Lenacapavir Injection and Defactinib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Lenacapavir Injection
Defactinib
No brand names on record
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 defactinib exposure and an increased risk of defactinib-related adverse effects
Interaction Deep Dive
Avoid concomitant use of defactinib (CYP3A4 substrate) with strong or moderate CYP3A inhibitors. Concomitant use of defactinib with inhibitors increases defactinib exposure, which may increase the risk of defactinib adverse reactions. In a drug interaction study, defactinib Cmax increased by 2.2-fold and AUC by 3.9-fold following concomitant use with itraconazole (strong CYP3A inhibitor) 200 mg daily for 10 days. M4 AUC increased by 2.2-fold and Cmax decreased by 6.8%1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of defactinib
Literature reports
1 report — tap to read
a) In a drug interaction study, defactinib Cmax increased by 2.2-fold and AUC by 3.9-fold following concomitant use with itraconazole (strong CYP3A4 inhibitor) 200 mg daily for 10 days. Major metabolite of defactinib, N-desmethyl amide (M4) AUC increased by 2.2-fold and Cmax decreased by 6.8% 1.
Common questions
Can I take Lenacapavir Injection and Defactinib together?
Increased defactinib exposure and an increased risk of defactinib-related adverse effects Always confirm with your pharmacist or prescriber before making any change.
How serious is the Lenacapavir Injection and Defactinib 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 "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Lenacapavir Injection or Defactinib 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: AVMAPKI(TM) FAKZYNJA(TM) CO-PACK oral capsules, tablets, avutometinib oral capsules, defactinib oral tablets. Verastem, Inc (per manufacturer), Needham, MA, 2025. DailyMed
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