazemetostat is taken together with CYP3A substrates, the exposure to those substrates may decline, which can diminish their efficacy. A drug interaction study in patients showed that giving tazemetostat 800 mg twice daily alongside oral midazolam (a sensitive CYP3A substrate) lowered the AUC of midazolam by 40% and its Cmax by 21%1.
Why it happens (mechanism)
Induction of CYP3A-substrate metabolism by tazemetostat
How to manage this interaction
Both drugs can be used together safely with planning. Your oncology team knows tazemetostat can lower abemaciclib levels, so they manage this proactively.
- Keep taking both exactly as prescribed unless your team tells you otherwise.
- Your abemaciclib dose may be adjusted and individualized by your care team, or they may choose an alternative.
- Expect closer monitoring of how well your treatment is working.
- Tell your pharmacist or oncologist about any new or stopped medicines, since many drugs affect this same pathway.
Raise any questions about your treatment response at your appointments.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a study evaluating drug interactions, giving tazemetostat 800 mg twice daily together with oral midazolam (a sensitive CYP3A substrate) in patients reduced the AUC of midazolam by 40% and its Cmax by 21% 1.
Common questions
Can I take Tazemetostat and Abemaciclib together?
Tazemetostat may lower abemaciclib levels and make it less effective, so your care team may adjust the dose or monitor your response more closely. Keep taking both as prescribed and discuss with your oncologist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Tazemetostat and Abemaciclib 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 is the Tazemetostat and Abemaciclib interaction managed?
Both drugs can be used together safely with planning. Your oncology team knows tazemetostat can lower abemaciclib levels, so they manage this proactively. Keep taking both exactly as prescribed unless your team tells you otherwise. Your abemaciclib dose may be adjusted and individualized by your care team, or they may choose an alternative. Expect closer monitoring of how well your treatment is wo… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Tazemetostat or Abemaciclib 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: TAZVERIK(R) oral tablets, tazemetostat oral tablets. Epizyme Inc (per FDA), Cambridge, MA, 2024. DailyMed
Keep reading about Tazemetostat
Keep reading about Abemaciclib
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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