SYLVANT
Clinical safety rating
cautionComprehensive clinical and safety monograph for SYLVANT (SYLVANT).
Comprehensive clinical and safety monograph for SYLVANT (SYLVANT).
Treatment of multicentric Castleman disease (MCD) in patients who are human immunodeficiency virus (HIV) negative and human herpesvirus-8 (HHV-8) negative.Off-label: Treatment of cytokine release syndrome, Castleman disease in HIV-positive or HHV-8-positive patients, and other IL-6-driven conditions.
Siltuximab is a chimeric monoclonal antibody that binds to human interleukin-6 (IL-6) and prevents its binding to the IL-6 receptor, thereby inhibiting IL-6-mediated signaling and the downstream inflammatory cascade.
| Metabolism | Siltuximab is a monoclonal antibody; its metabolism is not typical. It is degraded into small peptides and amino acids via catabolic pathways, similar to endogenous immunoglobulins. No specific metabolic enzymes are involved. |
| Excretion | Renal (minimal as intact IgG), primarily catabolized to amino acids; no significant biliary/fecal elimination. |
| Half-life | Terminal half-life ~21 days (range 14–28 days) at steady state; supports every-3-week dosing. |
| Protein binding | No specific protein binding; IgG4 monoclonal antibody does not bind significantly to plasma proteins. |
| Volume of Distribution | Vd ~6.0 L (0.08 L/kg for 70 kg adult); primarily confined to vascular space and interstitial fluid. |
| Bioavailability | IV administration: 100% bioavailable; no other routes approved. |
| Onset of Action | IV: Clinical response (e.g., fever, laboratory improvements) within 2–4 weeks after first dose. |
| Duration of Action | Duration of symptomatic relief sustained through 12 weeks of treatment; pharmacokinetic effects persist for ~3–5 half-lives after discontinuation. |
| Molecular Weight | 145 |
11 mg/kg intravenously every 3 weeks, administered over 1 hour.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl 30-89 mL/min). Not studied in severe renal impairment (CrCl <30 mL/min) or ESRD. |
| Liver impairment | No formal studies in hepatic impairment. Use with caution in patients with moderate to severe impairment (Child-Pugh B or C). |
| Pediatric use | Safety and efficacy not established in pediatric patients. |
| Geriatric use | No specific dose adjustment recommended; select dose with caution due to higher frequency of decreased hepatic, renal, or cardiac function and concomitant disease or drug therapy. |
| 1st trimester | Insufficient human data; animal studies show fetal harm. Avoid unless benefit outweighs risk. |
| 2nd trimester | May be used if clinically indicated; monitor for fetal growth restriction due to IL-6 inhibition. |
| 3rd trimester | May be used if clinically indicated; monitor for potential immunosuppression in neonate. |
Clinical note
Comprehensive clinical and safety monograph for SYLVANT (SYLVANT).
| Placental transfer | Likely minimal due to high molecular weight; IgG monoclonal antibodies cross placenta, especially in third trimester. |
| Breastfeeding | No human data; large molecular size likely limits transfer into breast milk, but unknown effects on infant. Consider benefits of breastfeeding vs. risk of exposure. |
| Lactation Rating | L4 |
| Teratogenic Risk | SYLVANT (siltuximab) is a monoclonal antibody (IgG1) that crosses the placenta in increasing amounts as pregnancy progresses, with the highest transfer in the third trimester. Animal studies have shown no evidence of teratogenicity in cynomolgus monkeys at doses up to 10 times the human clinical exposure. However, there are no adequate and well-controlled studies in pregnant women. Based on its mechanism of action (IL-6 inhibition), there is a potential risk of fetal harm due to interference with normal immune development and hematopoiesis. Therefore, SYLVANT should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. |
| Fetal Monitoring | Monitor pregnant women receiving SYLVANT for signs of infection, hematologic abnormalities, and hepatic function. Perform complete blood counts and liver function tests regularly. Monitor for fetal growth abnormalities and preterm labor via ultrasound. Consider neonatal monitoring for potential immune suppression or hematologic effects after birth. |
| Fertility Effects | No formal fertility studies have been conducted. In animal studies, no effects on male or female fertility were observed at doses up to 10 times the human exposure. However, given the role of IL-6 in reproductive processes, there is a potential for transient impairment of fertility in women during treatment. |
■ FDA Black Box Warning
None.
| Serious Effects |
History of hypersensitivity to siltuximab or any excipientsSevere active infection (e.g., sepsis, tuberculosis)
| Precautions | Risk of serious infections: Evaluate for active infections prior to initiating therapy; monitor for infections during treatment., Hypersensitivity reactions: Infusion-related reactions may occur; premedicate and monitor during infusion., Hematologic effects: Neutropenia, thrombocytopenia, and anemia may occur; monitor blood counts., Hepatotoxicity: Elevations of liver enzymes have been reported; monitor liver function., Immunogenicity: Anti-drug antibodies may develop and affect efficacy or safety., Vaccinations: Live vaccines should not be administered during treatment. |
| Food/Dietary | No clinically significant food interactions have been reported. Take with or without food as tolerated. |
| Clinical Pearls | SYLVANT (siltuximab) is an IL-6 antagonist indicated for idiopathic multicentric Castleman disease (MCD). Monitor for infections due to immunosuppression; do not administer live vaccines. Infusion reactions possible; premedicate with antihistamines/acetaminophen if needed. Assess baseline hepatic function, as transaminase elevations may occur. Discontinue if severe infusion reaction or anaphylaxis. |
| Patient Advice | Report signs of infection (fever, chills, sore throat) immediately. · Avoid live vaccines (e.g., MMR, varicella) during treatment and for 3 months after. · Notify your doctor if you experience symptoms of infusion reaction (headache, nausea, dizziness, rash). · Regular blood tests will be required to monitor liver function and blood counts. |
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