Abemaciclib and Lenacapavir: 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
Lenacapavir
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.
Here's what's going on. Lenacapavir (Sunlenca or Yeztugo) is a long-acting HIV medicine that gently slows down a liver enzyme called CYP3A. Abemaciclib (Verzenio), a cancer medicine, is broken down by that same enzyme. So when you take them together, your body may clear abemaciclib more slowly, and its levels can build up.
That can mean more of abemaciclib's usual side effects, like diarrhea, low blood counts, tiredness, or nausea. One thing to know: lenacapavir stays in your body a long time, so this effect can linger for months after your last dose. The good news is your care team can manage this by adjusting your dose and watching you more closely. Please talk with your doctor or pharmacist.
Mechanism: Lenacapavir is a moderate CYP3A inhibitor; abemaciclib is a sensitive CYP3A4 substrate. Inhibition reduces abemaciclib clearance, increasing its AUC/Cmax and raising the risk of concentration-dependent toxicity (diarrhea, neutropenia, hepatotoxicity, VTE, fatigue). Neither drug is a prodrug, so the direction is increased active-drug exposure.
- Direction: increased abemaciclib exposure/effect
- Severity/Evidence: major, theoretical
- Onset: unspecified; note lenacapavir's long half-life means the effect may persist up to ~9 months after the last dose
Management: Abemaciclib dose may need reduction per prescribing guidance for moderate CYP3A inhibitors, with closer monitoring for toxicity. Individualize and monitor.
What happens
Increased sensitive CYP3A substrate exposure and an increased risk of sensitive CYP3A substrate-mediated adverse reactions
Interaction Deep Dive
When lenacapavir, which acts as a moderate inhibitor of CYP3A, is given alongside a sensitive CYP3A substrate, the exposure to that sensitive CYP3A substrate may rise. For drugs that undergo metabolism chiefly through CYP3A and that are started within 9 months following the final lenacapavir dose, lenacapavir may raise their exposure, which in turn may heighten the possibility of adverse reactions12.
Why it happens (mechanism)
Inhibition of CYP3A substrate metabolism by lenacapavir
How to manage this interaction
The most important thing: keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This is manageable.
- Your oncology team may adjust and individualize your abemaciclib dose while you are on lenacapavir.
- They may monitor you more closely for side effects such as diarrhea, low blood counts, or liver changes.
- Because lenacapavir lasts a long time in the body, this caution can apply for months after your last lenacapavir dose.
- Report any new or worsening diarrhea, unusual tiredness, fever, or signs of bleeding.
Ask your pharmacist or prescriber to review both prescriptions together so the plan fits you.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abemaciclib and Lenacapavir together?
Lenacapavir can raise abemaciclib levels and increase its side effects, so your care team may lower the abemaciclib dose and monitor you more closely, including for months after your last lenacapavir dose. Do not change anything on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Lenacapavir 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 Lenacapavir interaction managed?
The most important thing: keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This is manageable. Your oncology team may adjust and individualize your abemaciclib dose while you are on lenacapavir. They may monitor you more closely for side effects such as diarrhea, low blood counts, or liver changes. Because lenacapavir lasts a long time in the body, this c… 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 Lenacapavir 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 (2)
- Product Information: SUNLENCA(R) oral tablets, subcutaneous injection, lenacapavir oral tablets, subcutaneous injection. Gilead Sciences Inc (per FDA), Foster City, CA, 2024. DailyMed
- Product Information: YEZTUGO(R) oral tablets, subcutaneous injection, lenacapavir oral tablets, subcutaneous injection. Gilead Sciences Inc (per manufacturer), Foster City, CA, 2025. DailyMed
Keep reading about Lenacapavir
Keep reading about Abemaciclib
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