Abemaciclib and Asciminib: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Abemaciclib
Asciminib
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 two cancer medicines, abemaciclib (Verzenio) and asciminib (Scemblix). Here's the simple version: your body uses a liver enzyme called CYP3A4 to break down abemaciclib. Asciminib can slow that enzyme down. When it does, abemaciclib can build up a bit higher than usual, which may make its side effects (like diarrhea, tiredness, nausea, or low blood counts) more likely.
The good news is this is expected and manageable. Right now this concern is theoretical, based on how the drugs work rather than lots of real-world reports. Your care team can watch you more closely and adjust your dose if needed. Please don't stop or change either medicine on your own, just talk with your oncologist or pharmacist.
Interaction: Asciminib is a CYP3A4 inhibitor; abemaciclib is a CYP3A4 substrate. Inhibition of CYP3A4-mediated metabolism is expected to increase abemaciclib exposure and the risk of dose-related adverse effects (diarrhea, neutropenia, fatigue, hepatotoxicity).
- Direction: increased abemaciclib exposure (AUC/Cmax)
- Magnitude: not quantified for this pair; midazolam probe showed AUCinf +24-88%, Cmax +11-58%
- Evidence: theoretical; severity: major; onset: unspecified
Management: With asciminib 200 mg BID, avoid pairing with sensitive CYP3A4 substrates where small changes risk serious toxicity. With asciminib 80 mg/day total, monitor closely for abemaciclib toxicity. Consider abemaciclib dose individualization per response and tolerability.
What happens
Increased CYP3A4 exposure and an increased risk of CYP3A4-related adverse reactions
Interaction Deep Dive
When asciminib, which inhibits CYP3A4, is taken together with a CYP3A4 substrate, the substrate's exposure rises, potentially heightening the likelihood of adverse reactions. In studies pairing asciminib with the CYP3A4 substrate midazolam, midazolam exposure went up, with AUC(inf) rising 24% to 88% and Cmax rising 11% to 58%. For patients on asciminib 200 mg twice daily, avoid combining it with any CYP3A4 substrate for which small shifts in concentration could trigger serious adverse reactions. For patients whose total asciminib dose is 80 mg/day, monitor carefully for adverse reactions if such a CYP3A4 substrate (one where minimal concentration changes may cause serious adverse reactions) is given at the same time1.
Why it happens (mechanism)
Inhibition of CYP3A4-substrate metabolism by asciminib
How to manage this interaction
Both medicines can usually be used together with care. Because asciminib can raise abemaciclib levels, your team's approach depends on your asciminib dose and how sensitive the situation is.
- Keep taking both as prescribed unless your oncologist tells you otherwise.
- Your abemaciclib dose may be adjusted and individualized by your care team, and they may monitor you more closely for side effects.
- Report side effects like diarrhea, marked fatigue, fever or signs of infection, nausea, or yellowing of the skin/eyes promptly.
At higher asciminib doses, your team may prefer to avoid this pairing; at lower doses, closer monitoring is typical. Ask your pharmacist or prescriber what applies to you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) When asciminib 40 mg twice daily was given together with midazolam (a CYP3A4 substrate), the AUC(inf) of midazolam rose by 28% and its Cmax rose by 11%. With asciminib 80 mg once daily, midazolam AUC(inf) and Cmax rose by 24% and 17%, respectively, and with asciminib 200 mg twice daily, midazolam AUC(inf) and Cmax rose by 88% and 58%, respectively 1.
Common questions
Can I take Abemaciclib and Asciminib together?
Asciminib can raise abemaciclib levels and side effect risk by slowing its breakdown, so your team may monitor you more closely or adjust your abemaciclib dose. Keep taking both as prescribed and report new or worsening side effects. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Asciminib 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 Abemaciclib and Asciminib interaction managed?
Both medicines can usually be used together with care. Because asciminib can raise abemaciclib levels, your team's approach depends on your asciminib dose and how sensitive the situation is. Keep taking both as prescribed unless your oncologist tells you otherwise. Your abemaciclib dose may be adjusted and individualized by your care team, and they may monitor you more closely for side effects. Re… Management is individual — always follow your own care team's guidance.
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 Abemaciclib or Asciminib 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: SCEMBLIX® oral tablets, asciminib oral tablets. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2025. DailyMed
Keep reading about Abemaciclib
Keep reading about Asciminib
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