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Siltuximab Approved for Rare Blood Disorder

Kate Traynor

Janssen Biotech on April 23 announced that FDA has approved siltuximab for the treatment of multicentric Castleman disease (MCD), a rare blood disorder that affects the lymph nodes.

About 1100–1300 Americans are estimated to have MCD, according to data cited by Janssen.

Siltuximab will be marketed as Sylvant. The product's launch date has not yet been announced.

The labeling (PDF).External Link for siltuximab describes it as a human–mouse chimeric monoclonal antibody that binds to interleukin-6, a cytokine that is overproduced in patients with MCD.

According to the labeling, a third of the 53 adult clinical trial participants with MCD who received siltuximab and supportive care had a "durable tumor and symptomatic response." No such response was observed in any of the 26 patients who received a placebo and supportive care.

The most common siltuximab-associated adverse events reported by clinical trial participants were itching, weight gain, rash, hyperuricemia, and upper-respiratory-tract infection.

Siltuximab should be used only in patients with MCD who test negative for HIV or human herpesvirus-8 infection, according to the labeling.

The biological should not be used in patients who have a serious infection, and patients treated with siltuximab should be monitored closely for infection during the course of treatment. Live vaccines should not be administered during siltuximab therapy because inhibition of interleukin-6 may interfere with patients' response to the vaccines.

The recommended dosage of siltuximab is 11 mg/kg of patient weight infused intravenously over one hour every three weeks until treatment failure occurs.

The lyophilized powder should be reconstituted with Sterile Water for Injection, USP, and should dissolve within an hour, according to the labeling.

Within two hours after reconstitution of the drug to 20 mg/mL, the desired dose should be slowly added to an infusion bag made of polyvinyl chloride (PVC)-containing diethylhexyl phthalate (DEHP) or polyolefin and containing sufficient 5% dextrose injection to yield a total infusion volume of 250 mL. The entire 250 mL should be infused into the patient within four hours after adding the reconstituted drug to the infusion bag. The i.v. administration set should have a 0.2-micron inline polyethersulfone filter and be lined with PVC-containing DEHP or polyurethane.

The infusion should be stopped if a patient has a mild-to-moderate infusion reaction while the biologic is being administered. The infusion may resume at a slower rate if the reaction resolves, and the use of antihistamines, acetaminophen, and corticosteroids should be considered.

Each dose of siltuximab should be administered at a health care facility that is prepared to treat anaphylaxis. Siltuximab therapy should be permanently discontinued in any patient who has an anaphylactic reaction to the therapy.

Blood-cell counts should be performed before each dose is administered during the first year of siltuximab therapy and then every three dosing cycles thereafter. If neutrophil, platelet, or hemoglobin levels do not meet the criteria described in the labeling, clinicians should consider delaying treatment but not reducing the dose, according to the labeling.

Siltuximab will be supplied in 100- and 400-mg single-use vials. The vials must be refrigerated at 2–8 °C and protected from light.

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