FASENRA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FASENRA (FASENRA).
Benralizumab is a humanized afucosylated monoclonal antibody that binds to the alpha subunit of the interleukin-5 receptor (IL-5Rα) expressed on eosinophils and basophils. This binding inhibits IL-5-mediated signaling and induces antibody-dependent cell-mediated cytotoxicity (ADCC), resulting in rapid and near-complete depletion of eosinophils from blood and tissues.
| Metabolism | Benralizumab is a monoclonal antibody degraded into small peptides and amino acids via catabolic pathways, primarily by reticuloendothelial system. No specific metabolic enzymes involved. |
| Excretion | Degraded into small peptides and amino acids via general protein catabolism; no significant renal or biliary/fecal excretion of intact drug. |
| Half-life | Terminal half-life approximately 25 days (range 24–27 days), supporting every-4-week subcutaneous dosing. |
| Protein binding | Approximately 99% bound to target IL-5 receptor alpha; not bound significantly to other plasma proteins. |
| Volume of Distribution | Approximately 3.0–3.5 L (0.04 L/kg for a 70 kg patient), indicating primarily vascular distribution with limited extravascular penetration. |
| Bioavailability | Subcutaneous: 66–82% (mean 73%) following SC injection; not administered intravenously. |
| Onset of Action | Subcutaneous: Reduction in blood eosinophil counts observed within 24 hours; clinical improvement in asthma symptoms may be noted within 4 weeks. |
| Duration of Action | Eosinophil suppression persists for at least 12 weeks after single dose; dosing every 4 weeks maintains therapeutic effect. |
30 mg subcutaneously every 4 weeks for the first 3 doses, then every 8 weeks thereafter.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for any degree of renal impairment. |
| Liver impairment | No dose adjustment required for mild or moderate hepatic impairment (Child-Pugh A or B); not studied in severe hepatic impairment (Child-Pugh C). |
| Pediatric use | Approved for ages 12 years and older: same as adult dosing (30 mg subcutaneously every 4 weeks for 3 doses, then every 8 weeks). |
| Geriatric use | No specific dose adjustment recommended; limited data in patients ≥65 years, but no overall differences in safety or efficacy observed. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FASENRA (FASENRA).
| Breastfeeding | No data on presence in human milk; maternal IgG is excreted in breast milk. Potential for local gastrointestinal effects and systemic absorption in infant. M/P ratio not available. Consider developmental benefits of breastfeeding vs. need for maternal therapy. |
| Teratogenic Risk | No adequate human data; animal studies show no evidence of fetal harm at doses up to 100 mg/kg IV (monoclonal antibody). IgG crosses placenta increasingly in second and third trimesters; potential for fetal immune suppression. Risk cannot be ruled out. |
■ FDA Black Box Warning
None
| Serious Effects |
["History of hypersensitivity to benralizumab or any excipients in the formulation"]
| Precautions | ["Hypersensitivity reactions (including anaphylaxis, angioedema, urticaria, rash) have occurred after administration.","Acute asthma symptoms or deteriorating disease should not be treated with FASENRA.","Risk of parasitic infections: Patients with pre-existing helminth infections should be treated before initiating therapy. Monitor for infection during treatment.","Do not discontinue systemic or inhaled corticosteroids abruptly upon initiation of FASENRA."] |
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| Fetal Monitoring |
| Monitor for maternal infections; fetal growth and well-being via ultrasound if used in pregnancy. Assess neonatal immune function at birth if exposed in utero. |
| Fertility Effects | No specific fertility studies; in animal studies, no adverse effects on male or female fertility at doses up to 100 mg/kg IV. |