Apalutamide 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
Apalutamide
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. Apalutamide (Erleada) speeds up the enzyme in your liver that breaks down belumosudil (Rezurock). When that enzyme works faster, your body clears belumosudil more quickly, so less of it stays in your blood. In studies with a similar strong inducer, belumosudil levels dropped by about 60 to 70 percent.
That matters because belumosudil is treating your graft-versus-host disease, and lower levels may mean it doesn't work as well. The good news is this is very manageable. Your care team can adjust your belumosudil dose to make up for it. Please don't change anything on your own, just talk with your doctor or pharmacist.
Interaction: Apalutamide is a strong CYP3A4 inducer; belumosudil is a CYP3A substrate (not a prodrug). Induction of CYP3A-mediated metabolism increases belumosudil clearance and reduces exposure, potentially lowering efficacy.
- Direction: Reduced belumosudil effect
- Magnitude: With rifampin, belumosudil Cmax fell 59% and AUC 72%
- Evidence: Probable; onset unspecified
- Management: When coadministered with a strong CYP3A inducer, increase belumosudil to 200 mg twice daily. 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 efficacy of belumosudil. A drug interaction study conducted in healthy subjects showed that giving belumosudil alongside rifAMPin (a strong CYP3A inducer) lowered the Cmax of belumosudil by 59% and its AUC by 72%. Should belumosudil be coadministered 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
This is manageable with a dose adjustment your team can make.
- Keep taking both exactly as prescribed unless your doctor tells you otherwise.
- Because apalutamide lowers belumosudil levels, the labeled approach is to increase belumosudil to 200 mg twice daily while the two are used together. Your prescriber will decide and make this change for you.
- Your team may watch your graft-versus-host disease symptoms more closely to be sure belumosudil is still working.
- Ask your pharmacist or prescriber before starting, stopping, or changing either drug.
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 Apalutamide and Belumosudil together?
Apalutamide can substantially lower belumosudil levels and weaken its effect, so your prescriber will likely raise the belumosudil dose (typically to 200 mg twice daily) while you take both. Keep taking both as prescribed and let your care team make the adjustment. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Apalutamide 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 Apalutamide and Belumosudil interaction managed?
This is manageable with a dose adjustment your team can make. Keep taking both exactly as prescribed unless your doctor tells you otherwise. Because apalutamide lowers belumosudil levels, the labeled approach is to increase belumosudil to 200 mg twice daily while the two are used together. Your prescriber will decide and make this change for you. Your team may watch your graft-versus-host disease… 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 Apalutamide 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 Apalutamide
Keep reading about Belumosudil
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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