Enzalutamide and Belumosudil: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Enzalutamide
Belumosudil
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.
Here's what's going on. Enzalutamide (Xtandi) speeds up a liver enzyme called CYP3A that your body uses to break down belumosudil (Rezurock). When that enzyme works faster, your belumosudil gets cleared out more quickly, so there is less of it in your blood. That means it may not work as well to control your graft-versus-host disease.
The good news is that this is a well-understood, manageable interaction. Please don't change anything on your own. Your care team can adjust your belumosudil dose and keep an eye on how you're doing so the medicine still does its job while you take both drugs together.
Effect: Enzalutamide, a strong CYP3A inducer, increases metabolism of belumosudil (a CYP3A substrate), lowering belumosudil exposure and potentially reducing efficacy. Neither drug's active moiety depends on activation by the affected enzyme, so induction reduces effect as expected.
- Magnitude: With rifampin (strong inducer), belumosudil Cmax fell 59% and AUC 72%; expect a comparable directional effect with enzalutamide.
- Evidence: Probable; onset unspecified (induction develops over days to weeks).
- Management: Increase belumosudil to 200 mg twice daily when coadministered with a strong CYP3A inducer, per labeling. Monitor GVHD response.
What happens
Reduced belumosudil exposure and reduced efficacy of belumosudil
Interaction Deep Dive
When belumosudil (a CYP3A substrate) is given together with a strong CYP3A inducer, belumosudil exposure may fall, potentially diminishing the drug's effectiveness. A drug interaction study conducted in healthy subjects showed that giving belumosudil alongside rifAMPin (a strong CYP3A inducer) lowered belumosudil Cmax by 59% and AUC by 72%. When belumosudil is used concurrently with a strong CYP3A inducer, raise the belumosudil dose to 200 mg twice daily1.
Why it happens (mechanism)
Induction of CYP3A-mediated belumosudil metabolism
How to manage this interaction
What your care team may do:
- Adjust your belumosudil dose. The product labeling recommends increasing belumosudil to 200 mg twice daily when it is taken with a strong CYP3A inducer like enzalutamide.
- Monitor how your GVHD is responding to make sure the medicine is still working.
What you should do:
- Keep taking both medicines exactly as prescribed. Do not change the dose yourself.
- Tell your pharmacist and prescriber that you take both drugs, and ask whether your belumosudil dose should be adjusted.
- Report any worsening of your GVHD symptoms.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction study conducted in healthy subjects, giving belumosudil together with rifAMPin (a strong CYP3A inducer) reduced belumosudil Cmax by 59% and AUC by 72% 1.
Common questions
Can I take Enzalutamide and Belumosudil together?
Enzalutamide can lower belumosudil levels and make it less effective; your care team can manage this by raising the belumosudil dose (to 200 mg twice daily per labeling) and watching your response, so keep taking both as prescribed and confirm the dose with your team. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Enzalutamide and Belumosudil 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 Enzalutamide and Belumosudil interaction managed?
What your care team may do: Adjust your belumosudil dose. The product labeling recommends increasing belumosudil to 200 mg twice daily when it is taken with a strong CYP3A inducer like enzalutamide. Monitor how your GVHD is responding to make sure the medicine is still working. What you should do: Keep taking both medicines exactly as prescribed. Do not change the dose yourself. Tell your pharmaci… 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 Enzalutamide or Belumosudil 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: REZUROCK(R) oral tablets, belumosudil oral tablets. Kadmon Pharmaceuticals LLC (per FDA), Bridgewater, NJ, 2024. DailyMed
Keep reading about Enzalutamide
Keep reading about Belumosudil
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