ZELBORAF
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZELBORAF (ZELBORAF).
Vemurafenib is a selective inhibitor of the BRAF serine-threonine kinase, specifically targeting mutations at codon 600 (BRAF V600E). It blocks the MAPK pathway, reducing cell proliferation in BRAF V600E mutation-positive melanoma cells.
| Metabolism | Primarily metabolized by CYP3A4, with minor contributions from CYP2C9, CYP2C19, CYP2D6, and CYP1A2. |
| Excretion | Renal excretion of unchanged drug is minimal (approximately 2% of the dose). Biliary/fecal elimination is the major route, with about 94% of the dose recovered in feces (primarily as metabolites) and 5% in urine. |
| Half-life | Terminal elimination half-life is approximately 52 hours (range 30–70 hours), supporting once-daily dosing and requiring about 10 days to reach steady-state. |
| Protein binding | >99% bound to human plasma proteins, primarily to albumin and alpha-1 acid glycoprotein (AAG). |
| Volume of Distribution | Apparent volume of distribution (Vd/F) is approximately 106–179 L (roughly 1.5–2.5 L/kg), indicating extensive tissue distribution. |
| Bioavailability | Absolute bioavailability is not determined; mean relative bioavailability of the tablet formulation is 95% compared to an oral solution. Bioavailability is decreased by high-fat meal (Cmax ↓ 40%, AUC ↓ 37%); therefore, avoid food 1 hour before or 2 hours after dose. |
| Onset of Action | Clinical effect (tumor response) onset is typically observed within 2–6 weeks of continuous oral dosing, as assessed by radiographic imaging. |
| Duration of Action | Suppression of ERK phosphorylation (pharmacodynamic effect) persists for approximately 7–10 days; clinical duration varies with disease progression and tolerated therapy. Median progression-free survival is about 5–7 months in BRAF V600E mutant melanoma. |
| Molecular Weight | 489.9 |
960 mg orally twice daily, approximately 12 hours apart, with or without food.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl ≥30 mL/min). Not recommended in severe renal impairment (CrCl <30 mL/min) due to lack of data. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose to 720 mg twice daily. Child-Pugh C: Not recommended. |
| Pediatric use | Safety and efficacy not established; no approved pediatric dosing. |
| Geriatric use | No specific dose adjustment recommended; monitor renal function and comorbidities commonly seen in elderly. |
| 1st trimester | Avoid. Vemurafenib is teratogenic in animal studies. Contraindicated during organogenesis. Use effective contraception. |
| 2nd trimester | Avoid. May cause fetal harm. No adequate human data. |
| 3rd trimester | Avoid. Risk of fetal toxicity; consider alternative therapy. |
Clinical note
Comprehensive clinical and safety monograph for ZELBORAF (ZELBORAF).
| Placental transfer | Animal studies indicate placental transfer. Human data lacking but expected due to low molecular weight. |
| Breastfeeding | No data on presence in human milk. Potential for serious adverse reactions in nursing infants. Discontinue breastfeeding or drug. |
| Lactation Rating |
■ FDA Black Box Warning
No black box warning.
| Serious Effects |
Hypersensitivity to vemurafenib or excipientsConcomitant use with drugs that prolong QT interval (unless monitored)
| Precautions | Cutaneous squamous cell carcinoma (cuSCC) and other skin malignancies: Monitor for new skin lesions, Severe dermatologic reactions (e.g., Stevens-Johnson syndrome), QT interval prolongation: Monitor electrolytes and ECG, Hepatotoxicity: Monitor liver function tests, Photosensitivity: Advise sun protection, Ocular effects: Uveitis, retinal vein occlusion, New primary malignancies (non-cutaneous), Pancreatitis: Monitor amylase and lipase, Hypersensitivity reactions |
| Food/Dietary | Avoid grapefruit and grapefruit juice (CYP3A4 inhibition may increase vemurafenib levels). No other significant food interactions reported. |
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| L5 |
| Teratogenic Risk | ZELBORAF (vemurafenib) has been shown to be embryotoxic and teratogenic in animal studies. Based on its mechanism of action (BRAF inhibitor) and animal data, there is a risk of fetal harm if used during pregnancy. First trimester: high risk of major malformations (e.g., cardiac, skeletal) and spontaneous abortion. Second and third trimesters: risk of fetal growth restriction, oligohydramnios, and potential neonatal toxicity. Adequate contraception is recommended during treatment and for at least 2 weeks after the last dose. |
| Fetal Monitoring | Monitor for fetal growth restriction and oligohydramnios via serial ultrasound. Assess for QT prolongation on maternal ECG, as vemurafenib can cause QT interval prolongation. Monitor liver function tests, renal function, and electrolytes. Watch for cutaneous squamous cell carcinoma and other skin lesions; perform dermatologic exams. Monitor for uveitis, iritis, and other ocular toxicities. In neonates, monitor for hypoglycemia, electrolyte disturbances, and hepatotoxicity if exposure occurred late in pregnancy. |
| Fertility Effects | In animal studies, vemurafenib caused testicular toxicity in males (reduced testicular weight, seminiferous tubule degeneration) and potential impairment of male fertility. Effects on female fertility are unknown; however, BRAF pathway inhibitors may disrupt ovarian function. Preclinical data suggest possible reversible impairment of spermatogenesis. Patients should be counseled on potential impact on fertility and consider fertility preservation before treatment. |
| Clinical Pearls | ZELBORAF (vemurafenib) is a BRAF kinase inhibitor indicated for BRAF V600E mutation-positive unresectable or metastatic melanoma and Erdheim-Chester disease. Monitor ECGs at baseline and monthly for QT interval prolongation. Watch for severe dermatologic reactions (e.g., Stevens-Johnson syndrome) and hepatotoxicity. Do not administer with strong CYP3A4 inducers or inhibitors; avoid concurrent use of CYP1A2 substrates with narrow therapeutic index. Contraception required during therapy and for 2 weeks after discontinuation. |
| Patient Advice | Take exactly as prescribed; do not crush or chew tablets. · Report any new skin changes, severe rash, or prolonged QT symptoms (fainting, palpitations). · Use effective contraception during treatment and for 2 weeks after stopping. · Avoid sun exposure; wear protective clothing and broad-spectrum sunscreen daily. · Notify your doctor if you experience severe nausea, vomiting, diarrhea, or vision changes. · Do not start new medications (including OTC or herbal) without approval from your healthcare provider. |