ONTAK
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ONTAK (ONTAK).
ONTAK is a recombinant fusion protein consisting of diphtheria toxin fragments A and B linked to interleukin-2 (IL-2). It binds to high-affinity IL-2 receptors on malignant cells, internalizes, and releases diphtheria toxin, which inhibits protein synthesis via ADP-ribosylation of elongation factor 2, leading to cell death.
| Metabolism | ONTAK is a protein; metabolism is expected via proteolytic degradation into small peptides and amino acids. Not metabolized by CYP450 enzymes. |
| Excretion | Renal: minimal (<1% as unchanged drug); biliary/fecal: likely primary route but exact % not established; metabolism to denileukin diftitox occurs via proteolysis, and catabolites are excreted in urine and feces. |
| Half-life | Terminal half-life approximately 70-80 minutes (range 50-100 min) after IV infusion; due to rapid clearance, clinical effects are dependent on receptor-mediated internalization and are not directly correlated with plasma levels. |
| Protein binding | Approximately 70% bound to plasma proteins (primarily albumin and alpha-1-acid glycoprotein). |
| Volume of Distribution | Vd approximately 0.07-0.10 L/kg, indicating limited distribution primarily to the vascular compartment. |
| Bioavailability | Not applicable (only administered IV); bioavailability is 100% by IV route. |
| Onset of Action | IV: Clinical response (e.g., reduction in tumor burden) may be observed after 2-4 weeks of treatment; peak effect typically after multiple cycles. |
| Duration of Action | Duration of clinical response is variable; typically 4-6 months after completion of therapy; may be prolonged in responders. |
9 or 18 mcg/kg/day intravenously on days 1-5 of a 21-day cycle.
| Dosage form | VIAL |
| Renal impairment | No dose adjustment recommended; monitor renal function. |
| Liver impairment | No formal guidelines; use caution in severe hepatic impairment. |
| Pediatric use | Safety and efficacy not established in pediatric patients. |
| Geriatric use | No specific dose adjustment; monitor for increased toxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ONTAK (ONTAK).
| Breastfeeding | It is unknown whether ONTAK is excreted in human breast milk. The molecular weight and protein nature suggest possible excretion. Due to the potential for serious adverse reactions in nursing infants, breastfeeding is not recommended during treatment and for at least 2 months after the last dose. No M/P ratio is available. |
| Teratogenic Risk | ONTAK (denileukin diftitox) is a pregnancy category C drug. Animal studies have shown adverse effects on fetal development, including increased resorptions and fetal anomalies. There are no adequate and well-controlled studies in pregnant women. Potential fetal risks include embryotoxicity and teratogenicity, particularly during the first trimester when organogenesis occurs. Use during pregnancy should be avoided unless the potential benefit outweighs the risk. |
■ FDA Black Box Warning
Serious hypersensitivity reactions (including anaphylaxis) have been reported; capillary leak syndrome (CLS) has been observed, including life-threatening cases. Monitor for edema, hypotension, and hypoalbuminemia.
| Serious Effects |
Hypersensitivity to diphtheria toxin, IL-2, or any components of the formulation; pre-existing capillary leak syndrome or severe edema.
| Precautions | Hypersensitivity reactions (including anaphylaxis), capillary leak syndrome (CLS), infections due to immunosuppression, hepatotoxicity, renal toxicity, infusion reactions, and increased risk of thrombotic events. Monitor vital signs and laboratory parameters regularly. |
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| Fetal Monitoring | Monitor complete blood count (CBC) with differential, hepatic function (AST, ALT, bilirubin), renal function (serum creatinine, BUN), and serum albumin. Assess for signs of capillary leak syndrome (hypotension, edema, hypoalbuminemia), vascular leak syndrome, and infusion reactions. Fetal monitoring via ultrasound for growth and development if inadvertent exposure occurs. |
| Fertility Effects | ONTAK may impair fertility in both males and females based on animal studies showing testicular degeneration and ovarian atrophy. The effects in humans are unknown but potential for reduced fertility is present. Preclinical data suggest possible inhibition of spermatogenesis and oogenesis. |