Lenacapavir Injection and Rilzabrutinib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Rilzabrutinib
Lenacapavir 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 rilzabrutinib exposure, an increased risk of rilzabrutinib-related adverse reactions, increased CYP3A substrate exposure and an increased risk of CYP3A4 substrate-related adverse reactions
Interaction Deep Dive
Avoid concomitant use of rilzabrutinib (CYP3A substrate) with moderate CYP3A inhibitors as it may increase rilzabrutinib exposure, which may increase rilzabrutinib-related side effects than usual. If a moderate CYP3A inhibitor cannot be avoided, and these inhibitors will be used short term (such as anti-infectives for seven days or less), interrupt treatment with rilzabrutinib. Additionally, coadministration of rilzabrutinib (moderate CYP3A inhibitor) and CYP3A substrates may increase CYP3A substrates exposure, which increases the risk of adverse reactions related to these substrates. Monitor for adverse reactions of the concurrently administered CYP3A substrate more frequently and consider dosage adjustment accordingly1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of rilzabrutinib; inhibition of CYP3A-substrate metabolism by rilzabrutinib
Literature reports
2 reports — tap to read
a) In a drug interaction study with healthy participants, concomitant use of a single dose of rilzabrutinib 400 mg with midazolam (sensitive CYP3A substrate) increased midazolam Cmax and AUC by 2.2-fold. Midazolam AUC is predicted to increase up to 3.0-fold in patients with immune thrombocytopenia following coadministration with 400 mg rilzabrutinib twice daily 1.
b) In a drug interaction study, concomitant use of rilzabrutinib with moderate CYP3A inhibitors (fluconazole, erythromycin and verapamil) is predicted to increase rilzabrutinib Cmax and AUC by approximately 3-fold at steady state 1.
Common questions
Can I take Lenacapavir Injection and Rilzabrutinib together?
Increased rilzabrutinib exposure, an increased risk of rilzabrutinib-related adverse reactions, increased CYP3A substrate exposure and an increased risk of CYP3A4 substrate-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Lenacapavir Injection and Rilzabrutinib 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 Lenacapavir Injection or Rilzabrutinib 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: WAYRILZ™ oral tablets, rilzabrutinib oral tablets. Genzyme Corporation (per FDA), Cambridge, MA, 2025. DailyMed
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